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Titolo:
Gas-phase acidities of aryldimethylsilanes
Autore:
Irie, M; Kikukawa, K; Shimizu, N; Mishima, M;
Indirizzi:
Kyushu Univ, Inst Fundamental Res Organ Chem, Higashi Ku, Fukuoka 8128581,Japan Kyushu Univ Fukuoka Japan 8128581 hem, Higashi Ku, Fukuoka 8128581,Japan Kyushu Univ, Fac Sci, Dept Chem, Higashi Ku, Fukuoka 8128581, Japan KyushuUniv Fukuoka Japan 8128581 em, Higashi Ku, Fukuoka 8128581, Japan Kinki Univ, Grad Sch Adv Technol, Iizuka, Fukuoka 8200055, Japan Kinki Univ Iizuka Fukuoka Japan 8200055 l, Iizuka, Fukuoka 8200055, Japan
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
fascicolo: 6, , anno: 2001,
pagine: 923 - 928
SICI:
1472-779X(2001):6<923:GAOA>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-AFFINITIES; SUBSTITUENT; BASICITIES; PHENOLS; ANIONS; SILANE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
31
Recensione:
Indirizzi per estratti:
Indirizzo: Mishima, M Kyushu Univ, Inst Fundamental Res Organ Chem, Higashi Ku, Fukuoka 8128581,Japan Kyushu Univ Fukuoka Japan 8128581 i Ku, Fukuoka 8128581,Japan
Citazione:
M. Irie et al., "Gas-phase acidities of aryldimethylsilanes", J CHEM S P2, (6), 2001, pp. 923-928

Abstract

Gas-phase acidities of aryldimethylsilanes have been determined by measuring equilibrium constants of proton-transfer reactions using a FT ion cyclotron resonance mass spectrometer. The acidity of dimethylphenylsilane was found to be 370.5 kcal mol(-1), i.e., it is a stronger acid than dimethylsilane by 2.7 kcal mol(-1). The acid-enhancing effect of the phenyl group is significantly smaller than in the carbon analog. In addition, the acidities of aryldimethylsilanes were linearly correlated with the standard substituent constant (sigma degrees), giving a rho of 4.6, indicating that the thermodynamic stabilities of silyl anions are less sensitive to the polar effectsof substituents than benzoate, phenoxide, anilide, and benzyl anions. Moreimportantly, it was found that the p-nitro group, which has a large pi -electron-accepting ability, also conforms to the sigma degrees correlation, suggesting that pi -delocalization does not play a role in the stabilizationof silyl anions; this is in contrast to the pi -effects observed in carbonanalogs. This is supported by theoretical stabilization energies and optimized geometrical features based on ab initio calculations.

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Documento generato il 20/09/20 alle ore 07:43:21