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Dye interaction analysis in hexafluoroisopropanol was used to determine end carboxyl groups in polyglycolic acid (PGA). The rate of heterogeneous hydrolysis of purified PGA in water at 37°C shows a first‐order dependence on carboxyl end group concentration at levels above 12 meq/kg. Reaction of molten PGA with a tetraarylorthocarbonate or a triarylketenimine gave end‐capped PGA with carboxyl levels as low as 1 meq/kg. These samples were somewhat more resistant to hydrolysis than untreated PGA despite an increased initial rate at the lower carboxyl levels.

2,4-Diphenyl-s-triazine (XI).-A solution of 1.1 g. of N-carbamoylbenzamidine,12 m.p. 130-132°, in 3 ml. of formamide was heated at 180-185°for an hour. The white solid which crystallized on cooling was extracted into petroleum ether. This solution was decanted from some insoluble oil and evaporated to give 0.10 g. (13%) of XI, m.p. 68-72°. Recrystallization from aqueous ethanol gave a sample which had m.p. 73-75°and an infrared spectrum identical with that of an authentic sample.233-Phenyl-l,2,4-triazolin-5-one (XII).-A mixture of 1.0 g.(0.007 mole) of N-cyanobenzamidine and 0.75 g. (0.007 mole) of hydrazine dihydrochloride in 15 ml. of 50% aqueous methanol and was refluxed for 3 hr. Most of the methanol was distilled. Upon cooling 0.30 g. (30%) of the starting material crystallized.A little sodium bicarbonate was added to the aqueous filtrate, from which XII slowly crystallized during 24 hr. The yield was 0.25 g. (23%), m.p. > 300°. It was recrystallized from 50% aqueous ethanol; m.p. 322-325°( lit.24•25 m.p. 321°and 324°).In another run, under slightly more strenuous conditions, a 15% yield of benzoylurea,1 23 m.p. 210-212°, was isolated in addition to a lesser amount of XII.3-Amino-5-phenyl-l,2,4-oxadiazole (XIII).-A solution composed of 1.0 g. of N-cyanobenzamidine, 0.50 g. of hydroxylamine hydrochloride, 3 ml. of ethanol, and 2 ml. of pyridine was refluxed for 30 min. and filtered hot to remove ammonium chloride.The filtrate was chilled to give 0.35 g. (31%) of XIII, m.p.156-160°. One recrystallization from ethanol raised the m.p.to 164-165.5°( lit,26•22 m.p. 164°and 164-165°).

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