Chemistry - mechanism and synthesis Essay Example | Topics and Well Written Essays - 2250 words

Chemistry - mechanism and synthesis - Essay Example Next, FGI agents are used to convert the methyl group to a nitrile one and the final product – scheme 1, product 2 – is formed. This lithium salt is undergoes acid hydrolysis to form the pentane-2-diol, the hydrate of the ketone, and this, in the absence of the organolithium any excess of which is destroyed by the addition of water, readily decomposes to form the ketone (Taylor, p. 95, 2002). The reagent acts as a source for , that acts as a nucleophile and replaces the leaving group in the halide. This forms the ketone. The organocopper is not strong enough to attack the ketone and the reaction stops here (Taylor, p. 103, 2002). Note to the above diagram: Grignard reagents usually react with carboxylic acid derivatives to form ketones as intermediate substances but ketones cannot be prepared in this manner because they react further with more Grignard reagents to form alcohols. Usually, to prepare ketones, a less reactive organocopper reagent that reacts with the carboxylic derivative but not with the ketone is used (Taylor, p. 84, 2002). In this case, is a nitrile with a functional group that has similar polarisation characteristics to the carbonyl group. Thus, it can undergo addition reaction with the Grignard reagent and form a magnesium salt of an imine. It is notable that the salt has no leaving group and is also negatively charged and does not react further with the Grignard reagent. Thus, it is treated with aqueous acid and the excess Grignard reagent is destroyed and the salt is now converted to the imine – pentane-2-imine. The imine is unstable in the aqueous acidic conditions and readily hydrolyses to the ketone (Taylor, p. 85-86, 2002). This is the least stable radical as the relevant carbocation is flanked on either sides by other carbocations while only one side is somewhat stabilised by the alkyl electron-releasing group (Taylor, p. 126, 2002). (Part b): The technical