红外光谱法研究液态邻位取代的苯甲酸类衍生物的氢键行为

用红外光谱法研究了高温下熔融态的邻位取代苯甲酸衍生物的氢键行为。邻卤(F,Cl,Br,I)苯甲酸在固态时以羧基二聚体形式存在,熔融后二聚体部分解聚,仍有部分分子以二聚体形式存在。固态和液态邻乙氧基苯甲酸的红外吸收无明显差异,表明两者均为分子内氢键的结构。固态邻甲氧基苯甲酸以羧基二聚体形式存在,其熔融后二聚体全部解聚形成了分子内氢键,即甲氧基的氧与羧基的氢形成了氢键。

INFRARED STUDY ON THE HYDROGEN-BONDING BEHAVIOR OF ORTHO SUBSTITUTED BENZOIC ACIDS IN THE LIQUID STATE

IR spectroscopy has been used to study the hydrogen-bonding behavior of ortho substituted benzoic acids. Carboxyl dimers, which exist in the solid state o-halogen benzoic acid and benzoic acid, dissociate partially in the melt form, but some dimers still exist. In the solid and liquid states, the o-ethoxybenzoic acid has intramolecular H-bonding structure, shown by the identity of the spectra in the two states. By comparing the similarity and difference of spectra of o-methoxy and o-ethoxy benzoic acids in the melt form and in CCl_4, we concluded that o-methoxybenzoic acid in the solid state exists as carboxyl dimers, the carboxyl dimers dissociate at melting and the hydrogen of carboxyl group forms H-bonding with oxygen atom of the methoxy group in the liquid state.