79239-18-2

Upstream product

• 19920-04-8 tetrakis-(4-methoxy-phenyl)-ethanone 
• 94-36-0 dibenzoyl peroxide 
• 437-30-9 4,4',4-trimethoxytrityl tetrafluoroborate 
• 18819-89-1 tetrabutylammonium benzoate 
• 3010-81-9 tris(4-methoxyphenyl)methanol 
• 98-88-4 benzoyl chloride 

Relevant academic research and scientific papers

Stabilities of trityl-protected substrates: The wide mechanistic spectrum of trityl ester hydrolyses

Ionization rates of para-substituted triphenylmethyl (trityl) acetates, benzoates, and para-nitrobenzoates have been determined in aqueous acetonitrile and aqueous acetone at 25 °C. Conventional and stoppedflow techniques have been used to evaluate rate constants ranging from 1.38 × 10-5 to 2.15 × 102S-1 by conductimetry and photospectrometry methods. The varying stabilities of the differently substituted tritylium ions account for a gradual change of reaction mechanism. Poorly stabilized carbocations are generated slowly by the ionization of their covalent precursors and trapped fast by water. Better stabilized carbocations are generated more rapidly and accumulate, so that ionization and trapping by water can be observed as separate steps in a single experiment. Finally, highly stabilized tritylium ions do not react with water, and only the rates of their formation could be measured. The ionization rate constants correlate linearly with Winstein's ionizing powers Y; the low slopes (0.17 + parameters is excellent for symmetrically substituted tritylium derivatives, deviations for unsymmetrically substituted systems are observed. The failing rate-equilibrium relationship between the rates of ionizations (log kion) and the stabilities of the carbocations in aqueous solution (pKR+) may be explained by the late " development of resonance between a p-amino group and the carbocationic center of the tritylium ion during the ionization process.

One-electron Oxidation of Closed-shell Molecules. Part 3. Oxidative Cleavage of 1,2,2,2-Tetrakis-(p-methoxyphenyl)ethanone with Dibenzoyl and Bis(3,5-dinitrobenzoyl) Peroxides: Mechanistic Changeover of the Peroxide Function from Radical to Molecular Oxidation

1,2,2,2-Tetrakis-(p-methoxyphenyl)ethanone (anispinacolone) (1) is cleaved by dibenzoyl peroxide (2) or bis-(3,5-dinitrobenzoyl) peroxide (3), affording tris-(p-methoxyphenyl)methyl benzoate (or 3,5-dinitrobenzoate) and benzoic (or 3,5-dinitrobenzoic) p-methoxybenzoic anhydride as the principal cleavage products. 13C N.m.r.CIDNP studies by use of labelled anispinacolone (An3*C-*COAn ; *C 90percent 13C) indicated that p-methoxybenzoyl radical is formed, presumably by way of the radical cation +. which is produced by a single-electron transfer (s.e.t.) mechanism.The formation of the p-methoxybenzoyl radical was also indicated by spin-trapping experiments.The decomposition rates of (2) at 50.0 deg C are unaltered on addition of (1) in nonpolar solvents such as dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, and benzene, whereas those of (3) are markedly accelerated.The cleavage of (1) by (2) is supressed by added 3,4-dichlorostyrene by a factor of 6.7, whereas that of (1) by (3) is almost unaffected.These results suggest that in the case of dibenzoyl peroxide (2) the thermally produced benzoyloxyl radical works as a one-electron acceptor (or oxidant) upon (1), whereas when bis-(3,5-dinitrobenzoyl) peroxide (3) is used the peroxide molecule oxidizes (1), probably by way of an s.e.t. mechanism even in such nonpolar solvents.On the other hand, in polar solvents such as (CF3)2CHOH, teramethylene sulphone, and acetonitrile the decomposition of (2) is accelerated by added anispinacolone, suggesting that the intermolecular s.e.t. reaction is partially involved in such polar solvents.Consequently, the oxidative cleavage of anispinacolone (1) by diaroyl peroxides provides the first example of dichotomy in the s.e.t. reaction of diaroyl peroxides, which can be considered a counterpart of the SN1-SN2 dichotomy in nucleophilic substitution, as far as the molecularity of the peroxide is concerned.