84507-45-9Relevant academic research and scientific papers
Silicon Effects. V. β-Silicon Effect in the Solvolysis of 2-Phenylethyl Compounds
Hayakawa, Fumie,Watanabe, Sin-ichiro,Shimizu, Nobujiro,Tsuno, Yuho
, p. 153 - 157 (1993)
The rates of the solvolysis of 2-aryl-2-(trimethylsilyl)ethyl compounds, ArCH(SiMe3)CH2X (4: X=Cl and OCOCF3; Ar=C6H5 and p-MeOC6H4), have been measured in various solvents at 25 deg C.The solvolysis of the chloride, 4 (X=Cl; Ar=C6H5), exhibited an m valu
The Mechanism of the Gas-Phase Pyrolysis of Esters. Part 13. The Very Strong Activating Effects of β-Trialkylmetal Groups
Eaborn, Colin,Mahmoud, Foad M. S.,Taylor, Roger
, p. 1313 - 1320 (2007/10/02)
The rates of gas-phase pyrolysis of β-substituted ethyl acetates AcOCH2CH2X where X=SiMe3, SiEt3, GeEt3, and SiMe2Ph, and of 1-aryl-2-trimethylsilylethyl acetates have each been measured over a minimum of 50 deg C, between 282 and 397 deg C; the rates of pyrolysis of 2-aryldimethylsilylethyl acetates have been measured at 396.9 and 378.2 deg C.The β-organometallic substituents are not themselves eliminated (except at considerably higher temperatures) but strongly accelerate the normal elimination of acetic acid, the relative rates per β-hydrogen at 327 deg C for X being: H, 1.0; SiMe3, 125; SiEt3, 179; GeEt3, 108; SiMe2Ph, 144.These groups appear to activate by a combination of increasing the acidity of the β-hydrogen via stabilisation of the forming β-carbanion through (p->d)? bonding, stabilisation of the incipient α-carbocation by C-X hyperconjugation, and steric acceleration.The effect of substituents in the aryl ring of 1-aryl-2-trimethylsilylethyl acetates gave an excellent correlation with ?+ values with ρ - 0.52 at 327 deg C.The lower ρ-factor for this reaction compared to that for 1-arylethyl acetates (-0.66) is consistent with either conjugative stabilisation of the α-carbocation or increased β-hydrogen acidity.Substituents in the aryl ring of 2-aryldimethylsilylethyl acetates gave a very small positive ρ-factor indicating that overall their effect on β-hydrogen acidity is larger than that on the forming carbocation.The product of pyrolysis of AcO.CH2.CH2.GeEt3 viz.CH2=CHGeEt3 underwent increasingly rapid elimination of successive moieties, believed to be ethylene, in a reaction of stoicheiometry 4.0, which did not occur with the silicon analogue.
