Average increase in chain length of crystalline long chain compounds per carbon atom

Abstract

AbstractA comprehensive survey has been made of published crystal X‐ray diffraction data in order to select an authentic overall value ford90, the average increase in chain length of crystalline long chain compounds per carbon atom, for general use in calculating angle of tilt. Data were available for 10 isomorphous homologous series including the normal hydrocarbons, alkanoic acids, primary alcohols, ketones, dicarboxylic acids, symmetrical saturated triglycerides, potassium acid salts, quarter‐hydrates of Na‐1‐alkanesulfonates, hydrazides and the dihydrazides of dicarboxylic acids. The results, supported by data for other specific long chain derivatives show that (a) 1.27 Å is the best value for this constant, and (b) there is no justification for the value 1.30 Å, which has been used in the recent literature as the accepted value in estimating the angle of tilt. The information developed can be used to predict the effective length of one molecule in the crystal of any specific long chain member of any of the homologous series studied.