Excited molecules, reaction nitrous oxide with

The Reaction of Nitrous Oxide with Excited Molecules in the Radiolysis and Photolysis of Liquid Alkanes... 

In the 1470-A. photolysis of cyclohexane-nitrous oxide solutions, nitrous oxide reacts with excited cyclohexane molecules to form nitrogen and oxygen atoms. The reaction of N20 with photoexcited 2,2,4-trimethylpentane molecules is much less efficient than with cyclohexane. In the radiolysis of these solutions, G(N2) is the same for different alkanes at low 5 mM) N20 concentrations. At higher concentrations, G(N2) from the radiolysis of cyclohexane is greater than G(N2) from the radiolysis of 2,2,4-trimethylpentane solutions. The N2 yields from 2,2,4-trimethylpentane are in excellent agreement with the theoretical yields of electrons expected to be scavenged by N20. The yield of N2 in the radiolysis of cyclohexane which is in excess of that formed from electrons is attributed to energy transfer from excited cyclohexane molecules to nitrous oxide. 

There are several possible explanations which need to be considered for the formation of N2 in the photolysis of cyclohexane-nitrous oxide solutions. These include direct absorption of vacuum ultraviolet light by nitrous oxide, photoionization of the solvent followed by electron attachment by nitrous oxide, and reaction of nitrous oxide with either excited cyclohexene or excited cyclohexane molecules. Of these possibilities only the last explanation—reaction of excited cyclohexane molecules with nitrous oxide—is important. 

Radiolysis. The photochemical experiments suggest that in the radiolysis a reaction of nitrous oxide with excited molecules would be expected in cyclohexane but should be less important in 2,2,4-trimethylpentane. The radiolysis results (Figure 3 and Table III) show that at nitrous concentrations less than 10 mM, where reactions of excited molecules are unimportant, G(N2) is the same for cyclohexane and 2,2,4-trimethylpentane solutions. At concentrations of nitrous oxide from 20 to 160 mM, G(No) from cyclohexane solutions is greater than G(N2) from 2,2,4-trimethylpentane solutions, and the excess yield increases with the concentration of nitrous oxide. [The nitrogen yields reported here for the concentration range 5-200 mM are in good agreement with those reported by Sherman (20)] Nitrous oxide reduces G(H2) from cyclohexane (16, 17, 18, 20, and Table III), but it has little effect on G(H2) and G(CH4) from 2,2,4-trimethylpentane. 

Hobroyd RA (1968) The reaction of nitrous oxide with excited molecules in the radiolysis and photolysis of liquid alkanes. In Gould RF (ed) Radiation chemistry II. Advances in Chemistry Series. American Chemical Society, Washington... 

Kinetic studies of the competitive reactions of other electron scavengers support this hypothesis (18, 20). In the radiolysis of solutions of nitrous oxide in alkanes, reactions with other intermediates must be considered. Radicals, hydrogen atoms, and positive ions can be eliminated (5, 20), but a reaction with excited molecules is possible. It has been reported... 

In other alkanes the reaction of excited molecules with nitrous oxide is less important, and in some cases it may not occur at all. In n-hexane the N2 yields are about one-half what they are in cyclohexane. In other alkanes such as 2,2,4-trimethylpentane the yields of N2 were quite low. A small yield could be attributed to one of the other effects discussed, but if it is attributed to excited alkane molecules, then energy transfer to nitrous oxide is much less important in 2,2,4-trimethylpentane than in cyclohexane. 

Emission from electronically excited TiO molecules has been observed by Palmer and co-workers from the reaction of titanium tetrachloride or tetrabromide with potassium vapour in the presence of oxygen [277] and of nitrous oxide [278]. The potassium atoms presumably strip the halogen atoms from the titanium tetrahalide, and the titanium atoms then react with the oxygen or nitrous oxide producing electronically excited TiO molecules. 

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