6238was determined as a function of concentration [(0.94 -25.16) X MI relative to the chloroform signal at 7 2.73 (727 Hz downfield from TMS) (Figure 4). The spectra of the acetates (I and 11, coupling constants were determined either from first-order analyses or from appropriate ABX approximation^.^^ R = Ac) also were obtained in carbon tetrachloride and benzene-& (0.50-0.93 M ) . In general, all spectra were recorded under identical conditions and were reproducible. Chemical shifts and 1959, Chapter 6.Abstract: Basicity constants determined by proton nmr are reported for several types of ketones. Carbonyl substituent chemical shifts are plotted against Hammett acidity (Ho) yielding half-protonation values that reproduce spectrophotometric basicity constants. The nmr method facilitates basicity measurements for extremely weak ketone bases in superacid media. Basicity constants for several a-halogen substituted acetones are reported. Fluoro, chloro, and bromo substituents all reduce ketone basicity substantially. The three halogens are approximately equal in their effect. Carbonyl compounds that are not stable enough for spectrophotometric basicity studies may be evaluated by nmr. The nmr basicity constant for acetaldehyde (pK = -10.2) indicates that the aldehyde is far less basic than expected. Several ketones are used as a set of indicators for rapid evaluation of (Hammett) medium acidity by nmr. Applicability of the nmr method for acidity evaluation over the entire Hammett scale (currently Ho = 0 to -17.5) allows facile measurements in both superacid and conventional acid systems.he quantitative study of ketones as weak organic (b) D. G. Lee, Cart.

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