Ammonium carbonate group

Table 219. Colour reactions of ions in the ammonium carbonate-group...

Hydroxyl Group. The OH group of cyanohydrins is subject to displacement with other electronegative groups. Cyanohydrins react with ammonia to yield amino nitriles. This is a step in the Strecker synthesis of amino acids. A one-step synthesis of a-amino acids involves treatment of cyanohydrins with ammonia and ammonium carbonate under pressure. Thus acetone cyanohydrin, when heated at 160°C with ammonia and ammonium carbonate for 6 h, gives a-aminoisobutyric acid [62-57-7] in 86% yield (7). Primary and secondary amines can also be used to displace the hydroxyl group to obtain A/-substituted and Ai,A/-disubstituted a-amino nitriles. The Strecker synthesis can also be appHed to aromatic ketones. Similarly, hydrazine reacts with two molecules of cyanohydrin to give the disubstituted hydrazine. 

Chromate Anion Polystyrene matrix Tertiary or quaternary ammonium functional groups Sodium carbonate or alkaline NaCl... 

The experiments described above indicated amino acids were oxidatively deaminated in liver and their a-amino groups converted to urea. A start on investigations of the mechanism of urea biosynthesis was made by Schultzen and Nenki (1869) who concluded that amino acids gave rise to cyanate which might combine with ammonia from proteins to produce urea. Von Knieren (1873) demonstrated that when he drank an ammonium chloride solution, or gave it to a dog, there was an increase in the formation of urea, without any rise in urinary ammonia. His results were consistent with the cyanate theory but did not eliminate the possibility that urea arose from ammonium carbonate which could be dehydrated to urea ... 

Low et al. (1991) reported that the photooxidation of aromatic compounds containing amino and nitro groups by UV light in the presence of titanium dioxide resulted in the formation of ammonium, carbonate, and nitrate ions. 

Interest has focused on derivatives of mannitol hexanitrate (14) as potential explosives because although this nitrate ester is a powerful explosive it has some property characteristics of a primary explosive. Treatment of mannitol hexanitrate (14) with pyridine or ammonium carbonate " in aqueous acetone leads to a very selective denitration with the formation of mannitol-1,2,3,5,6-pentanitrate (77). Marans and co-workers synthesized the acetate (78), the propionate (79), and the phenylacetate (80) derivatives of mannitol-1,2,3,5,6-pentanitrate and all have significantly lower melting points than mannitol hexanitrate. The incorporation of such groups can also help to increase the solubility of an explosive in the melt of another explosive. 

Metyrosine Metyrosine, (-)a-methyltyrosine (12.3.11), is synthesized in a few different ways, the simplest of which is the synthesis from 4-methoxybenzylacetone, which is reacted with potassium cyanide in the presence of ammonium carbonate to give the hydan-toin (12.3.9). Treating this with hydrogen iodide removes the methyl-protecting group on the phenyl hydroxyl group and the product (12.3.10) is hydrolyzed by barium hydroxide into a racemic mixture of a-methyl-D,L-tyrosine, from which the desired L-isomer is isolated (12.3.11) [83-86]. 

The apparently quite broad structural requirements for anticonvulsant activity, noted earlier in this chapter, extend to yet another class of five-membered heterocycles that include an imide function. Imidazo-2,4-diones, better known as hydan-toins, have comprised some of the most widely used drugs for treating severe motor and psychomotor epileptic seizures. The general reaction used to prepare this heterocyclic system involves the treatment of a carbonyl compound with ammonium carbonate and potassium cyanide. The first step in the complex sequence can be visualized as the addition of the elements of ammonia and hydrogen cyanide to give an a-aminonitrile (88-2). Addition of ammonia to the cyano group would then lead to an amidine (88-3). Carbon dioxide or carbonate ion present in the reaction... 

All members of this group react Barium (II), Ba+2 Ammonium carbonate Ammonium oxalate Dilute sulfuric acid... 

An anomeric acetyl group can be removed selectively by treatment with hydrazine acetate or ammonium carbonate in DMF (Scheme 2.15c).46 The latter transformations are of great importance for the preparation of glycosyl donors such as anomeric trichloroacetimidates. 

In 2000 a new technique for preserving frescoes was announced by Baglioni, by then heading a group of surface chemists from six Italian universities, and all of them experts in various aspects of fresco conservation. Their new technique is to follow the ammonium carbonate treatment with a colloidal dispersion of calcium hydroxide in the solvent 1-propanol.1011 This penetrates the fresco better, and over time it again reacts with carbon dioxide from the air to regenerate calcium carbonate. This technique can restore frescoes that earlier conservators would have deemed almost impossible to save. Sadly some frescoes are beyond even this restorative technique. 

The group reagents used for the classification of most common cations are hydrochloric acid, hydrogen sulphide, ammonium sulphide, and ammonium carbonate. Classification is based on whether a cation reacts with these reagents by the formation of precipitates or not. It can therefore be said that classification of the most common cations is based on the differences of solubilities of their chlorides, sulphides, and carbonates. 

II, and III. They form precipitates with ammonium carbonate in the presence of ammonium chloride in neutral or slightly acidic medium. Cations of this group are calcium, strontium, and barium. 

Group reagent there is no common reagent for the cations of this group. Group reaction cations of the fifth group do not react with hydrochloric acid, hydrogen sulphide, ammonium sulphide or (in the presence of ammonium salts) with ammonium carbonate. Special reactions or flame tests can be used for their identification. 

Ammonium chloride or ammonium carbonate solution gelatinous precipitate of silicic acid. This reaction is important in routine qualitative analysis since silicates, unless previously removed, will be precipitated by ammonium chloride solution in Group IIIA. 

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