Orientation in films of long-chain esters

Monolayers of long-chain fats and esters present some interesting features in molecular orientation, particularly as regards the effect of this orientation on the rate of hydrolysis when spread on alkaline solutions. The dibasic and tribasic long-chain esters (e.g. glycol dipalmitate and tripalmitin) orientate themselves in the interface, with their chains adjacent to one another. The monobasic esters of palmitic acid, however, as Adam (1929) has shown, behave somewhat differently, in that the alkyl chain, if shorter than five carbon atoms and lying extended on the surface in the expanded state, can on compression be forced under the surface into a vertically orientated position opposing the long acidic chain.