556-68-3

Basic information

• Product Name: hexadecamethylcyclooctasiloxane
• Synonyms: hexadecamethylcyclooctasiloxane;2,2,4,4,6,6,8,8,10,10,12,12,14,14,16,16-Hexadecamethylcyclohexadecaneoctasiloxane;1,1,3,3,5,5,7,7,9,9,11,11,13,13,15,15-hexadecamethyl-2,4,6,8,10,12,14,16-octaoxa-1,3,5,7,9,11,13,15-octasilacyclohexadecane
• CAS NO: 556-68-3
• Molecular Formula: C₁₆H₄₈O₈Si₈
• Molecular Weight: 593.23152
• EINECS: 209-137-2
• Mol File: 556-68-3.mol
• Article Data: 4

Chemical Properties

• Melting Point: 31.5°C
• Boiling Point: 168°C/20mmHg(lit.)
• Flash Point: 175.2°C
• Appearance: /solid
• Density: 1.1770
• Vapor Pressure: 0.0037mmHg at 25°C
• Refractive Index: 1.4060
• Storage Temp.: Refrigerator
• Solubility: Benzene, Chloroform (Slightly)
• CAS DataBase Reference: hexadecamethylcyclooctasiloxane(CAS DataBase Reference)
• NIST Chemistry Reference: hexadecamethylcyclooctasiloxane(556-68-3)
• EPA Substance Registry System: hexadecamethylcyclooctasiloxane(556-68-3)

Safety Data

• Hazardous Substances Data: 556-68-3(Hazardous Substances Data)

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

• 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 
• 75-78-5 dimethylsilicon dichloride 
• 78-62-6 diethoxy dimethylsilane 

Relevant articles and documents

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.

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.