( 144) 



Chemistry. — nThe rale of sKbdifidlon of a nilrof/roiip hij an 

 oxalkyr'. By Prof. C. A. LoiuiY de Bruyn. Witli roferonce 

 to Dr. a. Steger's dissertation. 



Up to this moment uo investigation had taken phice of the velo- 

 city of substitution of the atoms or atomgroups, immediately connected 

 with the benzene molecule by other groups; yet such an investiga- 

 tion was of importance for the knowledge of the qualities of the 

 benzene-nucleus and tlie influence of the ditterent places on each 

 other. A reaction which was excellently fit for this purpose I had 

 formerly met in a comparative study on the three dinitrobenzenes 

 viz. the substitution of one of the nitrogroups in ortho- and para- 

 dinitrobenzene by oxymethyl or oxyethyP) according to the equation: 



Co II. ^l] + Ka O CH3 (C, II,) = Co H, ^^^^^ ^^' ^^'^ + Na NO,. 



A preliminary expeiiraent had already shown me that the para- 

 dinitrobenzene at 0° is more speedily substituted with natrium- 

 methylate than ortho-dinitrobenzene. 



Now Mr. Steger has studied quantitatively the four above 

 mentioned reactions at temperatures of 25°, 35° and 45° ; besides 

 the influence of concentration, that of the presence of a natriuniion 

 and that of the gradual adjunction of water were also examined. 

 The results of this study, published by Mr. Steger as a dissertation, 

 are of general interest, to which I think I may draw attention. 



In the first place then it is now proved tluit tlie velocity of 

 substitution is greater with paradinitrobenzene than with ortho- 

 dinitrobenzene ; for both the transposition takes place more speedily 

 with natriumethylate than with natriummethylate, a phenomenon 

 that agrees with the observations of others. The conduct of ortho- 

 and paradinitrobenzene is not the same for the two alkylates, a 

 difference that may be brought back to the influence of the two 

 alcohols that served as solvents. The influence of the temperature 

 however, being difi'ereut for the two dinitrobenzenes, was equal for 

 each of them towards the two alcoholates. 



The question as to the influence of the concentration on tlie ve- 

 locity of reaction was important with a view to an investigation by 

 Hecht, Conrad and Bruckner^) on the vcdocity of acthcnforniation, 



1) Kecuoil 13 (1891) Kll, 100. 



2) Z. f. phys. Cli. 5 (LS'JÜ) 289. 



