THE REACTION OF tert-BUTOXY RADICALS WITH 2,6-Di-tert-BUTYL-4-METHYLPHENOL AND 2,6-Di-tert-BUTYLPHENOL

Abstract

The products of the reaction of t-butowy radicals with 2,6-di-t-butyl-4-meth~lphei101 and 2,6-di-t-butplphenol ill carbon tetrachloride have been analyzed quantitatively. There is a satisfactory agreement between the measured and calculated yields of t-butanol u i t h both phenols. The deuterium isotope effect ( k~l k~) for abstraction of the pheilolic hydrogen from 2,6-di-t-butyl-4-methylphenol is about 6.4.The abstraction of hydrogen atoms by alkoxy radicals from substrates in the liquid phase is of particular interest in relation to autoxidation phenomena (1). These radicals are produced in the chain branching deco~llposition of the initially formed hydroperoxides and are therefore responsible for the autocatalytic nature of most autoxidations.The t-bu toxy radical is particularly suitable for studying the relative rates of reaction [2] with different substrates since it may either abstract a hydrogen to give t-butanol o r decdmpose t o give acetone and a methyl radical. The ratio, [t-butanol]/[acetone], produced in different substrates therefore gives a measure of the relative rates of hydrogen abstraction fro-m the substrates. These radicals are readily prepared by the decomposition of di-t-butyl peroxide and the reactions can be represented by, This technique has been employed by a number of workers in recent years to measure the relative rates of hydrogen abstraction by t-butoxy radicals from a variety of substrates such as hydrocarbons (2-9), ethers, (10, l l ) , alcohols (12), and amiiles (13,14). As a part of our general program for studying the inhibition of autoxidation by phenols (15-17) we considered that an examination of the reaction of t-butoxy radicals with phenols might throw considerable light on the overall mechanism of inhibition. In particular, we were interested to see whether the phenolic hydrogen was abstracted by the t-butoxy radical in the rate-determining step.In view of the comparative ease with which an isotope effect was detected in the reaction of peroxy radicals with 2,6-di-t-butyl-4-methylphenol (BLIP) (15, 16) this compound was chosen for the present investigation. There have also been numerous studies in recent years of the products of oxidation of this pl~enol by a variety of oxidizing agents (18)(19)(20)(21)(22)(23)(24)(25). Some results on the reaction of t-butoxy radicals with 2,6-di-t-butylphenol (BP) are also reported.

Phenols as Antioxidants

“…3 ) at the para position 28 , whereas the more reactive tertbutoxyl radical gives dimeric products of the type shown in Scheme 1. This could occur through 'hydrogen migration' from the methyl group, as proposed, however dimerization via a quinone methide, 3a, is more likely 29 . Alternately, the reactive tert-butoxyl can abstract hydrogen directly from the para methyl, a known reaction 30 .…”

Regiodivergent Chlorine‐Atom‐Transfer Ring‐Opening Reactions of Trichloromethylcyclopropanes

“…can abstract a chlorine atom as a chloride ion (Table 1). [8][9][10] When 2,3-trans-1a was treated with ZnMe 2 (2 equiv.) in toluene at room temperature, the ring-opening product was not obtained and starting material 1a was completely recovered (entry 1).…”

Antioxidants and stabilizers. XLI. reaction of tert‐butyl hydroperoxide with 2,2′‐methylenebis(4‐methyl‐6‐tert‐butylphenol)

“…Although the determination of the relative concentration of isobutylene with respect to the other components in the reaction mixture is well reproducible, we considered the concentration values of isobutylene to be only approximative and did not use them for the mass balance of the reaction. Isobutylene can be formed in the reaction mixture by reaction of tert-butoxyl and tert-butylperoxyl radicals with bisphenol, or by splitting-off of the tert-butyl groups from methylenebisphenol [ 9 ] . To verify the method of its formation, experiments were carried out with a benzene solution of methylenebisphenol (always 0.025 molell.)…”

“…The respective amounts at 157°C are only 37% and 33%; at 132°C there is a further decrease to 26 and 19.4%, respectively. If Ingold's assumption [9] about the formation of isobutylene via the reaction of the methyl radicals with ortho-tert-butylated phenols were correct, then the amount of isobutylene should be proportional to the concentration of acetone, and the portion of tert-butyl alcohol should not be affected to any major degree. The stability of the forming tert-butyl radicals is very markedly influenced by the medium.…”

“…The cleavage of the tert-butoxyl radicals into the methyl radicals and acetone is a competitive reaction with respect to the splitting-off of the hydrogen. Ingold [9] has found that a certain amount of tert-butyl chloride is formed during the decomposition of di-tert-butyl peroxide in tetrachloromethane solution. tert-Butyl chloride can be formed only from the tert-butyl radicals or by asymmetric splitting of di-tert-butyl peroxide.…”