Six Structures of the Hydrazine Dimer

Abstract

All possible structures of the hydrazine dimer have been investigated in a systematic way for all combinations of the two hydrazine conformers. Three structures with two hydrogen bonds, three with three hydrogen bonds and no structure with only a single hydrogen bond have been found. Two structures with four hydrogen bonds are saddle points of the potential energy surface. In the first step, the geometries of all investigated structures were optimized at the MP2/aug-cc-pVDZ level of theory. In the second step, the intermolecular parameters of all stable structures were determined at the CCSD(T)/aug-cc-pVTZ level. The binding energies of the six stable conformations include the BSSE correction. The frequency shifts of the antisymmetric wagging mode and the NH-stretching modes were calculated with the MP2/6-31++(2df,2p) method. The barrier heights of three rearrangement reactions were determined at the CCSD(T)/aug-cc-pVTZ level.

Threshold Collision-Induced Dissociation of Proton-Bound Hydrazine and Dimethylhydrazine Clusters

“…In contrast, TS g + /c and TS g – /t are sufficiently high in energy, >9 kJ/mol, that interchange between the t and c isomers and the g – and g + isomers is unlikely at room temperature. Finally, we note that TS g – /t is similar to the saddle point found by Dyczmons for the neutral hydrazine dimer …”

“…The difference in relative energies from 0 to 298 K is linked to the entropy and extent of hydrogen bonding. As mentioned above, Dyczmons 12 found six conformations for the neutral hydrazine dimer, whereas we locate only four for the proton-bound analogue. This difference is simplistically accounted for by the protonation site, which can only donate a hydrogen bond, restricting the number of isomers.…”

“…With this model, they determined binding energies and the shift, relative to the monomer, in the antisymmetric NH 2 wagging modes for three dimer and four trimer structures of neutral hydrazine. Building on this work, Dyczmons found an additional three dimer and 24 trimer conformations, including a single saddle point transition state (TS) between two conformations of the dimer.…”

Discrimination of hydrogen-bonded complexes with axial chirality

“…16 with BSSE͒, and Ϫ9.35 ͑Ϫ6.69 with BSSE͒ kcal/mol for the B3LYP/6-31ϩG**, MP2/6-31ϩG**, and MP2/6-311ϩϩG** calculations, respectively͔. In the case of hydrazine 4 both the homochiral and the heterochiral dimers have been calculated, the second one was the most stable by 0.5-0.8 kcal/mol ͓MP2/6-31ϩϩG** and CCSD͑T͔͒ 19 ͑see Table I, 0.5-0.7 kcal/mol͒. This author was not interested in chiral discrimination but IR spectroscopists found that the Sa/Ra dimer of hydrazine explain better the experimental observations than the Sa/Sa(Ra/Ra) dimer.…”

Synthesis of organochalcogen compounds in basic reducing systems

“…64 If asso ciation involves the hydrazine hydrogen atoms, this in creases the nucleophilicity of the hydrazine molecule. 64 If asso ciation involves the hydrazine hydrogen atoms, this in creases the nucleophilicity of the hydrazine molecule.…”