Bonded and nonbonded interactions in saturated alcohols, ethers, thiols, thioethers, and amines

Abstract

The enthalpies of formation (ΔH°f) of alcohols, ethers, thiols, thioethers, and amines are expressed as linear combinations of structure parameters. The linear coefficients are determined from experimental ΔH°f using the least squares criterion. For these calculations eight structure parameters are used for thiols and thioethers, nine for amines, and ten for alcohols and ethers. The mean and root-mean-square deviations between calculated and experimental values are, respectively, ±0.17 and ±0.25 kcal mole−1 for 30 gaseous alcohols and ethers, ±0.17 and ±0.25 kcal mole−1 for 32 liquid and ±0.19 and ±0.27 kcal mole−1 for 31 gaseous thiols and thioethers, and ±0.12 and ±0.23 kcal mole−1 for 18 liquid amines. Liquid phase data of 28 alcohols and ethers and gas phase data of 13 amines are also treated with this model but the results are not satisfactory. The linear coefficients may be used for predicting unknown ΔH°f and for estimating enthalpy differences between certain conformers. Those corresponding to the various 1,4 nonbonded interactions indicate that the gauche CCCC, CCOC, CCNC, CCOH, and CCNH interactions are repulsive, but the gauche CCCO and CCCN, interactions are attractive. The only 1,5 interactions considered are the gauche–gauche prime CCOCC and CCSCC interactions and they are found highly repulsive. The relative stability of conformers predicted on the basis of these nonbonded interactions agrees quite well with results from experiments and molecular orbital calculations.