Laser‐initiated chemical reactions: Cl+H2S→HCl+HS: Rate constant, product energy distribution, and direct detection of a chain mechanism
摘要:
Laser-initiated, time-resolved infrared chemiluminescence techniques are used to study the detailed kinetics of chlorine/hydrogen sulfide systems. Measurements on the Cl+H2S→HCl+HS reaction are carried out by pulsed laser photolysis of S2Cl2→S2Cl+Cl in a flowing mixture with H2S, while detecting vibrational chemiluminescence from the HCl product. The measured rate constant for the Cl+H2S reaction is 6.0 ±1.2×10−11 cm3 molecule−1 sec−1 at 296°K. The vibrational product distribution is predominately excitation of HCl to v=1 and v=2, with the ratio (v=1):(v=2) =15. The dynamical interpretation of the Cl+H2S reaction data is discussed. Photolysis of Cl2→2Cl in the presence of H2S produces a rapid chain reaction, Cl+H2S→HCl+HS, HS+Cl2→HSCl+Cl. The chain mechanism and its real time development are observed directly from the product chemiluminescence signal.
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A detailed kinetic and experimental analysis is presented for chemical chain reaction processes initiated by well-controlled, low power laser pulses. Realtime evolution of the chain reaction is followed by direct detection of infrared chemiluminescence from vibrationally excited HCl product molecules produced by one of the propagation reactions in the chain. By appropriate choice of conditions, the chain reactions may be analyzed separately for pseudofirst-order, radical–reagent processes as well as for second-order, radical–radical events. The pulsed laser initiation technique is applied to three sample chain systems which exhibit distinctly different chain lengths, rates, and termination behaviors. These systems are Cl2/H2S, Cl2/H2, and Cl2/CH3SH. In the case of Cl2/H2S, detailed rate constant data are obtained for the fundamental chain propagation steps, and appropriate chain termination steps are assigned from the observations. The results demonstrate a new, general technique for the quantitative study of chemical chain reactions and related combustion processes.
US6103729
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Stock, A.; Wintgen, R., Chemische Berichte, 1920, vol. 53, p. 837 - 842