Reactivity of ester groups on insoluble polymer supports

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Abstract
A study was made of the comparative rates of reaction of active ester functional groups (p‐nitrophenyl and 2,4‐dinitrophenyl esters) situated on three types of insoluble support polymers and on small, soluble analogs of the polymer molecules. The supports consisted of a styrene—divinylbenzene bead‐type polymer (2% DVB), a styrene—divinylbenzene popcorn polymer (0.2% DVB), and a popcorn polymer with 2,3‐dimethylbutadiene and substituted styrene units in the chain. p‐Nitrophenyl benzoate and 2,4‐dinitrophenyl p‐isopropylbenzoate were used as soluble analogs. Rates of aminolysis by small molecules (2‐aminoethanol and n‐tetradecylamine) in pyridine and of solvolysis in alcohols catalyzed by both small (N‐methylimidazole) and large (polyvinylimidazole) molecules were determined. With the small amines, finely divided particles of popcorn and bead type styrene polymers reacted at about the same rate, which was approximately 1/5 the rate of reaction of the homogeneous analogs. With a high molecular weight reagent, polyvinylimidazole, the heterogeneous reactions were much slower and the popcorn polymer reacted faster than the bead polymer. In catalyzed solvolyses, the styrene popcorn derivative reacted faster in benzyl alcohol and slower in 1‐hexanol than the dimethylbutadiene popcorn polymer derivatives.

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