EXPERIMENTAL STUDIES OF THE ANOMERIC EFFECT .5. THE INFLUENCE OF SOME SOLVENTS ON THE CONFORMATIONAL EQUILIBRIA IN 2-METHOXY-TETRAHYDROPYRAN AND 2-(2', 2', 2'-TRIFLUOROETHOXY)-TETRAHYDROPYRAN

被引：18

作者：

BOOTH, H

DIXON, JM

READSHAW, SA

机构：

[1] Department of Chemistry, University of Nottingham, Nottingham

来源：

TETRAHEDRON | 1992年 / 48卷 / 29期

关键词：

D O I：

10.1016/S0040-4020(01)89861-6

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

The DELTA-H-degrees(a-->e) and DELTA-S-degrees(a-->e) values for conformational equilibria in 2-methoxytetrahydropyran have been determined by variable temperature nmr spectroscopy in solvents CD2Cl2, ether/CD2Cl2, ether/toluene and ether/methanol, whilst the corresponding values for conformational equilibria in 2-(2',2',2'-trifluoroethoxy)-tetrahydropyran have been determined in ether/toluene and ether/methanol. Replacement of toluene and methanol causes increases in DELTA-H-degrees(a-->e) and DELTA-S-degrees(a-->e). These changes are consistent with a preferential hydrogen bonding of methanol to axial alkoxy groups, causing a decrease in both entropy and enthalpy of axial conformations relative to their equatorial counterparts. The enthalpy decrease is probably a result of an enhancement of the stabilising endoanomeric effect.

引用

页码：6151 / 6160

页数：10

共 14 条

[1] CALORIMETRIC DETERMINATION OF CONFORMATIONAL ENTHALPY AND ENTROPY OF 2-PHENYL-1,3-DIOXANE - EFFECTIVELY FREE ROTATION OF AN EQUATORIAL 2-PHENYL GROUP - CONFORMATIONAL EQUILIBRIA IN 2,2-DISUBSTITUTED 1,3-DIOXANES [J].