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The primary reaction products from 248-nm chlorine azide photolysis are identified in a collision-free experiment. In contrast to all previous reports, the radical channel producing Cl + N3 (95 � 3%) is seen to dominate the photochemistry. The molecular channel producing NCl + N2 (5 � 3%) was also observed. 2004 Elsevier B.V. All rights reserved.

Measurements of NCl(a) kinetics are being carried out in support of the effort to develop an NCl(a) driven iodine laser. Photolysis of ClN 3 has been used as a radical source in several previous kinetic studies, as this produces high yields of NCl(a). It had been assumed that NCl(a) was a primary photoproduct. Measurements made under collision-free conditions now indicate that NCl(a) is a minor product, and that Cl and N 3 are produced with a branching fraction of 0.95. In the present study we show that NCl(a) is efficiently produced by secondary photochemical reactions when ClN 3 is photolyzed at moderate pressures. The implications of this finding for kinetic studies that rely on phot olytic NCl(a) generation are considered. The effect of temperature on NCl(a) quenching rate constants is being investigated because the NCl(a)/I laser operates at elevated te mperatures (>400 K). Quenching by H 2 , HCl, Cl 2 , and O 2 in the temperature range from 295-460 K has been examined in the present study. Keywords: All gas-phase iodine laser, nitrogen chloride, chlorine azide photolysis, energy transfer kinetics.

Electron attachment to chlorine azide (ClN(3)) was studied using a flowing-afterglow Langmuir-probe apparatus. Electron attachment rates were measured to be 3.5x10(-8) and 4.5x10(-8) cm(3) s(-1) at 298 and 400 K, respectively, with an estimated 35% absolute accuracy. Cl(-) was the sole ion product of the attachment reaction; weak ion signals were observed for other anions and attributed to impurities and secondary ion-molecule reactions. Assuming a relative uncertainty of +/-10% for these data, an activation energy for the attachment reaction may be given as 24+/-10 meV.

UCl6, fur das eine verbesserte Darstellungsvorschrift angegeben wird, last sich mit Chloridionen zum Hexachlorouranat(V) und mit wasserstoffhaltigen Losungsmitteln wie H2CCl2 zu Uranpentachlorid reduzieren. Mit Chlorazid bildet es die Uranchloridazide UCl5N3 und UCl4(N3)2, die sich jedoch nur in schlechter Ausbeute als Gemisch isolieren lassen, weil sie mit dem Losungsmittel weiterreagieren. Ist das Losungsmittel H2CCl2 oder 1,2-Dichlorathan, so entsteht dabei NH4UCl6 als Hauptprodukt; mit CCl4 als Losungsmittel wird das Triazidocarbenium-Salz [C(N3)3]UCl6 in hoher Ausbeute erhalten. Der Reaktionsweg zu diesen Endprodukten verlauft uber Zwischenstufen, die IR-spektroskopisch identifiziert werden konnten. Das Infrarotspektrum von UCl5N3 und UCl4(N3)2 wird mitgeteilt, auserdem werden Angaben zur Kristallstruktur von [C(N3)3]UCl6 gemacht. About the Chemistry of Uranium Hexachloride and Uranium Pentachloride Azide UCl6, for which an improved method of preparation is given, can be reduced with chloride ions to give hexachlorouranate(V) and with solvents containing hydrogen such as H2CCl2 to give uranium pentachloride. With chlorine azide the uranium chloride azides UCl5N3 and UCl4(N3)2 are formed, but they can only be obtained in low yields as a mixture because of their reactivity towards the solvent used. With H2CCl2 or 1.2-dichloroethane as solvent, NH4UCl6 is the main product; with CCl4 as solvent, the triazidocarbenium salt [C(N3)3]UCl6 is formed with high yield. Intermediates of the reaction path to these products could be identified by I. R. spectroscopy. The infrared spectra of UCl5N3 and UCl4(N3)2 are reported and data about the crystal structure of [C(N3)3]UCl6 are given.

The dialkylmetal azides [(CH3)2AlN3]3, [(C2H5)2GaN3]3, [(C2H5)2,InN3]2 and [(C2H5)2TI]+N−3 were prepared from the corresponding metal trialkyls and chlorine azide. Their properties are given and their structures were determined from their vibrational spectra (IR and Raman). The trimeric azides of Al and Ga form planar six-membered metal-nitrogen rings (symmetry D3h), the dimeric azide of indium probably forms a planar four-membered In2N2-ring and the structure of diethylthallium azide is ionic.

The microwave spectra of four isotopic species of chlorine azide, ClN3, have been observed in the frequency range 26–48 GHz. From the measured values of the rotational constants, the molecule has been deduced to be planar with the following internuclear parameters: r(Cl–N(1)) = 1.745 ± 0.005 A, r(N(1)–N(2)) = 1.252 ± 0.010 A, r(N(2)–N(3)) = 1.133 ± 0.010 A, ∠ClN(1)N(2) = 108°40′ ± 30′, ∠N(1)N(2)N(3) = 171°56′ ± 30′, with Cl and N(3) trans. Values for the chlorine quadrupole coupling constants were obtained for all isotopic species, and for the most abundant, 35Cl14N3, were transformed into the principal field gradient axis system. The values obtained are consistent with the deduced structure.

Publisher Summary This chapter discusses the chemistry of the halogen azides. Fluorine azide is best prepared from dry hydrazoic acid and fluorine in the gas phase. Decomposition reactions of the fluorine azide are avoided when the reactants are diluted with N 2 . Because in this reaction chlorine azide is produced in high concentrations locally, explosions can occur. For preparative purposes, the most convenient method is the reaction of chlorine gas, diluted with nitrogen, with an aqueous solution of sodium azide. Solutions of bromine azide in hexane, carbon tetrachloride, and other inert solvents are obtained from silver azide and bromine when the suspension contains some dry sodium sulfate, to avoid decomposition of the BrN 3 by traces of water. For preparative purposes, solutions of bromine azide in dichloromethane or pentane can be prepared by addition of bromine to an agitated two-phase system held at 0°C, the aqueous phase of which consists of sodium azide and 30% HC1.

Publisher Summary This chapter discusses the chemistry of the halogen azides. Fluorine azide is best prepared from dry hydrazoic acid and fluorine in the gas phase. Decomposition reactions of the fluorine azide are avoided when the reactants are diluted with N 2 . Because in this reaction chlorine azide is produced in high concentrations locally, explosions can occur. For preparative purposes, the most convenient method is the reaction of chlorine gas, diluted with nitrogen, with an aqueous solution of sodium azide. Solutions of bromine azide in hexane, carbon tetrachloride, and other inert solvents are obtained from silver azide and bromine when the suspension contains some dry sodium sulfate, to avoid decomposition of the BrN 3 by traces of water. For preparative purposes, solutions of bromine azide in dichloromethane or pentane can be prepared by addition of bromine to an agitated two-phase system held at 0°C, the aqueous phase of which consists of sodium azide and 30% HC1.

The electronic structure of the ground states of chlorine isocyanate and chlorine azide is investigated using ab initio LCAO–MO–SCF calculations with a moderately large basis. The difference in strength of the Cl—N bond for the two compounds is found to be caused by a greater contribution from the N s orbital of the azide. The calculations also show that the total charge on chlorine in these compounds is positive.