Methylhydrazine radical

Our work on the first electron transfer, I 11, became possible when it was realized that tetraalkyl-hydrazine radical cations have a reasonably long lifetime in solution, even at room temperature. This discovery was made completely by accident, when tetra-methylhydrazine radical cation, 1 was observed by ESR... 

To shed light on the reaction pathway, a cyclization with methylhydrazine was carried out (70ZOR439 73ZOR832), since pyrazoles with nonequivalent positions 3 and 5 are obtained in this case. From l-methoxybut-l-en-3-yne and methylhydrazine sulfate a 4 5 mixture of 1,3- (110) and 1,5-dimethylpyrazoles (111) was formed (GLC) (70ZOR439). In the reaction of methoxybutenyne homologs (R = Ft, -Pr) with methylhydrazine (72°C, H", H2O, 2 h), lengthening of the alkyl radical leads to an increase in the content of 1,5-isomer (111), with yields of 50-60%. Thus, when R = Ft, the ratio is 2 3 (73ZOR832). 

Before the advent of enediyne antitumor antibiotics, there had been few examples of carbon radicals believed to mediate DNA cleavage. The simplest of all, the methyl radical has been shown to effect DNA cleavage under enzymatic as well as chemical conditions [24]. Oxidation of methylhydrazine by horseradish peroxidase or ferricyanide (Fig. 5) gave high yields of methyl radicals, which were shown to cleave DNA by purine ring alkylation. 

The radical reaction of hydrazine and methylhydrazine with some a,(3-unsaturated ketones 54 initiated by 2,2-dipenyl-l-picrylhydrazyl (DPPH) is described in [60]. At — 78°C the treatment is practically regioselective and yields pyrazoles 55, while regioisomeric heterocycles 56 are observed in trace amounts (Scheme 2.13). 

In addition, silybin might interact with the free radical intermediates produced during the metabolic activation of CCI4 and methylhydrazine. These effects suggest that silybin is potentially protective against harmful free radical-mediated toxic damage [62]. 

Reactive alkyl radicals and nonradical products generated by lipid peroxidation chain reactions are potential alkylating agents. Reactive methyl radicals can also arise by the irradiation or oxidation of methyl compounds such as methylhydrazine (33). 

The ESR parameters of the radical species obtained (75CPB1516) from the reaction of methylhydrazine with different analogues have similar characteristics with respect to the hyperfine splittings. Consequently, the basic structure of these radical species can be considered the same, namely 46 <-> 47 - 48, the high resonance stabilization of which contributed to... 

The limited yield of biphenyl (<5%), the trace amounts of trapped phenyl radical, and the absence of oxygenated phenyl products are consistent with the reaction sequence of Eqs. (7-17) and (7-18), and with the reaction intermediate of Eq. (7-18). The reaction of O2 - with methylhydrazine is analogous to that for phenylhydrazine with methane the major product. The slower rate is consistent with the enhanced stabilization of radical intermediates by aromatic substituents. 

Harris GW, Atkinson R, Pitts, JN. 1979. Kinetics of the reactions of the OH radical with hydrazine and methylhydrazine. J Phys Chem 83 2557-2559. 

MethylhydrazIne. Harris al. (325) have determined, using a flash photolysis-resonance fluorescence technique, a rate constant of k (6.5 +1.3) X 10 cm molecule" sec , independent of temperature over the range 298-424°K, for this compotmd. By comparison with the rate constant for the reaction of OH radicals with hydrazine, determined In the same study (k > (6.1 + 1.0) x 10 11 cm3 molecule sec Independent of temperature over the range 298-424°K), It Is postulated that the reaction proceeds via H atom abstraction from the N-H bonds. 

The difunctionality of NH2 moiety in the methylhydrazine derivatives has also been underlined by the reaction of (156) with trimethylorthobenzoate to afford the l-phospha-2,3,5,6-tetrazine derivative (163), which on oxidation with benzoquinone can be transformed to the radical species (164). EPR and ENDOR spectroscopic experiments clearly point to a spin polarization through the spirocyclic phosphorus atom to the other phosphorus and nitrogen nuclei in the phosphazene ring of (164). ... 

The formation of N2H3 radicals during the low-pressure Hg( Pi)-photosensitized decomposition of gaseous hydrazine was demonstrated by adding dimethyl mercury to give mono-methylhydrazine [12]. 

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