The kinetics and mechanism of noncatalytic liquid phase oxidation of but 1 ene and but 2 ene with nitrous oxide in a benzene solution in the temperature range from 180 to 240 °C were studied. Oxidation proceeds via the 1,3 dipolar cycloaddition mechanism to form carbo nyl compounds. Both of these reactions occur with close rates and activation energies and have the first orders with respect to the alkene and N 2 O. A considerable fraction (39%) of but 1 ene involved in oxidation undergoes cleavage at the double bond yielding propanal and an equiva lent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but 2 ene proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation of terminal and internal alkenes C 2 -C 8 with nitrous oxide were analyzed using the previously published data.Nitrous oxide (N 2 O) attracts attention as an oxidizing agent for the gas phase catalytic oxidation. Reactions of this type are strikingly exemplified by the selective oxida tion of benzene and other aromatic compounds to the corresponding phenols in the presence of iron containing zeolites FeZSM 5. The works in this area are considered in several reviews. 1- 6 It has previously been shown that nitrous oxide can also be an efficient oxidizing agent in liquid phase oxida tion. These reactions are mainly alkene epoxidation and alcohol oxidation, occurring with ~100% selectivity in the presence of the Ru porphyrin complexes, 7,8 metal containing polyoxometallates, 9,10 and some metal-oxide systems. 11 Meanwhile, the most remarkable feature of nitrous oxide is, probably, its capability for noncatalytic liquid phase alkene oxidizing to form carbonyl com pounds. 12-15 Cyclopentene and cyclohexene are oxidized with N 2 O at 150-250 °C, transforming into the corre sponding cyclic ketones with 96-99% selectivity. 14,15 The reaction proceeds via the nonradical 1,3 dipolar cycload dition mechanism to form an intermediate 1,2,3 oxa diazoline complex (Scheme 1).The energy route of cyclohexene oxidation was com pletely described 16,17 by the quantum chemical method. The results agree well with the experimental data.The recent screening of substrates shows 18 that nitrous oxide can noncatalytically oxidize alkenes of different classes, including linear, cyclic, and heterocyclic alkenes and their derivatives. The rate and selectivity of the reac tion depend strongly on the substrate composition and structure. In particular, those effects are especially pro nounced for linear alkenes C 2 -C 8 , whose behavior dif fers considerably depending on the position of the double bond. However, it is difficult to compare quantitatively the results obtained for different alkenes, because even under strictly standardized experimental conditions (re actant concentration, reaction temperature, and pressure) the real conditions of alkene oxidation are different due to different boiling points of alkenes. For instance, for the reaction temperature 220 °C, the m...

The article reports on the noncatalytic transformation of a polybutadiene (number‐average molecular weight = 128,000) into a functionalized liquid rubber via the carboxidation of the polymer CC bonds by nitrous oxide. The reaction was conducted in a benzene solution at 160–230 °C and a pressure of 3–6 MPa. The carboxidation mechanism was determined. The main route (95%) of the reaction proceeded without cleavage of CC bonds and led to the formation of ketone groups in the polymer backbone. A minor route (5%) of the reaction proceeded with the cleavage of CC bonds, yielding two smaller fragments containing aldehyde and vinyl end groups. The availability of the cleavage route could lead to a dramatic decrease in the molecular weight, which, depending on the carboxidation degree, could be 1–2 orders of magnitude less than that of the initial material. Thus, the carboxidation of more than 15% of the polybutadiene CC bonds transformed it into a CO‐functionalized liquid rubber with a narrow molecular weight distribution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2510–2520, 2006

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ATR-FTIR spectroscopy was used in situ to study nine unsaturated polyketones derived from cis-1,4-polybutadiene rubber, each containing a different concentration of carbonyl groups, under high-pressure CO2 conditions (up to 100 bar). The study was aimed to systematically determine the relationship between the concentration of carbonyl groups in the polyketones and their ability to absorb CO2 and swell. A linear relationship between increasing carbonyl concentration and the overall degree of swelling and CO2 sorption was observed for polyketones with a concentration of carbonyl groups below a specific value based on quantitative analysis from the ATR-FTIR spectra. However, polyketones, which had the highest concentration of carbonyl groups, did not follow this correlation. Instead, there was evidence of intermolecular interactions between the carbonyl groups in the polymer chains, which decreases the total CO2 sorption capacity and inhibited swelling. The effect of the different molecular weights of polymer was also studied with respect to polyketone swelling and CO2 sorption. No correlation was observed when comparing polymers with different molecular weights but contained a similar concentration of carbonyl groups. Hence, the main physical properties that affect the overall swelling and CO2 sorption into polyketone samples were quantitatively determined using ATR-FTIR spectroscopy.

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