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Titolo:
ALKENE TRIPLETS AS 1,2-BIRADICALS - THE PHOTOADDITION OF P-ACETYLSTYRENE TO STYRENE
Autore:
CALDWELL RA; DIAZ JF; HRNCIR DC; UNETT DJ;
Indirizzi:
UNIV TEXAS,DEPT CHEM RICHARDSON TX 75083
Titolo Testata:
Journal of the American Chemical Society
fascicolo: 18, volume: 116, anno: 1994,
pagine: 8138 - 8145
SICI:
0002-7863(1994)116:18<8138:ATA1-T>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
ABSOLUTE RATE CONSTANTS; ALKYL RADICALS; TETRAMETHYLENE DIRADICALS; LIFETIMES; KINETICS; THERMOCHEMISTRY; ENERGIES; OLEFINS; KETONES; SYSTEM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
60
Recensione:
Indirizzi per estratti:
Citazione:
R.A. Caldwell et al., "ALKENE TRIPLETS AS 1,2-BIRADICALS - THE PHOTOADDITION OF P-ACETYLSTYRENE TO STYRENE", Journal of the American Chemical Society, 116(18), 1994, pp. 8138-8145

Abstract

The photoaddition of p-acetylstyrene (PAS) triplet to styrene (STY) has been studied. Direct irradiation of PAS in the presence of styrene yielded trans-1-(4-acetylphenyl)-2-phenylcyclobutane, an expected addition product, its cis isomer, and 1-(4-acetylphenyl)-1,2,3,4-tetrahydronaphthalene. The rate of addition of (3)PAS to styrene was determinedby laser flash photolysis to be 3.2 X 10(6) M(-1) s(-1), and by quantum yield measurements as 2.0 X 10(6) M(-1) s(-1). The rate is 1 order of magnitude greater than that of addition of a primary alkyl radical to styrene and thus in only fair agreement with the 1,2-biradical model. The reaction of 3PAS with p-methoxystyrene is even faster. A rough estimate of the rate constant for (STY)-S-3 + STY is in better agreement with expectation. The possible involvement of a weak exciplex between the perpendicular PAS triplet and the styrene ground state is suggested to rationalize the rate enhancement. The validity of the 1,2-biradical representation of alkene triplets is discussed.

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Documento generato il 02/12/20 alle ore 15:03:29