Benzoic acid

About: Benzoic acid is a research topic. Over the lifetime, 11832 publications have been published within this topic receiving 167127 citations. The topic is also known as: Retardex & E210.

Absolute rate constants for reactions of phenyl radicals

Abstract: The absolute rate constant for the addition of p-carboxyphenyl radical to p-bromobenzoate anion in aqueous solution has been determined by optical pulse radiolysis and time-resolved ESR (electron spin resonance) experiments to be 7.6 x 10/sup 6/ M/sup -1/ s/sup -1/ (corrected to zero ionic strength). The rate constants for addition of phenyl radicals to typical aromatic systems should be of this same magnitude. Addition of p-carboxyphenyl radical to benzene occurs with a similar rate constant and results in the formation of a substituted cyclohexadienyl radical that can be quantitatively oxidized to biphenyl-4-carboxylic acid. Abstraction from hydrogen donors results in the quantitative formation of benzoic acid. By reference to the absolute rate for addition to p-bromobenzoate the rate constant for H abstraction from isopropyl alcohol has been determined from competitive measurements of benzoic acid formation to be 5.2 x 10/sup 6/ M/sup -1/ s/sup -1/. Measurements by optical pulse radiolysis and time-resolved ESR methods give comparable values. H atom abstraction from other alcohols is found to be only modestly slower. It is clear from these measurements that the lifetime of phenyl radicals in the presence of most organic materials will usually be very low so that reactions second order in phenylmore » radicals will not normally be important.« less

Preparation and characterization of mu-nitrido diiron phthalocyanines with electron-withdrawing substituents: application for catalytic aromatic oxidation.

Abstract: μ-Nitrido-bis [tetra-(hexyl-sulfonyl)phthalocyaninatoiron] (3a) and μ-nitrido-bis [tetra-(tert-butylsulfonyl) phthalocyaninatoiron] (3b) complexes have been prepared and fully characterized by electrospray ionization mass spectrometry, UV-Vis, FTIR, EPR, Mossbauer techniques as well as by X-ray photoelectron and Fe K-edge X-ray absorption spectroscopies. Small changes at the periphery of the phthalocyanine ligand introduce a difference in the iron oxidation state. While 3b with tert-butyl substituents is a neutral complex with a mixed-valence Fe3.5–N–Fe3.5 structural unit, 3a having n-hexyl substituents is an oxidized cationic FeIV–N–FeIV complex. The structural parameters of N-bridged diiron phthalocyanine with a Fe3.5–N–Fe3.5 unit were determined for the first time. Iron atoms in 3b are displaced out of plane by 0.24 A and the Fe–N bond distance of the linear Fe–N–Fe fragment is equal to 1.67 A. Both complexes selectively catalyze benzylic oxidation of alkyl aromatic compounds by tBuOOH. Toluene was oxidized to benzoic acid with 80% selectivity, and the total turnover number was as high as 197. p-Toluic acid was the principal product of p-xylene oxidation. In this case the turnover number achieved 587 substrate molecules per molecule of catalyst. The described catalytic system is complementary to the recently reported system based on μ-nitrido diiron tetrabutylphthalocyanine–H2O2 which effectively oxidizes the benzene ring.