Hydrates of ammonia

Ammonia forms two hydrates, NH3. H2O and 2 NH3. H2O, and the crystal structure of the latter has been studied at 170°K. The crystal apparently consists of a hydrogen-bonded framework of composition NH3.H2O, in which 

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Formation of ice minerals (ca. 140 K) (to include water ice, solid hydrates of ammonia, methane, and rare gases). 

Urine typically has a particularly high content of ammonia nitrogen which is present in weakly alkaline media in the form of non-dissociated hydrate of ammonia with very toxic effects on fish. 

For this second reaction Kjgs = 181 x 10" and hence pK, for ammonia solution is 4.75. The entity NHj. H2O is often referred to as ammonium hydroxide, NH4OH, a formula which would imply that either nitrogen has a covalency of five, an impossible arrangement, or that NH4OH existed as the ions NH4 and OH". It is possible to crystallise two hydrates from concentrated ammonia solution but neither of these hydrates is ionic. Hence use of the term ammonium hydroxide is to be discouraged in favour of ammonia solution . 

The base strength of hydrazine is, however, lower than that of ammonia. As might be expected, hydrazine is readily soluble in water from which the hydrate N2H4.H2O can be crystallised. 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Evolution of ammonia from a boiling dilute solution of diammonium phosphate gradually reduces the pH. This process is used commercially to control the precipitation of alkaH-soluble—acid-insoluble coUoidal dyes on wool. Other ammonium orthophosphate salts of interest are ammonium hemiphosphate [28537-48-6] NH4H2PO4 H3PO4, and its hydrate [28037-74-3], as well as the trihydrate [78436-07-4] of DAP. 

Examples are given of common operations such as absorption of ammonia to make fertihzers and of carbon dioxide to make soda ash. Also of recoveiy of phosphine from offgases of phosphorous plants recoveiy of HE oxidation, halogenation, and hydrogenation of various organics hydration of olefins to alcohols oxo reaction for higher aldehydes and alcohols ozonolysis of oleic acid absorption of carbon monoxide to make sodium formate alkylation of acetic acid with isobutylene to make teti-h ty acetate, absorption of olefins to make various products HCl and HBr plus higher alcohols to make alkyl hahdes and so on. 

Cyanamidopyrimidine (15) was converted to the thioureido derivative 16 by reaction with hydrogen sulfide and ammonium hydroxide and then cyclrzed to 18 with hydrazine hydrate. Cyclization to 18 presumably took place by elimination of a molecule of ammonia from the aminoguanidine intermediate 17 (65JCS3357) (Scheme 11). 

According to REM, hydrazine hydrate Is reacted with 2 mols of ammonium thiocyanate to produce 1,2-bislthlocarbamoyl) hydrazine which by loss of ammonia and rearrangement produces 5-amino-2-mercapto-1,3,4-thiadiazole. That compound is acetyied with acetic anhydride. 

Panal is stable in aqueous media (pH 1-5) at room temperature, except for a gradual hydration that can be reversed with an aqueous acid. Panal is activated into chemiluminescent compounds upon treatment with the salts of ammonia or primary amines. 

On mixing, an exothermic reaction takes place with some loss of ammonia. As the reaction proceeds crystalline phases are formed. All workers are in agreement that these are the tetrahydrate schertelite, or the hexahydrate struvite, or a mixture of both. They also agree that schertelite is first formed, which is then hydrated further, if water is available, to form struvite. The relative amounts thus depend on the water available for hydration. Sometimes dittmarite, MgNH4P04. HjO, and stercorite, NaNH4HP04.4H20, are found in minor amounts. 

Abdelrazig, Sharp El-Jazairi (1988, 1989) prepared a series of mortars based on a powder blend of MgO and ADP with a quartz sand filler. They were hydrated by mixing with water. A mortar I (MgO ADP silica water = 17T 12-9 70-0 12-5), with a water/solid ratio of 1 8, formed a workable paste which set in 7 minutes with evolution of ammonia. The main hydration product, struvite, was formed in appreciable amounts within 5 minutes and continued to increase. Schertelite also appeared, but only in minor amounts, within the first 5 minutes and persisted only during the first hour of the reaction. Dittmarite appeared in minor amounts after 15 minutes, and persisted. 

Kostic et al. recently reported the use of various palladium(II) aqua complexes as catalysts for the hydration of nitriles.456 crossrefil. 34 Reactivity of coordination These complexes, some of which are shown in Figure 36, also catalyze hydrolytic cleavage of peptides, decomposition of urea to carbon dioxide and ammonia, and alcoholysis of urea to ammonia and various carbamate esters.420-424, 427,429,456,457 Qggj-jy palladium(II) aqua complexes are versatile catalysts for hydrolytic reactions. Their catalytic properties arise from the presence of labile water or other solvent ligands which can be displaced by a substrate. In many cases the coordinated substrate becomes activated toward nucleophilic additions of water/hydroxide or alcohols. New palladium(II) complexes cis-[Pd(dtod)Cl2] and c - Pd(dtod)(sol)2]2+ contain the bidentate ligand 3,6-dithiaoctane-l,8-diol (dtod) and unidentate ligands, chloride anions, or the solvent (sol) molecules. The latter complex is an efficient catalyst for the hydration and methanolysis of nitriles, reactions shown in Equation (3) 435... 

Dichloroacetamide has been prepared from ethyl dichloroace-tate with alcoholic ammonia1 or aqueous ammonium hydroxide,2 from ethyl dichloromalonate and alcoholic ammonia,3 by the action of ammonia on pentachloroacetone,4 chloral cyanohydrin,5 and hexachloro-i,3,5-cyclohexanetrione,6 from chloral ammonia and potassium cyanide,7 by the action of hydrogen chloride on dichloroacetonitrile,8 from the reaction of asparagine with the sodium salt of N-chloro- -toluenesulfonamide,9 and by the action of an alkali cyanide and ammonia on chloral hydrate.10... 

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