Carbamic acid salts

Impurities in CL have also been destroyed by oxidation with ozone22 followed by distillation. Ozonation treatment of waste CL leaves no ionic impurities. However, the most commonly used oxidizing agents are potassium permanganate, perboric acid, perborate, and potassium bromate. Treatment of CL with these oxidizing agents is carried out in a neutral medium at 40-60°C. Strongly alkaline or acidic conditions accelerate the oxidation of CL to form isocyanates. Hie undesirable oxidation reaction is fast above pH 7 because of the reaction with isocyanate to form carbamic acid salts, which shifts the equilibrium to form additional isocyanate. 

Carbamic acid salts 560, generated in situ from primary amines and carbon dioxide, react with DCC in the presence of triethylamine to give 1,3-disubstimted ureas 561 and dicyclohexylurea. ... 

The new method of EAMP isolation from the reaction medium and puriflcation has been proposed. This method includes water evaporation under the reduced pressure at 30 °C with the following EAMP carbamic acid salt thermodecomposition at 65-70 °C equilibrium A, scheme) and product distillation. 

Abstract. Infrared analysis of reacting foams has been used to determine the sequence of chemical reactions that occurs in the foaming process and to relate this sequence of reactions to the stages evident in the formation of foam measured by rate-of-rise techniques. A reaction sequence model has been developed in which at the earliest stage of foaming, out-of-phase carbamic acid and carbamic acid salts, formed by hydrolysis of isocyanate, are the main species present tending to stabilize the froth-like foam. These species are in turn converted into polyureas. In the latter stages of the reaction sequence, urethane formation becomes predominant as the foam develops substantial bulk modulus... 

A further variant can be used with strongly basic aliphatic amines and has proved especially valuable for diamines whose hydrochlorides do not react with phosgene first, dry carbon dioxide is led into a solution of the amine in a solvent suitable for the phosgene reaction, this giving a carbamic acid salt ... 

Carbamates Formation and hydrolysis. Amines form carbamic acid salts on reaction with CO2 in the presence of Cs2COj. Carbamate esters are isolated after alkylation. When the alkylating agent is an a-bromoalkyl epoxide, 5-(a-hydroxy-alkyl)oxazolidin-2-one is the product. Apparently, epoxide opening by the amine precedes A-carboxylation. 

Recently, Bazito with coworkers have reported that a 4-TBSO-proline 29-catalysed asymmetric aldol reaction of acetone with 4-nitrobenzaldehyde can run in supercritical (sc) CO2 or sc-COj/IL green solvent systems with a poor yield and low enantiomeric excesses. The moderate catalytic performance of 29 in SC-CO2 may be attributed to the known capability of primaiy and secondary amines to generate carbamic acid salts with CO2, which hamper the catalytic process. 

A method for the preparation of halosilyl carbamates and isocyanate involves direct synthesis from amines via halosilyl carbamate intermediates [277]. A primary amine is converted to its carbamic acid salt, which is then treated with a silane containing > 2 halogen atoms bonded to Si. Gentle heating of the resulting halosilyl carbamate gives the isocyanate. In an alternative (exchange) procedure, the carbamic acid salt is treated with any halosilane to form a silyl carbamate, which is trans-silylated. 

The new selective amination protocol of unprotected sugar derivatives was also reported by Likhosherstov and coworkers who used the same reagent, but with the major advantage of an easy isolation of the reaction product. Most importantly, the N-glycosylamines formed by the reaction with ammonia are precipitated as carbamic acid salts and this prevents... 

The reaction commences at about 120° the carbamic acid formed decomposes immediately into carbon dioxide and ammonia. The latter may form the ammonium salt with unreacted acid the ammonium salt also reacts with urea at temperatures above 120° to yield the amide ... 

The acid chloiide (chloioformamide [463-72-9] "uiea chloiide"), NH2COCI, and its salts have been prepared. Ammonium carbamate [1111 -78-OJ can be obtained as a white crystalline sobd by reaction of dry carbon dioxide and ammonia. It is an impurity in commercial ammonium carbonate [506-87-6] (see Ammonium compounds). Esters of carbamic acid are quite stable. The best known is the ethyl ester usually called urethane [51 -79-6],... 

Nitrocarbamates. Salts of Nitrocarbamic Acid. See under Carbamic Acid and Derivatives in Vol 2, C40-Lff... 

Chemical/Physical Forms water-soluble salts (Hartley and Kidd, 1987). When heated to 75 °C, asulam decomposed to sulfanilic acid, carbamic acid, and sulfanilamide. At 90 °C, 4-nitro- and 4-nitrosobenzene sulfonic acids were released (Rajagopal et al., 1984). 

Synonyms Zinc diethyldithiocarbamate (ZDEC Ethyl Ziram zinc bis-diethyldithio-carbamate diethyldithiocarbamic acid, zinc salt) zinc dibutyldithiocarbamate (ZDBC zinc bis-dibutyldithiocarbamate dibutyldithiocar-bamaic acid, zinc salt) zinc dimethyldithio-carbamate (ZDMC Ziram zinc bis-dimethyldithiocarbamate dimethyldithio-carbamic acid, zinc salt)... 

Upon dissolving the copolymer/catalyst mixture in ethylbutylamine (EtBuNH) the introduction of CO2 at atmospheric pressure results in formation of an equilibrium mixture of carbamic acid and the quaternary ammonium salt of carbamate. The carbamic acid serves to remove the copolymer from the metal center, at which time it precipitates in the ionic liquid and is isolated by filtration. The metal catalyst... 

A series of solid-state reactions has been explored by Kaupp et al., in which gaseous amines were reacted with aldehydes to give imines. Analogous reactions with solid anhydrides, imides, lactones or carbonates, and isothiocyanates were used to give, respectively, diamides or amidic carboxylic salts or imides, diamides, carbamic acids, and thioureas [24]. In general the yields were found to be quantitative. Ammonia and other gaseous amines, in particular methyl-amine, have also been shown to aminolyse thermoplastic polycarbonates [25]. 

Other useful dehydrating agents are dimethylaminosulfur trifluoride (DAST), methyl A -(triethylammoniosulfonyl)carbamate (Burgess salt), acetic anhydride, oxalyl chloride, and phosphorous oxychloride, each one in combination with triethylamine (89). Dehydration of O-sUylated hydroxamic acids using trifluoro-methanesulfonic anhydride and triethylamine under mild conditions also gave nitrile oxides, which in the presence of olefins led to the formation of 2-isoxazolines in moderate to good yields (90). In view of the less readily available starting materials, this method probably will be of limited use. 

Carbamates can be prepared by O-alkylation of carbamic acids R2N-CO2H. Carba-mic acids are usually susceptible to decarboxylation, but the corresponding salts can be prepared from amines and carbon dioxide under basic reaction conditions and... 

The detailed mechanism of sarcosine NCA polymerisation may be radically modified by a change of solvent. For example, in dimethyl formamide this reaction is first order with respect to growing ends [see e. g. ref. (44)] instead of being second order as in nitrobenzene. The higher acidity of the former solvent reduces the basicity of the dissolved amine and, therefore, destroys its catalytic action. This effect influences also the equilibrium between the amine and the dissolved C02. In nitrobenzene, the carbamic acid produced is associated with the free amine forming the respective ammonium salt (ion-pairs), whereas in the more acidic dimethyl formamide it exists as an un-ionised acid. 

The basic problem is raised by the second question, namely, which mechanism of propagation operates in the polymerisation giving the high molecular weight polypeptide. The writer proposes, therefore, the following experiment which may resolve the present controversy. Let us prepare a radio-active salt of carbamic acid, say,... 

D is found in compounds like quinolyl esters of N-substituted dithio-carbamic acids. A wide variety of compounds containing the quinoline system are herbicides. Derivatives and salts of 8-quinolinecarboxylic acid as well as quinolyl carbamates are each useful insecticides. The copper salt of 8-hydroxyquinoline is an effective fungicide. 

Carbamic Acid Amidocarbonic Acid or Aminoformic ActW(called Carbamidsaure Kohlensaure-monoamid or Aminoameisensaure in Get) HaN.COOH mw 61.04, N 22.95 the theoretical, first simplest aminoacid known in aq solns, are called carbamates, and other derivs. The prepn props of aq solns of carbamic acid and its salts are described in detail in Refs 1 2. See also Refs 3 4... 

Corbonic Acid, H2C03. The soln of C02 in H O exhibits feeble acid props it is unstable, however, and has never been isolated it is known only in the form of its salts (carbonates), acid salts 0bicarbonates), amides (carbamic acid or urea), and as acid chlorides (carbonyl chloride). This is also an old term for carboxylic acid Ref Hackh s(1944), 169... 

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