Thai scientists have devised a faster, environmentally-friendly route to alkyl lactates - compounds widely used by the cosmetic and food industries.

Khamphee Phomphrai and his team, from Mahidol University, Bangkok, use lithium, potassium and calcium catalysts to make a range of alkyl lactates from lactides in a matter of minutes.  The lactides are derived from lactic acid which is made from the fermentation of carbohydrates such as corn - a renewable feedstock.

Lactates are widely used in the cosmetic industry to make moisturisers and skin rejuvenating creams and can be found in food as flavourings and preservatives. Lactates are also used as effective solvents or cleaning agents, replacing more harmful solvents.

Sjoerd Harder, from the Universität Duisburg-Essen in Germany, an expert in s-block metal catalysis, says that Phomphrai's research is 'especially noteworthy not only because it is based on a renewable feedstock but also on account of the environmentally-friendly nature of the metals used as catalysts'.

Currently alkyl lactates are made by reacting lactic acid with excess alcohol at temperatures of 80 °C or higher for up to eight hours.  Phomphrai's metal catalysed reaction produces pure alkyl lactates in five minutes at significantly lower temperatures, and even works at room temperature in some cases. 

Another problem with the current method is the formation of polymer by-products which need to be removed, requiring even more time and energy. Depending on the metal catalyst used, Phomphrai's reaction can be tailored to produce alkyl lactyllactate or alkyl lactate, with the problem of side-products eradicated.

'It remains to be seen, whether alkyl lactacte or lactyllactate production from lactides is economically feasible,' says Harder, but the product selectivity and its easily extendable range might make this method convenient.

'We are now working on using our process for the synthesis of other commercially valuable compounds having the lactic acid functionality,' says Phomphrai.

Ruth Doherty