Polymers and group interaction. V. Reaction of diazomethane on polymethacroyl chloride

Abstract

AbstractIn order to follow the course of the Arndt‐Eistert reaction on a polymeric system, polymethacryol chloride has been reacted with diazomethane in dioxane solution using different molar ratios of diazomethane/acid chloride at different temperatures. The structure of the reaction products has been determined by chemical methods and by infrared spectrometry. The contents of acid chloride and diazoketone units have been evaluated from chlorine and nitrogen analyses, respectively; conductometric and potentiometric titrations allow determination of the percentages of ketene and pseudo‐acid groups. From these data it is concluded that the first reaction products of diazomethane on an acid chloride unit are diazoketone groups, as expected; however, the interaction of these primary groups with the neighboring acid chloride units yields principally β‐ketocycloketene functions. The presence of these groups and their content have been confirmed by a decarboxylation reaction effected by hydrolysis in acidic medium, during which carbon dioxide is evolved, while the acid content decreases and cyclic ketones are formed. Their presence has also been confirmed by oxidation with dilute nitric acid, which transforms the polymer into polymethacrylic acid. These results of decarboxylation and of oxidation are unreconcilable with the formation of the higher homolog of polymethacrylic acid, the polyisopropenylacetic acid, which would be the normal chainlengthening reaction product of the Arndt‐Eistert reaction. Infrared spectrometry shows, in the triple bond region, absorption bands at 4.65 and 4.73 μ, and, in the double bond region, bands at 5.55, 5.70, 5.80, and 6.10 μ. By comparison with the data in the literature, and especially with the spectrum of the glutaric bisdiazoketone, these different bands have been assigned and their relative intensities interpreted. The spectrometric results confirm the presence of diazoketone and β‐ketoketene groups; moreover, they show relatively low amounts of cyclopentanone rings and of ester functions.