556-67-2 Usage
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
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.]
Check Digit Verification of cas no
The CAS Registry Mumber 556-67-2 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,5 and 6 respectively; the second part has 2 digits, 6 and 7 respectively.
Calculate Digit Verification of CAS Registry Number 556-67:
(5*5)+(4*5)+(3*6)+(2*6)+(1*7)=82
82 % 10 = 2
So 556-67-2 is a valid CAS Registry Number.
InChI:InChI=1/C8H24O4Si4/c1-13(2)9-14(3,4)11-16(7,8)12-15(5,6)10-13/h1-8H3
556-67-2Relevant articles and documents
Andrianov et al.
, p. 1992,1996 (1968)
Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes
Comas-Vives, Aleix,Eiler, Frederik,Grützmacher, Hansj?rg,Pribanic, Bruno,Trincado, Monica,Vogt, Matthias
supporting information, p. 15603 - 15609 (2020/04/29)
The dehydrogenation of organosilanes (RxSiH4?x) under the formation of Si?Si bonds is an intensively investigated process leading to oligo- or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si?Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo- and polysilanes that is highly selective and proceeds under mild conditions. New low-valent nickel hydride complexes are used as catalysts and secondary silanes, RR′SiH2, are obtained as products in high purity.
Tris(pentafluorophenyl)borane-Catalyzed Reactions of Siloxanes: A Combined Experimental and Computational Study
Mathew, Jomon,Eguchi, Katsuya,Nakajima, Yumiko,Sato, Kazuhiko,Shimada, Shigeru,Choe, Yoong-Kee
, p. 4922 - 4927 (2017/09/13)
The reaction of 1,1,3,3-tetramethyldisiloxane with 1-octene as a model reaction of silicone curing catalyzed by B(C6F5)3 resulted in the redistribution of the disiloxane into dimethylsilane and cyclic oligosiloxanes, and the subsequent hydrosilylation reaction of dimethylsilane afforded dimethyldioctylsilane. To obtain insights into the reaction mechanism and possibility alter the reaction pathway to favor the hydrosilylation over the redistribution, mechanistic analysis of the reaction between a hydrosiloxane (1,1,3,3-tetramethyldisiloxane, silox-H) and a vinylsiloxane (1,1,3,3-tetramethyl-1,3-divinyldisiloxane, silox-vin) in the presence of B(C6F5)3 was performed through density functional theory calculations. The results of the calculations indicate that the activation of a Si–H bond in silox-H by B(C6F5)3 initiates the reaction to form the B(C6F5)3–silox-H complex with a Lewis acidic silicon atom and a hydridic hydrogen atom. The B(C6F5)3–silox-H complex can undergo two different reaction pathways, that is, trisiloxane formation and the hydrosilylation of silox-vin by silox-H. The trisiloxane formation involves trisilyloxonium ions as intermediates and can lead to either the homotrisiloxane of silox-H or a mixed trisiloxane of silox-H and silox-vin. The energetics of the reaction pathways predict the preference of trisiloxane formation over hydrosilylation, and the fine tuning of the steric and electronic natures of the substrates could alter the thermodynamic and kinetic favorability.