Abstract
Infrared studies of the NC-H stretching frequencies of selected trimethylammonium salts, including acetylcholine, were made in an attempt to obtain evidence that intramolecular NC-H—O hydrogen bonding is responsible for the existence in solution of a quasi-ring conformation for acetylcholine. Acetylcholine and related compounds were also examined by nuclear magnetic resonance spectroscopy. The carbonyl stretching frequencies of an homologous series of acetoxy alkyl sulphones were measured in dioxan solution to gain information on the effect of electron withdrawing substituents in the absence of intermolecular hydrogen bonding. The observed high ester carbonyl absorption frequency in acetylcholine may be interpreted in terms of the inductive effect from the onium nitrogen atom but the results are not incompatible with the existence of a quasi-ring conformation involving C-H—O hydrogen bonding between one of the N-methyl groups and the acetoxy oxygen atom.
摘要:通过红外研究选择性三甲基铵盐(包括乙酰胆碱)的NC-H伸缩频率,试图获得证据表明分子内的NC-H—O氢键是乙酰胆碱在溶液中存在准环构象的原因。乙酰胆碱及相关化合物还通过核磁共振光谱进行了检查。在二氧六环溶液中测量了一系列同系列的乙氧基烷基磺酮的羰基伸缩频率,以了解在无分子间氢键作用下电子吸引取代基的影响。乙酰胆碱中观察到的高酯羰基吸收频率可以解释为来自离子氮原子的归纳效应,但结果与涉及N-甲基基团之一与乙酰氧原子之间的C-H—O氢键作用的准环构象的存在并不矛盾。