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Hexamethyldisiloxane

PubChem CID
24764
Structure
Hexamethyldisiloxane_small.png
Hexamethyldisiloxane_3D_Structure.png
Molecular Formula
Synonyms
  • HEXAMETHYLDISILOXANE
  • 107-46-0
  • Disiloxane, hexamethyl-
  • Oxybis(trimethylsilane)
  • HMDSO
Molecular Weight
162.38 g/mol
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Dates
  • Create:
    2005-03-26
  • Modify:
    2025-01-11
Description
Hexamethyldisiloxane is an organosiloxane consisting of two trimethylsilyl groups covalently bound to a central oxygen.
See also: Vinyltrimethylsilyloxy silicate (monomer of); Dimethicone (annotation moved to).

1 Structures

1.1 2D Structure

Chemical Structure Depiction
Hexamethyldisiloxane.png

1.2 3D Conformer

1.3 Crystal Structures

2 Names and Identifiers

2.1 Computed Descriptors

2.1.1 IUPAC Name

trimethyl(trimethylsilyloxy)silane
Computed by Lexichem TK 2.7.0 (PubChem release 2021.10.14)

2.1.2 InChI

InChI=1S/C6H18OSi2/c1-8(2,3)7-9(4,5)6/h1-6H3
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.3 InChIKey

UQEAIHBTYFGYIE-UHFFFAOYSA-N
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.4 SMILES

C[Si](C)(C)O[Si](C)(C)C
Computed by OEChem 2.3.0 (PubChem release 2024.12.12)

2.2 Molecular Formula

C6H18OSi2
Computed by PubChem 2.2 (PubChem release 2021.10.14)

2.3 Other Identifiers

2.3.1 CAS

107-46-0
9006-65-9

2.3.3 Deprecated CAS

1463472-97-0, 1650537-56-6, 864719-97-1
864719-97-1

2.3.4 European Community (EC) Number

2.3.5 UNII

2.3.6 ChEBI ID

2.3.7 ChEMBL ID

2.3.8 DSSTox Substance ID

2.3.9 HMDB ID

2.3.10 NCI Thesaurus Code

2.3.11 Nikkaji Number

2.3.12 NSC Number

2.3.13 RXCUI

2.3.14 Wikidata

2.3.15 Wikipedia

2.4 Synonyms

2.4.1 MeSH Entry Terms

hexamethyldisiloxane

2.4.2 Depositor-Supplied Synonyms

3 Chemical and Physical Properties

3.1 Computed Properties

Property Name
Molecular Weight
Property Value
162.38 g/mol
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Donor Count
Property Value
0
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Acceptor Count
Property Value
1
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Rotatable Bond Count
Property Value
2
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Exact Mass
Property Value
162.08961826 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Monoisotopic Mass
Property Value
162.08961826 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Topological Polar Surface Area
Property Value
9.2 Ų
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Heavy Atom Count
Property Value
9
Reference
Computed by PubChem
Property Name
Formal Charge
Property Value
0
Reference
Computed by PubChem
Property Name
Complexity
Property Value
76.2
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Isotope Atom Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Covalently-Bonded Unit Count
Property Value
1
Reference
Computed by PubChem
Property Name
Compound Is Canonicalized
Property Value
Yes
Reference
Computed by PubChem (release 2021.10.14)

3.2 Experimental Properties

3.2.1 Physical Description

Dry Powder; Liquid
Liquid; [HSDB] Colorless liquid; [MSDSonline]

3.2.2 Color / Form

FLUID
Clayton, G. D. and F. E. Clayton (eds.). Patty's Industrial Hygiene and Toxicology: Volume 2A, 2B, 2C: Toxicology. 3rd ed. New York: John Wiley Sons, 1981-1982., p. 3041

3.2.3 Boiling Point

99 °C
Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V3: 2518

3.2.4 Melting Point

-66 °C
Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V3: 2518

3.2.5 Flash Point

-30 °C
Clayton, G. D. and F. E. Clayton (eds.). Patty's Industrial Hygiene and Toxicology: Volume 2A, 2B, 2C: Toxicology. 3rd ed. New York: John Wiley Sons, 1981-1982., p. 2397

3.2.6 Solubility

In water, 0.93 mg/L at 25 °C
Kochetkov A et al; Environ Toxicol Chem 20: 2184-88 (2001)
0.93 mg/L @ 25 °C (exp)
The Good Scents Company Information System

3.2.7 Density

0.7638 at 20 °C
Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V3: 2518

3.2.8 Vapor Pressure

42.0 [mmHg]

3.2.9 LogP

log Kow = 4.2
Sangster J; LOGKOW Databank. Sangster Res. Lab., Montreal Quebec, Canada (1994)

3.2.10 Henry's Law Constant

Henry's Law constant = 4.53X10-2 atm-cu m/mol at 25 °C
Kochetkov A et al; Environ Toxicol Chem 20: 2184-88 (2001)

3.2.11 Decomposition

When heated to decomposition it emits acrid smoke, fumes.
Sax, N.I. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand Reinhold, 1984., p. 1521

3.2.12 Viscosity

0.51 centistokes at 20 °C
Mazzoni SM et al; pp 53-81 in Handbook Environ Chem, Vol 3. Chandra G, ed. Berlin, Germany: Springer (1997)

3.2.13 Refractive Index

Index of Refraction: 1.3774 at 20 °C
Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V3: 2518

3.2.14 Kovats Retention Index

Semi-standard non-polar
597.4 , 597.4 , 598 , 645 , 646

3.2.15 Other Experimental Properties

FREEZING POINT: -68 °C
Clayton, G. D. and F. E. Clayton (eds.). Patty's Industrial Hygiene and Toxicology: Volume 2A, 2B, 2C: Toxicology. 3rd ed. New York: John Wiley Sons, 1981-1982., p. 2397
Insoluble in most solvents, water repellent, resistant towards oxidation and chemical attack /Silicone resins/
Bingham, E.; Cohrssen, B.; Powell, C.H.; Patty's Toxicology Volumes 1-9 5th ed. John Wiley & Sons. New York, N.Y. (2001)., p. V6: 987
Hydroxyl radical reaction rate constant = 1.38X10-12 cu cm/molec-sec at 24 °C
Atkinson R; Environ Sci Technol 25: 863-6 (1991)

3.3 SpringerMaterials Properties

3.4 Chemical Classes

Metals -> Metalloid Compounds (Silicon)

3.4.1 Drugs

Pharmaceuticals
S10 | SWISSPHARMA | Pharmaceutical List with Consumption Data | DOI:10.5281/zenodo.2623484

3.4.2 Cosmetics

Antistatic; Antifoaming; Emollient; Skin conditioning
S13 | EUCOSMETICS | Combined Inventory of Ingredients Employed in Cosmetic Products (2000) and Revised Inventory (2006) | DOI:10.5281/zenodo.2624118

4 Spectral Information

4.1 1D NMR Spectra

1 of 2
1D NMR Spectra
NMR: 6468 (Sadtler Research Laboratories Spectral Collection)
2 of 2
1D NMR Spectra

4.1.1 1H NMR Spectra

1 of 3
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Spectra ID
Instrument Type
JEOL
Frequency
400 MHz
Solvent
CDCl3
Shifts [ppm]:Intensity
0.06:406.00, 0.07:208.00, 0.12:24.00, 0.03:23.00, 0.06:1000.00
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Instrument Name
Varian A-60
Source of Sample
PCR, Inc., Gainesville, Florida
Copyright
Copyright © 2009-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.1.2 13C NMR Spectra

1 of 3
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Spectra ID
Instrument Type
Varian
Frequency
25.16 MHz
Solvent
CDCl3
Shifts [ppm]:Intensity
1.94:1000.00
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Source of Sample
Harvard University, Cambridge, Massachusetts
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.1.3 17O NMR Spectra

1 of 2
Copyright
Copyright © 2016-2024 W. Robien, Inst. of Org. Chem., Univ. of Vienna. All Rights Reserved.
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2 of 2
Copyright
Copyright © 2016-2024 W. Robien, Inst. of Org. Chem., Univ. of Vienna. All Rights Reserved.
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4.1.4 29Si NMR Spectra

1 of 2
Copyright
Copyright © 2016-2024 W. Robien, Inst. of Org. Chem., Univ. of Vienna. All Rights Reserved.
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2 of 2
Copyright
Copyright © 2016-2024 W. Robien, Inst. of Org. Chem., Univ. of Vienna. All Rights Reserved.
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4.2 Mass Spectrometry

4.2.1 GC-MS

1 of 11
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Spectra ID
Instrument Type
EI-B
Ionization Mode
positive
Top 5 Peaks

147.0 99.99

73.0 17.83

148.0 16.54

66.0 14.42

59.0 13.02

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Notes
instrument=JEOL JMS-D-3000
2 of 11
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Spectra ID
Instrument Type
EI-B
Ionization Mode
positive
Top 5 Peaks

147.0 99.99

148.0 15.48

73.0 14.49

66.0 10.43

149.0 7.65

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Notes
instrument=HITACHI RMU-7M

4.2.2 Other MS

1 of 3
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Other MS
MASS: 10489 (NIST/EPA/MSDC Mass Spectral database, 1990 version); 630 (National Bureau of Standards EPA-NIH Mass Spectra Data Base, NSRDS-NBS-63)
2 of 3
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Authors
MASS SPECTROSCOPY SOC. OF JAPAN (MSSJ)
Instrument
JEOL JMS-D-3000
Instrument Type
EI-B
MS Level
MS
Ionization Mode
POSITIVE
Ionization
ENERGY 70 eV
Top 5 Peaks

147 999

73 178

148 165

66 144

59 130

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License
CC BY-NC-SA

4.3 IR Spectra

IR Spectra
IR: 5573 (Coblentz Society Spectral Collection)

4.3.1 FTIR Spectra

1 of 2
Instrument Name
Bio-Rad FTS
Technique
Neat (KBr)
Source of Spectrum
Forensic Spectral Research
Copyright
Copyright © 2012-2024 John Wiley & Sons, Inc. All Rights Reserved.
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Technique
Layer between KBr
Source of Sample
Th. Goldschmidt AG, Essen
Copyright
Copyright © 1989, 1990-2024 Wiley-VCH Verlag GmbH & Co. KGaA. All Rights Reserved.
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4.3.2 ATR-IR Spectra

1 of 2
Instrument Name
PerkinElmer SpectrumTwo
Technique
ATR-IR
Copyright
Copyright © 2012-2024 John Wiley & Sons, Inc. All Rights Reserved.
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2 of 2
Source of Sample
Aldrich
Catalog Number
205389
Copyright
Copyright © 2018-2024 Sigma-Aldrich Co. LLC. - Database Compilation Copyright © 2018-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.3.3 Near IR Spectra

1 of 2
Instrument Name
BRUKER IFS 88
Technique
NIR
Source of Spectrum
Prof. Buback, University of Goettingen, Germany
Copyright
Copyright © 1989, 1990-2024 Wiley-VCH Verlag GmbH & Co. KGaA. All Rights Reserved.
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2 of 2
Instrument Name
BRUKER IFS 88
Technique
NIR
Source of Spectrum
Prof. Buback, University of Goettingen, Germany
Copyright
Copyright © 1989, 1990-2024 Wiley-VCH Verlag GmbH & Co. KGaA. All Rights Reserved.
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4.3.4 Vapor Phase IR Spectra

1 of 2
Instrument Name
DIGILAB FTS-14
Technique
Vapor Phase
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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2 of 2
Source of Spectrum
Sigma-Aldrich Co. LLC.
Source of Sample
Sigma-Aldrich Co. LLC.
Catalog Number
205389
Copyright
Copyright © 2021-2024 Sigma-Aldrich Co. LLC. - Database Compilation Copyright © 2021 John Wiley & Sons, Inc. All Rights Reserved.
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4.4 Raman Spectra

1 of 2
Raman Spectra
Raman: 1194 (Sadtler Research Laboratories Spectral Collection)
2 of 2
Catalog Number
205389
Copyright
Copyright © 2017-2024 Sigma-Aldrich Co. LLC. - Database Compilation Copyright © 2017-2024 John Wiley & Sons, Inc. All Rights Reserved.
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6 Chemical Vendors

7 Food Additives and Ingredients

7.1 Associated Foods

8 Pharmacology and Biochemistry

8.1 Absorption, Distribution and Excretion

To examine the distribution of low molecular weight silicones in body organs, separate groups of female CD-1 mice were injected with either breast implant distillate composed primarily of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and tetradecamethylcycloheptasiloxane or a polydimethylsiloxane oil containing low molecular weight linear siloxanes. Mice were injected subcutaneously in the suprascapular area and killed at different times. Levels of individual low molecular weight silicones were measured in 10 different organs (brain, heart, kidney, liver, lung, mesenteric lymph nodes, ovaries, spleen, skeletal muscle, and uterus). In mice treated with the cyclosiloxane mixture and killed at 3, 6, or 9 weeks, highest levels of cyclosiloxanes were found in the mesenteric lymph nodes, ovaries, and uterus, but all organs examined contained cyclosiloxanes. In a cohort killed at 1 year, most organs contained measurable cyclosiloxanes with highest levels in mesenteric lymph nodes, abdominal fat, and ovaries. Of the individual cyclosiloxanes measured, selective retention of decamethylcyclopentasiloxane and dodecamethylcyclohexasiloxane relative to octamethylcyclotetrasiloxane was seen in all organs at all time points studied. Organs from animals receiving the linear siloxane mixture were harvested at 9, 12, and 15 weeks. ... Maximum levels in the brain, lungs, and mesenteric lymph nodes /were found/, but all other organs contained measurable levels. These data are, to the best of our knowledge, the first demonstration that after a single subcutaneous injection silicones are widely distributed throughout the body and can persist over an extended period.
Kala SV et al; Am J Pathol 152 (3): 645-9 (1998)

8.2 Metabolism / Metabolites

Urine is a primary route of elimination of hexamethyldisiloxane (MM) in the form of metabolites. Accordingly, to aid in the pharmacokinetic investigations, major metabolites of MM were identified in urine collected from Fischer rats (F-344) administered (14)C-MM orally and via intravenous injection ... The structural assignments were based on GC-MS analysis of the tetrahydrofuran or methylene chloride extracts of urine containing the metabolites. Some of the metabolites in the extract required protection with trimethylsilyl groups prior to GC-MS analysis using bis(trimethylsilyl)trifluoroacetamide or highly purified hexamethyldisiloxane ... The following are among the major metabolites identified: Me2Si(OH)2; HOMe2SiCH2OH; HOCH2Me2SiOSiMe2CH2OH (predominant); HOCH2Me2SiOSiMe3; HOMe2SiOSiMe3; Me3SiOH. Besides these there were also three other metabolites- HOMe2SiOSiMe2CH2OH, 2,2,5,5- tetramethyl-2,5-disila-1,3-dioxalane and 2,2,5,5-tetramethyl-1,4-dioxa-2,5- disilacyclohexane inferred from GC-MS analyses. Their presence in the HPLC metabolite profile was not established. No parent MM was present in urine. The presence of certain metabolites such as Me2Si(OH)2 and HOMe2SiCH2OH clearly established some demethylation at the silicon-methyl bonds. Metabolites of this linear siloxane are structurally different from that obtained for cyclic siloxanes (D4 and D5) except for the commonly present Me2Si(OH)2. A mechanistic pathway for the formation of the metabolites was proposed.
Silicones Environmental, Health and Safety Council of North America; Siloxane Research Program: Hexamethyldisiloxane. Available from, as of June 15, 2006: https://www.sehsc.com/srp-research-reports.asp
Major metabolites of hexamethyldisiloxane (MM) a... were identified in urine collected from Fischer (F-344) rats administered (14)C-MM ... orally and via intravenous injection. ... The following are among the major metabolites identified in the case of MM: Me(2)Si(OH)(2), HOMe(2)SiCH(2)OH, HOCH(2)Me(2)SiOSiMe(2)CH(2)OH, HOMe(2)SiOSiMe(2)CH(2)-OH, HOCH(2)Me(2)SiOSiMe(3), and Me(3)SiOH. No parent MM ... was present in urine. The presence of certain metabolites such as HOMe(2)SiCH(2)OH and Me(2)Si(OH)(2) in MM ... clearly established the occurrence of demethylation at the silicon-methyl bonds. Metabolites of the linear siloxane are structurally different from that obtained for cyclic siloxane except for the commonly present Me(2)Si(OH)(2). Mechanistic pathways for the formation of the metabolites were proposed.
Varaprath S et al; Drug Metab Dispos 31 (2): 206-14 (2003)
Phenyltrimethylsilane given intragastrically to rats was absorbed and eliminated in urine. Three percent of total urinary activity was shown to be from hexamethyldisiloxane.
FESSENDEN ET AL; J MED CHEM 13 (1): 52 (1970)

8.3 Human Metabolite Information

8.3.1 Cellular Locations

Membrane

9 Use and Manufacturing

9.1 Uses

EPA CPDat Chemical and Product Categories
The Chemical and Products Database, a resource for exposure-relevant data on chemicals in consumer products, Scientific Data, volume 5, Article number: 180125 (2018), DOI:10.1038/sdata.2018.125
Sources/Uses
Used to make silicone fluids, elastomers, octamethylcyclotetrasiloxane, and fluorosilicone oils; Also used in cosmetics and in photolithography applications (adhesion promoter/priming agent); [HSDB]
Hydraulic fluid /Organo Silicate MLO 5277/
Browning, E. Toxicity and Metabolism of Industrial Solvents. New York: American Elsevier, 1965., p. 696
Chemical intermediate for silicone fluids and elastomers
SRI
Hexamethyldisiloxane is used in cosmetic and personal care products, in the production of octamethylcyclotetrasiloxane, as an adhesion promotor-priming agent for photolithography applications, and as an end blocking agent in the production of fluorosilicone oils.
Chemcyclopedia 87; The Manual of Commercially Available Chemicals. Kuney, JH, Ed. American Chemical Society, Washington, DC 5: 180 (1986); Hardman BB, Torkelson A; Kirk-Othmer Encycl Chem Tech 3rd NY: Wiley 20: 922-62 (1982); Kim YK; Kirk-Othmer Encycl Chem Tech 3rd NY: Wiley 11: 74-81 (1980)
/Used/ ... for headlights ... as a protective layer 20-30 nm thick ... effective diffusion barrier (condensed water resistance is 1000 times greater than without coating) ... . Other applications include the hydrophilic coating of contact lenses and the coating of medical materials to improve biocompatibility.
Ullmann's Encyclopedia of Industrial Chemistry. 6th ed.Vol 1: Federal Republic of Germany: Wiley-VCH Verlag GmbH & Co. 2003 to Present, p. V. 27 544 (2003)
Used as antifoams in aqueous systems, in petroleum processing, and in laundry detergents ... In human and veterinary medicine ... used as antiflatulent agents ... Useful as lubricants (eg, for films, yarn, medical articles, wine corks, and fillers). /Polydimethylsiloxanes/
Ullmann's Encyclopedia of Industrial Chemistry. 6th ed.Vol 1: Federal Republic of Germany: Wiley-VCH Verlag GmbH & Co. 2003 to Present, p. V. 32 543 (2003)

9.1.1 Use Classification

Cosmetics -> Antistatic; Antifoaming; Emollient; Skin conditioning
S13 | EUCOSMETICS | Combined Inventory of Ingredients Employed in Cosmetic Products (2000) and Revised Inventory (2006) | DOI:10.5281/zenodo.2624118

9.1.2 Industry Uses

  • Intermediate
  • Solvent
  • Intermediates
  • Adhesives and sealant chemicals
  • Viscosity modifiers
  • Insulators
  • Anti-adhesive agents
  • Cleaning agent
  • Surface active agents
  • Terminator/Blocker
  • Paint additives and coating additives not described by other categories
  • Diluent
  • Other

9.1.3 Consumer Uses

  • Insulators
  • Intermediate
  • Solvent
  • Diluent
  • Other
  • Lubricating agent

9.2 Methods of Manufacturing

Acid hydrolysis of chlorotrimethylsilane and purification by distillation.
SRI

9.3 U.S. Production

Aggregated Product Volume

2019: 20,000,000 lb - <100,000,000 lb

2018: 20,000,000 lb - <100,000,000 lb

2017: 20,000,000 lb - <100,000,000 lb

2016: 20,000,000 lb - <100,000,000 lb

This chemical is listed as a High Production Volume (HPV) (65FR81686). Chemicals listed as HPV were produced in or imported into the U.S. in >1 million pounds in 1990 and/or 1994. The HPV list is based on the 1990 Inventory Update Rule. (IUR) (40 CFR part 710 subpart B; 51FR21438).
EPA/Office of Pollution Prevention and Toxics; High Production Volume (HPV) Challenge Program. Available from, as of May 18, 2006: https://www.epa.gov/hpv/pubs/general/opptsrch.htm
(1977) At least 4.58x10+8 g (est.)
SRI
(1986) >1 million-10 million pounds
US EPA; Non-confidential Production Volume Information Submitted by Companies for Chemicals Under the 1986-2002 Inventory Update Rule (IUR). Hexamethyldisiloxane (107-46-0). Available from, as of May 18, 2006: https://www.epa.gov/oppt/iur/tools/data/2002-vol.html
(1990) >1 million-10 million pounds
US EPA; Non-confidential Production Volume Information Submitted by Companies for Chemicals Under the 1986-2002 Inventory Update Rule (IUR). Hexamethyldisiloxane (107-46-0). Available from, as of May 18, 2006: https://www.epa.gov/oppt/iur/tools/data/2002-vol.html
For more U.S. Production (Complete) data for HEXAMETHYLDISILOXANE (7 total), please visit the HSDB record page.

9.4 General Manufacturing Information

Industry Processing Sectors
  • Plastics Product Manufacturing
  • Wood Product Manufacturing
  • Construction
  • All Other Chemical Product and Preparation Manufacturing
  • Plastics Material and Resin Manufacturing
  • Synthetic Rubber Manufacturing
  • Soap, Cleaning Compound, and Toilet Preparation Manufacturing
  • All Other Basic Inorganic Chemical Manufacturing
  • All Other Basic Organic Chemical Manufacturing
  • Paint and Coating Manufacturing
  • Other (requires additional information)
  • Adhesive Manufacturing
EPA TSCA Commercial Activity Status
Disiloxane, 1,1,1,3,3,3-hexamethyl-: ACTIVE
... Used as a hydraulic fluid and comes in contact with heated metal surfaces of engines operating at high temperatures. /Organo Silicate MLO 5277/
Browning, E. Toxicity and Metabolism of Industrial Solvents. New York: American Elsevier, 1965., p. 696

10 Safety and Hazards

10.1 Hazards Identification

10.1.1 GHS Classification

1 of 3
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Note
Pictograms displayed are for 99.9% (3589 of 3594) of reports that indicate hazard statements. This chemical does not meet GHS hazard criteria for 0.1% (5 of 3594) of reports.
Pictogram(s)
Flammable
Environmental Hazard
Signal
Danger
GHS Hazard Statements

H225 (98.8%): Highly Flammable liquid and vapor [Danger Flammable liquids]

H400 (92.7%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410 (20.1%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

H411 (71.4%): Toxic to aquatic life with long lasting effects [Hazardous to the aquatic environment, long-term hazard]

Precautionary Statement Codes

P210, P233, P240, P241, P242, P243, P273, P280, P303+P361+P353, P370+P378, P391, P403+P235, and P501

(The corresponding statement to each P-code can be found at the GHS Classification page.)

ECHA C&L Notifications Summary

Aggregated GHS information provided per 3594 reports by companies from 24 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Reported as not meeting GHS hazard criteria per 5 of 3594 reports by companies. For more detailed information, please visit ECHA C&L website.

There are 23 notifications provided by 3589 of 3594 reports by companies with hazard statement code(s).

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown.

10.1.2 Hazard Classes and Categories

Flam. Liq. 2 (98.8%)

Aquatic Acute 1 (92.7%)

Aquatic Chronic 1 (20.1%)

Aquatic Chronic 2 (71.4%)

Flammable liquids - Category 2

10.1.3 Hazards Summary

An eye irritant; Oral LD50 (rat) = >5000 mg/kg; [HSDB] In a 28-day feeding study of rats, 8 mg/kg/day was the no toxic effect level; Food consumption was decreased and changes were seen in the liver and blood cells in animals fed 640 mg/kg/day; [TSCA Sub-Acute Oral Toxicity Study in Rats] May cause irritation; [MSDSonline]

10.1.4 Skin, Eye, and Respiratory Irritations

Vapors have a very low toxicity for ... humans ... /It/ irritates conjunctiva but does not attack the cornea.
Lefaux, R. Practical Toxicology of Plastics. Cleveland: CRC Press Inc., 1968., p. 110
Hexamethyldisiloxane has been noted to give off vapors which are transiently irritating to the conjunctiva, but no injury has been observed.
Grant, W. M. Toxicology of the Eye. 2nd ed. Springfield, Illinois: Charles C. Thomas, 1974., p. 547

10.2 Safety and Hazard Properties

10.2.1 Critical Temperature & Pressure

Critical temperature: 245 °C
Mazzoni SM et al; pp 53-81 in Handbook Environ Chem, Vol 3. Chandra G, ed. Berlin, Germany: Springer (1997)

10.3 Accidental Release Measures

10.3.1 Disposal Methods

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

10.4 Regulatory Information

The Australian Inventory of Industrial Chemicals
Chemical: Disiloxane, hexamethyl-
REACH Registered Substance
New Zealand EPA Inventory of Chemical Status
Hexamethyldisiloxane: Does not have an individual approval but may be used under an appropriate group standard

10.4.1 TSCA Requirements

Section 8(a) of TSCA requires manufacturers of this chemical substance to report preliminary assessment information concerned with production, exposure, and use to EPA as cited in the preamble in 51 FR 41329.
40 CFR 712.30; U.S. National Archives and Records Administration's Electronic Code of Federal Regulations. Available from, as of June 21, 2006: https://www.ecfr.gov
Pursuant to section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule. The section 8(d) model rule requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies. Hexamethyldisiloxane is included on this list.
40 CFR 716.120; U.S. National Archives and Records Administration's Electronic Code of Federal Regulations. Available from, as of June 20, 2006: https://www.ecfr.gov

10.5 Other Safety Information

Chemical Assessment
IMAP assessments - Disiloxane, hexamethyl-: Human health tier II assessment

10.5.1 Special Reports

European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from the database query page: http://ecb.jrc.it/esis/esis.php as of July 31, 2006
After the siloxanes class of chemicals was designated to the Interagency Testing Committee (ITC) Priority Testing List, an industry consortium, the Silicones Environmental, Health and Safety Council of North America (SEHSC), worked in cooperation with the ITC and the U.S. Environmental Protection Agency (EPA) to sponsor a voluntary health and safety program for siloxanes. Abstracts of each research report funded through SEHSC are posted under Siloxane Research Program on the SEHSC website [http://www.sehsc.com/srp-research-reports.asp]. The SEHSC also provides information on obtaining full copies of the reports from the EPA on this website.

11 Toxicity

11.1 Toxicological Information

11.1.1 Adverse Effects

Occupational hepatotoxin - Secondary hepatotoxins: the potential for toxic effect in the occupational setting is based on cases of poisoning by human ingestion or animal experimentation.

11.1.2 Acute Effects

11.1.3 Toxicity Data

LC50 (rat) = 15,956 ppm/4h

11.1.4 Interactions

... Hexamethyldisiloxane (HMDS) coadministered with ethinyl estradiol (EE) did produce a small, but statistically significant reduction in uterine weight compared to EE alone.
McKim JM et al; Toxicol Sci 63 (1): 37-46 (2001)

11.1.5 Antidote and Emergency Treatment

Basic Treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Encourage patient to take deep breaths. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . /Irritating materials/
Currance, P.L. Clements, B., Bronstein, A.C. (Eds).; Emergency Care For Hazardous Materials Exposure. 3Rd edition, Elsevier Mosby, St. Louis, MO 2005, p. 157
Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Early intubation at the first sign of upper airway obstruction may be necessary. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... .Treat seizures with diazepam or lorazepam ... Use proparacaine hydrochloride to assist eye irrigation ... . /Irritating materials/
Currance, P.L. Clements, B., Bronstein, A.C. (Eds).; Emergency Care For Hazardous Materials Exposure. 3Rd edition, Elsevier Mosby, St. Louis, MO 2005, p. 157

11.1.6 Human Toxicity Excerpts

/HUMAN EXPOSURE STUDIES/ /Hexamethyldisiloxane/ was submitted to determine its ability to sensitize the skin of normal volunteer subjects using a repeated insult patch test. One-hundred subjects completed the study. Patches were applied to the infrascapular area of the back. The entire study extended over a six week period. It involved three phases: induction, rest, and challenge. The induction phases consisted of nine consecutive applications and subsequent evaluations of the test sites. The rest period lasted fourteen days. The challenge phase used identical patches applied to sites previously unexposed to the test material. Under the conditions employed in this study, there was no evidence of sensitization to the test substance.
European Chemicals Bureau; IUCLID Dataset, Octamethyltetrasiloxane (556-67-2) (2000 CD-ROM edition). Available from, as of June 15, 2006: https://esis.jrc.ec.europa.eu/
/SIGNS AND SYMPTOMS/ Hexamethyldisiloxane has been noted to give off vapors which are transiently irritating to the conjunctiva, but no injury has been observed.
Grant, W. M. Toxicology of the Eye. 2nd ed. Springfield, Illinois: Charles C. Thomas, 1974., p. 547
/OTHER TOXICITY INFORMATION/ Vapors have a very low toxicity for ... humans. ... /it/ irritates conjunctiva but does not attack the cornea.
Lefaux, R. Practical Toxicology of Plastics. Cleveland: CRC Press Inc., 1968., p. 110

11.1.7 Non-Human Toxicity Excerpts

/LABORATORY ANIMALS: Acute Exposure/ Guinea pig maximization test: not sensitizing
European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from, as of July 31, 2006: https://esis.jrc.ec.europa.eu/
/LABORATORY ANIMALS: Acute Exposure/ Skin irritation: Rabbit: not irritating. A repeated skin irritation study was conducted. ... The procedure followed was based on (modified) methods of the CTFA Safety Testing Guidelines, Toiletries and Fragrances Association (Sept 27, 1985( and Preclinical Safety Evaluation of Materials used in Medical Devices HIMA report 85-1 "Skin Irritation." The test substance appears to cause no irritation in repeated, occluded contacts. However, irritation did develop outside of the application site which later spread to the site.
European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from, as of July 31, 2006: https://esis.jrc.ec.europa.eu/
/LABORATORY ANIMALS: Acute Exposure/ Skin irritation: Rabbit: not irritating. The procedure followed was the modified method as required by the EPA Toxic Sustances Control Act ... Health Effects Testing Guidelines, "Primary Skin Irritation."
European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from, as of July 31, 2006: https://esis.jrc.ec.europa.eu/
/LABORATORY ANIMALS: Acute Exposure/ A group of 10 albino rabbits was tested with a single dose of 2000 mg/kg undiluted test substance, no deaths or untoward behavioral reactions were noted ... Several studies show dermal LD50 in rabbit to be greater, but mortality was seen at 10,000 mg/kg. Toxic effects at 10,000 mg/kg in all animals included gross pathological findings (lungs, kidney, bladder, heart) while clinical findings (altered activity, ataxia, gasping and eschar formation) occurred in small numbers of rabbits. In contrast to rabbits, dermal exposure in rats did not produce mortality or signs of toxicity at the dose tested.
European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from, as of July 31, 2006: https://esis.jrc.ec.europa.eu/
For more Non-Human Toxicity Excerpts (Complete) data for HEXAMETHYLDISILOXANE (18 total), please visit the HSDB record page.

11.1.8 Non-Human Toxicity Values

LD50 Rat oral > 5000 mg/ kg
European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from, as of July 31, 2006: https://esis.jrc.ec.europa.eu/
LD50 Mouse ip 4500 mg/kg
Sax, N.I. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand Reinhold, 1984., p. 1521

11.1.9 TSCA Test Submissions

The mutagenicity of hexamethyldisiloxane (HMDS) was evaluated in bacterial Salmonella tester strains TA98, TA100, TA1535, TA1537 and TA1538 and yeast Saccharomyces tester strain D4, both in the presence and absence of added metabolic activation by Aroclor-induced rat liver S9 fraction. HMDS, diluted in ethanol, was tested for mutagenicity at concentrations up to 5.0 ul/plate using the plate incorporation method. The mutagenicity of HMDS was also tested in bacterial E. coli indicator organisms, although the concentrations used and numerical results were not reported. HMDS did not cause a positive response in any of the bacterial or yeast tester strains, either with or without metabolic activation.
Litton Bionetics, Inc.; Mutagenicity Evaluation of Hexamethyldisiloxane, Final Report. (1978), EPA Document No. FYI-OTS-0286-0469, Fiche No. OTS0000469-0
The ability of hexamethyldisiloxane to induce specific locus mutations at the TK locus in cultured L5178Y mouse lymphoma cells (Mouse Lymphoma Mutagenesis Assay) was evaluated in the presence and absence of Aroclor-induced rat liver S9 metabolic activation. Based on preliminary toxicity determinations, both nonactivated and S9 activated cultures were treated with 0.0125, 0.0250, 0.0500, 0.1000, or 0.2000 ul/ml which produced a range of 104 - 32% total growth for nonactivated cultures and from 107 - 0.3% total growth for S9-activated cultures. None of the nonactivated or activated cultures produced mutant frequencies significantly greater than the solvent controls (ethanol).
Litton Bionetics, Inc.; Mutagenicity Evaluation of Hexamethyldisiloxane, Final Report. (1978), EPA Document No. FYI-OTS-0286-0469, Fiche No. OTS0000469-0
Hexamethyldisiloxane was examined for DNA modifying activity in Escherichia coli strains W3110 polA+ and P3478 polA- (DNA repair deficiency assay) with and without metabolic activation provided by Aroclor-induced rat liver S9 fraction. The test article did not produce zones of inhibition in either strain when spotted on plates at volumes ranging from 0.001 to 5 ul in the presence or absence of metabolic activation.
Litton Bionetics, Inc.; Mutagenicity Evaluation of Hexamethyldisiloxane Final Report (1978), EPA Document No. FYI-OTS-0286-0469, Fiche No. OTS0000469-0
The frequency of sister chromatid exchange (SCE) was determined in L5178Y mouse lymphoma cells exposed in vitro to hexamethyldisiloxane with and without metabolic activation provided by mouse liver S9 fraction (induction of liver enzyme activity was not reported). The test article was administered at concentrations of 0.025, 0.05, 0.1 and 0.2 ul/ml in the absence of activation, and at concentrations of 0.025, 0.05 and 0.1 ul/ml in the presence of activation. A statistically significant (students t-test) increase in the mean number of SCE's/cell was observed at 0.05 ul/ml (p < 0.01) in the activated assays, and at 0.025 ul/ml (p < 0.01) and 0.1 ul/ml (p < 0.05) in the nonactivated assays. Statistically significant increases in the mean number of chromosomes/cell with SCE's, and in the mean number of SCE's/chromosome in chromosomes with SCE's were not observed under any condition. The test article was reported to be toxic to cells at concentrations greater than 0.2 ul/ml.
Litton Bionetics, Inc.; Mutagenicity Evaluation of Hexamethyldisiloxane (Me3Si)2O, Final Report (1978), EPA Document No. FYI-OTS-0286-0469, Fiche No. OTS0000469-0
For more TSCA Test Submissions (Complete) data for HEXAMETHYLDISILOXANE (6 total), please visit the HSDB record page.

11.2 Ecological Information

11.2.1 Ecotoxicity Values

LC50 Oncorhynchus mykiss (rainbow trout) ca 3.02 mg/L/96 hr, flow-through bioassay
European Chemicals Bureau; IUCLID Dataset, Hexamethyldisiloxane (107-46-0) (2000 CD-ROM edition). Available from, as of July 31, 2006: https://esis.jrc.ec.europa.eu/

11.2.2 Environmental Fate / Exposure Summary

Hexamethyldisiloxane's production and use as a chemical intermediate in the synthesis of silicone fluids, elastomers and fluorosilicone oils as well as in photolithography, personal care products and cosmetics may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 42.1 mm Hg at 25 °C indicates hexamethyldisiloxane will exist solely as a vapor in the atmosphere. Vapor-phase hexamethyldisiloxane will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 18 days. Methyl siloxanes are transparent to UV radiation >290 nm, and therefore hexamethyldisiloxane is not expected to undergo direct photolytic degradation. If released to soil, hexamethyldisiloxane is expected to have slight mobility based upon an estimated Koc of 4,600. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 0.0453 atm-cu m/mole. Hexamethyldisiloxane may volatilize from dry soil surfaces based upon its vapor pressure. However, adsorption to soil is expected to attenuate volatilization. No biodegradation data regarding hexamethyldisiloxane were found; however dimethyl siloxanes in general are highly resistant to biodegradation. As a member of this class, biodegradation is not expected to be an important environmental fate process. Polydimethylsiloxane fluids undergo siloxane bond rearrangement to form low molecular weight linear and cyclic oligomers that are water soluble, indicating that soil mediated hydrolysis of hexamethyldisiloxane may be an important environmental fate process for hexamethyldisiloxane. If released into water, hexamethyldisiloxane is expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 1.3 hours and 5 days, respectively. However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column. The estimated volatilization half-life from a model pond is 30 days if adsorption is considered. An estimated BCF of 340 suggests the potential for bioconcentration in aquatic organisms is high. Occupational exposure to hexamethyldisiloxane may occur through inhalation and dermal contact with this compound at workplaces where hexamethyldisiloxane is produced or used. The most likely pathway by which the general public is exposed to hexamethyldisiloxane is by inhalation and dermal contact when personal care products and cosmetics containing this substance are used. (SRC)

11.2.3 Artificial Pollution Sources

Hexamethyldisiloxane's production and use as a chemical intermediate in the synthesis of silicone fluids, elastomers and fluorosilicone oils as well as in photolithography(1), personal care products and cosmetics(2) may result in its release to the environment through various waste streams(SRC).
(1) Butts M; in Kirk-Othmer Encyclopedia of Chemical Technology. (2005). NY, NY: John Wiley & Sons; Silicones. Online Posting Date: Dec 20, 2002.
(2) Schweigkofler M, Reinhard N Environ Sci Technol 33: 3680-3685 (1999)

11.2.4 Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 4,600(SRC), determined from a log Kow of 4.2(2) and a regression-derived equation(3), indicates that hexamethyldisiloxane is expected to have slight mobility in soil(SRC). Volatilization of hexamethyldisiloxane from moist soil surfaces is expected to be an important fate process(SRC) given a estimated Henry's Law constant of 0.0453 atm-cu m/mole(4). Hexamethyldisiloxane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 42.1 mm Hg(5). However, adsorption to soil is expected to attenuate volatilization(SRC). No biodegradation data regarding hexamethyldisiloxane were found; however, dimethyl siloxanes in general are highly resistant to biodegradation(6). As a member of this class biodegradation is not expected to be an important fate process.
(1) Swann RL et al; Res Rev 85: 17-28 (1983)
(2) Sangster J; LOGKOW Database. A databank of evaluated octanol-water partition coefficients (Log P). Available from database query at https://logkow.cisti.nrc.ca/logkow/search.html as of Apr 20, 2006.
(3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 4-9 (1990)
(4) Kochetkov A et al; Environ Toxicol Chem 20: 2184-2188 (2001)
(5) Flaningam OL; J Chem Eng Data 31: 266-272 (1986)
(6) Frye CL; Sci Tot Environ 73: 17-22 (1988)
TERRESTRIAL FATE: Poly(dimethylsiloxane) (PDMS) fluids in intimate contact with many soils undergo siloxane redistribution and hydrolysis, resulting in the formation of low molecular weight cyclic and linear oligomers. Low molecular weight hydroxy-functional hydrolysis products are water soluble, and the cyclics and trimethylsiloxy-end-blocked oligomers are volatile, thus providing materials which can partition from the soil to the water and atmospheric environmental compartments(1). /Poly(dimethylsiloxane)/
(1) Buch RR, Ingebrigtson DN; Envir Sci Technol 13 (6): 676-679 (1979)
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 4,600(SRC), determined from a log Kow of 4.2(2) and a regression-derived equation(3), indicates that hexamethyldisiloxane is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon a Henry's Law constant of 0.0453 atm-cu m/mole(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 1.3 hours and 5 days, respectively(SRC). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column. The estimated volatilization half-life from a model pond is 30 days if adsorption is considered(5). According to a classification scheme(6), an estimated BCF of 340(SRC), from its log Kow(2) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is high(SRC). Polydimethylsiloxane fluids undergo siloxane bond rearrangement to form low molecular weight linear and cyclic oligomers that are water soluble(8), indicating that hydrolysis of hexamethyldisiloxane may be an important environmental fate process leading to products that will predominantly partition into the atmosphere. No biodegradation data regarding hexamethyldisiloxane were found; however dimethyl siloxanes in general are highly resistant to biodegradation(9). As a member of this class biodegradation is not expected to be an important fate process.
(1) Swann RL et al; Res Rev 85: 17-28 (1983)
(2) Sangster J; LOGKOW Database. A databank of evaluated octanol-water partition coefficients (Log P). Available from database query at https://logkow.cisti.nrc.ca/logkow/search.html as of Apr 20, 2006.
(3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 4-9, 15-1 to 15-29 (1990)
(4) Kochetkov A et al; Environ Toxicol Chem 20: 2184-2188 (2001)
(5) US EPA; EXAMS II Computer Simulation (1987)
(6) Franke C et al; Chemosphere 29: 1501-14 (1994)
(7) Meylan WM et al; Environ Toxicol Chem 18: 664-72 (1999)
(8) Buch RR, Ingebrightson DN; Environ Sci Tech 13: 676-679 (1979)
(9) Frye CL; Sci Tot Environ 73: 17-22 (1988)
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), hexamethyldisiloxane, which has a vapor pressure of 42.1 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase hexamethyldisiloxane is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 18 days(SRC), calculated from its rate constant of 1.4x10-12 cu cm/molecule-sec at 25 °C(3). Methyl siloxanes are transparent to UV radiation >290 nm(4) and therefore hexamethyldisiloxane is not expected to undergo direct photolytic degradation(SRC).
(1) Bidleman TF; Environ Sci Technol 22: 361-367 (1988)
(2) Flaningam OL; J Chem Eng Data 31: 266-272 (1986)
(3) Atkinson R; Environ Sci Tech 25: 863-866 (1991)
(4) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 8-12 (1990)
(5) Hardman BB, Torkelson A; Kirk-Othmer Encycl Chem Tech 3rd NY, NY: Wiley 20: 922-62 (1982)

11.2.5 Environmental Biodegradation

AEROBIC: No biodegradation data regarding hexamethyldisiloxane were found(SRC, 2006); however dimethyl siloxanes in general are highly resistant to biodegradation(1). As a member of this class biodegradation is not expected to be an important fate process.
(1) Frye CL; Sci Tot Environ 73: 17-22 (1988)

11.2.6 Environmental Abiotic Degradation

The rate constant for the vapor-phase reaction of hexamethyldisiloxane with photochemically-produced hydroxyl radicals has been reported as 1.4X10-12 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 18 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Polydimethylsiloxane fluids undergo siloxane bond rearrangement to form low molecular weight linear and cyclic oligomers that are water soluble(2), indicating that hydrolysis of hexamethyldisiloxane may be an important environmental fate process leading to products that will predominantly partition into the atmosphere. Methyl siloxanes are transparent to UV radiation >290 nm(3) and therefore hexamethyldisiloxane is not expected to undergo direct photolytic degradation(SRC).
(1) Atkinson R; Environ Sci Tech 25: 863-866 (1991)
(2) Buch RR, Ingebrightson DN; Environ Sci Tech 13: 676-679 (1979)
(3) Hardman BB, Torkelson A; Kirk-Othmer Encycl Chem Tech 3rd NY, NY: Wiley 20: 922-62 (1982)

11.2.7 Environmental Bioconcentration

An estimated BCF of 340 was calculated for hexamethyldisiloxane(SRC), using a log Kow of 4.2(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is high(SRC), provided the compound is not metabolized by the organism(SRC).
(1) Sangster J; LOGKOW Database. A databank of evaluated octanol-water partition coefficients (Log P). Available from database query at https://logkow.cisti.nrc.ca/logkow/search.html as of Apr 20, 2006.
(2) Meylan WM et al; Environ Toxicol Chem 18: 664-72 (1999)
(3) Franke C et al; Chemosphere 29: 1501-14 (1994)

11.2.8 Soil Adsorption / Mobility

The Koc of hexamethyldisiloxane is estimated as 4,600(SRC), using a log Kow of 4.2(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that hexamethyldisiloxane is expected to have slight mobility in soil.
(1) Sangster J; LOGKOW Database. A databank of evaluated octanol-water partition coefficients (Log P). Available from database query at https://logkow.cisti.nrc.ca/logkow/search.html as of Apr 20, 2006.
(2) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 4-9 (1990)
(3) Swann RL et al; Res Rev 85: 17-28 (1983)

11.2.9 Volatilization from Water / Soil

The Henry's Law constant for hexamethyldisiloxane is 0.0453 atm-cu m/mole(1). This Henry's Law constant indicates that hexamethyldisiloxane is expected to volatilize rapidly from water surfaces(2). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 1.3 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 5 days(SRC). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column. The estimated volatilization half-life from a model pond is 30 days if adsorption is considered(3). Hexamethyldisiloxane's Henry's Law constant indicates that volatilization from moist soil surfaces may occur(SRC). Hexamethyldisiloxane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 42.1 mm Hg(4).
(1) Kochetkov A et al; Environ Toxicol Chem 20: 2184-2188 (2001)
(2) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 15-1 to 15-29 (1990)
(3) US EPA; EXAMS II Computer Simulation (1987)
(4) Flaningam OL; J Chem Eng Data 31: 266-272 (1986)

11.2.10 Effluent Concentrations

Hexamethyldisiloxane was detected in two separate domestic waste sites in Munich Germany at concentrations of 0.01 and 0.31-0.45 mg/cu m(1). Hexamethyldisiloxane was also detected in the respective sewage treatment plants at concentrations of 0.14-0.17 and 0.18-0.20 mg/cu m, respectively(1).
(1) Schweigkofler M, Reinhard N; Environ Sci Technol 33: 3680-3685 (1999)

11.2.11 Atmospheric Concentrations

SOURCE DOMINATED: Hexamethyldisiloxane was detected but not quantified in volatile chemical emissions from sponge rubber, bonded urethane and prime urethane carpet cushions(1).
(1) Schaeffer VH et al; J Air Waste Management Assoc 46: P813-820 (1996)

11.2.12 Other Environmental Concentrations

Hexamethyldisiloxane was detected but not quantified in volatile chemical emissions from sponge rubber, bonded urethane and prime urethane carpet cushions(1). Hexamethyldisiloxane was detected but not quantified in emissions from new carpet vapors(2).
(1) Schaeffer VH et al; J Air Waste Management Assoc 46: P813-820 (1996)
(2) U.S. Consumer Product Safety Comission; Status Report on Chemical Emissions from New Carpets (1993)

11.2.13 Probable Routes of Human Exposure

... SILICONES OF A LOW DEGREE OF CONDENSATION CAN PRESENT PROBLEMS IN INDUSTRIALTOXICOLOGY ... HEXAMETHYLSILOXANE /IS A/ ... SUBSTANCE OF RELATIVELY LOW BOILING POINT.
Lefaux, R. Practical Toxicology of Plastics. Cleveland: CRC Press Inc., 1968., p. 110
NIOSH (NOES Survey 1981-1983) has statistically estimated that 14,234 workers may be exposed to hexamethyldisiloxane in the US(1). Occupational exposure to hexamethyldisiloxane may occur through inhalation and dermal contact with this compound at workplaces where hexamethyldisiloxane is produced or used(SRC). The most likely pathway by which the general public is exposed to hexamethyldisiloxane is by inhalation and dermal contact when personal care products and cosmetics containing this substance are used(SRC).
(1) NIOSH; National Occupational Exposure Survey (NOES) (1984)

12 Literature

12.1 Consolidated References

12.2 NLM Curated PubMed Citations

12.3 Springer Nature References

12.4 Thieme References

12.5 Wiley References

12.6 Chemical Co-Occurrences in Literature

12.7 Chemical-Gene Co-Occurrences in Literature

12.8 Chemical-Disease Co-Occurrences in Literature

13 Patents

13.1 Depositor-Supplied Patent Identifiers

13.2 WIPO PATENTSCOPE

13.3 Chemical Co-Occurrences in Patents

13.4 Chemical-Disease Co-Occurrences in Patents

13.5 Chemical-Gene Co-Occurrences in Patents

14 Biological Test Results

14.1 BioAssay Results

15 Taxonomy

16 Classification

16.1 MeSH Tree

16.2 NCI Thesaurus Tree

16.3 ChEBI Ontology

16.4 ChemIDplus

16.5 UN GHS Classification

16.6 EPA CPDat Classification

16.7 NORMAN Suspect List Exchange Classification

16.8 EPA DSSTox Classification

16.9 Consumer Product Information Database Classification

16.10 EPA TSCA and CDR Classification

16.11 EPA Substance Registry Services Tree

16.12 MolGenie Organic Chemistry Ontology

17 Information Sources

  1. Australian Industrial Chemicals Introduction Scheme (AICIS)
  2. CAS Common Chemistry
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    The data from CAS Common Chemistry is provided under a CC-BY-NC 4.0 license, unless otherwise stated.
    https://creativecommons.org/licenses/by-nc/4.0/
  3. ChemIDplus
    ChemIDplus Chemical Information Classification
    https://pubchem.ncbi.nlm.nih.gov/source/ChemIDplus
  4. DTP/NCI
    LICENSE
    Unless otherwise indicated, all text within NCI products is free of copyright and may be reused without our permission. Credit the National Cancer Institute as the source.
    https://www.cancer.gov/policies/copyright-reuse
  5. EPA Chemical Data Reporting (CDR)
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    Disiloxane, 1,1,1,3,3,3-hexamethyl-
    https://www.epa.gov/chemical-data-reporting
  6. EPA Chemicals under the TSCA
    Disiloxane, 1,1,1,3,3,3-hexamethyl-
    https://www.epa.gov/chemicals-under-tsca
    EPA TSCA Classification
    https://www.epa.gov/tsca-inventory
  7. EPA DSSTox
    CompTox Chemicals Dashboard Chemical Lists
    https://comptox.epa.gov/dashboard/chemical-lists/
  8. European Chemicals Agency (ECHA)
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    https://echa.europa.eu/web/guest/legal-notice
  9. FDA Global Substance Registration System (GSRS)
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    https://www.fda.gov/about-fda/about-website/website-policies#linking
  10. Hazardous Substances Data Bank (HSDB)
  11. Human Metabolome Database (HMDB)
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    http://www.hmdb.ca/citing
  12. New Zealand Environmental Protection Authority (EPA)
    LICENSE
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    https://www.epa.govt.nz/about-this-site/general-copyright-statement/
  13. ChEBI
  14. ChEMBL
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  15. Crystallography Open Database (COD)
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    https://creativecommons.org/publicdomain/zero/1.0/
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  17. Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
    LICENSE
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    https://haz-map.com/About
  18. NITE-CMC
    Hexamethyldisiloxane - FY2011 (New/original classication)
    https://www.chem-info.nite.go.jp/chem/english/ghs/11-mhlw-0018e.html
    Hexamethyldisiloxane - FY2018 (Revised classification)
    https://www.chem-info.nite.go.jp/chem/english/ghs/18-meti-2010e.html
  19. FooDB
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    https://foodb.ca/about
  20. NMRShiftDB
  21. SpectraBase
    Silane, 1,4-phenylenebis[trimethyl-
    https://spectrabase.com/spectrum/CasffboF7fm
    HEXAMETHYLDISILOXANE;BIS-(TRIMETHYLSILYL)-ETHER
    https://spectrabase.com/spectrum/AJpKdZJOPeq
    (CH3)3SI(OSI(CH3)3);HEXAMETHYDISILOXANE
    https://spectrabase.com/spectrum/DWOOKuxUXzX
    (ME3SI)2O;HEXAMETHYLDISILOXANE
    https://spectrabase.com/spectrum/A1AVazgGXhg
  22. MassBank Europe
  23. MassBank of North America (MoNA)
    LICENSE
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    https://mona.fiehnlab.ucdavis.edu/documentation/license
  24. NIST Mass Spectrometry Data Center
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    Data covered by the Standard Reference Data Act of 1968 as amended.
    https://www.nist.gov/srd/public-law
    Disiloxane, hexamethyl-
    http://www.nist.gov/srd/nist1a.cfm
  25. Japan Chemical Substance Dictionary (Nikkaji)
  26. Natural Product Activity and Species Source (NPASS)
  27. NCI Thesaurus (NCIt)
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  28. NLM RxNorm Terminology
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    https://www.nlm.nih.gov/research/umls/rxnorm/docs/termsofservice.html
  29. NORMAN Suspect List Exchange
    LICENSE
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    https://creativecommons.org/licenses/by/4.0/
    DIMETHICONE
    NORMAN Suspect List Exchange Classification
    https://www.norman-network.com/nds/SLE/
  30. Springer Nature
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  32. Thieme Chemistry
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  38. GHS Classification (UNECE)
  39. Consumer Product Information Database (CPID)
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    https://www.whatsinproducts.com/contents/view/1/6
    Consumer Products Category Classification
    https://www.whatsinproducts.com/
  40. EPA Substance Registry Services
  41. MolGenie
    MolGenie Organic Chemistry Ontology
    https://github.com/MolGenie/ontology/
  42. PATENTSCOPE (WIPO)
CONTENTS