ChemInform Abstract: KATALYISCHE FLUESSIGPHASEN‐OXIDATION ALKYLIERTER STICKSTOFFHETEROCYCLEN MIT OZON

Abstract

Die methylierten Heterocyclen (I) und (III) (analog auch 5‐Methyl‐, 1,3‐Dimethyl‐, 1,5‐Dimßethyl‐pyrazol, 2‐Methyl‐5‐äthyl‐pyridin) lassen sich in 70%igem wäßrigem H2SO4 in Gegenwart von MnSO4 und Cr,(SO4)3 bei 60‐80°C (Reaktionsdauer 1‐3 Std.) mit O3 zu den Carbonsäuren (II) bzw. (IV) oxidieren.

Corrosion Resistance of Hastelloy-B in the Ozonized Medium

“…These reactions clarify the dissolution of nickel and, hence, the alloys of Ni-Mo type in the ozonized solutions of sulfuric acid. It is also necessary to take into account that as the concentration of sulfuric acid increases up to 40%, the ozone solubility decreases to almost zero [13]. Consequently, we may assume that adding ozone to solutions of sulfuric acid contributes to neutralization of hydtrogen ions on the metal surface [11], whereas its rate is a function of H + concentration in the double electric layer.…”

Concerning chemistry, reactivity, and mechanism of transition metal catalysed oxidation of benzylic compounds by means of ozone

“…Now, oxidation of the i-propyl group turned out to be predominant with over 65% selectivity under standard conditions (see Table 2), which favours a mechanism including radical species. According to Tyupalo and Yakobi [22] and Partenheimer [1] a plausible reaction mechanism for this reaction can be suggested involving an initial radical abstraction of hydrogen, followed by the formation of an i-propyloxyl radical. The final step is the abstraction of a CH 3 radical forming the acetyl group, as shown in Scheme 2.…”

“…On the one hand, Tyupalo and Yakobi [22] proposed that metal-catalysed ozonisation is initiated by the formation of a high-valent metal ion species giving Mn(III) and free • OH radicals. On the other hand, Jacobson et al [23] suggested an oxygen atom transfer to give the "manganyl" ion MnO 2+ , avoiding the formation of • OH radicals.…”

“…To obtain information about the reaction mechanism of transition metal catalysed ozonisations, oxidation of pcymene (22) was considered. On the one hand, Tyupalo and Yakobi [22] proposed that metal-catalysed ozonisation is initiated by the formation of a high-valent metal ion species giving Mn(III) and free • OH radicals.…”

The Effect of Ozone on the Corrosion of Steels in the Processes of Oxidation of Pyridines

“…At present, of great interest are reactions of ozone with pyridine homologs to effectively produce pyridinecarboxylic acids and pyridine-N-oxides, which serve as semiproducts in syntheses of polymeric materials and pharmaceutical preparations [1,2]. Dilute solutions of acetic acid are used as supporting media in the syntheses.…”