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. Can. J. Chem. 60, 1953Chem. 60, (1982. Enthalpies of solution of representative ketones, phenols, alcohols, and ethers have been determined in a,a,a-trifluorotoluene, benzene, toluene, and mesitylene, and combined with heats of vaporization to give enthalpies of transfer from vapor to the aromatic solvents [AH(v+S)]. Comparison of these values with AH(v-+S) of nonpolar model compounds provides an estimate of the special interactions (dipole -induced dipole or charge transfer, and hydrogen bonding) of the polar solutes with each aromatic solvent. Unless the model compound is perfectly matched, an alternative procedure, the pure base method, is superior for evaluating hydrogen bonding.The special interactions of ketones and ethers with aromatic solvents increase with decreasing x electron density of the solvent.By contrast, m-cresol shows the strongest special interaction with the most electron-rich solvent (mesitylene > toluene > benzene > trifluorotoluene). These results demonstrate that -OH and -OR groups undergo quite different interactions, and that a distinctive interaction occurs between the hydroxyl group and the aromatic ring.Calorimetric heats of vaporization have been measured for the solutes n-butyl ether (10.68 + 0.02kcal/mol), 2,2,4,4-tetramethylpentane (9.20 + 0.03), n-pentane (6.36 0.02), 1-butanol (12.46 + 0.00), and 2-methyl-2-butanol(11.94 + 0.02). On a mesure par calorimttrie les chaleurs de vaporisation des solutes: ether 11-butylique (10,68 + 0,02 kcal/mol), tetramethyl-2,2,4,4 pentane (9,20 + 0,03), 11-pentane (6,36 + 0,02), butanol-1 (12,46 + 0,OO) et methyl-2 butanol-2 (1 1.94 +_ 0,02).[Traduit par le journal]

A recently developed gc–calorimetry procedure involving a combination of gas chromatography and heat of solution measurements has been used to measure heats of vaporization of 17 esters, including methyl 2,2-dimethylpropanoate, butyl acetate, glyceryl triacetate, diethyl phthalate, methyl 9-octadecenoate, and 12 methyl esters of C3- to C15-fatty acids. Comparison with measurements of ΔHv reported in the literature indicates that the gc–calorimetry method often has smaller uncertainties in measurements (0.25 to 1.00 kJ mol−1) and more consistent methylene increments for the series of fatty acid methyl esters. Two of the experimental ΔHv measurements which differ appreciably from recent literature values have been verified by vaporization calorimetry.

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Dc,pcrriritetti c!f Clr~ttti.si~:\*, Utri~r~'siiy oJ'Hor,.siott. Horr.siori, TX 7700-1, U . S . A Received January 16, 1979 RICHARD FUCHS and L. ALAN PEACOCK. Can. J. Chem. 57.2302Chem. 57. ( 1979. The heats of vaporization of I-methylcyclopentene, 3-methylcyclopentene, ethylidenecyclopentane, 1-ethylcyclopentene, methylenecyclohexane, allylcyclopentane, vinylcyclohexane, ethylidenecyclohexane, allylcyclohexane, 3,3-diethylpentane, 2,2,4,4-tetramethylpentane, and trnns-2,2,5,5-tetramethyl-3-hexene have been measured by the gas chromatography -calorimetry method. These values have been combined with previously reported liquid heats of formation to give gaseous values of AH,. The results indicate that the internal double bond is favored by about 0.5 kcal over the exo in both 5-and 6-membered rings, but the endo-exo differences are much smaller than previously believed. Several of the liquid heat capacities that were measured were not well predicted by group additivity schemes.RICHARD FUCHS et L. ALAN PEACOCK. Can. J. Chem. 57.2302Chem. 57. (1979. Utilisant une niethode combinant la chromatographie en phase gazeuse et la calorimetric, on a mesure les chaleurs de vaporisation des hydrocarbures suivants: niCthyl-1 cyclopentene, methyl-3 cyclopentene, ethylidenecyclopentane, ethyl-1 cyclopentene, mCthyltnecyclohexane, allylcyclopentane, vinylcyclohexane, tthylidenecyclohexane, allylcyclohexane, diethyl-3,3 pentane, tetramethyl-2,2,4,4 pentane et tttramtthyl-2,2,5,5 hexene-3 trnns. On a combine ces valeurs avec les chaleurs deformation de ces liquides qui avaient Ctt rapporttes anterieurement afin d'en tirer les valeurs de AH, en phase gazeuse. Les resultats indiquent que les doubles liaisons internes sont favorisees par environ 0.5 kcal/mol par rapport aux doubles liaisons exo dans les cycles a 5 et a 6 chainons; toutefois la difference entre ettdo et exo est beaucoup plus faible que ce qu'on croyait anterieurement. En se basant sur les schkmas d'additivite des groupes, il aurait ete impossible de predire adtquatement plusieurs des capacites calorifiques mesurkes.[Traduit par le journal]A much discussed conceDt more than two decades ago was the idea that the internal (endocyclic) double bond is thermodynamically favored over the exocyclic double bond in six-membered ring systems, whereas the reverse was believed to be true in fivemembered rings (1). However, Turner and Garner (2) measured the heat of hydrogenation (acetic acid solution, 25°C) of 1-methylcyclohexene, methylenecyclohexane, 1-methylcyclopentene, and methylenecyclopentane, and found that hydrogenation of the exo double bond is more exothermic in both the five-membered ring (by 3.7 kcal/mol) and sixmembered ring (2