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556-67-2

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Identification

Name
Octamethylcyclotetrasiloxane
CAS
556-67-2
Synonyms
D4
DIMETHYLSILOXANE CYCLIC TETRAMER
OCTAMETHYLCYCLOTETRASILOXANE
OCTAMETHYLTETRASILOXANE
VOLASIL(TM) 244
2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
CO9810
cyclicdimethylsiloxanetetramer
Cyclotetrasiloxane,octamethyl-
kf994
NUC Silicone VS 7207
nucsiliconevs7207
O9810
Octamethylcyclotetraoxysilane
octamethyl-cyclotetrasiloxan
octamethylcyclotetrasiloxane(volasil244)
Oktamethylcyklotetrasiloxan
sf1173
siliconesf1173
tetracyclosiloxane,octamethyl-
EINECS(EC#)
209-136-7
Molecular Formula
C8H24O4Si4
MDL Number
MFCD00003269
Molecular Weight
296.62
MOL File
556-67-2.mol

Chemical Properties

Appearance
Colorless clear liquid
Melting point 
17-18 °C (lit.)
mp 
17-18 °C(lit.)

Boiling point 
175-176 °C (lit.)
bp 
175-176 °C(lit.)

density 
0.956 g/mL at 25 °C(lit.)

vapor density 
1 (vs air)

refractive index 
n20/D 1.396(lit.)

Fp 
140 °F

storage temp. 
2-8°C
solubility 
<0.001g/l Hydrolysis
form 
liquid
Specific Gravity
0.956
color 
colorless
explosive limit
0.4-11.7%(V)
Water Solubility 
INSOLUBLE
Sensitive 
Moisture Sensitive
Usage
Fungicide
Merck 
14,6747
BRN 
1787074
InChIKey
HMMGMWAXVFQUOA-UHFFFAOYSA-N
Uses
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.
CAS DataBase Reference
556-67-2(CAS DataBase Reference)
NIST Chemistry Reference
Cyclotetrasiloxane, octamethyl-(556-67-2)
EPA Substance Registry System
556-67-2(EPA Substance)

Safety Data

Hazard Codes 
Xn
Risk Statements 
R53:May cause long-term adverse effects in the aquatic environment.
R62:Possible risk of impaired fertility.
Safety Statements 
S36/37:Wear suitable protective clothing and gloves .
S46:If swallowed, seek medical advice immediately and show this container or label .
S51:Use only in well-ventilated areas .
S61:Avoid release to the environment. Refer to special instructions safety data sheet .
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

Raw materials And Preparation Products

Hazard Information

Chemical Properties
Colorless clear liquid
Definition
ChEBI: A cyclosiloxane that is the octamethyl derivative of cyclotetrasiloxane.
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.

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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