Hydrogen Bonding of Water in Substances containing the Amide Group

Abstract

IT is generally accepted that the main groups which attract water in the proteins keratin and silk are the amide (NHCO) groups. The partial molar heat of absorption (ΔH) of water at zero water content is −3 kcal/mole referred to liquid water, and this has been considered to represent the excess strength of two OH—O=C hydrogen bonds relative to two OH—O–H bonds in liquid water. Recent work¹ has shown that although other polymers containing the amide group, such as polyvinyl acetamide and polyvinyl butyramide, give a similar result, corresponding simple liquid amides such as N-methyl acetamide and N-n-butyl acetamide give values of ΔH about −1 kcal/mole. This would appear to be a property common to many polar polymers and related “monomers”.