The kinetics of the alkaline hydrolysis of trinitrotoluene, TNT, in an aqueous solution is a possible approach to destroying the active agent in unwanted munitions. The kinetics are shown to have a rapid initial step, step A, in which a highly coloured species, X (max=450 nm) is formed via an equilibrium reaction: TNT+OH-X. The bimolecular rate constant for the forward part of this equilibrium process, k1, is: 0.099±0.004, 0.32±0.02 and 1.27±0.05 dm3 mol-1 s-1, at 25, 40 and 60°C, respectively. The activation energy for the forward process is 60 kJ mol-1. The first-order rate constant for the reverse of this process, k-1, is: (5.3±2.6)×10-4, (1.2±1.0)×10-3 and (7.7±2.9)×10-3 s-1 at 25, 40 and 60°C, respectively. The activation energy for the overall equilibrium process (k1/k-1) is ca.-5 kJ mol-1. The subsequent alkaline hydrolysis of X to form the final product P, i.e. step B, is much slower than step A and appears to comprise two processes coupled in series, i.e. steps B1 (X+2OH-Z) and B2 (Z+OH-P). At 25°C, Step B1 appears rate determining throughout the decay process. At 45°C and, more so, at 60°C, step B appears increasingly biphasic with increasing alkaline concentrations, as step B2 begins to compete with step B1 for position as the rate determining step. The trimolecular rate constant for step B1 is: 0.017±0.001, 0.0085±0.0002 and 0.0011±0.0001 dm6 mol-2 s-1 at 25, 40 and 60°C, respectively, and the process has an activation energy of 64 kJ mol-1. The transition from uniform kinetics, described by step B1, to mixed kinetics, described by steps B1 and B2, as the reaction temperature and alkali concentration are increased most likely occurs because (a) step B2 has a lower activation energy than B1, although it was not possible to measure the former parameter, and (b) step B2 has a lower (1st) order dependence upon [OH-] compared with that of step B1 (2nd). The bimolecular rate constant for step B2 is 0.0035±0.03 dm3 mol-1 s-1 at 60°C. A brief NMR study of the initial hydrolysis product in water, acetone and chloroform, coupled with UV/visible spectra, provides evidence that species X is a Meisenheimer complex

Urea derivatives have significant applications in the synthesis of resin precursors, dyes, agrochemicals, and pharmaceutical drugs. Furthermore, polyureas are useful plastics with applications in coating, adhesive, and biomedical industries. However, the conventional methods for the synthesis of urea derivatives and polyureas involve toxic reagents such as (di)isocyanates, phosgene, CO, and azides. We present here the synthesis of (poly)ureas using much less toxic reagents(di)amines and methanolvia a catalytic dehydrogenative coupling process. The reaction is catalyzed by a pincer complex of an earthabundant metal, manganese, and liberates H 2 gas, valuable by itself, as the only byproduct, making the overall process highly atomeconomic. A broad variety of symmetrical and unsymmetrical urea derivatives and polyureas have been synthesized in moderate to quantitative yields using this catalytic protocol. Mechanistic insights have also been provided using experiments and DFT computation, suggesting that the reaction proceeds via an isocyanate intermediate.

We report here the first example of the direct synthesis of polyureas from the dehydrogenative coupling of diamines and methanol using a ruthenium pincer catalyst. The present methodology replaces the...

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