OCTAMETHYLCYCLOTETRASILOXANE

Octamethylcyclotetrasiloxane = D4

CAS Number: 556-67-2
EC Number: 209-136-7
Linear Formula: [-Si(CH3)2O-]4
Molecular Weight: 296.62

Octamethylcyclotetrasiloxane, also called D4, is an organosilicon compound with the formula [(CH3)2SiO]4.
Octamethylcyclotetrasiloxane is a colorless viscous liquid.

Octamethylcyclotetrasiloxane is a common cyclomethicone.
Octamethylcyclotetrasiloxane is widely used in cosmetics.

General description of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane (D4) is a volatile methylsiloxane (VMS) with a relatively low molecular weight.
Octamethylcyclotetrasiloxane has a silicon-oxygen bond in a cyclic arrangement and methyl groups are attached to the silicon atom.
Octamethylcyclotetrasiloxane can be used in the manufacture of silicone based polymers for use in medical devices and personal care products.

Applications of Octamethylcyclotetrasiloxane:
D4 can be polymerized through ring opening mechanism with a rare earth solid super acid as a catalyst for potential usage in the synthesis of vinyl coated polydimethylsiloxane (PDMS).
Octamethylcyclotetrasiloxane may also be used as a probe liquid for nuclear magnetic resonance cryoporometry (NMRC) to analyze the pore size distribution (PSD) of oil-bearing tight sandstone.
Chemical vapor deposition (CVD) of Octamethylcyclotetrasiloxane may be utilized for the preparation of siloxane based thin films.

Production and polymerization of Octamethylcyclotetrasiloxane:
Commercially Octamethylcyclotetrasiloxane is produced from dimethyldichlorosilane.

Hydrolysis of the dichloride produces a mixture of cyclic dimethylsiloxanes and polydimethylsiloxane.
From this mixture, the cyclic siloxanes including Octamethylcyclotetrasiloxane can be removed by distillation.

In the presence of a strong base such as KOH, the polymer/ring mixture is equilibrated, allowing complete conversion to the more volatile cyclic siloxanes:
[(CH3)2SiO]4n → n [(CH3)2SiO]4

Octamethylcyclotetrasiloxane and D5 are also precursors to the polymer.
The catalyst is again KOH.

Uses of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used as a monomer in the manufacture of polymeric materials, which are widely used in various industrial and consumer applications, topical pharmaceutical formulations, and as breast implants.
The polymers contain some residual monomers.
Certain food products are processed using silicone antifoam containing Octamethylcyclotetrasiloxane, which is contained as impurity.

Octamethylcyclotetrasiloxane is used as a cosmetic emollient, skin conditioner, hair conditioner and solvent.
Ungraded products supplied by Spectrum are indicative of a grade suitable for general industrial use or research purposes and typically are not suitable for human consumption or therapeutic use.

Synonyms: Cyclotetrasiloxane

Formula: C8H24O4Si4
Molecular mass: 296.6
Boiling point: 175°C
Melting point: 17.5°C
Relative density (water = 1): 0.96
Solubility in water: none
Vapour pressure, Pa at 21.7°C: 133.3
Flash point: 56°C

Octamethylcyclotetrasiloxane, also called D4, is an organosilicon compound with the formula [(CH3)2SiO]4.

KEYWORDS:
556-67-2, 209-136-7, D4, Cyclotetrasiloxane octamethyl-, NUC silicone VS 7207, UNII-CZ227117JE, octamethyl-cyclotetrasiloxane, CHEBI:25640, CZ227117JE, OMCTS

Occurrence of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is among the most important of all the cyclic siloxanes, with a global production volume of 136 million kilograms in 1993.
100,000–1,000,000 tonnes per year of Octamethylcyclotetrasiloxane is manufactured and/or imported in the European Economic Area.

About Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is registered under the REACH Regulation and is manufactured in and / or imported to the European Economic Area, at ≥ 10 000 to < 100 000 tonnes per annum.
Octamethylcyclotetrasiloxane is used by consumers, in articles, by professional workers (widespread uses), in formulation or re-packing, at industrial sites and in manufacturing.

Consumer Uses of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used in the following products: cosmetics and personal care products, washing & cleaning products, polishes and waxes and inks and toners.
Other release to the environment of Octamethylcyclotetrasiloxane is likely to occur from: indoor use (e.g. machine wash liquids/detergents, automotive care products, paints and coating or adhesives, fragrances and air fresheners) and outdoor use.

Article service life of Octamethylcyclotetrasiloxane:
Release to the environment of Octamethylcyclotetrasiloxane can occur from industrial use: industrial abrasion processing with low release rate (e.g. cutting of textile, cutting, machining or grinding of metal) and of articles where the substances are not intended to be released and where the conditions of use do not promote release.
Other release to the environment of Octamethylcyclotetrasiloxane is likely to occur from: indoor use in long-life materials with low release rate (e.g. flooring, furniture, toys, construction materials, curtains, foot-wear, leather products, paper and cardboard products, electronic equipment).
Octamethylcyclotetrasiloxane can be found in products with material based on: paper (e.g. tissues, feminine hygiene products, nappies, books, magazines, wallpaper) and leather (e.g. gloves, shoes, purses, furniture).

Widespread uses by professional workers of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used in the following products: cosmetics and personal care products, washing & cleaning products, laboratory chemicals, polishes and waxes and coating products.
Octamethylcyclotetrasiloxane is used in the following areas: scientific research and development, formulation of mixtures and/or re-packaging and building & construction work.
Octamethylcyclotetrasiloxane is used for the manufacture of: Other release to the environment of this substance is likely to occur from: indoor use (e.g. machine wash liquids/detergents, automotive care products, paints and coating or adhesives, fragrances and air fresheners) and outdoor use.

Formulation or re-packing of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used in the following products: cosmetics and personal care products, leather treatment products, lubricants and greases and textile treatment products and dyes.
Release to the environment of Octamethylcyclotetrasiloxane can occur from industrial use: formulation of mixtures.

Uses at industrial sites of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used in the following products: laboratory chemicals, non-metal-surface treatment products, polymers, semiconductors, leather treatment products, lubricants and greases and textile treatment products and dyes.
Octamethylcyclotetrasiloxane has an industrial use resulting in manufacture of another substance (use of intermediates).
Octamethylcyclotetrasiloxane is used in the following areas: scientific research and development.
Octamethylcyclotetrasiloxane is used for the manufacture of: chemicals.
Release to the environment of Octamethylcyclotetrasiloxane can occur from industrial use: as an intermediate step in further manufacturing of another substance (use of intermediates), for thermoplastic manufacture, in processing aids at industrial sites and as processing aid.

Manufacture of Octamethylcyclotetrasiloxane:
Release to the environment of Octamethylcyclotetrasiloxane can occur from industrial use: manufacturing of the substance.

Preferred IUPAC name:
Octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane

Other names:
D4
D4
OMCTS

Identifiers:
CAS Number: 556-67-2
CHEBI:25640
ChemSpider: 10696
ECHA InfoCard: 100.008.307
EC Number: 209-136-7
PubChem CID: 11169
UNII: CZ227117JE
CompTox Dashboard (EPA): DTXSID7027205

SilQon OMCTS ( Octamethylcyclotetrasiloxane ) is a clear liquid which has C8H24O4Si4 as chemical formula.
Octamethylcyclotetrasiloxane is a cyclic organic silicon substance which can be used as monomer in the production of silicone polymers such as rubber, resins and greases.
Octamethylcyclotetrasiloxane is also known as D4.

Applications of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used as a monomer in the production of silicone polymers and as an intermediate in the production of other organosilicon substances.
Further it finds Octamethylcyclotetrasiloxanes application in electronics, textiles, personal care products and household care products.

Packaging of Octamethylcyclotetrasiloxane:
Special packaging is available on request.

Storage of Octamethylcyclotetrasiloxane:
Store Octamethylcyclotetrasiloxane in a cool, dry and well-ventilated area and in line with legal requirements.

Properties of Octamethylcyclotetrasiloxane:
Chemical formula: [(CH3)2SiO]4
Molar mass: 296.616 g·mol−1
Density: 0.956 g/mL
Melting point: 17–18 °C (63–64 °F; 290–291 K)
Boiling point: 175–176 °C (347–349 °F; 448–449 K)
Solubility in water: 56.2±2.5 ppb (23 °C)
log P: 6.98±0.13
Vapor pressure: 124.5±6.2 Pa (25 °C)

Octamethylcyclotetrasiloxane, or D4, is an industrial chemical which was not manufactured by any company in Canada in 2006 in a quantity above the reporting threshold of 100 kg, but which was imported into the country in 2006 at a total quantity between 1 000 000 and 10 000 000 kg as an essentially pure substance, in mixtures with other cyclic siloxanes, as a residual in silicone polymers, and in finished consumer products.
The principal sources of release of Octamethylcyclotetrasiloxane to the environment are industrial processes in which it is reacted to form silicone polymers, from blending, formulation and packaging operations.

Octamethylcyclotetrasiloxane is also released from the use and disposal of personal care products.
Air, wastewater and agricultural soil are the principal receiving environmental media for Octamethylcyclotetrasiloxane based on its physical-chemical properties and its use patterns.

Physicochemical Information of Octamethylcyclotetrasiloxane:
Boiling point: 176 °C (1013 hPa)
Density: 0.95 g/cm3 (25 °C)
Explosion limit: 0.4 - 11.7 %(V)
Flash point: 51 °C
Ignition temperature: 400 °C
Melting Point: 18 °C
Vapor pressure: 1.3 hPa (20 °C)
Viscosity kinematic: 1.6 mm2/s (20 °C)
Solubility: <0.001 g/l Hydrolysis

Summary of Health Effects of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane (D4) can interfere with the body’s hormones.
In animals, Octamethylcyclotetrasiloxane can affect the reproductive system.

How is Octamethylcyclotetrasiloxane used?
Octamethylcyclotetrasiloxane is a high production volume chemical1 and is often used in personal care products and sunscreens.

Toxicity: What are Octamethylcyclotetrasiloxanes health effects?
Octamethylcyclotetrasiloxane is classified as a category 1 endocrine disruptor by the European Commission.
A 2018 study commissioned by the Danish EPA identified Octamethylcyclotetrasiloxane as an endocrine disruptor.
The Global Harmonized System Label Requirements classified Octamethylcyclotetrasiloxane as suspected to produce reproductive toxicity.

Octamethylcyclotetrasiloxane was added to the Toxic Substances Control Act work plan due to reproductive toxicity, moderate environmental persistence, and high bioaccumulation potential.
Adverse reproductive effects including estrogenic effects have been observed in rodents.
The European Chemicals Agency characterized Octamethylcyclotetrasiloxane as a persistent, bioaccumulative, and toxic chemical, and designated D4 as a Substance of Very High Concern.

Exposure: How can a person come in contact with Octamethylcyclotetrasiloxane?
A person can come in contact with Octamethylcyclotetrasiloxane from skin contact with consumer products, eating contaminated food, drinking contaminated water, or by breathing it in.
The Danish Environmental Protection Agency detected Octamethylcyclotetrasiloxane in perfume, toys, and children’s cosmetics and articles.

Octamethylcyclotetrasiloxane has been detected in fish, sediment, indoor dust and air, outdoor air, and drinking and surface water.
Biomonitoring studies have also detected Octamethylcyclotetrasiloxane in the blood of Norwegian and German adults.

D4, also known as cyclotetrasiloxane and Octamethylcyclotetrasiloxane.
Octamethylcyclotetrasiloxane is an industrial product used in many applications, primarly in cosmetic products and polymers, in its pure form and in mixtures with other siloxanes.
All silicone polymers have residual of Octamethylcyclotetrasiloxane, because it is a byproduct of polymerisation.

Octamethylcyclotetrasiloxane was identified as a harmfull compound to the environment, and it may accumulate in living organisms and cause complications.
Government of Canada issued a notice to prevent or limit Octamethylcyclotetrasiloxane releases to the environment from industrial effluents.

PO-Laboratories developed sensitive and reliable method of analysis of Octamethylcyclotetrasiloxane siloxane in industrial effluents.
Environment Canada has audited PO-Laboratories, examined the Octamethylcyclotetrasiloxane method and run interlaboratory comparison study.
As a result, PO-Laboratories has been certified and accredited by Environment Canada as an independent laboratory to perform Octamethylcyclotetrasiloxane testing in industrial and environmental samples.

Octamethylcyclotetrasiloxane (OMCTS), a common constituent of household products, triggers the transformation of bismuth to the volatile toxic derivative trimethylbismuth by Methanosarcina barkeri, which is a representative member of the sewage sludge microflora.
Comparative studies with the ionophores monensin and lasalocid, which induce effects similar to those observed for OMCTS, indicated that the stimulation of bismuth methylation is not specific for the siloxane and suggested that the stimulation observed is mainly due to facilitated membrane permeation of the metal ion.

Molecular Weight: 296.61
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 4
Rotatable Bond Count: 0
Exact Mass: 296.07516538
Monoisotopic Mass: 296.07516538
Topological Polar Surface Area: 36.9 Å²
Heavy Atom Count: 16
Formal Charge: 0
Complexity: 197
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count   : 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes

Chemical Properties of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is also known as D4.
Octamethylcyclotetrasiloxane is an odorless, colorless non-oily silicone fluid which has C8H24O4Si4 as chemical formula.
Octamethylcyclotetrasiloxane is a cyclic organic silicon substance which can be used as monomer in the production of silicone polymers such as rubber, resins and greases.

Uses of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane is used as a monomer in the production of silicone polymers and as an intermediate in the production of other organosilicon substances.
Further Octamethylcyclotetrasiloxane finds its application in electronics, textiles, personal care products and household care products.
Polydimethylsiloxane by the Polymerization of Octamethylcyclotetrasiloxane: To a resin flask equipped with a thermometer, stirrer, and reflux eondenser is added 1000 gm of octamethylcyclotetrasiloxane.

The siloxane is heated to 165°C, and then 0.14gm of a potassium hydroxide-isopropanol complex (neutral equivalent = 193.5) is added to give a Si : Κ ratio of 4470:1.
In 25 min the stirrer begins to stall, and the polymer is now heated for 3(1/2) hr at 150°C to complete polymerization.
The resulting polymer has an intrinsic viscosity of 1.5 dl/gm corresponding to a molecular weight of 804,600.

Definition of Octamethylcyclotetrasiloxane:
ChEBI: Octamethylcyclotetrasiloxane is a cyclosiloxane that is the octamethyl derivative of cyclotetrasiloxane.
Octamethylcyclotetrasiloxane is an organosilicon compound and a cyclosiloxane.
Octamethylcyclotetrasiloxane derives from a hydride of a cyclotetrasiloxane.

Preparation of Octamethylcyclotetrasiloxane:
Commercially Octamethylcyclotetrasiloxane is produced from dimethyldichlorosilane.
Dimethyldichlorosilane is added dropwise to water, the temperature is maintained at 30-40°C, stratified, the acid water is released, the oily material is hydrolyzed with sodium hydroxide solution, the hydrolysate and 0.5%-2% potassium hydroxide are added to the cracking kettle and cracked at 120-140°C and 99.8 kPa vacuum.
The cracked material is fractionated and the fraction is collected at 173-176°C to obtain octamethylcyclotetraoxysilane.

General Description of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane (D4) is a volatile methylsiloxane (VMS) with a relatively low molecular weight.
This silicone fluid has a silicon-oxygen bond in a cyclic arrangement and methyl groups are attached to the silicon atom.
D4 can be used in the manufacture of silicone based polymers for use in medical devices and personal care products.

Health Hazard of Octamethylcyclotetrasiloxane:
Octamethylcyclotetrasiloxane (D4) can interfere with the body’s hormones.
In animals, Octamethylcyclotetrasiloxane can affect the reproductive system.
Octamethylcyclotetrasiloxane is classified as a category 1 endocrine disruptor by the European Commission.

A 2018 study commissioned by the Danish EPA identified Octamethylcyclotetrasiloxane as an endocrine disruptor.
The Global Harmonized System Label Requirements classified Octamethylcyclotetrasiloxane as suspected to produce reproductive toxicity.

Safety Profile of Octamethylcyclotetrasiloxane:
A skin irritant.
When heated todecomposition it emits acrid smoke and irritating vapors.

Purification Methods of Octamethylcyclotetrasiloxane:
The solid exists in two forms, m 16.30o and 17.65o.
Dry Octamethylcyclotetrasiloxane over CaH2 and distil it.
Further fractionation can be effected by repeated partial freezing and discarding the liquid phase.

Description of Octamethylcyclotetrasiloxane:
Catalogue Number: 814750
Synonyms: Octamethyltetrasiloxane

Product Information of Octamethylcyclotetrasiloxane:
CAS number: 556-67-2
EC index number: 014-018-00-1
EC number: 209-136-7
Hill Formula: C₈H₂₄O₄Si₄
Molar Mass: 296.62 g/mol
HS Code: 2931 90 00

Linear Formula:
[-Si(CH3)2O-]4

CAS Number:
556-67-2

Molecular Weight:
296.62

Beilstein:
1787074

EC Number:
209-136-7

MDL number:
MFCD00003269

PubChem Substance ID:
24853994

NACRES:
NA.23

Safety and environmental considerations:
Octamethylcyclotetrasiloxane is of low acute toxicity.
The LC50 for a single four hour inhalation exposure in rats is 36 mg/L.
The oral LD50 in rats is above 4800 mg/kg and the dermal LD50in rats is above 2400 mg/kg.

As the smallest cyclic dimethylsiloxane that does not experience considerable ring strain, Octamethylcyclotetrasiloxane is one of the most abundant siloxanes in the environment, e.g. in landfill gases.
Octamethylcyclotetrasiloxane and D5 have attracted attention because they are pervasive.

Cyclic siloxanes can be detected in some species of aquatic life.
An independent, peer-reviewed study in the US found "negligible risk from Octamethylcyclotetrasiloxane to organisms" while a scientific assessment by the Australian government stated, "the direct risks to aquatic life from exposure to these chemicals at expected surface water concentrations are not likely to be significant."

In the European Union, Octamethylcyclotetrasiloxane was characterized as a substance of very high concern (SVHC) due to its PBT and vPvB properties and was thus included in the candidate list for authorisation.
Octamethylcyclotetrasiloxane shall not be placed on the market in wash-off cosmetic products in a concentration equal to or greater than 0.1% by weight of either substance, after 31 January 2020.

Conversely, a detailed review and analysis of the science by the State of Washington in 2017 led to the removal of D4 from their CHCC listing.
That decision prompted the State of Oregon to follow suit in 2018.

Octamethylcyclotetrasiloxane is a member of the cyclic siloxane, or cyclomethicone, family.
Octamethylcyclotetrasiloxane is often called simply D4 because of its four dimethylsiloxane units.
Octamethylcyclotetrasiloxane exists as an oily liquid or low-melting solid.

In 1946, Winton Patnode and Donald F. Wilcock at General Electric (Schenectady, NY) prepared Octamethylcyclotetrasiloxane as part of an extensive study of methylpolysiloxanes made by hydrolyzing methylchlorosilanes.
In one the many reactions they reported, they mixed dimethyldichlorosilane1 (Me2SiCl2) with large volumes of water to produce a colorless oil with a composition that had an empirical formula close to that of Me2SiO.

Analysis of the oil showed that it was primarily a mixture of cyclic oligomers of the formula (Me2SiO)x, with isolated compounds ranging from x = 3 to x = 10.
The relative amounts of each of the cyclosiloxanes varied with hydrolysis conditions such as the Me2SiCl2/H2O ratio and the presence of cosolvents, acids, or bases.
In general, D4 (x = 4) was the most abundant product.

Today, Octamethylcyclotetrasiloxane is commercially produced by the same general method.
Octamethylcyclotetrasiloxane mixture is separated into its components via distillation.

Octamethylcyclotetrasiloxane and the other oligomers are used to prepare poly(dimethylsiloxane)2 [(Me2SiO)n], familiarly known as silicone oil.
Octamethylcyclotetrasiloxane itself is used as an additive to plastic and rubber products, paints, adhesives, cosmetics, food packaging, and many other product areas.
Octamethylcyclotetrasiloxanes worldwide production is in the hundreds of thousands of tonnes.

Because of its widespread production and use, Octamethylcyclotetrasiloxane has come under scrutiny for its adverse environmental and health effects.
Last September, the US Environmental Protection Agency announced an evaluation of the environmental risks of its industrial uses.
Octamethylcyclotetrasiloxane will be up to the Food and Drug Administration to determine whether its food, health care, and personal care uses are evaluated.

PROPERTIES of Octamethylcyclotetrasiloxane:
vapor density:
1 (vs air)

Quality Level:
200

assay:
98%

form:
liquid

refractive index:
n20/D 1.396 (lit.)

bp:
175-176 °C (lit.)

mp:
17-18 °C (lit.)

density:
0.956 g/mL at 25 °C (lit.)

SMILES string:
C[Si]1(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O1

InChI:
1S/C8H24O4Si4/c1-13(2)9-14(3,4)11-16(7,8)12-15(5,6)10-13/h1-8H3

InChI key:
HMMGMWAXVFQUOA-UHFFFAOYSA-N

Identification of Octamethylcyclotetrasiloxane:
Chemical name: Octamethylcyclotetrasiloxane (D4)
Synonyms: D4; Cyclotetrasiloxane, octamethyl-; Octamethyltetracyclosiloxane; 2,2,4,4,6,6,8,8 octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane; cyclic dimethylsiloxane tetramer
CAS number: 556-67-2
Molecular formula: C8H24O4Si4

Chemical and physical properties of Octamethylcyclotetrasiloxane:
Physical state and appearance: Clear fluid
Odor description: Odorless
Molecular weight: 296.61 g/mol
Conversion factors: 1 ppm = 12 mg/m3 at 22°C (71.6°F)
1 mg/m3 = 0.0824 ppm at 22°C (71.6°F)
Melting point: 17.7°C (63.86°F)
Boiling point: 175°C (347°F)
Vapor pressure: 0.99 mm Hg at 25°C (77°F)
Flammability limits: LEL: 0.75% in air; UEL: 7.40% in air
Flash point: 61°C (open cup, measured); 51°C (closed cup, measured)
Autoignition temperature: 384–387°C (723.20–728.60°F)
Specific gravity: 0.95 at 25°C (77°F)
Solubility in water: 0.056 mg/L at 23°C (73.40°F)
Stability: Stable
Reactivity and incompatibilities: Silicone foam, particularly when quartz is used as filler, has good flammability characteristics.
Partition coefficient: 6.49 at 20°C (68°F)

Octamethylcyclotetrasiloxane (D4; CAS No. 556-67-2) is used as a monomer in the manufacture of polymeric materials, which are widely used in various industrial and/or medical applications, such as breast implants.
Octamethylcyclotetrasiloxane has a relatively low order of toxicity following acute administration via the oral, dermal, and inhalation routes of exposure and is not considered to be a dermal or eye irritant or to be a dermal sensitizer.
There is no appreciable dermal absorption of Octamethylcyclotetrasiloxane based on results from in vivo and in vitro studies.

Octamethylcyclotetrasiloxane has not been shown to be genotoxic/mutagenic when tested in a number of short-term in vitro and in vivo assays.
Overall, studies have demonstrated adverse effects on specific female reproductive endpoints at higher exposure concentrations; however, no Octamethylcyclotetrasiloxane exposure-specific effects were noted with respect to developmental endpoints.
Inhalation exposure of rats to 700 ppm Octamethylcyclotetrasiloxane for up to 24 months produced effects in the liver, kidney, and uterus (weight changes, hepatocellular hypertrophy, endometrial hyperplasia, and nephropathy).

Changes in the nasal epithelium (eosinophilic globules) were also noted at 150 and 700 ppm.
Despite 24 months of exposure, only mild to minimal inflammatory responses were found at 150 ppm, and overall, the basic integrity of the respiratory tract was unchanged at this dose.
At 700 ppm, there was an increased incidence of endometrial adenomas in female rats.

Based on the adverse changes in the respiratory tract, kidney, and female reproductive tract in the chronic inhalation study, 150 ppm was determined to be the no-observed-adverse-effect level (NOAEL) and was selected as the point of departure for the derivation of the workplace environmental exposure level (WEEL) value.
The inhalation NOAEL was adjusted to account for interindividual variability and residual uncertainty regarding upper respiratory tract changes still occurring at 150 ppm.
An 8-h time-weighted average WEEL value of 10 ppm is expected to provide a significant margin of safety against any potential adverse health effects in workers exposed to airborne Octamethylcyclotetrasiloxane.

OCTAMETHYLCYCLOTETRASILOXANE
556-67-2
Cyclotetrasiloxane, octamethyl-
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
Oktamethylcyklotetrasiloxan
Cyclic dimethylsiloxane tetramer
NUC silicone VS 7207
Oktamethylzyklotetrasiloxan
octamethyl cyclotetrasiloxane
UNII-CZ227117JE
octamethyl-cyclotetrasiloxane
2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane
CHEBI:25640
CZ227117JE
OMCTS
DSSTox_CID_7205
DSSTox_RID_78349
DSSTox_GSID_27205
Union carbide 7207
Silicone SF 1173
MFCD00003269
C8H24O4Si4
CAS-556-67-2
CCRIS 1327
HSDB 6131
Oktamethylcyklotetrasiloxan [Czech]
EINECS 209-136-7
KF 994
NSC 345674
SF 1173
UC 7207
VS 7207
BRN 1787074
volasil(tm) 244
bmse000765
EC 209-136-7
SCHEMBL18354
BIDD:ER0157
Dimethylsiloxane Cyclic Tetramer
CHEMBL1869229
DTXSID7027205
HMMGMWAXVFQUOA-UHFFFAOYSA-
Octamethylcyclotetrasiloxane, 98%
Tox21_201398
Tox21_300547
7595AH
CO9810
NSC345674
AKOS008901191
ZINC169743112
MCULE-2162943570
NSC-345674
NCGC00164099-01
NCGC00164099-02
NCGC00164099-03
NCGC00254406-01
NCGC00258949-01
CS-0213747
FT-0688100
O0142
O9810
Octamethylcyclotetrasiloxane, analytical standard
Cyclotetrasiloxane, 2,2,4,4,6,6,8,8-octamethyl-
octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
Q2013804
UNII-NMQ347994Z component HMMGMWAXVFQUOA-UHFFFAOYSA-N
Cyclotetrasiloxane, 2,2,4,4,6,6,8,8-octamethyl-, homopolymer
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane #
Cyclomethicone 4, United States Pharmacopeia (USP) Reference Standard
D4 Cyclomethicone, Pharmaceutical Secondary Standard; Certified Reference Material
25037-57-4
Octamethylcyclotetrasiloxane [Wiki]
1787074 [Beilstein]
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocan [German] [ACD/IUPAC Name]
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane [ACD/IUPAC Name]
2,2,4,4,6,6,8,8-Octaméthyl-1,3,5,7,2,4,6,8-tétroxatétrasilocane [French] [ACD/IUPAC Name]
209-136-7 [EINECS]
556-67-2 [RN]
CYCLOMETHICONE 4
Cyclotetrasiloxane, 2,2,4,4,6,6,8,8-octamethyl- [ACD/Index Name]
CZ227117JE
D4 Cyclomethicone
GZ4397000
MFCD00003269 [MDL number]
[556-67-2] [RN]
104986-37-0 [RN]
2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane; D4
3-Methylbut-2-en-1-ol
4-04-00-04125 [Beilstein]
4-04-00-04125 (Beilstein Handbook Reference) [Beilstein]
83874-62-8 [RN]
C024064
CO9810
cyclic dimethylsiloxane tetramer
cyclotetrasiloxane, octamethyl-
D4
EINECS 209-136-7
NCGC00164099-01
NUC silicone VS 7207
O9810
Octamethyl cyclotetrasiloxane
octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
Octamethylcyclotetrasiloxane D4
Octamethylcyclotetrasiloxane(D4)
octamethyltetrasiloxane
Oktamethylcyklotetrasiloxan
Oktamethylcyklotetrasiloxan [Czech]
Oktamethylzyklotetrasiloxan
OMCTS
Silicone SF 1173
UNII:CZ227117JE
UNII-CZ227117JE
Union carbide 7207
volasil 244

Regulatory process names:
Cyclic dimethylsiloxane tetramer
Cyclotetrasiloxane, 2,2,4,4,6,6,8,8-octamethyl-
Cyclotetrasiloxane, octamethyl-
KF 994
NUC silicone VS 7207
Octamethylcyclotetrasiloxane
octamethylcyclotetrasiloxane
Octamethylcyclotetrasiloxane
D4
octamethylcyclotetrasiloxane; [D4]
Oktamethylcyklotetrasiloxan
OMCTS
Silicone SF 1173
UC 7207
Union carbide 7207
VS 7207

Translated names:
octamethylcyclotetrasiloxaan; [D4] (nl)
octamethylcyclotetrasiloxan; [D4] (da)
Octamethylcyclotetrasiloxan; [D4] (de)
octametilciclotetrasiloxan; [D4] (ro)
Octametilciclotetrasiloxano; [D4] (es)
octametilciclotetrassiloxano [D4] (pt)
octaméthylcyclotétrasiloxane; [D4] (fr)
oktamethylcyklotetrasiloxan; [D4] (cs)
oktametilciklotetrasiloksan; [D4] (hr)
oktametilciklotetrasiloksan; [D4] (sl)
oktametilciklotetrasiloksanas; [D4] (lt)
oktametilciklotetrasiloksāns; [D4] (lv)
oktametilciklotetrasziloxán; [D4] (hu)
oktametylcyklotetrasiloksan (no)
oktametylcyklotetrasiloxan; [D4] (sv)
oktametylcyklotetrasiloxán; [D4] (sk)
oktametylocyklotetrasiloksan; [D4] (pl)
oktametyylisyklotetrasiloksaani; [D4] (fi)
Oktametüültsüklotetrasiloksaan; [D4] (et)
ottametilciclotetrasilossano; [D4] (it)
ottametilċiklotetrasiloksan; [D4] (mt)
οκταμεθυλοκυκλοτετρασιλοξάνιο· [D4] (el)
октаметилциклотетрасилоксан; [D4] (bg)

CAS names:
Cyclotetrasiloxane, 2,2,4,4,6,6,8,8-octamethyl-

IUPAC names:
2,2,2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasiloxane
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane
2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane
2,2,4,4,6,6,8,8-octamethyl-1,3,5,7-tetraoxy-2,4,6,8-tetrasilacyclooctane
cyclosiloxane
Cyclotetrasiloxane, 2,2,4,4,6,6,8,8-octamethyl-
Cyclotetrasiloxane, octamethyl-
Cyclotetrasiloxane,2,2,4,4,6,6,8,8,-octamethyl-
D4
octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
octamethylcyclotetra
Octamethylcyclotetrasiloxan
octamethylcyclotetrasiloxan
OCTAMETHYLCYCLOTETRASILOXANE
Octamethylcyclotetrasiloxane
octamethylcyclotetrasiloxane
Octamethylcyclotetrasiloxane
octamethylcyclotetrasiloxane
Octamethylcyclotetrasiloxane, D4
octamethylcyclotetrasiloxane, D4
Octaméthylcyclotetrasiloxane
octomethylcyclotetrasiloxane

Trade names:
D4
DOW CORNING(R) 244 FLUID
F-28
F-42S
KF-994
Octame.cy.tetrasil
OCTAMETHYLCYCLOTETRASILOXANE
SF 1173
SILBIONE TETRAMERE D4
T-07V
T-07v
T-206
TETRAMERE D4
TETRAMERE D4 SP
VS-7207

Other identifiers:
014-018-00-1
104986-37-0
104986-37-0
117563-66-3
117563-66-3
1257661-59-8
1257661-59-8
556-67-2
83874-62-8
83874-62-8