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Computed chemical shifts and coupling constants for xanthone in deuteriochloroform and trifluoroacetic acid are in agreement with experimental data at 60,100, and 220 MHz. The increased dispersion of the signals a t 220 M H z in deuteriochloroform shows four distinct aromatic proton signals which can be analysed directly by first-order methods. Fundamental parameters for xanthone in carbon tetrachloride, pentadeuteriopyridine, hexadeuterioacetone, and hexadeuteriodimethyl sulphoxide have also been measured. Additive diamagnetic shifts for urtho-, meta-, and para-hydroxy-, alkoxy-, and alkyl substituents have been determined empirically and experimental and predicted chemical-shifts for natural and synthetic xanthones are in agreement, providing steric hindrance of vicinal groups is considered. The influence of been correlated.

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