Hydrazine reaction with oxygen

The hydrazine reaction with oxygen is slow, but with the advent of organic catalysts such as hydroquinone (which speeds up the reaction 50-fold or so), hydrazine is also the product of choice in medium-pressure (say, over 650 to 950 psig) industrial and cogeneration plants. 

Hydrazine is conventionally added in an amount equivalent to at least KX) of the dissolved oxygen content. In principle, additions should be made after thermal deaeration to economise on reagent usage, but in practice in some cases more thorough scavenging is found to result if hydrazine is added before the deaerator. This may reflect the kinetic aspects of the reaction with oxygen. 

Hydrazine produces several reactions with oxygen ... 

Hydrazine is a powerful reducing agent and has been widely used as a rocket propellant. For example, its reaction with oxygen is highly exothermic ... 

Hydrazine (N2H4) is used as a fuel in liquid-fueled rockets. When hydrazine reacts with oxygen gas, nitrogen gas and water vapor are produced. Write a balanced equation and use bond energies from Table 8.4 to estimate AW for this reaction. 

The use of hydrazine is not subject to similar objections, but its slow reaction with oxygen and partial decomposition into NH3 should be taken into account in calculating proper dosages. Also, NH3 is a possible cause of stress-corrosion cracking of copper-base alloys in the condenser system, should oxygen accidentally contaminate the condensate. 

The most studied example of II was tetraphenylhydrazine cation radical, whose purple color led Hiinig to coin the term "violenes" ( ) for the series of vinologous species his group has studied extensively (3). The solution ESR spectrum of hydrazine radical cation had been recorded in a flow system (4). Aromatic examples of III had received extensive study (5), and diphenyl-picrylhydrazyl was the first example of a neutral radical stable both to dimerization and reaction with oxygen. The chemistry of 1,1-dimethyldiazenium cation had been studied (6), and interesting electrochemical work on arylhydrazine oxidations had been carried out by Cauquis and Genies (7). 

Oxygen scavengers other than hydrazine are also used, especially catalyzed sodium sulfite, which reacts rapidly with oxygen even at room temperatures to form sodium sulfate. Catalyzed hydrazine formulations are now commercially available that react with oxygen at ambient temperatures at rates comparable to catalyzed sulfite (189). At elevated temperatures, the reaction rates are all similar. Table 14 Hsts the standard hydrazine solution products offered by Olin Corp. for sale to the water-treatment market. Other concentrations are available and other companies offer similar products. 

By removing oxygen completely, corrosion by this gas is eliminated. It can be achieved by the addition of sodium sulfite or hydrazine, which reacts with oxygen. The reaction product will not normally cause any problems. 

A piridazine ring forms the nucleus for a rather unusual nontricyclic antidepre.ssant. Condensation of the keto ester 136 with hydrazine leads to the cyclic hydrazide 137. Oxidation, for example with bromine, gives the corresponding pyridazone 138. The oxygen is then replaced by chlorine by reaction with phosphorus oxychloride. Displacement of the halogen in 139 with N-ethylami-nomorpholine affords minaprine 140 [30]. 

Hydrazine has the advantage that its use does not increase the dissolved solids content of the boiler water. The products both of its reaction with dissolved oxygen and of its decomposition are gaseous or liquid ... 

The stoichiometric relationship for hydrazine with oxygen is 1 1, but it is always added at between two and four times theoretical to ensure that the reaction proceeds to completion. Even so, it may be some time after startup (often one to two weeks) before hydrazine appears in the BW as a reserve. This probably is due to the hydrazine reducing all existing ferric oxide in the system first. During this time, the color of the oxide debris and surface oxides change from reddish brown to black (passivation). 

Most reactions with hydrazine are carried out with aldehydes and ketones in the presence of alkali. The reduction proper is preceded by formation of hydrazones that decompose in alkaline medium at elevated temperatures to nitrogen and compounds in which the carbonyl oxygen has been replaced by two hydrogens. The same results are obtained by alkaline-thermal decomposition of ready-made hydrazones of the carbonyl compounds. Both reactions are referred to as Wolff-Kizhner reduction [280]. 

Alkyl halides would not react with [CrCl2(MeCN)2], but the alkyl derivatives [RCr(salen)(H20)] and [RCr(salphen)(H20)] (R = Me, Ph) are said to form on reaction of the organic hydrazines with the Crm-Schiffs base complexes in MeCN under nitrogen followed by oxidation with oxygen and hydrolysis.1128... 

The present author has used the method to obtain an approximate rate constant for the oxidation of an arylhydrazine with oxygen, and to show that the reaction occurred in film . A saturated solution of the hydrazine in an aqueous sodium chloride solution was reacted... 

---