Reliability of k Values

It is appropriate to estimate the error involved in such a complex procedure. The simplest empirical approach is to compare standard rate coefficients calculated for the same compound from different sets of data (at different temperatures or from different areas of the rate profiles). Most of the variation lies within 0.3 log units from the mean value, and it has therefore been assumed that the maximum error should be 0.35 log units [78JCS(P2)861], this being subject to the qualification noted above regarding the assumption of a constant AH value. 

Support for the reliability of the standard rate coefficients so defined is given by the results obtained by applying the standard procedures to the few data for exchange (of benzene derivatives) in mineral acids other than sulfuric acid The extrapolated standard rate coefficients agree within a factor of 5 or better [73JCS(P2)1077]. 

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