On the Thermochemistry of Organic Compounds

Abstract

A discussion of different arguments on the dissociation energy of CO and on the role of the 5S state of carbon is given. The consistency of the 169.735 kcal./mole value of the heat of sublimation of carbon into 5S carbon atoms given by Gerö in spite of some arguments of Long and Norrish is shown. The energy required to rupture ethane into two methyl radicals results to be {C–C}ethane=82.78 kcal./mole, in excellent agreement with the value which can be obtained by a cycle proposed by Van Artsdalen without the use of the heat of sublimation value of carbon. The difference of the mean C–C bond energies in diamond and in the higher members of the paraffin series is 2.04 kcal./mole. The energy required to rupture the double bond in 1-heptene, {C=C}1-heptene=145.43 kcal./mole, in 2-methyl−1-butene {C=C}2-methyl−1-butene=148.70 kcal./mole. In the acetylene hydrocarbons {C≡C}1-pentyne=198.67 kcal./mole, {C≡C}acetylene=194.28 kcal./mole.