48 



D. SHUGAR 



.A. , 



C^HB 



f? 



*- 



W s 



Fig. 3. Simple source of high intensity 253.7 m/* radiation constructed from germi- 

 cidal lamp; for description see text [Shugar and Wierzchowski, unpublished]. 



2. Preparative Photochemistry 



Photochemical procedures, although limited in scope because of the fre- 

 quent difficulty of predicting the course of a reaction, have nonetheless been 

 profitably applied to the synthesis of a large number of new compounds, 

 and reference should be made to the excellent and detailed articles of 

 Schenck 37 and Masson et a/. 38 on the applications of photochemistry in syn- 

 thetic organic chemistry. It will be shown in Section V that a variety of 

 pyrimidine derivatives, including nucleosides and nucleotides, are trans- 

 formed into new derivatives instead of undergoing ring rupture. 39 We have 

 found the source described in the previous section suitable for the prepara- 

 tion of 50-60 mg. quantities of such photoproducts in a single run; but this 

 could undoubtedly be stepped up considerably by sealing the tube T to the 

 lamp at the upper end and introducing a continuous flow of the reactant. 



3. Light Intensity Measurements 



By far the most convenient procedure, as well as the most accurate, for 

 the measurement of light intensities, is by chemical actinometry. The uranyl 



37 G. O. Schenck, Angew. Chem. 64, 12 (1952); 69, 579 (1957). 



38 C. R. Masson, V. Boekelheide, and W. A. Noyes, in "Techniques of Organic 

 Chemistry" (A. Weissberger, ed.), Vol. II. Interscience, New York, 1956. 



39 D. Shugar and K. L. Wierzchowski, Postepy Biochem. 4, Suppl., p. 243 (1958). 



