Oxygen‐17 NMR study on substituted α, α, α‐trifluoroacetophenones

An excellent linear correlation of oxygen‐17 substituent chemical shifts (SCS) for twelve α, α, α‐trifluoroacetophenones with single σ+ constants, δ = 24·6σ+ + 556·3 (correlation coefficient 0·998) has been observed. However, from this plot, an SCS of 34·3 ppm for 1,1,1‐trifluoroacetone will give a corresponding σ+ (γ+) value of 1·44 for a methyl group, which is not in agreement with 0·63–0·79 obtained from solvolytic rate data.