Hydrazine conformation

For a good review of hydrazine conformational work through 1973, see Shvo, Y., in "The Chemistry of Hydrazo, Azo, and Azoxy Groups, 1975, Pt. 2.,... 

Like hydrogen peroxide the inorganic substances hydrazine (H2NNH2) and hydroxylamine (H2NOH) possess conformational mobility Wnte stmctural representations or build molecular models of two different staggered conformations of (a) hydrazine and (b) hydroxylamine... 

Figure 11.S Possible conformations of N2H4 with pyramidal N. Hydrazine adopts the gauche C l form with N N 145 pm, H-N- II 108°. and a twist angle of 95 as shown in the lower diagram.

Dinitrogen tetrafluoride, N2F4, is the fluorine analogue of hydrazine and exists in both the staggered (trans) C2h and gauche C2 conformations... 

Rotation around the NN bond in hydrazine yields three staggered conformers, one in whieh the lone pairs are anti and the other two (equivalent struetures) in which they are gauche. 

Depending on the molar ratio, 8 reacts with SiF4 to give the acyclic or cyclic compounds 9 or 10. 10 represents the first halofunctional hydrazine ring system. The ring is far from planar and has a twist conformation [4,5]. 

Figure 3.63 illustrates the gauche effect for vicinal lone pairs and polar C—F bonds with the examples of (a) hydrazine and (b) 1,2-difluoroethane, respectively. As seen in Fig. 3.63(a), the

lone pairs are anti to one another (thus squandering their powerful donor strength on vicinal moieties with no acceptor capacity) is disfavored by 3.2 kcal mol-1 relative to the preferred = 93.9° conformer in which each nN hyperconjugates effectively with... 

The conjugate addition of activated nitrogen nucleophiles, such as hydroxylamine and hydrazine derivatives, to a,/3-unsaturated bicyclic lactam 284 gave the corresponding /3-amino product 285 in good yield and excellent diastereoselectivity. These products can be manipulated to afford enantiopure /3-aminopyrrolidinones of potential application as conformationally constrained, substituted glutamate templates (Equation 45) <2001J(P1)2997>. 

A typical R4R3 A—ARi R2 molecule is hydrazine, a system which has attracted an enormous amount of theoretical interest. The syn, anti and gauche conformers of NH2—NH2 are depicted below along with an enumeration of the dominant interactions which obtain in each case ... 

Clearly, the preferred order of relative stability is gauche > anti > syn, since the n-o interaction is much stronger than the a—a interaction. Furthermore, anti 0nh-°nh is more favorable than syn aNH—aNH interaction. Ab initio calculations show that the preferred conformation of hydrazine is the gauche conformer with a dihedral angle of IOO0314. ... 

Compounds in which the amino group is directly connected with another functional group like hydrazines, hydroxylamines, enamines and amides were already briefly mentioned in Section II.C. In several cases it has been shown that orbital interactions of these systems can be used for conformational analysis by PES66,67. 

The conformational changes also explain the slow electron transfer between two hydrazine moieties separated by a bridge (Gleiter et al. 1996, Nelsen et al. 1975, 1976, 1997b). In all the cases, the inner reorganization energy is high when electron transfer occurs. Particularly, when the unpaired electron is transferred from the planar hydrazine cation-radical unit to the tetrahedral... 

Kinetic studies of hexacyanoferrate(III) oxidations have included the much-studied reaction with iodide and oxidation of the TICI2 anion, of hydrazine and hydrazinium, and of phenylhydrazine and 4-bromophenylhydrazine. These last reactions proceed by outer-sphere mechanisms, and conform to Marcus s theory. Catalyzed [Fe(CN)g] oxidations have included chlororuthenium-catalyzed oxidation of cyclohexanol, ruthenium(III)-catalyzed oxidation of 2-aminoethanol and of 3-aminopropanol, ruthenium(VI)-catalyzed oxidation of lactate, tartrate, and glycolate, and osmium(VIII)-catalyzed oxidation of benzyl alcohol and benzylamine. ... 

Density fnnctional calculations on 215b-d at the B3P86 level have been carried ont as part of a detailed study of the HERON reaction of hydrazines (see Section VI.C). These afforded symmetrical gauche structures l(EE) as lowest energy conformers N—N (1.37 A), N—C(0) (1.38 A) and N—O (1.40 A) bond lengths were similar to those from HF/6-31G calculations. ... 

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