Radical of benzoic acid

Fhoto loaned by Frau Hiickei, GSttingen, Germany Wohler in Later Life,4 Professor of chemistry at GcSttingen. Famous for his researches on cyanogen, cyanuric acid, and the radical of benzoic acid, and on the metals titanium, aluminum, yttrium, beryllium, and vanadium. German translator of Berzelius Textbook of Chemistry and Hisinger s Mineral Geography. ... 

The American Journal of Science and Arts Researches Respecting the Radical of Benzoic Acid (p. 261)... 

The circumstance that a body composed of carbon, hydrogen, and oxygen, combines with other bodies, particularly with such as form salts, after the manner of a simple body, proves that there are ternary composed atoms (of the first order) and the radical of benzoic acid is the first example proved with certainty, of a ternary body possessing the properties of an element. It is true indeed that we have before considered sulphwret of cyanogen (Schwefelcyan) as such, but you are aware that its combinations may be viewed as sulphurets and the body itself seems to be a sulphuret of cyanogen. 

Alkaloids of the Aconites.—The different species of Aconitam contain, probably, a number of alkaloids, but our knowledge of them is as yet extremely imperfect. The substances described as aconitin. lycoctanin, napellin are impure." It appears, however, that the principal alkaloids of aconitum napellus and of A. ferox, although differing from each other, are both compounds formed by the union of aeonin, CseHsgITOii, with the radical of benzoic acid in the former, and with that of veratric acid in the latter. 

Benzyl Chloride. Benzyl chloride is manufactured by high temperature free-radical chlorination of toluene. The yield of benzyl chloride is maximized by use of excess toluene in the feed. More than half of the benzyl chloride produced is converted by butyl benzyl phthalate by reaction with monosodium butyl phthalate. The remainder is hydrolyzed to benzyl alcohol, which is converted to ahphatic esters for use in soaps, perfume, and davors. Benzyl salicylate is used as a sunscreen in lotions and creams. By-product benzal chloride can be converted to benzaldehyde, which is also produced directiy by oxidation of toluene and as a by-product during formation of benzoic acid. By-product ben zotrichl oride is not hydrolyzed to make benzoic acid but is allowed to react with benzoic acid to yield benzoyl chloride. 

Phenyl radicals can be generated by the thermal decomposition of lead tctrabcnzoate, phenyl iodosobenzoate, and diphenyliodonium hydroxide,- - and by the electrolysis of benzoic acid.- These methods have been employed in the arylation of aromatic compounds, including heterocycles. A method of promise which has not been applied to the arylation of heterocycles is the formation of aryl radicals by the photolysis of aromatic iodides at 2537... 

Pyridine has been phenylated with the following free-radical sources benzenediazonium chloride with aluminum trichloride the Gomberg reaction " phenylhydrazine and metal oxides A -nitroso-acetanilide dibenzoyl peroxide phenylazotriphenylmethane di-phenyliodonium hydroxide and electrolysis of benzoic acid. ° Although 2-phenylpyridine usually accounts for over 50% of the total phenylated product, each of the three phenyl derivatives can be obtained from the reaction by fractional recrystallization of the... 

The initiator-derived radical products generate a-tocopheroxyl radicals (2) from a-tocopherol (1). The radicals 2 are further oxidized to ort/io-quinone methide 3 in a formal H-atom abstraction, thereby converting benzoyloxy radicals to benzoic acid and phenyl radicals to benzene. The generated o-QM 3 adds benzoic acid in a [ 1,4] -addition process, whereas it cannot add benzene in such a fashion. This pathway accounts for the observed occurrence of benzoate 11 and simultaneous absence of a 5 a-phenyl derivative and readily explains the observed products without having to involve the hypothetical C-centered radical 10. 

If we make the assumption that the reverse of reaction 15.5 is diffusion-controlled and assume that the activation enthalpy for the acyl radicals recombination is 8 kJ mol-1, the enthalpy of reaction 15.5 will be equal to (121 - 8) = 113 kJ mol-1. This conclusion helps us derive other useful data. Assuming that the thermal correction to 298.15 K is small and that the solvation enthalpies of the peroxide and the acyl radicals approximately cancel, we can accept that the enthalpy of reaction 15.5 in the gas phase is equal to 113 kJ mol-1 with an estimated uncertainty of, say, 15 kJ mol-1. Therefore, as the standard enthalpy of formation of gaseous PhC(0)00(0)CPh is available (-271.7 5.2 kJ mol-1 [59]), we can derive the standard enthalpy of formation of the acyl radical Af//°[PhC(0)0, g] -79 8 kJ mol-1. This value can finally be used, together with the standard enthalpy of formation of benzoic acid in the gas phase (-294.0 2.2 kJ mol-1 [59]), to obtain the O-H bond dissociation enthalpy in PhC(0)0H DH° [PhC(0)0-H] = 433 8 kJ mol-1. 

The phenylation of thiophene with benzoyl peroxide gave a considerable amount of 2,2 -dithienyl one suggested mechanism involved the formation of 2-thienyl radicals by oxidation, and their subsequent dimerization. More recent studies indicate that the 2,2 -dithienyl is formed through an initial addition of benzoyloxy radicals to the thiophene nucleus followed by dimerization of the resulting radical and loss of two molecules of benzoic acid (Scheme 15). 

The OH radicals are trapped by reaction with benzoic acid, forming hydroxybenzoic acid, which is measured by fluorescence. Organic peroxides ROOH form RO + OH-, but the derivatives of benzoic acid formed by the reaction of the RO radicals do not fluoresce under the conditions chosen to measure H202. Thus, in principle, this second channel measures H202. However, in practice, it was found to give about a 30% response to hydroxymethyl hydroperoxide as well, so that the results from this channel must be corrected for this contribution (Lee et al., 1993). 

The production of hydroxyl radicals was also shown by the oxidation of benzoic acid, a specific scavenger, with stimulated human granulocytes and by the formation... 

Some support for this mechanism derives from our observation of benzyl radical from phenylacetic acid, phenoxymethyl radical from phenoxy-acetic acid, and possibly the phenyl radical from benzoic acid. Radical spectra were not found for several aryl acids with longer side chains but this is not inconsistent because the 0-phenylethyl and higher radicals are not expected to absorb strongly above 300 m/z. The case of the heterocyclics is complicated by the possibility of excitation either via the 7r-system or a lone pair electron on the heteroatom, and discussion of this group will be deferred until additional experimental data are obtained. 

X-ray ionization of o-vinylbenzaldehyde (136) in argon matrices leads to the quinoketene (137) via die radical cation, detected by IR spectroscopy.298 The product identity was confirmed by the independent preparation of (137) and (137+-) by the photo-stimulated ring-opening of 2-methylbenzocyclobutenone (138) (Scheme 21). The reactions of benzaldehyde, acetophenone, and benzophenone with OH, 0 and SC>4 have been studied by pulse radiolysis in aqueous solution.299 The addition of OH to the carbonyl moiety of benzaldehyde predominates over addition to the aromatic ring, whereas ring addition is predominant in the case of acetophenone. Disproportionation of the exocyclic OH adduct is proposed to explain the formation of benzoic acid, which is a major product in the reaction of benzaldehyde and OH or SO4T Rate constants for each reaction have been calculated. 

Oturan MA, Pinson J. Hydroxylation by electrochemically generated OH radicals. Mono- and polyhydroxylation of benzoic acid products and isomers distribution. J Phys Chem 1995 99 13948-13954. 

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