Purines tautomerism, electronic aspects

The tautomeric forms can be frozen when a particular hydrogen is replaced by a methyl group. These methyl derivatives show, m most cases, very characteristic UV spectra similar to their parent NH compounds. When the assignment of the Wmethylpurines is unambiguous, the most favored NH tautomer can be determined on the basis of the similarity of the UV spectra. Moreover H, C, and N NMR spectroscopy can now be used to deleimine prototropic tautomerism. Electronic aspects of tautomerism have been discussed. A recent review summarizes a number of data. The main tautomeric forms of various purines and their methods of detection are summarized in Table 2. 

Pullman, A., Pullman, B., Electronic Aspects of Purine Tautomerism, 13, 77. 

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