Condensation of aliphatic aldehydes with 1,3-diketones and ammonia to lutidine derivatives

Condensation of aliphatic aldehydes with 1,3-diketones and ammonia to form lutidine derivatives 

3-cyclohexanedione (dihydroresorcinol CHD) 5,5-di-methyl-l,3-cyclohexanedione (dimedone)] and ammonia to form fluorescent lutidine derivatives [432]. These reactions of the diketones have been suggested for precolumn derivatization of aldehydes [433-435]. 

The reagent comprises an aqueous solution containing 25 g of ammonium acetate, 1 g of CHD and 8 ml of cone. HC in 1(X) ml. In order to remove contaminants, it is heated for ih at 60 °C and, after cooling, passed through a Ci8 Bond-Elut cartridge. 

Equal volumes of reagent and sample are heated in sealed tubes for ih at 60 °C. After cooling on ice, an aliquot is used for analysis by HPLC. 

The optimum pH for reaction is around 5 for CHD, whereas formaldehyde reacts with dimedone best at about pH 7. CHD and dimedone derivatives have much higher fluorescence quantum yields than those of acetylacetone derivatives [432]. 

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