Ammonium chloride route

THE AMMONIUM CHLORIDE ROUTE TO ANHYDROUS RARE EARTH CHLORIDES—THE EXAMPLE OF YCI3... 

Among the methods for the preparation of anhydrous rare earth metal trichlorides, MCI3 (M = La-Lu,Y,Sc), the so-called ammonium chloride rout is probably the most popular and frequently used because it is inexpensive and straightforward even for large scale quantities. It was originally believed that the conversion of rare earths, M2O3, to trichlorides. 

The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides 147... 

Anhydrous lanthanide halides are ionic substances with high melting points which take up water immediately when exposed to air to form hydrates (r>Br >Ch) [48]. Straightforward synthetic access and a favorable complexation/solva-tion behavior make the lanthanide halides the most common precursors in organolanthanide chemistry. Many important Ln-X bonds (X=C, Si, Ge, Sn, N, P, As, Sb, Bi, O, S, Se, Te) can be generated via simple salt metathesis reactions [4,8]. The so-called ammonium chloride route either starting from the lanthanide oxides or... 

Meyer, G. (1989) The ammonium chloride route to anhydrous rare earth chlorides - the example of YClj. Inorg. Synth,25,146-150. 

Direct Meutra.liza.tion, Because of the avadabiHty of by-product ammonium salts, the double decomposition routes are usually more favorable economically for ammonium chloride manufacture. However, where surplus hydrogen chloride is available, the direct neutralisation process has been used (15)... 

The reactants ate fed into the tail flame of a d-c nitrogen plasma. The reaction occurs rapidly at temperatures around 1500°C and the HCl reacts with excess ammonia to form ammonium chloride. Similar reactions have been carried out using furnaces, lasers, and r-f plasmas (34) as the source of heat. Other routes using titanium tetrachloride starting material include... 

In 1959 a new non-protein L-a-amino acid was isolated from the seeds of Acacia willardiana and later from other species of Acacia-, it proved to be l-/3-amino-/3-carboxyethyluracil (977) (59ZPC(316)164). The structure was confirmed by at least four syntheses in the next few years. The most important involves a Shaw synthesis (Section 2.13.3.1.2e) of the acetal (975) and hydrolysis to the aldyhyde (976) followed by a Strecker reaction (potassium cyanide, ammonia and ammonium chloride) to give DL-willardiine (977) after resolution, the L-isomer was identical with natural material (62JCS583). Although not unambiguous, a Principal Synthesis from the ureido acid (978) and ethyl formylacetate is the most direct route (64ZOB407). 

Earlier, the reduction of y-nitro esters with zinc and ammonium chloride had been shownto provide a suitable route to A-hydroxy 2-pyiTolidones, e.g., 42. Various catalytic hydrogenation procedures can also effect the same reductive cyclization. ... 

The practical route for oxidizing leuco diphenylmethanes 15 demands inital conversion to an imine salt 16. The imine salt is obtained by heating a mixture of diphenylmethane, sulfur, ammonium chloride, and sodium chloride at 175°C in a current of ammonia or by heating a mixture of diphenylmethane, urea, sulfamic acid, sulfur, and ammonia at 175°C (Scheme 3). Dyes 16 can be represented as the quinonoid resonance structure 17. Dyes of this class, known as auramines, are all yellow, with the only commercial representative being auramine O 16a. Due to its poor lightfastness and instability to hot acids and bases, its use has been restricted to dyeing and printing cotton, paper, silk, leather, and jute. 

Some years ago a hydrometallurgical route, called the AmMAR concept, was presented [24], The concept (Fig. 14.15) represented a general processing route for a wide variety of feed materials. The detailed design of each specific process involved a specific number of known chemical operations, combined in unique ways. The main thread was the ammonia ammonium chloride or carbonate leach solution and its extraordinary chemical flexibility. 

Conversion of substituted nitrobenzenes to the arylhydroxylamine is easily achieved by reduction in neutral or slightly acid solution. In the first classical experiments, Haber [35] used a platinum cathode and ammonia ammonium chloride buffer and die process was improved by Brand [57] using either a nickel or silvered copper cathode in an acetate buffer. The hydroxylamine can also be obtained from reduction in dilute sulphuric acid provided tire temperature is kept below 15° C to suppress furtlier reduction [58]. This electrochemical route to arylhydroxylamines due to Brand is superior to the chemical reduction using zinc dust and ammonium chloride solution. The latter process is known to give variable yields depending on... 

The present method offers a more efficient and convenient two-step route to the parent a,B-unsaturated acylsilane derivative. The first step in the procedure involves the conversion of allyl alcohol to allyl trimethylsilyl ether, followed by metalation (in the same flask) with tert-butyllithiura at -75°C. Protonation of the resulting mixture of interconverting lithium derivatives (2 and 3) with aqueous ammonium chloride solution furnishes (1-hydroxy-2-propenyl)trimethylsilane (4), which is smoothly transformed to (1-oxo-2-propenyl)trimethylsilane by Swern oxidation. The acylsilane is obtained in 53-68% overall yield from allyl alcohol in this fashion. 

The requisite hydroxylamine function for such cyclizations can also be generated from a precursor having a nitro group. This novel route has provided access to hitherto unknown l-hydroxy-6-allyl-, and -6,6-bisallyl-piperazine-2,5-diones (91UP1). The starting material is an W-nitroacetyl amino acid ester that can be either mono-or bis-allylated at the methylene adjacent to the nitro group. Reduction of the N02 to NHOH using zinc/ ammonium chloride, followed by cyclization, leads to the desired products (Scheme 76). Compound (215) is unique in that it possesses a chiral center at C-3 and a quaternary carbon at C-6 on a l-hydroxypiperazine-2,5-dione system. 

Kraus and Greer1 originally prepared a few organotin hydrides with considerable difficulty from the reaction between an organotin sodium compound and ammonium bromide or ammonium chloride in liquid ammonia. Their procedure remained the only synthetic route to these compounds for some 25 years until 1947 when Finholt, Bond, Wilzbach, and Schlesinger2 obtained the methyltin hydrides in a more facile manner by reducing a mixture of the methyltin chlorides with lithium aluminum hydride (lithium tetrahydroaluminate). 

Trimethylorthoformate 17 is a highly activated Cl building block and a formic acid equivalent which is commonly applied in organic condensation reactions. 17 can be produced on an industrial scale by two major routes. The first starts with chloroform and sodium methanolate, but produces 3 equiv. of sodium chloride as waste. The second route is based on the acidic methanolysis of cyanhydric acid, which also produces stoichiometric amounts of ammonium chloride. Despite the reduced salt waste, the use and handling of cyanhydric acid mean high safety costs. Therefore, anodic methoxylation of formaldehyde dimethylacetal (16) to... 

Diaryl ketimines, Ar1C=NH. The patent literature has described the preparation of (C6H5)2C=NH by direct reaction of benzophenone with ammonia, but this route has not been investigated further. Actually, a number of diaryl ketimines can be obtained in >95% yield by reaction of a diaryl ketone with liquid ammonia and a catalytic amount of ammonium chloride in THF in a sealed tube at 120° (60 bar). 

This boron-nitrogen heterocycle is a convenient route to the synthesis of borazine and -substituted borazines.1-6 The procedure described here is a modification of the reaction of boron trichloride with ammonium chloride.7-9... 

---