To a 2-liter four-necked flask equipped with a thermometer, stirring apparatus, condenser and dropping funnel were added 340.51 g (1.0 mole) of 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 72.06 g (1.0 mole) of acrylic acid, 500 g of toluene and 209.47 g (2.07 moles) of triethylamine. After replacing the air in the container with nitrogen, 105.8 g (0.69 mole) of phosphorus oxychloride was added dropwise with stirring. After completion of the dropwise addition, the reaction solution was kept at 80° C. for 1 hour. Thereafter, the organic layer was washed with water until it became neutral, and toluene was removed under reduced pressure. The residue was then recrystallized from n-hexane to obtain 374.8 g of a white crystalline 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate having a melting point of 132° to 134° C. Yield, 95%.
