The enthalpies of formation (Dgr;Hdeg;f) of alcohols, ethers, thiols, thioethers, and amines are expressed as linear combinations of structure parameters. The linear coefficients are determined from experimental Dgr;Hdeg;fusing 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 roothyphen;meanhyphen;square deviations between calculated and experimental values are, respectively, plusmn;0.17 and plusmn;0.25 kcal moleminus;1for 30 gaseous alcohols and ethers, plusmn;0.17 and plusmn;0.25 kcal moleminus;1for 32 liquid and plusmn;0.19 and plusmn;0.27 kcal moleminus;1for 31 gaseous thiols and thioethers, and plusmn;0.12 and plusmn;0.23 kcal moleminus;1for 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 Dgr;Hdeg;fand for estimating enthalpy differences between certain conformers. Those corresponding to the various 1,4 nonbonded interactions indicate that thegaucheCCCC, CCOC, CCNC, CCOH, and CCNH interactions are repulsive, but thegaucheCCCO and CCCN, interactions are attractive. The only 1,5 interactions considered are thegauchendash;gaucheprime 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.
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