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Titolo:
Molecular orbital study of the conformational energies (-Delta G degrees or A values) of 2-alkyltetrahydro-2H-thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes)
Autore:
Freeman, F; Phornvoranunt, A; Hehre, WJ;
Indirizzi:
Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA Univ Calif Irvine Irvine CA USA 92697 ne, Dept Chem, Irvine, CA 92697 USA Wavefunct Inc, Irvine, CA 92612 USA Wavefunct Inc Irvine CA USA 92612Wavefunct Inc, Irvine, CA 92612 USA
Titolo Testata:
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
fascicolo: 3, volume: 12, anno: 1999,
pagine: 176 - 186
SICI:
0894-3230(199903)12:3<176:MOSOTC>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
ROTATIONAL BARRIERS; MECHANICS; 3,6-DIHYDRO-1,2-DITHIIN; CYCLOHEXANE;
Keywords:
conformational energy; 2-alkyltetrahydro-2H-thiopyrans; tetrahydrothiopyrans; thiacyclohexanes; thianes; molecular orbital study;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
54
Recensione:
Indirizzi per estratti:
Indirizzo: Freeman, F Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA Univ Calif Irvine Irvine CA USA 92697 em, Irvine, CA 92697 USA
Citazione:
F. Freeman et al., "Molecular orbital study of the conformational energies (-Delta G degrees or A values) of 2-alkyltetrahydro-2H-thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes)", J PHYS ORG, 12(3), 1999, pp. 176-186

Abstract

Ab initio 6-31G* and MP2/6-31G*//6-31G* methods and density functional (pBPDN**) theory were used to calculate the geometries and relative energies of the chair, boat, and twist-boat conformations of tetrahydro-2H-thiopyrans(tetrahydrothiopyrans, thiacyclohexanes, thianes). The chair conformation of thiacyclohexane is 5.3 and 8.0 kcal mol(-1), respectively, (1 kcal = 4.184 kJ) more stable than the twist-boat and boat structures at the MP2/6-31G* 6-31G* level. Ab initio methods were used to calculate the relative energies of the rotamers in the chair conformations of 2-alkylthiacyclohexanes (CH3, C2H5, i-C3H7, t-C4H9, neo-C5H11, SiMe3). The MP2/6-31G*// 6-31G* conformational energies (-Delta G degrees or A values, kcal mol(-1)) of the 2-alkylthiacyclohexanes (Me = 1.00; Et = 1.16; i-Pr = 1.02; t-Bu = 3.56; neo-Pent = 1.04; SiMe3 = 2.05) are smaller than those calculated for the corresponding alkylcyclohexanes and 4-alkylthiacyclohexanes. Plots of the calculated conformational energies (-Delta G degrees) for the 2-alkylthiacyclohexanes versus the calculated conformational energies for the corresponding alkylcyclohexanes are linear (slope = 0.680 and r = 0.983 for 6-31G* and slope =0.667 and r = 0.989 for MP2/6-31G*// 6-31G*). The C(2)-S(1) bond lengths are in the range 1.827-1.840 Angstrom and the C(6)S(1) bond lengths are in the range 1.815-1.819 Angstrom. With the exception of the axial 2-t-Bu substituent (103.0 degrees), the C-S-C angles vary from 98.6 degrees to 100.4 degrees. The S(1)-C(2)-C(7) angle in the most stable axial conformer is larger that the corresponding angle in its most stable equatorial conformer. Copyright (C) 1999 John Wiley & Sons, Ltd.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 10/07/20 alle ore 11:06:26