Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)

Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) is a chemical compound composed of 4 sterically hindered phenols linked through a pentaerythritol core. It is used as primary antioxidant for stabilizing polymers, particularly polyethylene and polypropylene.

Synthesis
Base catalysed Michael addition of methyl acrylate to 2,6-di-tert-butylphenol forms the intermediate butyl-phloretic ester. High temperature transesterification of this with pentaerythritol gives the final product. Driving this reaction to completion can be difficult and commercial samples often contain low levels of the tri-ester.

Properties
The linking of phenols together with pentaerythritol maintains their activity with greatly reduced volatility. This is important during the processing and molding steps where the plastic is heated to molten, typically several hundred degrees.