Solvent and structure effects on rotamerization in 3,4-alkylenedioxy- and 3,4-dialkoxy-2,5-bis[di(<i>tert</i>-butyl) hydroxymethyl]thiophenes: an NMR, IR, molecular mechanics and single-crystal x-ray study
作者:John S. Lomas、Jacqueline Vaissermann
DOI:10.1002/poc.696
日期:2004.2
Solvent effects on the rotational equilibria of two-rotor systems consisting of 3,4-alkylenedioxy- and 3,4-dialkoxy-2,5-bis[di(tert-butyl)hydroxymethyl]thiophenes have been investigated. In these systems there are three rotational isomers: syn,syn (SS); anti,syn (AS or SA) and anti,anti (AA) (syn, [free] hydroxy group; anti, intramolecularly hydrogen-bonded hydroxy group). In non-hydrogen-bonding solvents
已研究了溶剂对由3,4-亚烷基二氧基和3,4-二烷氧基-2,5-双[二(二(叔丁基)羟甲基)噻吩组成的两转子系统的旋转平衡的影响。在这些系统中,存在三种旋转异构体:syn,syn(SS); 反,顺式(AS或SA)和抗,抗(AA)(顺式,[游离]羟基;抗,分子内氢-键合的羟基基团)。在非氢键溶剂(如氯仿和苯)中,AA对于较大的桥(三个或四个亚甲基)和二烷氧基衍生物,优选旋转异构体,AS / SA是次要成分,SS几乎不可检测。相反,3,4-亚甲基二氧基噻吩衍生物主要是SS,AS / SA较小,只是可以感知。3,4-乙撑二氧噻吩(EDOT)衍生物以相似的量显示所有三个异构体。在氢键受体溶剂,如吡啶和DMSO中,两个均衡AA ⇋ AS / SA和AS / SA ⇋ SS移赞成AS / SA和SS分别形式。平衡常数K 1K 2和K 2对溶剂氢键碱度的敏感性不同,后者的敏感性比前者低约25%(log /