ON ABSORPTION SPECTRA OF ORGANIC COMPOUNDS. 241 



are not balanced the condensation ■will not be so g*eat, and a balance of force 

 lines of one type will remain uncompensated. If this balance be removed in 

 6ome way then there will be nothing to prevent the condensation from proceed- 

 ing further with the escape of more fundamental infra-red quanta and the 

 formation of a more highly condensed phase. It may be noted in passing that 

 an uncompensated balance of force lines remaining after the condensation of 

 the force field has take place is in all probability the origin of what is known 

 to chemists as residual affinity, Let the case be considered of a molecule which 

 possesses residual affinity of an acid type, and let this molecule be brought 

 into the neighbourhood of another molecule which possesses a force field basic 

 in type. The two will together form a complex, and since the residual affinity 

 of the first is now compensated there is no reason why its force field should 

 not undergo further condensation with the evolution of one or more funda- 

 mental infra-red quanta. Provided that the fundamental infra-red frequencies 

 of the two molecules are similar, these quanta mav be absorbed by the second 

 molecule, which is thereby converted into a less condensed phase. The 

 similarity of the infra-red fundamental frequencies necessary for this trans- 

 ference of energy quanta is very probable, because, in the first place, observa- 

 tion shows that the fundamental infra-red frequencies of at any rate organic 

 compounds are very near together. In the second place, it has been found 

 that when two substances with not very different fundamental infra-red fre- 

 nuencies form a complex, this complex becomes endowed with a new funda- 

 mental infra-red frequency of its own which lies between those of its com- 

 ponents. This is of material importance, not only because it shows that the 

 complex is a definite entity, but also because the mechanism for transference 

 of fundamental infra-red quanta from one component to the other is perfect. 

 It would seem that in this process is to be found the explanation of the change 

 of phase which frequently takes place when organic compounds pass into 

 solution. 



It is not possible to avoid mentioning the bearing of this \ipon the whole 

 problem of catalysis. It has already been stated that each phase of a given 

 molecule is endowed with its own reactivity, and that in order to cause 

 a molecule to enter into a specific reaction it is necessary to bring it into 

 the proper phase. This change of phase mav be produced by the action of 

 light, in which case the reaction is called a photochemical one. On the other 

 hand, the chauge in pha?e may be produced by a material substance which 

 is called a catalyst. The substance is a catalyst because it increases the 

 velocity of the particular reaction, owing to the fact that it brincr.s more 

 molecules into the reactive phase than would otherwise pxist in that phase. 

 Not thp Ipast interesting apnlication of tbe present theory is to the phenomenon 

 of catalvsis, a phenomenon which has not hitherto found a completely satisfactory 

 explanation. 



After what has been stated of the existeno° of molecular phases, fach with 

 its own characteristic frequency in the visible or ultra-violet, a frequen^'v 

 which is an exact multiple of the infra-red fundamental, it is perhaps scarcelv 

 ppcessary to discuss many of the observations of the absorption spectra of 

 "rp-aiic compounds, sinco the application of the theory is obvious. In nrrJpr 

 to illustrate this amplication, however, some of the observations rppoi-ded in 

 the earlier pases of this report may be considered, and the case of ethyl aceto- 

 acptate and its derivatives may be selected first. It was shown nuito clearly 

 thnt neither the original theory of tautompric ^-quilibrium nor the Hantzsrh 

 siy-memhprpd ' ring ' formula can explain the absorption band shown bv the 

 soHium salt. The absorption band is due t^o the fact that the substance in 

 the presence of a basic solvent is chauwed i"to a phase thp characteristic 

 ahsnrption band of which lies in the ultra-violet region. This alteration of 

 phaop is characteristic of the ketonic form, since the disubstitut«d compound, 

 ethvl dimethvlacptoacetat*. shows the same band when dissolved in a basic 

 solvent. It is nnteworthv that exactly the same bands are shown when these 

 compounds are dissolvpd in piperidine. 



Thpi reason why the two derivativps, ethyl /?-ethoxycrotonate and ethvl 

 dimethylacetoacetate, show only general ah.sorption in alcoholic solution is 

 because they exist in a phase the characteristic band of which lies in the extreme 

 1920 » 



