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Title: Enzyme-catalyzed Transesterification Reactions of Fluorinated and Non-fluorinated Esters: Comparative Study
Other Titles: تفاعلات الأسترة العبورية المنشطة إنزيميا للإسترات المفلورة و نظائرها
Authors: Murtadha Al-Mousawi 
Supervisor: Prof. Osman M. E. El-Dusouqui
Keywords: Fluorinated carbogens organic compounds pharmaceutical and agrochemical products fluoromethyl Enzyme-catalyzed Transesterification Reactions ester enantioselectivity atoms compounds
Issue Date: 2011
Publisher:  Kuwait university - college of graduate studies
Abstract: Fluorinated carbogens are an important class of organic compounds due to their wide range of applications. Fluorinated derivatives find use in the preparations of pharmaceutical and agrochemical products. A comparative study of enzyme-catalyzed transesterification reactions of a series of fluorinated and non-fluorinated esters has been undertaken in this work using three different lipases CAL-B, PSC-II and AK. The effect on the enzyme-catalyzed transesterification reaction of esters was evaluated based on the number of aryl fluorine atoms present in the substrate, and on the relative size of the fluoromethyl group and its proximity to the reaction site. The effect of lipase catalysts on the rate of reaction and on enantioselectivity was also assessed in order to compare the behavior of fluorinated and non-fluorinated primary and secondary esters. In the enzymecatalyzed transesterification of 1-phenylethyl acetate and its fluorinated derivatives; CAL- (B) shows tolerance to the presence of fluorine in the aromatic ring reaching above 45% conversion in 24h reaction time, but, however, with variation in enantioselectivity towards the fluorinated ester. Presence of (F) atom in an ortho-position reduced the enantioselectivity. In contrast, the presence of fluorine in the para-position had the lowest effect on enantioselectivity. The effect of both the number and molecular positions of the fluorine substituent is much more pronounced on conversion and on enantioselectivity with the other two lipase enzymes: PSC-II and AK. In the comparative study of the transesterification of primary/secondary acetate esters, presence of fluorine (as part of (CF3) at the α-position of the ester carbonyl group) had no considerable effect on the rate of reaction of secondary esters, while it has highly decreased the reaction rate of the fluorinated primary acetate esters. on the other hand, the (F) atoms reduced the enantioselectivity of the enzyme in the resolution of both primary and secondary esters.
Appears in Programs:0420 Chemistry (M.Sc.)

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