556-68-3

Usage

Uses

Hexadecamethylcyclooctasiloxane is a major component of the crude extract of Bacillus cereus S1 that exhibits antibacterial activity against five bacterial pathogens.

Definition

ChEBI: A macrocyclic organosiloxane composed from eight repeating Me2SiO units.

InChI:InChI=1/C16H48O8Si8/c1-25(2)17-26(3,4)19-28(7,8)21-30(11,12)23-32(15,16)24-31(13,14)22-29(9,10)20-27(5,6)18-25/h1-16H3

Synthetic route

C16H48Cl2O7Si8 → hexadecamethylcyclooctasiloxane (556-68-3)

Conditions	Yield
In diethyl ether; water at 20 - 30℃; Alkaline conditions;	56%

1,1,3,3-Tetramethyldisiloxane (3277-26-7) + dodecamethyl-cyclohexasiloxane (540-97-6) → tetradecamethylcycloheptasiloxane (107-50-6) + hexadecamethylcyclooctasiloxane (556-68-3) + iododimethylsilane (2441-21-6)

Conditions	Yield
With iodine	A 22% B 12% C n/a

diethoxy dimethylsilane (78-62-6) → hexadecamethylcyclooctasiloxane (556-68-3)

Conditions	Yield
With hydrogenchloride Kochen der erhaltenen Reaktionsprodukte mit 20prozentig. wss. HCl;
With hydrogenchloride

dimethylsilicon dichloride (75-78-5) → hexadecamethylcyclooctasiloxane (556-68-3)

Conditions	Yield
With water

n-butyllithium (109-72-8, 29786-93-4) + Hexamethylcyclotrisiloxane (541-05-9) + [(η7-C7H6)Ti(η5-C5H4)](OSiMe2)(SiMe2) → tetradecamethylcycloheptasiloxane (107-50-6) + hexadecamethylcyclooctasiloxane (556-68-3) + [(η7-C7H6)Ti(η5-C5H4)](OSiMe2)2(SiMe2) + C23H40OSi3Ti

Conditions	Yield
Stage #1: n-butyllithium; [(η7-C7H6)Ti(η5-C5H4)](OSiMe2)(SiMe2) In tetrahydrofuran at 20℃; for 2h; Stage #2: Hexamethylcyclotrisiloxane With chloro-trimethyl-silane In tetrahydrofuran for 2h;

dodecamethylcyclohexasilane (4098-30-0) → tetradecamethylcycloheptasiloxane (107-50-6) + hexadecamethylcyclooctasiloxane (556-68-3) + octadecamethyl cyclononasiloxane (556-71-8) + Hexamethylcyclotrisiloxane (541-05-9) + octamethylcyclotetrasiloxane (556-67-2) + decamethylcyclopentasiloxane (541-02-6) + dodecamethyl-cyclohexasiloxane (540-97-6) + 1,1,3,3,5,5,7,7,9,9,11,11,13,13,15,15-hexadecamethyloctasiloxane-1,15-diol (4938-87-8) + 1,1,3,3,5,5,7,7,9,9,11,11-dodecamethylhexasiloxane-1,11-diol (4029-00-9) + C30H92O16Si15 + eicosamethylcyclodecasiloxane (18772-36-6) + tetracosamethyl cyclododecasiloxane (18919-94-3) + Tricontamethylcyclopentadecasiloxan (23523-14-0) + α,ω-Dihydroxy-tetradecamethyl-heptasiloxan (3195-63-9) + Docosamethylcycloundecasiloxane (18766-38-6) + α,ω-Dihydroxy-polydimethylsiloxan + hexacosamethyl-cyclotridecasiloxane (23732-94-7) + Octacosamethylcyclotetradeca-siloxane (149050-40-8) + α,ω-Dihydroxy-octadecamethyl-nonasiloxan (18678-58-5) + 1,1,3,3,5,5,7,7,9,9,11,11,13,13,15,15,17,17,19,19,21,21,23,23,25,25,27,27,29,29,31,31-dotriacontamethylhexadecasiloxane-1,31-diol + Dotriacontamethylcyclohexadecasiloxane + tetratriacontamethylcycloheptadecasiloxane + C22H68O12Si11 + C24H74O13Si12 + C34H104O18Si17 + permethyldecasiloxane-1,19-diol + C28H86O15Si14

Conditions	Yield
Stage #1: dodecamethylcyclohexasilane With potassium tert-butylate In tetrahydrofuran at 20℃; for 0.5h; Inert atmosphere; Schlenk technique; Stage #2: With hydrogen; C62H51N2Ni2(1-)*K(1+)*2C4H10O2 In tetrahydrofuran at 45℃; under 1500.15 Torr; for 24h; Schlenk technique; Stage #3: With water In tetrahydrofuran at -40 - 20℃; for 12h; Schlenk technique;

...Expand

Upstream product

• 75-78-5 dimethylsilicon dichloride 
• 109-72-8 n-butyllithium 
• 541-05-9 Hexamethylcyclotrisiloxane 
• 4098-30-0 dodecamethylcyclohexasilane 
• 3277-26-7 1,1,3,3-Tetramethyldisiloxane 
• 540-97-6 dodecamethyl-cyclohexasiloxane 
• 78-62-6 diethoxy dimethylsilane 

Relevant academic research and scientific papers

Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes

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.

High-efficiency macrocyclic dimethyl siloxane compound preparation method

The invention discloses a high-efficiency macrocyclic dimethyl siloxane compound preparation method which comprises the following steps: (1) utilizing tetramethyl disiloxane and octamethyl cyclotetrasiloxane as raw materials, performing ring-openingopen cycle in a sodium hydroxide or potassium hydroxide water solution and then inserting again to obtain dimethyl hydrogen silicone end capped direct-linked siloxane; (2) chlorinating the dimethyl hydrogen silicone end capped direct-linked siloxane with acetyl chloride under a catalytic effect of aluminum trichloride to obtain dimethyl chlorosilane end capped direct-linked siloxane; (3) hydrolyzing the direct-linked siloxane under the alkali condition to obtain varieties of macrocyclic diemthyl silicon ring bodies. The preparation method has simple steps and economical and safe technology and can be used for obtaining varieties of high-purity macrocyclic diemthyl silicon ring body products from simple raw materials; thus, high-difficulty distillation is avoided, and the preparation method is very suitable for industrial production.

Siloxane-bridged [n]troticenophanes: Syntheses, structures and ring-opening reactions

Salt elimination reactions between dilithiotroticene [(η7- C7H6Li)Ti(η5-C5H 4Li)]·pmdta (1) (pmdta = N,N′ ,N′ ,N″ ,N″-pentamethyldiethylenetriamine) and siloxane dichlorides ClMe 2Si-(OSiMe2)m-Cl (m = 1-3) at low temperature allowed the synthesis and isolation of the siloxane-bridged [n]troticenophanes [(η7-C7H6)Ti(η5-C 5H4)](OSiMe2)m(SiMe2) (2, m = 1; 3, m = 2; 4, m = 3) as blue crystalline solids in moderate yield. The compounds were characterized by 1H, 13C and 29Si NMR spectroscopy, elemental and single-crystal X-ray diffraction analyses. The molecular structures of 2 and 3 showed a low degree of strain indicated by the dihedral (α= 4.8° for 2; 4.9/3.7° for 3) and distortion (δ = 176.2° for 2; 174.3/176.3° for 3) angles between the two rings. The structure of 4 was severely disordered. Compounds 2-4 are thermally resistant to ring-opening polymerization, as revealed by differential scanning calorimetry studies, with 2 exhibiting the higher melting temperature. Moreover, the observation of two endotherms in the DSC spectrum of 2 suggests a solid state transition as a result of polymorphism. The reactions of 2-4 with basic initiators such as potassium siloxanolate, ammonium siloxanolate or n-BuLi and analysis of the product distribution by electron ionization mass spectrometry revealed the formation of oligotroticenylsiloxanes incorporating one or more troticenyl units, ring-opened troticenes and ringexpanded troticenophanes [(η7-C7H6) Ti(η 5-C5H4)](OSiMe 2)r(SiMe2) (r > m). Similar cleavage and extension of the ring were observed by treatment of 2-4 with the acidic initiator Purolite CT-175, and ring-opened troticenes having mixed terminal -OH and -SiMe3 groups were detected. Attempts to copolymerize 2-4 and cyclotrisiloxane with n-BuLi afforded essentially the monomeric and polymeric siloxanes [Me2SiO]w (w = 7, 8), Me2(nBu) Si[OSiMe2]yOSiMe2 (y = 3-6) and Me 2(n-Bu)Si[OSiMe2]zOH (z = 1-7), together with the ring-opened and ring-expanded products mentioned above.

New route to permethylcyclosiloxanes

A new method for preparing permethylcyclosiloxanes, based on reaction of 1,1,3,3-tetramethyldisiloxane with iodine (molar ratio 1:1) in inert organic solvents (alkanes, alkyl halides, benzene) is proposed. The products of the reaction react with ethoxytrimethylsilane and tetramethoxysilane in hexamethyldisiloxane to give respectively pentamethyldisiloxane and products of successive substitution of the methoxy groups in Si(OMe)4 by Me2SiHO. A probable scheme of their formation is discussed.