Wibaut

Characteristics of the system as nitrating reagents Wibaut, who introduced the competitive method for determining reactivities (his experiments with toluene, benzene and chlorobenzene were performed under heterogeneous conditions and were not successful), pointed out that solutions of nitric acid in acetic anhydride are useful in making comparisons of reactivities because aromatic compounds are soluble in them. ... 

First-order nitrations. The kinetics of nitrations in solutions of acetyl nitrate in acetic anhydride were first investigated by Wibaut. He obtained evidence for a second-order rate law, but this was subsequently disproved. A more detailed study was made using benzene, toluene, chloro- and bromo-benzene. The rate of nitration of benzene was found to be of the first order in the concentration of aromatic and third order in the concentration of acetyl nitrate the latter conclusion disagrees with later work (see below). Nitration in solutions containing similar concentrations of acetyl nitrate in acetic acid was too slow to measure, but was accelerated slightly by the addition of more acetic anhydride. Similar solutions in carbon tetrachloride nitrated benzene too quickly, and the concentration of acetyl nitrate had to be reduced from 0-7 to o-i mol 1 to permit the observation of a rate similar to that which the more concentrated solution yields in acetic anhydride. 

Wibaut, J. P. (1915). Reel Trav. chim. Pays-Bas Belg. 34, 241. 

Dibromopyridine [626-05-1 ] M 236.9, m 117-119 , 118.5-119 , b 249 /757.5mm, pKErt< - Purified by steam distn then twice recrystd from EtOH. Does not form an HgCl2 salt, [den Hertog and Wibaut Rec Trav Chim Pays Bas 51 381 1932.]... 

This explanation has been revised recently by Bickel, who has shown that the product, C,Hii03N, first formed in this reaction, is the monohydrate of iV-methyl-3-methoxypyridone-4, MeO. CgHjONMe, H2O, the chloride, C,Hio02NCl, is the hydrochloride, MeO. C HgONMe, HCl of the same base, and the substance formed when the chloride is heated is N-methyl-3-hydroxypyridone-4. The constitution of the latter had already been established by Wibaut and Kleipol, who had synthesised it by the action of methylamine on meconic acid (V) and decarboxylation of the resulting product (VI) to the desired substance (VII = IV). 

Bickel and Wibaut found in feeding experiments with rats and mice that leucenol is probably the toxic constituent of Leuccena glauca seeds, but they did not observe with these animals the loss of hair which seems to occur when these seeds are fed to cattle. ... 

New syntheses of wopelletierine and its N-methyl derivative have been provided by Wibaut et by an extension of the process used... 

There is great similarity among the first three alkaloids in this table, and the suggestion has been made that they are identical, though a-yohimbine is laevorotatory and the other two are dextrorotatory. Also ethyl yohimbate has m.p. 190 , whilst ethyl woyohimbate is usually stated to melt at 243°, though Wibaut and van Gastel recorded 202° for the ester monohydrate. 

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