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Titolo:
Pressure-dependent NMR spectroscopy indicates that internal rotation of gas-phase formamide follows statistical kinetics
Autore:
Taha, AN; True, NS;
Indirizzi:
Univ Calif Davis, Dept Chem, Davis, CA 95616 USA Univ Calif Davis Davis CA USA 95616 Davis, Dept Chem, Davis, CA 95616 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY A
fascicolo: 38, volume: 104, anno: 2000,
pagine: 8609 - 8616
SICI:
1089-5639(20000928)104:38<8609:PNSITI>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
C-N BOND; INTRAMOLECULAR VIBRATIONAL REDISTRIBUTION; COLLISIONAL ENERGY-TRANSFER; NUCLEAR-MAGNETIC-RESONANCE; RING INVERSION; BIMOLECULAR REGION; HIGH-RESOLUTION; H-1-NMR; MOLECULES; CYCLOHEXANE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
57
Recensione:
Indirizzi per estratti:
Indirizzo: True, NS Univ Calif Davis, Dept Chem, 1 Shields Ave, Davis, CA 95616 USA Univ Calif Davis 1 Shields Ave Davis CA USA 95616 s, CA 95616 USA
Citazione:
A.N. Taha e N.S. True, "Pressure-dependent NMR spectroscopy indicates that internal rotation of gas-phase formamide follows statistical kinetics", J PHYS CH A, 104(38), 2000, pp. 8609-8616

Abstract

Pressure-dependent internal rotation rate constants for [N-15]formamide ingas mixtures containing 1.3 Ton of [N-15]formamide and SF6 pressures ranging from 150 to 5225 Ton were determined from analysis of exchange-broadenedH-1 NMR spectra obtained at 333 K. They agree well with RRKM calculations using experimental vibrational frequencies and rotational constants for theground state and appropriately scaled 6-311++G** parameters for the transition states. The strong collision model, with a hard sphere diameter of 4.8Angstrom, yields satisfactory agreement. Activated formamide molecules have an average calculated energy specific rate constant, [k(E)], of ca. 5.3 x10(9) s(-1) and a state density of ca. 7.2 cm(-1). Statistical internal rotation kinetics requires activated formamide molecules to have vibrational lifetimes of <200 ps and average intervibrational coupling matrix elements of greater than or equal to 0.1 cm(-1). These results are compared to kinetic studies of similar low-energy unimolecular processes.

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Documento generato il 08/07/20 alle ore 23:40:07