Question

Why extra pair of amines needed in dye structure?

Answer 1

Amine Structure

Nitrogen has 5 valence electrons and so is trivalent with a lone pair. As per VSEPR theory, nitrogen present in amines is sp3 hybridized and due to the presence of lone pair, it is pyramidal in shape instead of tetrahedral shape which is a general structure for most sp3 hybridized molecules. Each of the three sp3 hybridized orbitals of nitrogen overlap with orbitals of hydrogen or carbon depending upon the configuration of amines. Due to the presence of lone pair, the C-N-H angle in amines is less than 109 degrees which is a characteristic angle of tetrahedral geometry. The angle of amines is near about 108 degrees.