The Benzidine Rearrangement. III. Kinetics of the Rearrangements of Hydrazobenzene

Electrochemical investigations on 5-methyl-4-(4 -substituted phenylhydrazono)- 2-(5-thioxo-4,5dihydro-[1,3,4]oxadiazole-2-ylmethyl)-2,4dihydro-pyrazol-3-ones

“…1. The half wave potential of the wave observed was more negative than that expected for the reduction of the simple azo group [17,31].…”

Rearrangements of Hydrazo, Azoxy and Azo Compounds: Kinetic, Product and Isotope Studies

“…Under normal conditions (usually dilute HCl in ca 50% aqueous dioxane or 50-75% aqueous ethanol) the products are mainly 2 and 3, usually quoted as being in a 2 : 3 ratio of 70 : 30 6 , although more recent work shows that the proportion of 2 may well be higher than this, depending upon reaction conditions 7 ; the most recent determination is 85 : 15 8 . The proportions of these and the other products 4, 5 and 6 depend on the substrate; for instance the presence of naphthyl rings leads to more 4, and a p-methoxy substituent to more 5 and 6.…”

“…[1-14 C]azobenzene and [1, 1 -13 C 2 ]azobenzene 8 were prepared from[2-14 C]acetone and[2-13 C]acetone, respectively, by converting them to[1-14 C]-and [1-13 C]-4-nitrophenol14 , the corresponding anilines being derived from these as described8 . [2, 2 , 4, 4 -13 C 4 ]azobenzene was obtained from the [2,6-13 C 2 ]aniline that could be prepared from[1,[3][4][5][6][7][8][9][10][11][12][13] C 2 ]acetone 15 . removing the NH 2 , reducing, acetylating, para-chlorinating and deprotecting, giving [2-14 C]-4-chloroaniline; condensation of this with unlabelled 4-chloroaniline gave the required product 16 .…”

N[1,3]-sigmatropic shift in the benzidine rearrangement: experimental and theoretical investigation

“…Acid-catalyzed benzidine rearrangements have been studied extensively over more than 150 years, 8 in which the parent N, N′-diphenyl hydrazine (1) gives p-benzidine (2, 70%) and diphenyline (3, 30%) 9,10 as the main products and some other secondary products such as o-benzidine (4), p-semidine (5), and o-semidine (6) (Scheme 1). 11 In some cases, o-benzidine, p-semidine, and o-semidine type products were obtained in considerable yields from certain substituted N,N′-diaryl hydrazines.…”