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After an exhaustive study of the system ammonia–dimethylchloramine in liquid ammonia, it was interesting to compare the reactivity of this system in liquid ammonia with the same system in an aqueous medium. Dimethylchloramine prepared in a pure state undergoes dehydrohalogenation in an alkaline medium: the principal products formed are N-methylmethanimine, 1,3,5-trimethylhexahydrotriazine, formaldehyde, and methylamine. The kinetics of this reaction was studied by UV, GC, and HPLC as a function of temperature, initial concentrations of sodium hydroxide, and chlorinated derivative. The reaction is of the second order and obeys an E2 mechanism (k1 = 4.2 × 10−5 M−1 s−1, ΔH○# = 82 kJ mol−1, ΔS○# = −59 J mol−1 K−1). The oxidation of unsymmetrical dimethylhydrazine by dimethylchloramine involves two consecutive processes. The first step follows a first-order law with respect to haloamine and hydrazine, leading to the formation of an aminonitrene intermediate (k2 = 150 × 10−5 M−1 s−1). The second step corresponds to the conversion of aminonitrene into formaldehyde dimethylhydrazone at pH 13). This reaction follows a first-order law (k3 = 23.5 × 10−5 s−1). The dimethylchloramine–ammonia interaction corresponds to a SN2 bimolecular mechanism (k4 = 0.9 × 10−5 M−1 s−1, pH 13, and T = 25°C). The kinetic model formulated on the basis of the above reactions shows that the formation of the hydrazine in an aqueous medium comes under strong competition from the dehydrohalogenation of dimethylchloramine and the oxidation of the hydrazine formed by the original chlorinated derivative. A global model that explains the mechanisms both in an anhydrous and in an aqueous medium was elaborated. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 340–351, 2008

The present study is concerned with the application of nonaqueous capillary electrophoresis (NACE) with electrochemical detection (ED) to the separation and quantitative determination of hydrazine (Hy) and its methyl derivatives. The best performance of NACE-ED was found when using 4 mM sodium acetate/10 mM acetic acid/methanol: acetonitrile = 1:2 as the running buffer, with a bare platinum working electrode set at +1.0 V in an end-column amperometric detection cell. The choice and ratio of suitable solvents for the separation and injection media played an essential role for the performance characteristics of the method. The limits of detection for Hy, methylhydrazine, symmetrical dimethylhydrazine, and unsymmetrical dimethylhydrazine were 5, 2, 12, and 1 ng/mL, respectively. This is between one and two orders of magnitude lower than that achieved by previously reported CE-ED methods in aqueous buffer systems in conjunction with various types of chemically modified electrodes. The practical utility of the new NACE-ED methodology is demonstrated in terms of the determination of traces of Hys in spiked environmental samples containing a wide range of explosives and related compounds.

Crosslinked chitosan membranes were synthesized using glutaraldehyde and characterized by infra-red (IR) and wide-angle X-ray diffraction (WAXD) spectroscopic methods. The membranes were applied for the pervaporation-based dehydration of the highly hazardous and hypergolic unsymmetrical dimethylhydrazine liquid propellant. The characterization techniques were an efficient tool in identifying polymer–liquid interaction sites and the separation mechanisms involved. The crosslinked polymer was found to have good potential for the separation of the aqueous azeotrope of the propellant (20 wt%) and its enrichment to >90% purity. An equilibrium sorption study examined the preferential affinity of the membrane amongst the two penetrating liquids. The pervaporation performance of the membrane was evaluated by varying the experimental parameters of feed composition, membrane thickness and permeate pressure, and found to be promising. © 2001 Society of Chemical Industry

Unsymmetrical dimethylhydrazine and monomethylhydrazine are the two well-known liquid propellants. Substantial amounts of sodium chloride present in the aqueous unsymmetrical dimethylhydrazine and monomethylhydrazine reaction liquors. Pervaporation experiments have been conducted using dense chitosan membrane for desalting of these reaction liquors. The effect of membrane thickness, salt concentration in the feed, and permeate pressures on flux and % rejection have been studied and discussed to optimize the conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 141–149, 1999

Hypergolic or self ignition delays of unsymmetrical dimethylhydrazine (UDMH) and several amine fuels, mixed with three fuming nitric acid oxidizers, have been determined, at room temperature, in a highly sensitive “Cup Test” apparatus. Ignition delay (ID) variations have been studied with respect to the chemical structure of fuel, oxidizer composition, and oxidizer-to-fuel (O/F) ratio. Probable preignition reactions and structure-hypergolicity correlations have been suggested. Some non-hypergolic hydrocarbons and petroleum fractions have been hypergolized by addition of UDMH, and ID variations have been studied with respect to UDMH-content in fuel and catalytic additives (ammonium metavanadate, ammonium dichromate, and cuprous oxide) in the red fuming nitric acid oxidizer (RFNA). Increment in UDMH-content improves the hypergolicity of fuels towards RFNA. For example, kerosene + UDMH 60:40 blend ignites with RFNA with a remarkably low ID of 6 ms. However, the catalytic effect of the additive in RFNA varies widely with the fuel-blend composition.

Monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH), but not N-methyl-N-formylhydrazine (MFH), a mushroom poison, can be oxidized by the weak oxidant 2,6-dichlorophenolindophenol. Hydrogen peroxide is formed by this oxidation, and has been found to cause decay of DNA in aqueous solution as measured by the decreased viscosity of a DNA solution in the presence of the hydrazines. Furthermore, MMH and UDMH but not MFH inhibit the incorporation of [3H]thymidine and [3H]uridine into DNA and RNA of Ehrlich ascites carcinoma (EAC) cells. These experiments show that MFH is an inactive compound in contrast to MMH and UDMH. Since the hydrolysis rate of MFH, to produce MMH, is low, it is concluded that MFH must be activated in vivo into toxic metabolites which are ultimately responsible for the known high carcinogenicity of MFH.

A method initially developed for aminozide [succinic acid mono (2,2 dimethylhydrazide)] determination in apple fruit, involving hydrolysis to unsymmetrical dimethylhydrazine and oxidation of the latter to form aldehyde, has been adapted for use with chrysanthemum tissues. Modifications include preparation of the standard curve from aminozide samples taken through the entire procedure, use of a smaller sample size routine concentration of distillates containing unsymmetrical dimethylhydrazine on a rotary evaporator to remove interfering volatile material and correction for low levels of ‘apparent aminozide’ found in untreated tissue.

A method for determining residues of ‘Alar’ (B-995) in apples has been developed. It is based on the alkaline hydrolysis of ‘Alar’ to yield unsymmetrical dimethylhydrazine. the latter is oxidised by selenium dioxide to yield formaldehyde which is determined colorimetrically using 2-hydrazinobenzothiazole.