AbstractIn the absence of mixed metal carboxylates, triaryl phosphites react rapidly with a model allylic compound for degrading vinyl, cinnamyl chloride, to yield phosphonium salts. On heating, these appear to yield allylidene phosphoranes by 1,1 elimination of HCl, with subsequent rearrangement to diphenyl phosphonates. With aryl alkyl phosphites, the phosphonium chloride intermediate undergoes rapid Arbusov rearrangement to the diphenyl phosphonate, eliminating alkyl chloride (or corresponding olefin). In the presence of zinc or cadmium carboxylates, Arbusov rearrangement is intercepted and chloride is transferred instead to the metal, forming the alkyl ester. The observed reaction paths appear to yield insight into the question of which phosphites are optimum for particular metal carboxylate blends and ratios in vinyl stabilizers, and into the related topic of which types of other additives are inappropriate.