The connection between the zig-zag structure of the hydrocarbon chain and the alternations in the properties of odd and even numbered chain compounds

Abstract

X-ray investigation of a single crystal on n-C₂₉H⁶⁰ has shown that the CH₂ groups of the chain molecule lie equally spaced on two parallel rows, the lines between successive centres thus forming a zig-zag. Analysis of X-ray photographs of similar substances leaves no doubt that the same chain persists not only through a whole series of hydrocarbons, but is also present in a large number of other carbon chain compounds. The object of this paper is to show how a number of observations on their physical properties are connected with the zig-zag structure of the chain molecule. The following fig. 1 represents a section through a crystal. X-rays show that the chains lie side by side, the parallel lines in the drawing being the chain axes. The ends of the molecules, marked by small circles, arrange themselves in equidistant parallel layers. In the following deductions we consider molecules in which the two end groups are chemically identical, such as hydrocarbons, dibasic acids, etc.