Question

After running a base catalyzed hydrolysis of nicotinitrile with anion-exchange resins, how can I determine if I ended up with niacin or nicotinamide, without melting point ranges, or NMR?

Answer 1

Hydrolysis of nitrile is catalyzed by acid or base. In both the reactions, corresponding amide is the intermediate. The amide is then hydrolysed into carboxylic acid.

RCN + H2O----> RCONH2 ----> RCOOH

In this reaction, sometimes amide is formed as major product or mixture of two product can be obtained. Hydroxide ion supported on anion exchange resin can be used as base.These resin are typically composed of polystyrene backbone linked with divinylbenzene. By using polymer supported hydroxide, the reaction mixture can be easily filtered away from the catalyst there by avoiding the neutralization step required when soluble base is used.

To determine which product is formed, we can analyze it with melting point or by studying spectral data. Apart from these methods, TLC (thin layer chromatography) can also be used to see which product is formed major. We will take the reaction mixture, dilute it with a suitable solvent and then apply to the chromatograhic plate. The plates are develop in 80:20 ethylacetate:hexane mixture and visualize them under UV light and iodine. carboxylic acid are polar in nature. So, the spot for carboxylic acid will be near the bottom. Amide are less polar in nature, so the spot for amide is above the carboxylic acid or near the solvent front. It can also be compared by using a standard solution of nicotinamide.