Ammonia , as solvent

Continuous processes have been developed for the alcohols, operating under pressure with Hquid ammonia as solvent. Potassium hydroxide (206) or anion exchange resins (207) are suitable catalysts. However, the relatively small manufacturing volumes militate against continuous production. For a while a continuous catalytic plant operated in Raveima, Italy, designed to produce about 40,000 t/yr of methylbutynol for conversion to isoprene (208,209). 

Let us next consider liquid ammonia as solvent, in which the positive ion (NH4)+ corresponds to (II30)+ in water. From this ion a proton can jump to an adjacent solvent molecule. 

Proton Transfers in Various Solvents. The Autoprotolysis of Methanol. Formic Acid as Solvent. The Sulfate Ion. Autoprotolysis of Formic Add. The Urea Molecule. Sulfuric Add and Liquid Ammonia as Solvents. 

Sulfuric Acid and Liquid Ammonia as Solvents. The proton transfer that takes place in pure sulfuric acid is believed to be... 

An alternative method for the conversion of an alkyne to an alkene uses sodium or lithium metal as the reducing agent in liquid ammonia as solvent. This method is complementary to the Lindlar reduction because it produces... 

Kinetic studies of base-catalysed hydrogen exchange have been carried out by Roberts, by Shatenshtein, and by Streitweiser and their coworkers. In earlier work, potassium amide was used as base in liquid ammonia as solvent, whereas later workers used lithium and caesium cyclohexylamides in cyclohexylamine. The reaction can be represented by equilibria (239) and (240)... 

Different synthetic routes have been used to prepare these carbenes (Scheme 8.6). The most common procedure is the deprotonation of the conjugate acid. In early experiments, sodium or potassium hydride, in the presence of catalytic amounts of either f-BuOK or the DMSO anion were used. ° Then, Herrmann et al. showed that the deprotonation occurs much more quickly in liquid ammonia as solvent (homogeneous phase), and many carbenes of type IV have been prepared following this procedure. In 1993, Kuhn and Kratz" developed a new and versatile approach to the alkyl-substituted N-heterocyclic carbenes IV. This original synthetic strategy relied on the reduction of imidazol-2(3//)-thiones with potassium in boiling tetrahydrofuran (THF). Lastly, Enders et al." reported in 1995 that the 1,2,4-triazol-5-ylidene (Vila) could be obtained in quantitative yield from the corresponding 5-methoxy-l,3,4-triphenyl-4,5-dihydro-l//-l,2,4-triazole by thermal elimination (80 °C) of methanol in vacuo (0.1 mbar). 

It is a system of acids, bases and salts with liquid ammonia as solvent instead of water. Thus the water system ... 

In addition, aryl chlorides, bromides, and iodides can be converted to arene-amines ArNH2 by the conjugate bases of amines. In fact, the reaction of potassium amide with bromobenzene is extremely rapid, even at temperatures as low as —33°, with liquid ammonia as solvent ... 

H. P. Cady and R. Taft sought if electrolytic oxidations can occur in systems containing no oxygen, and found that with liquid ammonia as solvent, thallous iodide, cuprous iodide, hydrazobenzene, and methyl- and ethylamine hydrochlorides can be oxidized. The properties of soln. of salts, etc., in liquid ammonia were studied by F. W. Bergstrom, T. J. Webb, E. C. Franklin and C. A. Kraus, etc. 

The corresponding action with liquid ammonia as solvent is termed ammonolysis. E.g. ... 

A general method of synthesis of l-hetera-4-telluracyclohexa-2,5-dienes 90 is founded in the nucleophilic addition of telluride anion to type 91 diacetylene derivatives. The telluride dianion is prepared in situ from the elements in liquid ammonia. The reaction was carried out with methanol or mixtures with DMSO and liquid ammonia as solvents, with the following diacetylenes di(l-alkynyl)sulfides (73RTC1326), I-alkynylethynyl sulfides (75RTCI63), di(l-alkynyl)sulfones (78RTC244), and di(l-alkynyl)phosphi-noxides (75RTC92). 

Although this reaction appears as though it might be a simple substitution, experiments indicate that it occurs by an elimination-addition mechanism. This mechanism is outlined in Figure 17.6 for the reaction of chlorobenzene with amide anion in liquid ammonia as solvent. 

Conversion of 129 to the desired sulfinamide requires the use of LiNH2 in ammonia as solvent, as other usual solvents do not give the reaction. 

Arylphosphonates may also be synthesized from sodium or potassium dialkyl phosphite salts and aryliodides by a SrnI reaction with photostimulation and such a procedure has been described in detail using liquid ammonia as solvent.73... 

The main disadvantages of the present industrial process are the use of large amounts of ammonia as solvent and the degradation of the Raney nickel catalyst either by attrition or leaching (solubilization in liquid ammonia). Considerable efforts are currently being made to search for efficient and resistant catalysts for the gas phase hydrogenation of adiponitrile with high hexamethylenediamine selectivity. 

Liquid ammonia as solvent sodium amide ammonium amalgam hydrazine hydroxylamine. 

Many of the SrnI reactions studied to date have employed liquid ammonia as solvent. This is an attractive solvent because it allows weak carbon acids such as acetone to be converted completely to their conjugate bases by reaction with amide... 

Where a reactive lower oxidation state results, a key concern is the necessary protection of the reduced complex from air or other potential oxidants, as they are often readily reoxidized. Usually, this requires their handling in special apparatus such as inert-atmosphere boxes or sealed glassware in the absence of oxygen. Where active metal reducing agents (such as potassium) are employed, special care with choice of solvent is also necessary. The nickel reduction reaction (6.33) can be performed in liquid ammonia as solvent, since the strongly-bound cyanide ions are not substituted by this potential ligand. 

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