No abstract

The data of this investigation give tJ.Hco = -2091.38 ± 0.54 absolute ki lojo ul es (or -499.S5 ± 0.13 kcal) per mole, at 25° C for the heat of combustion of gaseous cyclopropane in oxygen to form gaseous carbon dixoid e and liquid water. i~Tith this value, the heat of formation of gaseous cyclopropane, from solid carbon (graphite) and gaseous hydrogen each in its thermodynamic standard reference state, is calculated to be tJ.Hr = + 12.74 ± 0.14 kcal/ mole, at 25° C. The heat of isomerization of gaseous cyclopropane into ga eous propylene is calculated to be tJ. 1' [0 = -7.86 ± O.lS kcal/mole, at 25° C.

The data of the present investigation give for the heats evolved in the combustion of gaseous ethylene and propylene in oxygen, at 25° C and a constant pressure of 1 atmosphere, to form gaseous carbon dioxide and liquid water, the following values in international kilojoules p er mole: ethylene, 1410.97 ± 0.30; propylene, 2057.42 ± 0.62. Converted to kilocalories by means of the factor 1/4.1833, these values become, respectively, 337.28 ± 0.07 and 491.82 ± 0.15 kilocalories p er mole.A review of the existing data indicates that the hitherto " best" values for the heats of combustion of these ga~es differ fron the values obtained in the prese nt investigation by -1.6 percent for ethylene and -0.4 percent for propylene. These differences are, res pectively, about 75 and 12 times the estimated uncertainties in the new values.

Calorimetric measurements of the ratio of the heat evolved in the formation of 1 mole of liquid deuterium oxide, from gaseous deuterium and ordinary oxygen, to the heat evolved in the formation of 1 mole of ordinary liquid water, from gaseous ordinary hydrogen and oxygen, yielded the value 1.030 68 ± 0.000 29 for 25° C and a constant pressure of 1 atmosphere.Calorimetric measurements of the ratio of the heat of vaporization of 1 mole of deuterium oxide to that of 1 mole of ordinary water yielded the value 1.031 45 ± 0.00075 for 25° C and zero pressure. On the assumption that the bond energies in H~ and D, are the same, and likewise in H~O and D20, the difference in the zero-point energies of H~O(g) and D20(g) was calculated to be 14,841 ± 91 into j/mole (3,548 ± 22 cal/mole, or 1,243.0 ± 7.6 wave numbers). The accord of this value with that recently calculated by Darling and Dennison from the vibrational-rotational spectra of deuterium oxide and protium oxide, 1,245.5 ± 2.0 wave numbers, indicates that, within the assigned limits of uncertainty, the respective bond energies are independent of the mass of the nucleus of the atom .

Measurements of the heats of combustion of gaseous tetramethylmethane (neopentane) and gaseous 2-methylbutane (isopentane) in oxygen, at 25° C and a constant total pressure of 1 atmosphere, to form gaseous carbon dioxide and liquid water, yielded the following values in into kj/mole: tetramethylmethane, 3516.53 ±0.94; 2-methylbutane, 3528.03 ±0.62. Converted to kilocalories by means of the factor 1/4.1833, these values become, respectively, 840.61 ± 0.23 and 843.36 ±0.15 kcal/mole.Combination of these values with those previollsly reported from this laboratory for normal pentane shows that, in the gaseous state at 25° C and 1 atmosphere, the energy content of n ormal pentane is greater than that of 2-methylbutane by 8.09 ± 1.08 kit or 1.93 ± 0.26 kcal. per mole, and greater than that of tetramethylmethane by 19.59 ± 1.29 kj, or 4.68 ± 0.31 kcal, per mole.

Vol. 68 butyl peroxides have also been prepared having ¿-butyl alcohol of crystallization.3. The pyrolysis of ¿-butyl hydroperoxide has been studied at 95-100°and at 250°. At 95-100°¿ -butyl alcohol and oxygen are the only products formed, while at 250°the products formed are acetone, methyl alcohol, ¿-butyl alcohol, formaldehyde and water.4. The pyrolysis of di-¿-butyl peroxide has been studied at 200, 250 and 300°. Acetone and ethane are the only products formed.5. A free radical mechanism has been proposed to explain the pyrolysis of both ¿-butyl hydroperoxide and di-¿-butyl peroxide.Cambridge 39, Massachusetts

No abstract

The existing thermochemical data on the normal olefin (al kene-I) hydrocarbons are reviewed and conelated. These data are used in conjunction with the value previously proposea for the increase in the heat content per added CH2 group to obtain values for those members of this series of hydrocarbons for which no calorimetric data exist. For all these hydrocarbons in the gaseous state, selected "best" values are given for the h eats of combustion at 25°C and for the heats of formation, from solid carbon and gaseous hydrogen , at 25°C and OOK.As in the case of the previously reported values for the normal paraffin hydrocarbons and primary normal alkyl alcohols, the h eats of formation of the gaseous normal olefin (alkene-I ) hydrocarbons can he r epresented by means of an expression of the form t::.H = A+ Bn+t::., where t::.1-1 is the heat of formation, A and B are constant for a given temperature, n is the num be r of carbon atoms in the molecule Cn H2n, and t::. is the t erm giving the deviation from linearity, which is zero for n> 5. Values of the constants A and B and of t::. are given both for 25° C and 0° K.