Kinetics of the nitric acid oxidation of benzyl alcohols to benzaldehydes
1966; Elsevier BV; Volume: 22; Issue: 8 Linguagem: Inglês
10.1016/s0040-4020(01)99058-1
ISSN1464-5416
AutoresY. OGATA, Y. SAWAKI, Fujihisa MATSUNAGA, Hiroshi Tezuka,
Tópico(s)Organic Chemistry Cycloaddition Reactions
ResumoThe oxidation of benzyl alcohols to benzaldehydes by dilute nitric acid (≈10%) was studied kinetically in 10 vol% aqueous dioxan. The oxidation is initiated most effectively by nitrous acid, and the rate is proportional to the product of the concentrations of benzyl alcohol and nitric acid, being independent of that of nitrous acid. The rate of oxidation increases with increasing acidity of the media, the plot of logarithm of the rate constant vs. acidity function Ho being a line with a slope of ca. −2. the apparent energy and entropy of activation were 28·3 kcal mole−1 and +1·85 eu, respectively. The subtituent effect satisfied Hammet's equation, affording a ϱ-value of −2·25. A probable mechanism is discussed, which involves a rapid and reversible coupling of α-hydroxybenzyl radical with nitrogen dioxide followed by the hydrolysis of α-hydroxybenzyl nitrite (I).
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