ON DYNAMIC ISOMERISM; 81 



The introduction of a second — C=0 group in compounds such as 



I 



/ C(CH 3 )CO.OCH 3 



methyl methylcamphocarboxylate, C 8 H U / , does not 



x co / 



intensify the band, as the two carbonyls are not copulated owing to 

 the fact that they are separated by two single linkages instead of 



one. In camphorquinone C 8 H 14 / , on the other hand, the band 



X C=0 



is brought right into the visible region at 1/2050 and its persist' 

 ence is increased from log. thickness 0'3 to 1*6 ; the penetration of the 

 band is, however, practically the same as in camphor, log. thickness 

 2*6, the decrease in the frequency of the maximum absorption being 

 accompanied by no marked increase in its intensity. The decrease of 

 frequency gives rise to what Schutze has called a ' deepening ' of 

 colour, an effect which he has conveniently described as ' batho- 

 chromic,' in contrast with the ' hypsochromic ' action of compounds 

 which cause an increase of frequency and a ' lightening ' of the colour. 



yC = CH 2 



In methylene camphor, C 8 H M / , the introduction of the 



x c=o 



second unsaturated group produces an entirely different effect, the 

 frequency of the band being unaltered, but its penetration increased 

 to log. thickness 1"7. The copulation of the two groups is thus accom- 

 panied by an actual increase of specific or local absorption, an effect 

 which may be regarded as genuinely ' auxochromic. ' 



A further increase of penetration to log. thickness 0*3 is produced 

 by the introduction of a third unsaturated centre as in benzylidene 



yC : CH.C 6 H 5 

 camphor, C 8 Hj / , and the derivatives of oxymethylene 



X CO 



/C : CH.OR 

 camphor, C 8 H H <f | . The nature of the substituent radicle E 



x CO 

 in the enolic compounds, 



/C : CX.OE ,C.CO 



(a)C 8 H u < | and(6)C 8 H I4 < l| , 



X CO X C.OE 



has no marked influence on the penetration, but the frequency of the 

 band decreases by about 200 unitB when sodium is substituted for 

 hydrogen or methyl, whilst an increase of similar magnitude results 

 from the displacement of hydrogen by acetyl ; the bridging of the ethe- 

 noid linhage, which is the main difference between the enolic formulae 

 («) and (/>), is accompanied by a decrease of frequency. 



1910. 



Q 



