The two lowest singlet potential energy surfaces of the hydrazoic acid are explored using high-level quantum chemistry calculations, revealing isomeric forms, transition states, and a new path for the nitrogen ring closing mechanism in the ground state. The reaction of cyc-N-3 with hydrogen is shown to proceed through a barrierless path that dissociates to N-2 + NH((1)Delta) without reaching the HN3 global minimum. Several intersections between the two states are localized for,both N-3 isomers near the N-3 + H dissociation. The energies of stationary structures and dissociation asymptotes are obtained with the multireference configuration interaction method at the complete basis set limit A comparison with recent experimental data regarding the H-N-3 bond strength and the dissociation barrier in the excited state shows that the present results are of chemical accuracy (similar to 1 kcal mol(-1)).