Question

The purine heterocycle occurs mainly in the structure of DNA.Identify number of 'N' atoms having localised lone pair of electron.

Answer 1

${}^{\prime }{N}^{\prime }$ surrounded by three groups is hybridized. In purine; all nitrogen atoms are hybridised.

This is because the two ${}^{\prime }{N}^{\prime }$ atoms in the six membered ring and one of the ${}^{\prime }{N}^{\prime }$ atoms in five membered ring are surrounded by three groups.