Hydrazine Hydroquinon

Keywords anhydrous hydrazine, hydroquinone, dimethyl terephthalate, inclusion crystal, terephthalic acid dihydrazide... 

Keywords aldehyde, hydrazine, hydroquinone, ketone, isothiocyanate, solid-sol-id reaction, azine, thiosemicarbazide, diazepinone... 

The aldehyde/ketone 1 (4.00 mmol), or the ketone 7 (2.00 mmol), or the isothio-cyanate 5 (2.00 mmol) was ball-milled with the solid hydrazine-hydroquinone complex 2 (2.00 mmol) at 25-30 °C for lh (3 h in the case of Id). The yield was quantitative in all cases, as spectroscopically pure mixtures of 3, 6, 8 with 4 were obtained. Hydroquinone 4 was removed by 5 min trituration with 20 mL of water, filtration and three washings with 2 mL of water, each. The residue was dried in a vacuum to obtain the pure products. 4 was recycled from the aqueous washings by evaporation, addition of 1.0 g of 80% hydrazine hydrate in water per 4 mmol of initially reacted 2 and recrystallization to give 520 mg (91%) of pure 2 after filtration, washing with water and drying. 

Kaupp and Schmeyers subjected to ball milling the solid aldehydes and ketones with the hydrazine-hydroquinone complex 83 in a 2 1 ratio to obtain azines 84 at room temperature (Scheme 3.22) [19]. Experiments were carried out in Retsch MM2(X)... 

Kaupp G, Schmeyers J. Solid-state reactivity of the hydrazine-hydroquinone complex. J Phys Org Ghem 2000 13 388-94. 

A stripping column is used to remove impolymerized vinyl acetate from the poly(vinyl acetate) solution leaving the last reactor (Fig. 13). Methanol vapors are used to strip vinyl acetate from the solution (209,210). An inhibitor such as hydrazine, hydroquinone, sulfur, or quinone can be added to poly(vinyl acetate) solution leaving the reactor in order to prevent further polymerization in the stripping coliunn (176). The overhead fraction from the stripping column consisting of solvent and vinyl acetate may be passed to a recovery system, or directly recycled... 

Gravimetric methods more suitable for general use involve the precipitation of metallic gold from tetrachloraurate solutions by reduction with oxaUc acid, SO2, or hydroquinone. Formaldehyde, hydrazine, ferrous sulfate, and hypophosphorous acid also have been used but are considered less efficient (40). 

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. 

NOTE Cupric copper (Cu2+) is a catalyst for the hydrazine-oxygen reaction, as well as a catalyst for sulfite, DEHA, erythorbic acid, and hydroquinone. Cuprous copper (Cu+) acts as a complexing agent in the desirable formation of protective, pasivated copper oxide films. 

Hydroquinone is another safe alternative to hydrazine and was originally covered under a Betz patent. Related compounds and their alkyl-substituted derivatives were similarly patented, including o- and /7-diamino and aminohydroxybenzenes. 

Hydroquinone is a good oxygen scavenger, even in cold water, so much so that it is commonly employed as a catalyst for hydrazine, DEHA, and carbohydrazide. 

The methoxymethyl ether protecting groups of 33 were then cleaved using triphenylphosphine and carbon tetrabromide. The resulting hydroquinone function was oxidized by palladium on carbon under an atmosphere of air to afford the quinone 52 (70 %). A two-step procedure was implemented to install the diazo function. First, the ketone function of 52 was condensed with N,N -bis( tert-butyldimethylsilyl)hydrazine in the presence of scandium triflate, which formed the Af-tert-butyldimethylsilyl hydrazone 53. The hydrazone (53) was then oxidized using difluoroiodobenzene to afford kinamycin C (3) in 35 % yield. 

You, T. Y., Niu, L., Gui, J. Y, Dong, S. J., and Wang, E. K. (1999). Detection of hydrazine, methylhydrazine and isoniazid by capillary electrophoresis with a 4-pyrldyl hydroquinone self-assembled microdisk platinum electrode. /. Pharm. Biomed. Anal. 19, 231—237. 

In view of its importance, reductive dissolution of Fe oxides has been widely studied. Reductants investigated include dithionite, thioglycolic acid, thiocyanate, hydrazine, ascorbic acid, hydroquinone, H2S, H2, Fe ", tris (picolinato) V", fulvic acid, fructose, sucrose and biomass/bacteria (Tab. 12.3). Under the appropriate conditions, reductive dissolution may also be effected photochemically. As with protonation, the extent of reduction may be strongly influenced by ligand and proton adsorption on the oxide surface. 

A further variation is the reaction of isothiocyanates (e.g., 162f) with hydrazine that has been solidified by inclusion into the host hydroquinone (163). Ball-milling of the solids leads to a quantitative reaction and the auxiliary 165 is washed away with water [79] (Scheme 20). 

A number of nucleophilic molecules can lose electrons in enzyme-catalyzed reactions (e.g., peroxidase). Thus hydrazines, amines, hydroquinones, phenothiazines, thiols, and aminophenols can form free radicals by this mechanism. 

A mixture of powdered dimethyl terephthalate la (19.4 g, 0.1 mol) and 1 1 inclusion complex of hydroquinone and hydrazine (58.5 g, 0.4 mol) was kept under a nitrogen atmosphere at 100-125 °C for 25 h. To the reaction mixture was added MeOH and MeOH insoluble terephthalic acid dihydrazide 2a was obtained by filtration (17.1 g, 88.1% yield). 

The inclusion complex of an unstable reactant or reagent is sometimes useful in organic synthesis in the solid state. For example, very reactive anhydrous hydrazine can be trapped as a 1 1 inclusion complex with hydroquinone (24). This 1 1 inclusion compound (24) is a stable white powder that can easily be prepared by mixing aqueous hydrazine with powdered hydroquinone. Compound 24 is... 

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