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The crystal and molecular structure of 7-methyl-8-azaadenine (6-amino-7-niethyl-8-azapurine), CzH6N6, has been determined from three-dimensional x-ray counter data obtained using Mo Ka radiation. The material crystallizes in the orthorhombic space group Pbcn with eight formula units in a cell of dimensions a = 7.578 (2), b = 13.328 (3), and c = 12.566 ( 4 ) A. The observed and calculated densities are 1 .57 (3) and 1.572 g cmW3, respectively. The structure has been refined to a final value of the conventional R factor (on F ) of 0.041 using 1 I25 independent intensities. The azapurine ring is approximately planar. w i t h no atom deviating from the least-squares plane by more than 0.03 A. There is considerable intermolecular hydrogen bonding in the crystals, involving N ( I ) and N(3) as acceptors and the amino group as the donor. I t is noteworthy that neither N(8) nor N ( 9 ) participate in hydrogen bonding. A C N D 0 / 2 molecular orbital calculation provides a n explanation for this observation b j showing that the residual negative charges on K( I ) and N(3) (-0.27 and -0.23 electron, respectively) are much larger than those on N(8) and N(9) (-0.01 and -0.16 electron, respectively).T h e 8-azapurines ( I ) , which a r e purines (11) in which the imidazole ring has been changed t o a 1,2,3-triazole, a r e of H

Antiallergenic 8-Azapurines. 3. Structural Characterization of 2-(2-Propoxyphenyl)-8-azahypoxanthine, 2-(2-Propoxy-5-(propylsulfonyl)phenyl)-8-azahypoxanthine, and 2-(2-Propoxy-5-(7V-methyl-7V-isopropylsulfamoyl)phenyl-8-azahypoxanthine

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