Summary of Data for Methyl-substituted Compounds

To summarize the thermodynamic findings of these ionization processes, Laidler has made the following points. 

Firstly the fact that free energies for these processes in solution are quite strictly additive, whereas AH and TAB values are not, implies that AG is tx simpler function than are AH and TAB, Secondly the existence of these linear free energy relationships in cases where there arc no such relationships for ilif and TAB requires that the latter functions are affected by factors that leave A G unchanged. Since AG is the difference between A H and TA B this can only be so if certain factors influence AH and in a compensating manner so that there is little effect on AO, It is suggested that these factors are those associated with steric and solvent-sohite interactions. 

Variations in zl S and AS have been accounted for by the following three effects  

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