Kinetics and regioselectivity of the Autoxidation of Alkylaromatic Hydrocarbons

Abstract

Conclusions concerning the reactivities of alkylaromatic hydrocarbons in autoxidations are possible neither on the basis of the oxidizabilities nor on the basis of the chain propagation constants kp. In order to compare different alkylaromatic hydrocarbons, their rate constants with a definite peroxy radical, for example with the cumylperoxy radical, must be determined. Another possibility is the evaluation of relative rate constants by competitive oxidations of binary mixtures of hydrocarbons. These constants are not related to a definite peroxy radical. Nevertheless, these relative rate constants are real measures of the reactivities. If one also determines the composition of the reaction mixtures, which is especially convenient after LiAlH4 reduction, then it is possible to evaluate relative reactivities of the single C‐H bonds, for example in relation to the tertiary C‐H bond of cumene. This was done in our studies, and a great number of single bond reactivities is given in this survey. It is therefore possible to evaluate the activating effect of phenyl groups on different types of α‐C‐H bonds, and steric effects are also perceptible. In o‐substituted isopropyl aromatics, a desactivation by steric hindrance of mesomerism takes place.

Kinetic Studies of the Liquid-phase Oxidation of cis-pinane and of adamantane with molecular oxygen

“…Our results correspond to those of references 113, 141 as far as the regioselectivity is concerned. The gross reactivity of 0.27 is far more plausible than the gross reactivity of 2.27 (in both cases with a) consistency tests see [9]; calculated from 2 and 4: kl : k2 = 2.29 f 0.32; calculated from 3 and 5: kl : k2 = 2.51 + 0.16 a) gross reactivity with respect to cumene b, reactivity of one C-H bond with respect to the tertiary C-H bond of cumene respect to cumene) evaluated from the data given by Opejda [15, 161. We thank the "Fonds der Chemischen Industrie" for financial support.…”

Competitive Oxidation of cis/trans isomeric derivatives of cyclohexane with cumene. Relative reactivities of axial and equatorial tertiary C-H bonds

“…In continuation of our studies on kinetics and regioselectivity of autoxidation of alkylaromatic hydrocarbons [6] we have studied the cooxidation of the cis-and the trans-isomers of 1,2-, 1,3-and 1,Cdimethyl cyclohexane and of decaline with cumene at 100°C or ll0"C. In all cases we accomplished five competitive oxidations of mixtures with different proportions of the cyclohexane derivatives and cumene, reduced the oxidation mixtures with LiAIH4 and analyzed the mixtures of alcohols by gaschromatography. So it was possible not only to determine the gross reactivities of the cyclohexane derivatives but also the reactivities of their tertiary and secondary C-H bonds (with respect to the tertiary C-H bond of cumene).…”