The replacement substituent constants sigma(+), for some five-membered heteroaromatic rings were determined from O-17 NMR substituent chemical shifts of the carbonyl group in trifluoroacetyl derivatives, and from log ks for solvolyses of heteroaryl analogs of 1-tert-butylbenzyl bromide and chloride. No agreement with literature values could be found. Preliminary accounts of such observations are given.
