Rate of copper extraction and structure of model β-diketones and 4-acyl-5-pyrazolones

The rate of copper extraction with individual 4-acyl-5-pyrazolones and the stability of various enolic and keto forms and their monohydrates were studied. The rate of extraction depends mainly upon the structure of substituent at position 4 and falls when the substituent becomes spacy. The effect of the substituent at position 1 is rather low. The enolic form with intramolecular hydrogen bonding is the most stable. It can form hydrates with water molecules without intramolecular hydrogen bond breaking.