Thermodynamic Properties of Gaseous 1,3-Butadiene and the Normal Butenes above 25°C Equilibria in the System 1,3-Butadiene, n-Butenes, and n-Butane

Abstract

Tables of the thermodynamic functions C_p⁰, H⁰, S⁰, and F⁰ are given for 1,3‐butadiene and the normal butenes for temperatures from 298.16°K to 1500°K for the substances in the ideal gas states at one atmosphere pressure. These have been prepared using reliable spectroscopic and molecular data, together with calorimetric entropies, gaseous specific heats, and heats of formation. Equilibrium constants are given for reactions in the system 1,3‐butadiene, n‐butenes, and n‐butane. Available experimental data are compared with the calculations. The calorimetric data for 1,3‐butadiene furnish strong evidence for the existence of two geometric (cis‐trans) isomeric forms of 1,3‐butadiene in appreciable concentrations at room temperatures. The two forms differ in energy by 2.3 kcal. mole⁻¹, and are separated by a C–C rotational barrier 2.6 kcal. mole⁻¹ above the lowest energy level of the cis, or higher, energy form.