The Entropy of Long Chain Compounds in the Gaseous State

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Abstract
Equations are derived for the entropy of long chain compounds in the gaseous state at 25°C. (1) The translational entropy, computed classically, varies with chain length according to the relation St=a+b ln n. (2) The entropy of rotation of the molecule as a whole, calculated statistically, assuming either a ball‐like molecule or absolutely random kinking, is also linear with respect to ln n. (3) The entropy of internal vibrations, assumed (following Pitzer) to be an additive function of contributions associated with the various types of bonds and bond angles present, obeys the equation Siv=a+bn. (4) The entropy of internal randomness, for randomly‐kinked molecules with no rotation, with hindered rotation, or with completely free rotation, is likewise linear in n. The equation deduced for long chain paraffins, containing but one adjustable constant (connected with the degree of hindrance of the rotation about the C–C bonds) agrees quite well with values deduced from specific heat data for short chain paraffins.