2-Amino-4-phenyl-4H,10H-1,3,5-triazino[1,2-a]benzimidazol-3-ium chloride.

2-Guanidinobenzimidazole condenses with benzaldehyde in the presence of hydro-chloric acid to form 2-amino-3,4-dihydro-4-phenyl-1,3,5-triazino[1,2-a]benzimidazole, which was isolated as its hydro-chloride, C(15)H(14)N(5) (+)·Cl(-). The positive charge of the cation is formally placed on the double-bonded N atom of the dihydro-triazine ring. The six-membered dihydro-triazine that is fused with the benzimidazole ring system is relatively flat (r.m.s. deviation = 0.106 Å), with the methine C atom deviating most [0.164 (1) Å] from the mean-square plane. The phenyl ring connected to the methine C atom is disordered over two positions in a 0.558 (1):0.442 (1) ratio; the two orientations are aligned at 85.1 (1) and 89.6 (1)° with respect to the dihydro-triazine ring. In the crystal, adjacent cations and anions are linked by N-H⋯N and N-H⋯Cl hydrogen bonds, generating a double chain running along the b axis.