Organomagnesium Bromides Containing Heteroatoms

Enthalpies of formation of the magnesium bromide salts of the Bronsted acids are calculated from the measured enthalpies of the reaction of the Bronsted acid, HB, with pentylmagnesium bromide and the known enthalpies of formation of pentyhnagnesium bromide and pentane according to equation 11. Because some of the HB enthalpies of formation have been revised and others newly measured since the original publication, the BMgBr enthalpies of formation have been recalculated and appear in Table 4.  

There remain three Bronsted acids that have no liquid phase enthalpy of formation data that we know of dodecanethiol, cyclohexyl methyl amine and A-methyl dodecanamide. Although the enthalpy of formation of 1-dodecanethiol has not been measured, there are experimental values available for other members of its homologous series, C2-C7, Cjo. From a weighted least-squares analysis of the data from which a slope, —25.4, and an intercept, —23.3, are derived, the enthalpy of formation of dodecanethiol is —328.1 kJ moH The enthalpy of formation of dodecanethiolate magnesium bromide is thus estimated as —744.6 kJmoH. We can estimate the enthalpy of formation of cyclohexyl methyl amine by assuming equation 12 is thermoneutral. 

From the archival enthalpies of formation of the other species, the enthalpy of formation of cyclohexyl methyl amine is —145.4 kJmoH. From equation 11, the enthalpy of formation of the corresponding salt is —501.2 kJmoH. Attempts to estimate an enthalpy of formation for A-methyldodecanamide reveals a paucity of data to work with, primarily for unsubstituted and A-methylamides . There is much enthalpy of formation data for w-alkyl carboxylic acids, including dodecanoic acid. The methylene increment 

Joel F. Liebman, Torkil Holm and Suzanne W. Slayden 

Within the O—MgBr group are at least three subcategories the alkoxy and phenoxy, the carboxy and the fluorinated species. Within the alkoxy subgroup, the endothermic 

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