The Effect of Structure on the Reactivity of Some Organic Halogen Compounds.

Abstract

Laws that govern the reactivity of organic compounds are still unknown, although countless studies have been made on the various phases of isolated systems. On account of the important r81e of organic halogen compounds in organic synthesis there has been a never-ceasing endeavor to learn the laws governing the reactivity of this group. Up to the present time the rates of reaction can be predicted in only a few cases.Thermodynamics has given much information on the free energy and heat of combustion of organic compounds, but for the halogen compounds the available data of this type are of doubtful reliability; however, there is every reason to anticipate that reliable data will be available in the near future. The free energy and the heat of combustion data have aided little in solving the question of the time which a reaction will require to reach equilibrium. For a solution of this question theoretical speculation is directed toward the energy of activation. There is no general law known for the calculation of the energy of activation. From temperature coefficient data values of the energy of activation are calculated, but such values are restricted to the experimental accuracy of the data. These values of the energy of activation sometimes differ from the values obtained from spectroscopic data. This disparity of values emphasizes the possibility that energy factors other than the energy of activation may be entering into the values obtained. It has not been proven that the actual energy required to break the bond is the same as the energy of activation, and so far theory has not taken this factor into account. Nor have the number of degrees of freedom among which the energy must be distributed before reaction may occur been taken out from the realm of speculation. It is not surprising, therefore, that so little has been known about the fundamental nature of the reactivities of compounds.

A History of the Double-Bond Rule

“…The broader implications of the phenomenon, however, were also becoming apparent to others, usually without reference to the rule presented by Schmidt. Just before Schmidt's 1935 article in Chemical Reviews, Edith Wilson (25) reviewed previous work (Wislicenus, Clarke, Conant, etc.) and presented new correlations suggesting the unusually high reactivity of allyl-type halides and the unusually low reactivity of vinyl-type halides compared to simple saturated alkyl halides.…”