Preparation of Carboxylic Acids: Hydrolysis of Nitriles, Esters, Amides, and Other Methods, Study notes of Chemistry

Download Preparation of Carboxylic Acids: Hydrolysis of Nitriles, Esters, Amides, and Other Methods and more Study notes Chemistry in PDF only on Docsity! Low Molecular Weight Acids General methods of preparation of carboxylic acids ➢ Hydrolysis of Nitriles The C≡N triple bond undergoes nucleophilic additions in a similar way to a C=O. As with the carbonyl group, so often protonation is needed in order to activate it for the addition of weak nucleophiles such as water. As expected, when nitriles are hydrolyzed (by nucleophilic addition of water followed by nucleophile elimination), they form either carboxylic acids or amides, depending on the conditions. Fig. 1 Hydrolysis of nitriles ➢ Hydrolysis of Esters and Amides In typical reactions, the alkoxy (OR') group of an ester is replaced by another group. One such reaction is hydrolysis, literally "splitting with water." The hydrolysis of esters is catalyzed by either an acid or a base, and the reaction is reversible and does not go to completion. Fig. 2 Hydrolysis of ester Amides can be hydrolyzed in either acidic or basic solution, and hydrolysis of amides to carboxylic acids is an industrially important reaction. The mechanisms are much like those of ester hydrolysis, but the reactions are very much slower. Fig. 3 Hydrolysis of amide ➢ Carbonation of Grignard Reagents Grignard reagents react with carbon dioxide in two stages. i) Dry carbon dioxide is bubbled through a solution of the Grignard reagent. ii) The product is then hydrolyzed (reacted with water) in the presence of a dilute acid. Typically, we would add dilute sulphuric acid or dilute hydrochloric acid to the solution formed by the reaction with the CO2. Fig. 4 Carbonation of Grignard reagent ➢ Malonic Ester Synthesis Malonic ester is a reagent specifically used in a reaction which converts alkyl halides to carboxylic acids called the malonic ester synthesis. Malonic ester synthesis is a synthetic procedure used to convert a compound that has the general structural formula 1 into a carboxylic acid. Fig. 5 Malonic Ester Synthesis ➢ Ardnt-Eistert Synthesis