Rate coefficient with nitro compounds

Rate coefficients have been measured for the reaction of OH radicals with a number of organic ketonitrates (R-C0-CH(0N02)-R) and dinitrates (R-CH(0N02)-CH(0N02)-R) using a relative kinetic method. The compounds investigated included 1,2-propane-, 1,2-butane-, and 2,3-butanediol dinitrate, a-nitro-oxy acetone, l-nitro-oxy-2-butanone, 3-nitro-oxy-2-butanone, 3,4-dinitro-oxy-1-butene and cw-l,4-dinitro-oxy-2-butene (LACTOZ 90). The rate coefficients are listed in Chapter 2, Table la. and this study represented the first determination of the OH rate coefficients for these compounds. 

The log rate versus acid strength curve for the latter compound is of the exact form expected for reactions of the free base, whilst that of the former compound is intermediate between this form and that obtained for the nitration of aniline and phenyltrimethylammonium ion, i.e. compounds which react as positive species. That these compounds react mainly or entirely via the free base is also indicated by the comparison of the rate coefficients in Table 8 with those in Table 5, from which it can be seen that the nitro substituent here only deactivates weakly, whilst the chloro substitutent appears to activate. In addition, both compounds show a solvent isotope effect (Table 9), the rate coefficients being lower for the deuterium-containing media, as expected since the free base concentration will be lower in these. 

The next problem with this reaction is that the mononitro compound can add successive nitro groups to produce the di- and trinitro toluenes in the reactions. Fortunately, the rate coefficients for adding the second and especially the third nitro groups are much smaller than for adding the first so mononitrotoluene can be made with good efficiency by simply heating toluene in nitric acid (Figure 3-19). 

Rate coefficients have been determined for the reactions of NO3 with a number of aliphatic mono- and dialkenes and monoterpenes with a relative kinetic method. The measured rate coefficients are listed in Chapter 2, Table 2. The products of the reactions were also investigated using in situ FTIR. The formation of thermally unstable nitro-oxy-peroxynitrate-type compounds was observed. The final products included aldehydes/ketones, nitro-oxy-aldehydes and -ketones and dinitrate compounds. 

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