Synopsis.(1) In order to grasp the general trend of isomerization reactions of saturated hydrocarbons, the free energy equations, as a function of temperature convenient for practical calculations, are derived based on one of the more recent data available.The free energy equations of some of the useful reactions such as the formation of neohexane by alkylation, and the formation of isooctane by the coupling (4) Discussions in connection with these thermodynamical calculations for isomerization reactions are presented.(5) Discussions of the isomerization in connection with so-called "Bond Free Energy Equation" of Bruins and Czarnecki are presented.(6) In general, isomerization reactions of hydrocarbons, with few exceptions, are favoured thermodynamically at a lower temperature.(7) Isomerization reactions from simpler structures to more complicated and branched compounds are favoured thermodynamically, more or less, at a lower temperature.(8) In the isomerization reactions of di-or tri-methylated compounds involving merely an exchange of the position of the carbon to which methyl or ethyl groups are attached, a structure which is more non-symmetrical favours the isomerization thermodynamically at a higher temperature.(9) Free energy changes involved in the isomerization reactions are of small magnitude as compared with those of ordinary chemical reactions.(10) The errors involved in the data of the free energy changes of isomerizaticn often amount to a magnitude as big as the free energy change itself. Hence in the selection of data for such calculations, much caution should be taken into consideration.
