The widespread and long-term use of TNT has led to extensive study of its thermal and explosive properties. Although much research on the thermolysis of TNT and polynitro organic compounds has been undertaken, the kinetics and mechanism of the initiation and propagation reactions and their dependence on the temperature and pressure are unclear. Here, we report a comprehensive computational DFT investigation of the unimolecular adiabatic (thermal) decomposition of TNT. On the basis of previous experimental observations, we have postulated three possible pathways for TNT decomposition, keeping the aromatic ring intact, and calculated them at room temperature (298 K), 800, 900, 1500, 1700, and 2000 K and at the detonation temperature of 3500 K. Our calculations suggest that at relatively low temperatures, reaction of the methyl substituent on the ring (C-H alpha attack), leading to the formation of 2,4-dinitro-anthranil, is both kinetically and thermodynamically the most favorable pathway, while homolysis of the C-NO(2) bond is endergonic and kinetically less favorable. At approximately 1250-1500 K, the situation changes, and the C-NO(2) homolysis pathway dominates TNT decomposition. Rearrangement of the NO(2) moiety to ONO followed by O-NO homolysis is a thermodynamically more favorable pathway than the C-NO(2) homolysis pathway at room temperature and is the most exergonic pathway at high temperatures; however, at all temperatures, the C-NO(2) --> C-ONO rearrangement-homolysis pathway is kinetically unfavorable as compared to the other two pathways. The computational temperature analysis we have performed sheds light on the pathway that might lead to a TNT explosion and on the temperature in which it becomes exergonic. The results appear to correlate closely with the experimentally derived shock wave detonation time (100-200 fs) for which only the C-NO(2) homolysis pathway is kinetically accessible.

Multiphoton dissociation of SF6 has been used to generate a transient concentration of fluorine atoms in mixtures with argon and H2 or D2. Absolute rate constants for the F+H2 and F+D2 reactions have been determined as a function of temperature by monitoring the appearance rate of HF or DF product chemiluminescence. In the temperature range from 190 °K to 373 °K the results are fit by the expressions kH=1.0×10−10 exp(−(860±100)/RT) and kD=9.1×10−11 exp(−(1100±100)/RT), both in cm3 molecule−1 sec−1. These values are in rough agreement with those obtained recently using a similar technique. The value of the isotope effect kH/kD is in good agreement with two previously determined values.

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The lifetime and quantum yield of fluorescence from the 4F9/2 level of Dy3+ have been measured in perprotonated and perdeuterated dimethylsulfoxide and methylcyanide under various excitation conditions. The results are compared to those obtained in light and heavy water and with other rare earth ions and discussed with reference to the modified energy gap law in the theory of radiationless transitions. The specific energy gap in Dy3+ is such that efficiency of quenching depends on matching the electronic energy gap of the ion by a single vibration of C–H, C–D, or C–N and on the distance of the bond from the ion.

Time-dependent quantum wave packet studies of the F+HCl and F+DCl reactionsExamination of the Br+HI, Cl+HI, and F+HI hydrogen abstraction reactions by photoelectron spectroscopy of BrHI−, ClHI−, and FHI− Molecular beam scattering experiments on the abstraction and exchange reactions of deuterium atoms with the hydrogen halides HCl, HBr, and HI A laser photolysis/infrared fluorescence technique has been used to study the temperature dependence of the F + HCI, F + HBr, F + DBr, and F + HI absolute rate constants in the range from 195 to 373 oK.Multiphoton dissociation of SF 6 with a TEA CO 2 laser was used to provide a. transient concen~ratlon of fluorine atoms. Their subsequent reaction with hydrogen donors was momtored by observmg the appearance rate of HF(v ;:>: 1) through its infrared fluoresce~ce. The observed. rate co~stants show a marked nonlinear Arrhenius behavior which is consistent wIth a model m whIch reac~lOn takes pl.a~ both via direct attack by the fluorine atom at the hydrogen end of HX and via formation of a colhslon complex FXH which rearranges to FHX and then dissociates to HF and X products.