ORGANIC CHEMISTRY 551 



of benzene at low pressures is described in the section dealing 

 with Physical Chemistry in this number, while the study of 

 the crystal structure of some benzenoid compounds was the 

 subject of a special article in the December number of this 

 Journal. 



Optically Active Diazo-compoiinds. — Chiles and Noyes (/. 

 Amer. Chem. Soc, 1922, 44, 1798) have published an important 

 paper on optically active diazo-compounds of the type 



R N 



>c/ii 



R^/ \N 



Previously Marvel and Noyes (/. Amer. Chem. Soc, 1920, 42, 

 2259) had described unsuccessful attempts to prepare such 

 bodies, and since the publication of this earlier work Levene 

 and Mikeska (/, Biol. Chem., 192 1, 45, 593 ; 1922, 52, 485) 

 reported that they had obtained diethyl diazosuccinate in an 

 optically active form. The present authors now explain that 

 the lack of success in the earlier experiments was due to the 

 ease with which the compounds racemise and emphasise the 

 necessity of distilling the compounds at very low pressures. 

 The first compound obtained was an active diethyl diazo- 

 glutarate [xx] [a]D + o-85° to + 1-86° obtained by the usual 

 method from of-glutamic ester [xix] 



NH2\ /COgEt N. /COgEt 



C- -> II /C 



H-^ VH2 . CH2 . COaEt N^ ^CHa . CH2 . COaEt 



[xix] [xx] 



Other active compounds obtained were dimethyl a-diazo- 

 glutarate [a]D+0'Sg°, diethyl a-diazosuccinate [a]D~i'23°, 

 ethyl a-diazo-n-caproate [«]© "~ i'89°, ethyl a-diazo-?z-caproate 

 [a]D+i-84, and ethyl a-diazo-iso-caproate [a)D-i'52°. The 

 fundamental importance of these results has caused the authors 

 to give very careful consideration to possible impurities which 

 might account for the activity, and they have satisfied them- 

 selves that it is really due to the diazo-compound. The inter- 

 pretation of these results is a matter of some difficulty. Chiles 

 and Noyes consider that the Curtius formula [xxi] for these 

 active compounds cannot be reconciled with the ideas of 

 atomic structure and of non-polar valence proposed by Lewis 

 and Langmuir, but that the Thiele formula [xxii] can be so 

 reconciled if it is assumed that the polar valence between 



\ 



