UDMH—

Figure 2 shows the vapor pressures of anhydrous hydrazine (AH), monomethyUiydrazine [60-34-4] (MMH), and unsymmetrical dimethyUiydrazine [57-14-7] (UDMH) as a function of temperature (2). The partial pressures of N2H4 over aqueous solutions of various concentrations are plotted in Figure 3. 

Fig. 2. Vapor pressure of (—) anhydrous hydrazine (AH), (— - —) monomethyUiydrazine (MMH), and (-) unsymmetrical dimethyUiydrazine (UDMH).

MMHa.nd UDMH. MonomethyUiydrazine and yyz -dimethylhydrazine are manufactured by Olin Corp. using the same Raschig process and equipment employed for anhydrous hydrazine. Chloramine, prepared as described above, reacts with methylamine or dimethylamine instead of with... 

The estimated world production capacity for hydrazine solutions is 44,100 t on a N2H4 basis (Table 6). About 60% is made by the hypochlorite—ketazine process, 25% by the peroxide—ketazine route, and the remainder by the Raschig and urea processes. In addition there is anhydrous hydrazine capacity for propellant appHcations. In the United States, one plant dedicated to fuels production (Olin Corp., Raschig process), has a nominal capacity of 3200 t. This facihty also produces the two other hydrazine fuels, monomethyUiydrazine and unsymmetrical dimethyUiydrazine. Other hydrazine fuels capacity includes AH in the PRC, Japan, and Russia MMH in France and Japan and UDMH in France, Russia, and the PRC. 

Table 8 summarizes specifications for anhydrous grades of hydrazine. Propellant grades meet all requirements of the most recent Mditary Specification MIL-P-26536 D. Mditary specifications coveting the other propellant hydrazines ate MMH (Md-P-27404B, May 22, 1979) UDMH (Md-P-25604D, Amendment 1, Apt. 10,1978, Supplemental Data Sheet, Jan. 24, 1984) Aetozine-50 (Md-P-27402B, May 27,1969) H-70 (Md-P-87930, USAF, Oct. 25, 1977). 

Hydraziae is toxic and readily absorbed by oral, dermal, or inhalation routes of exposure. Contact with hydraziae irritates the skin, eyes, and respiratory tract. Liquid splashed iato the eyes may cause permanent damage to the cornea. At high doses it can cause convulsions, but even low doses may result ia ceatral aervous system depressioa. Death from acute exposure results from coavulsioas, respiratory arrest, and cardiovascular coUapse. Repeated exposure may affect the lungs, Hver, and kidneys. Of the hydraziae derivatives studied, 1,1-dimethylhydrazine (UDMH) appears to be the least hepatotoxic monomethyl-hydrazine (MMH) seems to be more toxic to the kidneys. Evidence is limited as to the effect of hydraziae oa reproductioa and/or development however, animal studies demonstrate that only doses that produce toxicity ia pregaant rats result ia embryotoxicity (164). 

The TLV is set at 0.1 ppm (hydraziae) 0.2 ppm (MMH) and 0.5 ppm (UDMH). The TLV is weU below the olfactory limit of 3—5 ppm (hydraziae). The latter does aot provide adequate warning when exposure exceeds the TLV therefore, monitoring the working environment by suitable means and providing adequate ventilation is necessary. 

Agricultural Uses. Pesticides represent the second largest commercial market for hydrazine. Hundreds of hydrazine derivatives have been patented for a wide range of agricultural appHcations. Table 13 presents a sampling of the 50—60 that are commercially available or developmental products. These compounds are made from hydrazine, MMH, and UDMH and are for the most part heterocycHc nitrogen compounds (see Insect control technology). 

Propellants and Explosives. Hydrazine fuels include anhydrous hydrazine (AH), monomethyUiydrazine (MMH), and unsymmetrical dimethyUiydrazine (UDMH) for military and space programs. These compounds are used mainly as bipropeUant fuels, ie, with oxidizers, in rockets such as the Titan, MX missile, and the Ariane (UDA4H7X30. Using oxygen or fluorine as the oxidizer, hydrazine is exceeded only by hydrogen in specific impulse, ie, kilograms of thmst developed for each kilogram of fuel consumed per second (196). 

EiquidPropellants Manual, contract NOw 62-0604-c, Chemical Propulsion Information Agency, Johns Hopkins University, Baltimore, Md., 1961, Unit 2 (AH), Unit 5 (UDMH) and Unit 11 (MMH) Placards of Chemical Pockets and Propellants Handbook, Vol. 3, CPIA/194, publ. no. AD 870259, National Technical Information Service, U.S. Dept, of Commerce, Washington, D.C., May 1972, Unit 9 (AH and MMH), Unit 10 (UDMH). 

The determination of organic compounds by their direct catalytic effect on indicator reaction rates is a relatively unexplored ai ea promising valuable analytical chai acteristics, as we have recently shown in the determination of traces of unsymmetrical dimethylhydrazine (UDMH) by the oxidation of 3,3, 5,5 -tetramethylbenzidine (TMB) by atmospheric oxygen initiated with persulfate [1]. 

Effects of compounds observable at lower concentrations ai e probably connected with the effect on the initiation/termination stages (transition metals in TMB-0, reaction with photoinitiation, UDMH in the same reaction with chemical initiation), while the compounds influencing only at higher concentrations may affect chain propagation stages. 

TABLE 12.12.1 Emergency Tolerance Limits for UDMH VaporVersus Exposure Time... 

Nitrogen Tetroxide + UDMH 296 seconds (liquid storable)... 

Uses It is one active ingredient present in water which has been purified by chlorination (Ref 6). It is used as an intermediate for.the prepn of hydrazine and substituted hydrazines. Recentiy there has been a renewed interest in chloramine as a possible intermediate for the prepn of UDMH (see Vol 7, H203-R) which avoids handling the highly carcinogenic dimethyl-nitrosamine (Refs 5 7)... 

Until recently the atmospheric chemistry of nitrogen-containing compounds such as the hydrazines, which are widely used as fuels in military and space vehicles, has received comparatively little attention. N,N-dimethyIhydrazine (also UDMH = unsymmetrical dimethylhydrazine) is used in liquid-fueled rockets, and thus there Is a possibility that its use, storage, and handling could result in its release in the atmosphere. 

Stability of UDMH at relatively high concentrations ( -4) there have been relatively few investigations of its atmospheric reactions. 

In view of its potential for nitrosamine formation, a more detailed knowledge of the atmospheric reactions and products of UDMH is clearly desirable. In order to provide such data for UDMH and other hydrazines we have studied their dark reactions in air, with and without added O3 or NO, and have investigated their atmospheric photooxidation in the presence of NO ( 9 ). In this paper, we report the results we have obtained to date for UDMH. 

Reactant and product analyses were obtained from the intensities of infrared absorption bands by successive subtraction of absorptions by known species. Low noise reference spectra for UDMH and several reaction products were generated for this purpose in order to minimize the increase in the noise level of the residual spectrum with each stage of subtraction. 

Dark Decay of UDMH in Air, UDMH was observed to undergo a gradual dark decay in the 30,000-liter Teflon chamber at a rate which depended on humidity. Specifically, at 41 C and 4% RH the observed UDMH half-life was " 9 hours (initial UDMH 4.4 ppm) and at 40 C and 15% RH, the half-life was -6 hours (initial UDMH 2.5 ppm). The only observed product of the UDMH dark decay was NH3, which accounted for only -5-10% of the UDMH lost. In particular, no nitrosamine, nitramine, or hydrazone were observed. Formaldehyde dimethyIhydrazone was observed in previous studies which employed higher UDMH concentrations and reaction vessels with relatively high surface/volume ratios (, ) ... 

The mechanism of the UDMH dark decay is unknown, but it is presumed to be heterogeneous in nature. It is probably not wall adsorption, since much slower decay rates were observed previously in the absence of O2 ( ) ... 

Dark Reaction of UDMH with Oq. When O3 was injected into UDMH-air mixtures, consumption of UDMH and O3 was "instantaneous" and formation of N-nitrosodimethylamine was immediately observed. The reaction was complete within 2 minutes, by which time either the hydrazine or the O3 was totally consumed. Figure 1 shows IR spectra before and 2 minutes after -2 ppm of O3 was injected into air containing -2 ppm of UDMH. The nitrosamine is positively identified by its IR absorptions at 1296, 1016, and 848 cm . ... 

Also formed in the UDMH-O3 system, but in lesser yields, were HCHO, H2O2, and HONO. 

The experimental conditions and products observed at selected times in the UDMH + O3 experiments are shown in Table I. In general, the nitrosamine yields ranged from -60% when the reaction was carried out in a slight excess of UDMH to -100% when O3 was in excess. The HCHO, H2O2, and HONO yields were -13%,... 

Table I, Experimental Conditions and Concentrations of Reactants and Products at Selected Times in the UDMH + O3 Dark Experiments...

Exp. No. T (avg) RH (avg) (%) Elapsed Time (min) UDMH 03 (CH3)2NN0 H2O2 HCHO NH3 HONO "Gaseous, Nitrate" (CH3)2NN02... 

Other possible mechanisms have been considered O), but they either predict formation of products which are not observed, do not explain the observed O3/UDMH stoichiometry, or are inconsistent with the results of the UDMH-NO stoichiometry and the formation of nitrosamine and H2O2 in this system. The other products observed, and the fact that the nitrosamine and H2O2 yields are somewhat less than the predicted 100% and 50% of the UDMH consumed, can be attributed to possible secondary reactions of the nitrosamine with the OH radical. 

It should be noted that the UDMH + O3 mechanism is probably quite different from that appropriate for hydrazines with hydrogens on both nitrogen atoms. In our study of the reactions of O3 with N2Hi and monomethyl hydrazine (MMH) 0,0, the data were best explained by assuming the initial hydrazine consumption reactions to be analogous to reactions (1) and (2), but with the N-amino radical formed reacting rapidly with O2, e.g.. 

Irradiation of the UDMH + Oq Reaction Products. One experiment was conducted in which the UDMH + O3 reaction products (with UDMH in slight excess) were irradiated by sunlight. The results are shown in Table I and Figure 1. It can be seen that rapid consumption of UDMH, the nitrosamine, and HONO occurred, with N-nitrodimethylamine (also dimethyInitramine) and additional formaldehyde being formed. The formation of nitramine upon irradiation of the nitrosamine is consistent with results of previous studies in our laboratories (9,10), and probably occurs as shown ... 

It should be noted that the immediate formation of the nitramine in the photolysis of the UDMH + O3 products indicates the presence of NO2 in that mixture. 

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