1H NMR研究溶质浓度对三碳多元醇水溶液氢键作用以及玻璃化的影响

摘要

为考察溶质浓度对三碳多元醇水溶液氢键作用以及不同物质玻璃态形成能力的影响,采用1H NMR外标法研究不同浓度的1-丙醇(NPA),2-丙醇(IPA),1,2-丙二醇(PG),1,3-丙二醇(PD)和丙三醇(glycerol)的水溶液在室温常压下质子化学位移.结果表明:具有CH3CH(OH)-基团的PG烷基质子的化学位移变化趋势与其他几种醇相比有较大差异.醇羟基质子与水分子的氧形成较强O-H…O氢键.相同摩尔分数下,羟基数的增加导致水质子和羟基质子的化学位移降低,而且羟基位置不同也会导致水质子和羟基质子化学位移差异.这几种三碳多元醇碱性强弱的顺序和降低冰的均相成核温度能力的顺序一致,即glycerol＞PG＞PD＞IPA＞NPA,1H NMR 技术表明glycerol和PG更适合用作低温保护剂.%We investigated the effects of solute concentration on the hydrogen bonding interactions of three-carbon polyalcohol aqueous solutions. In order to inspect the capacity of the solutions to form glass, proton nuclear magnetic resonance (1H NMR) chemical shifts were determined in binary mixtures of water and 1-propanol (NPA), 2-propanol (IPA), 1,2-propanediol (PG), 1,3-propanediol (PD), and glycerol at room temperature and at atmospheric pressure using the external reference method. We found that the alkyl proton chemical shifts of PG with the CH3CH(OH)- group showed biphasic behavior, which was different from other molecules. Water molecules formed relatively strong O - H ? ? ? O hydrogen bonds with the alcohol hydroxyls. The proton chemical shifts of H2O and the hydroxyl protons decrease with an increase in the number of alcohol hydroxyls at the same mole fraction. Moreover, the proton chemical shifts of H2O and hydroxyl protons with the same number of alcohol hydroxyls are different because of their different locations. The order of increased basicity agrees with the order of increased ice homogeneous nucleation suppression, that is, glycerol>PG>PD>IPA>NPA. This explains why glycerol and PG are more suitable as cryoprotective agents (CPAs) among the five polyalcohols.