92 



KINETICS OF CHEMILUMINESCENCE 



Structural Requirements 



All the DPD's that have been prepared produce light but many 

 similar compounds do not. This information is useful in showing what 

 structural features are necessary for the production of light. Drew 

 and co-workers have made an extensive investigation of this phase of 

 the problem of chemiluminescence. They have found that compounds 

 such as 







€s 



c^ 



-NCH3 



and 



C' 



^NCH3 

 .NCH3 



O O 



do not chemiluminesce (Drew et al, 1937). It should be noted that 

 these compounds cannot form the dienol form of the molecule. The 

 ability to form this molecule is presumably tied in with the ability to 

 produce chemiluminescence. Molecules such as 



OCHs 



X 



\/\c/ 



N 



I 

 I 



N 



and 



OCH3 



I 



N 



C 



r 



OH OCH3 



have also been found not to produce Hght (Drew and Garwood, 

 1937). The substitution of the methyl group for the hydrogen in the 

 enol forms can be acting to inhibit ionization or hydrolysis. Substitut- 

 ing methyl for one of the ionizable hydrogens inhibits the chemilumi- 

 nescence. This implies that both hydrogens are involved in steps leading 

 to chemiluminescence. 



Substituents in the benzene ring have a marked effect on the 

 intensity of the chemiluminescence ( Drew and Pearman, 1937; Zellner 

 and Dougherty, 1937). The effect of these substituents on the intensity 

 of the chemiluminescence could almost be predicted on the basis of 



