AbstractThe enthalpies of formation of the condensed phase and gaseousN,N‐dimethyl derivatives of pivalamide, 1‐adamantylcarboxamide and benzamide were determined by combustion calorimetry and the associated enthalpies of vaporization and sublimation. The enthalpies of formation of styrene and its α‐, trans‐β‐ and β,β‐methylated derivatives were determined from measurements of their enthalpies of hydrogenation in dilute hydrocarbon solution. Strain and resonance effects of amides and alkenes are discussed in terms of the exo‐/endothermicity of the following reactions:and in terms of the difference of enthalpies of formation of the isomeric (Z