MnO4 -oxidation of 5-X-furfurals: Rate data of MnO4 -oxidation of 5-X-furfurals in aqueous neutral medium correlated well with all the Hammett and Taft substituent constants for which we could not give any explanation. Yet the correlation with Hammett σmeta is slightly better (R = 0.9975) than the other two. This could be possible as the substituent and the functional group are separated by a pair of non-bonded electrons which come from oxygen (see scheme 3 structure E and F).