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Titolo:
Ab initio MO study of benzylic cations. Part 3. Protonated benzoyl derivatives
Autore:
Nakata, K; Fujio, M; Mishima, M; Tsuno, Y; Nishimoto, K;
Indirizzi:
KyushuJapan, Inst Fundamental Res Organ Chem, Higashi Ku, Fukuoka 8128581,Kyushu Univ Fukuoka Japan 8128581 gan Chem, Higashi Ku, Fukuoka 8128581, Inst Fundamental Chem, Kyoto 6068103, Japan Inst Fundamental Chem Kyoto Japan 6068103 tal Chem, Kyoto 6068103, Japan
Titolo Testata:
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
fascicolo: 12, volume: 11, anno: 1998,
pagine: 857 - 870
SICI:
0894-3230(199812)11:12<857:AIMSOB>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
ALPHA-METHYLBENZYL CHLORIDES; INTRINSIC RESONANCE DEMAND; YUKAWA-TSUNO EQUATION; GAS-PHASE BASICITIES; T-BUTYLBENZYL; SUBSTITUENT; SOLVOLYSIS; TOSYLATES; CARBOCATIONS; NITROBENZOATES;
Keywords:
Yukawa-Tsuno equation; substituent effect; alpha-hydroxybenzylic cation; benzoyl compound; ab initio calculation; basicity; proton affinity;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
56
Recensione:
Indirizzi per estratti:
Indirizzo: Fujio, M KyushuFukuokaInst Fundamental Res Organ Chem, Higashi Ku, 6-10-1 Hakozaki, Kyushu Univ 6-10-1 Hakozaki Fukuoka Japan 8128581 10-1 Hakozaki,
Citazione:
K. Nakata et al., "Ab initio MO study of benzylic cations. Part 3. Protonated benzoyl derivatives", J PHYS ORG, 11(12), 1998, pp. 857-870

Abstract

Structures of alpha-hydroxybenzylic cations and their conjugate bases, which cover a wide variation of stability, were optimized by means of ab initio molecular orbital method at the RHF/6-31G* level. Total energies were calculated at the MP2/6-31G*//RHF/6-31G* + ZPE (scaled 0.9) level. Calculated relative proton affinities of the respective neutral molecules (benzoyl compounds; conjugate bases of alpha-hydroxybenzylic cations) agreed well with the corresponding basicities in the gas phase. The geometries of alpha-amino-alpha-hydroxybenzyl and alpha-hydroxy-alpha-dimethylaminobenzyl cations were also optimized at the fixed dihedral angles between the cationic 2p pi orbital and the benzene pi orbital (phi), and between the cationic 2p pi orbital and lone pair electron orbital of the alpha-substituent (theta). The changes in Wiberg bond orders and the rotational potentials about phi and theta showed that the degree of resonance interaction between the cationic center and phenyl ring is balanced by the electronic effects of alpha-substituents in benzylic cations. The obtained theoretical indices of all parent cations such as Mulliken population, Wiberg bond order and bond lengths were correlated linearly with the resonance demand parameter (r value) which were given by the Yukawa-Tsuno substituent effect analysis in the gas phase and in aqueous solution. These relationships are consistent with those for other benzylic cations such as destabilized carbocations and sterically hindered cations studied previously. This confirms that the empirical r value has a definitive physical meaning, i.e. a measure of the resonance interaction between the cationic center and the aryl moiety. (C) 1998 John Wiley & Sons, Ltd.

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Documento generato il 21/09/20 alle ore 12:09:15