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Five hydroxyethyl-2-tetrazenes (1 - 5) and their methyl ethers (6 - 10) have been synthesized and hydrogen bonding in these compounds has been investigated by theoretical and spectroscopic (IR,  1 H NMR,  15 N NMR) methods. The structure of 1,1,4,4-tetrakis(2-hydroxyethyl)- 2-tetrazene (4) was determined byX-ray diffraction analysis. Several conformationswith intramolecular hydrogen bonds were investigated by ab initio B3LYP as well as semiempirical SCF calculations. In all cases, conformers with OH- - -N hydrogen bonds with azo nitrogen atoms as acceptors (conformers A, B, C) are found as most stable. Incompounds with small or flexible N 1 - and N 4 -substituents R besides the hydroxyethyl group (3, 4), hydrogen bonds forming six-membered rings, with the R groups taking syn positions at the N 1 -N 2  and N 3 -N 4  bonds (conformer A), are preferred over those with seven-membered rings and R taking anti positions (conformer B). Steric interaction in the other compounds (1, 2, 5) leads to destabilization of conformers A and conformers B become more stable. A special case is presented by compound 4 which has only hydroxyethyl substituents on the 2-tetrazene unit. In the most stable conformer (4C) there are two OH- - -O and one OH- - -N hydrogen bonds. By IR solution measurements intra- and intermolecular hydrogen bonds could be distinguished. Association shifts Δδ measured by  1 H NMR spectroscopy, indicate that the investigated compounds exhibit comparable association properties with intermolecular association clearly prevailing.  15 N NMR spectra of compounds 1 - 10 in two solvents have been measured if solubility was sufficient. The data indicate that all nitrogen atoms of 1 - 5 participate in H bonding. In the crystalline state, molecules 4 adopt a conformation without intramolecular H bonds (4D) and are associated by intermolecular OH- - -O hydrogen bonds that form a three-dimensional network. An untypical decomposition pattern was discovered for benzyl derivatives 5 and 10.

Hydrogen Bonding of 2-Tetrazenes, 2. Synthesis and Structural Studies of Hydroxyalkyl-Substituted 2-Tetrazenes