84 INFRA-RED ABSORPTION SPECTRA. 



AMIDO AND NITRO DERIVATIVES 01^ BENZENE, 



Aniune. CeHsNHj. (Fig. 91.) 



This compound differs from toluene, CeH^CHg, in that it has an NHj- 

 group instead of a CHg-group attached to the benzene nucleus. The 

 selection was made purposely to compare the effect of an NH2 to a 

 CHg group when substituted for an H atom in the benzene ring. The 

 result is a marked change in the region of 3 fi. The NH^-group has 

 the greatest effect ; at least it is able to manifest the 2.98 ju. band found 

 in NH3, as distinguished from the benzene band at 3.25/*, while the CH3- 

 group has only caused a shifting in the benzene maximum to 3.32 fi, 

 which is the mean of the 3.25 fi band of benzene and the 3,43 n band 

 found in CHg compounds. However, this may depend upon the actual 

 width of the lines. In the latter case the CHg-group would appear to 

 have the greater influence. At 6,1/1, the large spectrometer failed to 

 resolve the line, so that it is difficult to say whether the 6.25 /* band of 

 benzene is actually shifted or whether it is double, like the one at 3,2 /x. 

 This apparent shift is toward the shorter wave-lengths, just as observed 

 by Kriiss^ for nitrogen compounds. However, in the present case the 

 band of the original benzene nucleus still remains, with a new band 

 toward the shorter wave-lengths. It will be interesting to learn whether 

 Kruss actually found a shifting toward the shorter wave-lengths or 

 whether, in his nitro-indigo solutions, the original indigo band disap- 

 pears in the process of diluting the solution. As a whole, the introduc- 

 tion of the NHg-group has seriously disturbed the spectrum of the ben- 

 zene nucleus, except at 3.25 yu,. When compared with its isomer, picoline, 

 we find but few bands in common, except at 2.g2ix. The observations 

 were made of freshly distilled aniline. 



Methyl Aniune. CeHoNH (CH3) . (Figs. 32 and 93.) 



It The introduction of the methyl group in aniline 



vc-^^CH ^^^ decreased the intensity of the 2.97 /x band, while 



II I ^u the 3.25 IX band of benzene is almost obliterated by 



\_<^~ ^CH3 the one at 3.4/u.. The compound is far more trans- 



H parent, so that two strong bands at 13.3 fi and 14.5 /x 



could be located. The aniline film of same thickness becomes opaque 



at 12 ft. Certain bands of aniline are in common with this compound. 



The large spectrometer shows the 6,i ju, band of aniline shifted to 6,2 /t, 



while a new band occurs at 6,95 ju., 



*Kruss, loc. cit. 



