Redox Disproportionation Research Articles

Kinetics of the crossed Cannizzaro reaction of benzaldehyde with formaldehyde in aqueous solutions of potassium hydroxide

1. The kinetics of the crossed Cannizzaro reaction of benzaldehyde with formaldehyde was investigated spectrophotometrically in aqueous solutions of KOH at 25°C. 2. The activated complex of the reaction is formed from the twice ionized form of formaldehyde and a nonionized molecule of benzaldehyde. 3. The equilibrium constants of the ionization of formaldehyde (KIeq)FA = 0.51, benzaldehyde (Keq)BA = 14, and the ratio of the constants ktrue/(KIIeq)FA = 0.33 liters/mole min, characterizing the reactivity of the formaldehyde-benzaldehyde pair in redox disproportionation, were determined.

Mechanism of benzidine and semidine rearrangements. Part XXIV. Photochemical decomposition of hydrazoarenes

Ultraviolet irradiation of N-1-naphthyl-N′-phenylhydrazine (I), 1,1′-hydrazonaphthalene (II), 4-nitrohydrazobenzene (III), or 4-methoxyhydrazobenzene (IV), in n-hexane led to over 80% recovery of disproportionation products but only traces of those from benzidine-type rearrangements. The proportions of azo-compounds formed were greater than that expected for bimolecular redox disproportionation and were altered by changes in reaction temperature and substrate concentration.No azo-compounds were formed by cross-combination of the possible fission-fragments of (I), (III) or (IV), and isotopic analysis of products from deuteriated (I) and (II) confirmed that azo-compounds resulted from oxidation without fission of the N,N-bond. The rates of disappearance of isotopically normal (II) and hydrazobenzene and their corresponding [15N]-labelled analogues were the same.These results are consistent with a mechanism involving formation of a hydrazyl radical in the rate-limiting step.

Phosphorus–fluorine chemistry. Part XX. Redox disproportionation of difluorophosphines, RPF2, with electronegative substituents R

Difluorophosphines, RPF2, containing the electronegative substituents, R = CF3 and C6H5, will undergo redox disproportionation with formation of tetrafluorophosphoranes and cyclopolyphosphines, in accord with the overall equation 10 RPF2→ 5 RPF4+(RP)n(n= 4, 5 for R = CF3; n= 5 for R = C6H5). The identity of the products, all previously known, was established by comparison of their physical properties (n.m.r. and mass spectra, i.r. spectra, X-ray powder diagram, etc.) to those of the authentic compounds.

Isochinoline. 1. Mitteilung. Über die Umlagerung von α, α‐Dialkylhomophtalimiden zu Derivaten des 1‐Chlor‐3, 4‐dialkyl‐isochinolins

AbstractOn reinvestigation of the reaction of wet phosphorus oxychloride with α,α‐dimethylhomophthalimide, 1‐chloro‐3‐chloromethyl‐4‐methyl‐isoquinoline and 1‐chloro‐4‐chloromethyl‐3‐methyl‐isoquinoline were isolated as the main products (aside from some substances resulting from a redox disproportionation). The production of these two substances can be rationalized by assuming a mechanism in which the rearrangement product is a protonated derivative of 3,4‐dimethylene‐3, 4‐dihydroisoquinoline. With α, α‐diethyl‐homophthalimide the only isolated product was a derivative of 1‐chloro‐3, 4‐diethyl‐isoquinoline, with a chlorine atom in β‐position of one of the ethyl groups, while with α‐methyl‐α‐benzyl‐homophthalimide the isolated product was 1,3‐dichloro‐4‐methyl‐isoquinoline, i.e. elimination had taken place instead of rearrangement. Also these results are in agreement with the proposed mechanism.