alpha, beta-Diacryloxypropionic acid, a sensitizing impurity in commercial acrylic acid

In samples of commercial acrylic acid a strongly contact sensitizing constituent was discovered by application of Freund's Complete Adjuvant Test in guinea pigs. The skin reactions were due to the presence of varying quantities of alpha,beta- diacryloxypropionic acid (DAPA), which was identified after methylation. The commercial product is an example of a composition that defies gas-chromatographic quality-control: Under the circumstances of this analysis the secondary product that is formed during the synthesis of acrylic acid is so unstable that it does not pass polar liquid phases. Distilled acrylic acid does not contain the sensitizing acid.