How to make mercaptopropionic acid MPA?

How to make mercaptopropionic acid MPA?

There are three main methods for preparing mercaptopropionic acid: 

1. Acrylonitrile is synthesized by acidolysis after the addition reaction with sodium thiohydride;

   2. Acrylic acid is obtained by addition reaction with hydrogen sulfide, or by hydrolysis after addition of acrylic acid with sodium thiosulfate; 

   3.3- Chloropropionic acid is obtained by nucleophilic substitution with sodium trithiocarbonate and acid hydrolysis.