semiempirical SCF calculations show that O–H···N hydrogen bonds of 2-tetrazenes are medium strong. The δ-15N data and the quantum chemical calculations indicate that the amino nitrogen atoms of a 2-tetrazene are involved in intermolecular hydrogen bonding to a larger extent than the azo nitrogen atoms; the corresponding energy difference of the two types of hydrogen bonds is about 3 kJ mol−1. The hydrogen bonds