Exchange Reactions of Aldehydes and Ketones

Using intra-red spectre,copy, the equilibriull ~xcMnge times have been determined tor a aeri•• of keton••, aromatio aldehyde" and a-keto.sters re8ctin~ with oxYaen 18 enriched water. Theso exchange tilMs have been ev.luated in terma ot ateria and electronic coneideration., and applIed to • ,Uacus.ion of the exohange ti"e. of ohlorophyll. a and b and ohlorophyll derlvativeao Introduction This inve.tigation of the exchange reactions of aldehyde. and i keton•• with 018 enriched water has been undertaken in order to be able to examine the particlpatloD of chlorophyll carbonyl group. as chemical intermediate. in the oxidation of watGr during photosynthesis. Photosynthetic mechanism. have been propo.ed by Calvinl and Franok2 in which the .oparation ot oxidant and reductant. required tor oxygon evolution and carbon dioxide fixation. i. a ~hotocatalytical ohlorophyll reaction. Essential to the.e mechanisms i. the ability of a chlorophyll carbonyl group to undol'lO hydrationo The preratmt MOrk evaluates the excMnge ability ot chlorophyll in comparhon with .apl. ketone•• aldehydes, and a-ketoesters •. The literature on the 018 ftchange reaotiona of oarbonyl functions '. ./