Diazepam. Computer graphic of a molecule of diaze- pam, also known commercially as valium, a tranqu- illiser drug. The molecule's atoms are colour- coded: carbon (C) is blue, hydrogen (H) is white, chlorine (Cl) is green, nitrogen (N) is turquoise and oxygen (O) is red. Diazepam's chemical formula is C16H13ClN2O. Diazepam, a type of benzodiaze- pine, is a minor tranquilliser with anti-convulsant properties used in the treatment of anxiety and as a hypnotic. It acts centrally on the brain's limbic system. It may cause loss of muscle coordination (ataxia), involuntary movements of the eyes (nystagmus) and sedation. It may cause dependence in users, even in therapeutic doses.