Highly efficient and green approach of synthesizing carboxylic acids from aldehydes using sodium hexametaphosphate

Oxidation of aldehydes is considered as one of the important organic reactions and is a common reaction employed in the manufacturing of cosmetic products, dyestuff, plasticisers and fibres. Various literature and methods have been generated that are capable of oxidising aldehydes to carboxylic acids efficiently. However, there are some limitations in these catalytic systems including waste formation, use of expensive and toxic ox- idants, use of metals, sophisticated method of catalyst preparation and some of these reactions required to be performed under a pressurised condition. For the first time, an environmentally benign and highly efficient method for the preparation of carboxylic acids from aldehydes using the Sodium Hexametaphosphate (SHMP) and aqueous hydrogen peroxide is described. After the completion of reaction, the aqueous SHMP was separated from the organic layer. After being recharged with hydrogen peroxide, the aqueous SHMP was reused for five consecutive times without any significant loss of catalytic activity. Under the improved protocol, the yields of the desired products were recorded to be excellent (80 -97%). Furthermore, the desired products were yielded by precipitation method, with no column purification needed. The current protocol avoids the utilisation of haz- ardous reagents which is scientifically important, especially in achieving a more sustainable world.