The vibrational analysis and assignment of the infrared bands of 3,6-dichloro-pyridazine recorded in the region (300–4000 cm⁻¹) in KBr phase and electronic absorption band in the region (3625–3220 A) in vapour phase are reported.

This paper presents the investigations of the electronic and vibrational spectra of 2,4,6-trichloropyrimidine and 6-chloro 2,4-dimethoxypyrimidine. The electronic spectra have been recorded in the liquid and vapour states in the region 50000-28000 cm⁻¹. Then-π and π-π transitions are classified in each case. Infrared absorption spectra of 2,4,6-trichloropyrimidine in nujol have been recorded in the region 4000-400 cm⁻¹. It is concluded that substituents like Cl or OCH₃ do not have much influence on thesp² electron of the nitrogen atom of the ring. From infrared studies the mass-dependent modes and the modes insensitive to substitution have been pointed out. The assignments are tentative and are based on the group frequency approach and data available for similar molecules.