Kinetic measurements for the degradation of 4-hydroxyphenylpentazole (2a) and its salt 2b-NBu4 in CD3OD and in CD2Cl2 provided a set of activation parameters. The resulting free energies of activation in methanol (DeltaG298 = 19.7 kcal/mol for 2a and DeltaG298 = 20.6 kcal/mol for 2b-NBu4) were compared with previous results for the 4-chloro derivative, 2c, and collectively correlated with results of gas-phase calculations at the B3LYP/6-31+G(d,p) level of theory. This, and another linear correlation of the seven computed DeltaG298 values with the previously reported kinetic data of Ugi and Huisgen, gave the basis for the estimation of the stability of pentazole anion (1) and its derivatives in solutions. Thus, N5(-) is predicted to have t(1/2) = 2.2 d, while the half-lifetime for HN5 is expected to be only about 10 min in methanol at 0 degrees C. Controlled ozonolysis of 2b-NBu4 followed by 1H and 15N NMR spectroscopy shows a preferential destruction of the N5 ring, which excludes it from possible methods for preparation of the parent pentazole.

The present report describes the preparation and use of some dimethyl terephthalate derivatives in transition metal-catalyzed coupling reactions to produce new reactive flame retardants. Dimethyl iodoterephthalate and dimethyl 2,5-diiodoterephthalate were successfully employed in the preparation of phosphonic and boronic esters and acids. The latter were tested for heat release with a microcombustion calorimeter (ASTM D7309) to determine the potential for heat release reduction of these flame retardant molecules. The results showed that the addition of boronic or phosphonic acids greatly lowered the heat release, due to a condensed phase (char formation) mechanism. Adding ester groups to the boronic acids or phosphonic acids could either completely remove all flame retardant effects or make the molecule act more like a vapor phase flame retardant. Finally, the various potential flame retardants were solvent blended with a thermoplastic polyurethane to assess their flammability reduction effects by microcombustion calorimetry. The results of these experiments found that the molecules that reduced heat release the most by themselves showed the greatest reduction in heat release in a polyurethane as well, with the boronic acids yielding the greatest reduction in heat release.

Abstract-Preparation and complete characterization of 16 2,6-disubstituted halobenzenes, including nine new compounds, from two common starting materials is described. Seven of the new compounds contain one or two propylthio groups, which have been introduced in two ways. Direct reaction of arenediazonium salts with 1-propanethiolate gives yields comparable to those obtained in a three-step method through sulfonyl chlorides. The 1 H-and 13 C NMR chemical shifts of 17 1,2,3-trisubstituted benzenes have been correlated with the predicted values and the observed trends explained using commonly available modeling packages. ᭧