Predominance of 2-arylhydrazones of 1,3-diphenyl-propane-1,2,3-trione overits proton-transfer products

2-Phenylhydrazones of 1,3-diphenyl-1,2,3-trione are the dominant tautomeric form detected in chloroform solution by N-15 NMR chemical shifts. The subs tituent in the phenylhydrazone moiety does not affect this tautomeric prefe rence. The substituent effect is transmitted effectively only to the hydraz one nitrogen and hydrogen atoms. Ab initio calculations show that the ketoh ydrazone tautomer is really very much favoured over its proton-transfer pro ducts in chloroform solution. The same tautomer was also detected in the cr ystal state by X-ray crystallography. Copyright (C) 2001 John Wiley & Sons, Ltd.