Octamethylcyclotetrasiloxane Chemical Properties

Melting point:

17-18 °C (lit.)

Boiling point:

175-176 °C (lit.)

Density 

0.956 g/mL at 25 °C (lit.)

vapor density 

1 (vs air)

vapor pressure 

1.32hPa at 25℃

refractive index 

n20/D 1.396(lit.)

Flash point:

140 °F

storage temp. 

Store below +30°C.

solubility 

<0.001g/l Hydrolysis

form 

liquid

color 

colorless

Specific Gravity

0.956

explosive limit

0.4-11.7%(V)

Water Solubility 

INSOLUBLE

Sensitive 

Moisture Sensitive

Merck 

14,6747

BRN 

1787074

Dielectric constant

2.4（20℃）

InChIKey

HMMGMWAXVFQUOA-UHFFFAOYSA-N

LogP

6.98 at 21.7℃

CAS DataBase Reference

556-67-2(CAS DataBase Reference)

NIST Chemistry Reference

Cyclotetrasiloxane, octamethyl-(556-67-2)

EPA Substance Registry System

Octamethylcyclotetrasiloxane (556-67-2)

Safety Information

Hazard Codes 

Xn

Risk Statements 

53-62-10

Safety Statements 

36/37-46-51-61

RIDADR 

UN 1993 3/PG 3

WGK Germany 

1

RTECS 

GZ4397000

TSCA 

Yes

HazardClass 

3

PackingGroup 

III

HS Code 

29319090

Hazardous Substances Data

556-67-2(Hazardous Substances Data)

Toxicity

LD50 oral in rat: 1540mg/kg

MSDS

• Language:English Provider:SigmaAldrich
• Language:English Provider:ACROS
• Language:English Provider:ALFA

Octamethylcyclotetrasiloxane Usage And Synthesis

Chemical Properties

Octamethylcyclotetrasiloxane is also known as D4. It is an odorless, colorless non-oily silicone fluid which has C8H24O4Si4 as chemical formula. It 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

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 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

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

Preparation

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

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

Octamethylcyclotetrasiloxane (D4) can interfere with the body’s hormones. In animals, it can affect the reproductive system.
D4 is classified as a category 1 endocrine disruptor by the European Commission. A 2018 study commissioned by the Danish EPA identified D4 as an endocrine disruptor. The Global Harmonized System Label Requirements classified D4 as suspected to produce reproductive toxicity. D4 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 D4 as a persistent, bioaccumulative, and toxic chemical, and designated D4 as a Substance of Very High Concern.

Flammability and Explosibility

Flammable

Safety Profile

A skin irritant. When heated todecomposition it emits acrid smoke and irritating vapors.

Purification Methods

The solid exists in two forms, m 16.30o and 17.65o. Dry it over CaH2 and distil it. Further fractionation can be effected by repeated partial freezing and discarding the liquid phase. [Osthoff & Grubb J Am Chem Soc 76 399 1954, Hoffman J Am Chem Soc 75 6313 1953, Beilstein 4 IV 4125.]

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