4-Methoxy-phenol acidity constant

The chemical information available through LFER is primarily the reaction constant p, but this value depends upon the substituent constants selected for the construction of the LFER. The u values available are ct, ct", ct" or and Ui, these quantities are listed, for many substituents, in Tables 7-1, 7-3, 7-4, 7-6, and 7-7. A reasonable approach is to plot log k against the substituent constant defined by a standard reaction that is expected to be most like the reaction under study. It is also reasonable to plot log k against several of the ct quantities, seeking the best correlation. [In choosing between two types of substituent constants, it is necessary to make use of substituents for which the two scales (say ct and rr, for example) are not themselves correlated, for otherwise both LFERs will be acceptable. ] The ct or o constants should be applicable to reactions that do not combine reaction sites and para substituents of the + and — type (push-pull systems capable of through resonance) for example, one would not expect ct" or o to provide good correlations for reactions of phenols or anilines substituted with nitro or cyano or for reactions of benzoic acids substituted with amino or methoxy. 

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