A study of complexation of chloral hydrate with heteropoly anions having various structures

1H NMR was applied to study the interaction of chloral hydrate in deuterionitrobenzene solution with tetrabutylammonium salts of the heteropoly acids (HPA) belonging to five structural types: Keggin (H3PW12O40, H3PMo12O40, H4SiW12O40), Dawson (α-H6P2W18O62, α-H6P2Mo18O62, α-H4S2Mo18O62), H6P2W21O71(H2O)3, H6As2W21O69(H2O), and H21B3W39O132. The surface of the HPA anions is nonuniform in acid-base properties. A general rule for all HPA was found, namely, that the HPA acidity increases with a decrease in the specific anion charge (per W or Mo atom).