Kinetics of Chemiluminescence of the 

 2,3-Dihydrophthalazine-l,4-diones 



Paul C. Wilhelmsen," Rufus Lumry,! and Henry Eyring 

 Department of Chemistry, University of Utah, Salt Lake City, Utah 



The purpose of this paper will be to present some new data from 

 experiments on the chemiluminescence of the 2,3-dihydrophthalazine- 

 1,4-diones (DPD) and in particular the 5-amino derivative (luminol). 

 In addition, a brief discussion will be given of the known facts on 

 which a mechanism for the chemiluminescence of the DPD's must be 

 based. A tentative mechanism will be proposed which explains the 

 available facts and points out possible directions for further investiga- 

 tion. 



The most important data that this paper will discuss have to do 

 with the kinetics of the reaction. Chemiluminescent reactions such as 

 the oxidation of the DPD's are particularly well adapted for kinetic 

 studies. The intensity of the hght emitted by a chemiluminescent 

 reaction is the number of photons (I) emitted per second. The 

 number of photons emitted is in turn related to the number of excited _ ^^.■Jf'>'^'^ 

 molecules A* and the rate of emission k^: 



I = M* (1) 



The number of excited molecules is a function of their rate of produc- 

 tion 



B ^ .4* (2) 



* A research fellowship granted by the University of Utah Research Com- 

 mittee which greatly aided this author's contribution to this work is grate- 

 fully acknowledged. The work was partially supported by the United States 

 Atomic Energy Commission. 



f Present address: Institute of Technology, School of Chemistry, Uni- 

 versity of Minnesota, Minneapolis, Minnesota. 



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