Bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite is an organophosphite used as a polymer stabilizer in plastics.

Like other phosphite antioxidants it primarily acts to remove hydroperoxides and is typically used in combination with hindered phenolic antioxidants such as pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate).

It is formed by a reaction between phosphorus trichloride, pentaerythritol and 2,4-di-tert-butylphenol.

The poor solubility of pentererythritol can be an issue and non-nuncleophilic amines are often used to promote the reaction.

Trace levels of amine bases are often added to commercial material to slow hydrolysis and increase storage life.