Aqueous malonic acid

CH OfiSj, H2C(S03H)2- a colourless, crystalline solid which readily absorbs water vapour decomposes on distillation. The potassium salt is prepared by heating methylene chloride with an aqueous solution of potassium sulphite under pressure at 150-I60" C. The free acid is obtained by decomposing the sparingly soluble barium salt with sulphuric acid. The aryl esters are very stable, but the alkyl esters decompose on heating to give ethers. Resembles malonic acid in some of its reactions. 

Tribromoacetic acid [75-96-7] (Br CCOOH), mol wt 296.74, C2HBr302, mp 135°C bp 245°C (decomposition), is soluble in water, ethyl alcohol, and diethyl ether. This acid is relatively unstable to hydrolytic conditions and can be decomposed to bromoform in boiling water. Tribromoacetic acid can be prepared by the oxidation of bromal [115-17-3] or perbromoethene [79-28-7] with fuming nitric acid and by treating an aqueous solution of malonic acid with bromine. 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Beryllium, calcium, boron, and aluminum act in a similar manner. Malonic acid is made from monochloroacetic acid by reaction with potassium cyanide followed by hydrolysis. The acid and the intermediate cyanoacetic acid are used for the synthesis of polymethine dyes, synthetic caffeine, and for the manufacture of diethyl malonate, which is used in the synthesis of barbiturates. Most metals dissolve in aqueous potassium cyanide solutions in the presence of oxygen to form complex cyanides (see Coordination compounds). 

On heating with aqueous hydrochloric acid, the alkylated (or dialkylated) malonic ester undergoes hydrolysis of its two ester groups followed by decarboxylation (loss of C02) to yield a substituted monoacid. 

Although heating benzene-1,2-diamine with malonic acid in aqueous hydrochloric acid affords the parent dione 26 (R = H) in 62% yield,277 the method cannot be extended to substituted malonic acids because decarboxylation intervenes however, the reaction of benzene-1,2-diamines with diethyl malonate and its derivatives constitutes a general procedure for the synthesis of l,5-benzodiazepine-2,4-diones 26 selected examples are given.278... 

A third mechanism of protodeboronation has been detected in the reaction of benzeneboronic acids with water at pH 2-6.7625. In addition to the acid-catalysed reaction described above, a reaction whose rate depended specifically on the concentration of hydroxide ion was found. In a preliminary investigation with aqueous malonate buffers (pH 6.7) at 90 °C, 2-, 4-, and 2,6-di-methoxybenzeneboronic acids underwent deboronation and followed first-order kinetics. A secondary reaction produced an impurity which catalysed the deboronation, but this was unimportant during the initial portions of the kinetic runs. 

By hydrolysis of substituted malonic esters with 50 per cent, potassium hydroxide, followed by decarboxylation of the resulting malonic acid by heating above the m.p. or, better, by rendering the aqueous solution of the potassium salt of the dibasic acid strongly acid and refluxing the mixture, for example ... 

In ethyl acetoacetate the methylene group is united to —CO.CH3 and —COOR. Free acetoacetic acid is even much less stable than malonic acid and, on merely warming in solution, decomposes in fundamentally similar fashion, into acetbne and carbon dioxide. Since all synthetic derivatives of ethyl acetoacetate behave in the same way, so that the acetoacetic acids, obtained by hydrolysis of their esters with aqueous mineral acids, decompose spontaneously with loss of carbon dioxide when heated, numerous derivatives of acetone are made available by this synthesis, by what is called Icetonic hydrolysis, e.g. 

When reacted with trialkyl phosphite in benzene for 1 hr, dialkyl magnates (364, X = F) gave a mixture of amino(trifluoromethyl)methylene-malonates (365) (20% yields), dialkyl trifluoromethyl(substituted amino)-methylenemalonates (366) (40-45% yields), and dialkyl chlorophosphate (-20%) (86ZOB805). The reactions of dialkyl malonates (364, X = F, Cl) and triphenylphosphine in the presence of triethylamine in diethyl ether for 1 hr gave trihalomethyl(substituted amino)methylenemalonates (367) in 87-95% yields. The treatment of a solution of dialkyl trifluoromethyl-(substituted amino)methylenemalonates (366, R1 = Et) in benzene with aqueous hydrochloric acid gave amino(trifluoromethyl)methylene-malonates (368) in 82-84% yields (86ZOB805) (Scheme 32). 

The Belousov-Zhabotinsky (BZ) reaction involves the oxidation of an organic species such as malonic acid (MA) by an acidified aqueous bromate solution in the presence of a metal ion catalyst such as the Ce(m)/Ce(IV) couple. At excess [MA] the stoichiometiy of the net reaction is... 

Method C The malonic ester (15 mmol) is stirred with aqueous NaOH (50%, 30 ml) and TEBA-CI (3.54 g, 15 mmol). The alkylating agent (0.25 mmol) is then added and the mixture is stirred for 1 h at room temperature. The mixture is diluted with H,0 (75 ml) and extracted with Et,0 (3 x 25 ml). The dried (MgS04) extracts are evaporated to give the alkylated ester. Acidification of the aqueous phase with cone. HCI and extraction with Et,0 (3 x 25 ml) yields the alkylated malonic acid or r-butyl ester. 

Methanolic MeONa (3M, 0.12 ml) is added to the V-benzylquininium or quinidinium chloride (0.162 g, 0.36 mmol) in dry THF (2 ml) at room temperature. The mixture is stirred at room temperature for 10 min and the Meldrum s acid derivative (0.3 mmol) in dry PhMe (13 ml) is added at -50°C. The course of the reaction is monitored by GLC. On completion, the mixture is stirred for a further 15 min at -50°C and aqueous itric acid (3%, 30 ml) is added. The aqueous phase is separated, and extracted with Et20 (3 x 20 ml). The combined extracts are washed with brine (20 ml) and dried (Na2S04). Evaporation of the Et20 under reduced pressure gives the monomethyl malonic ester. 

Experimental Rate Constant Data Illustrating the Role of Steric Effects in Strengthening the Intramolecular Hydrogen Bond in the Monoanion of 2,2-Disubstituted Malonic Acids in Aqueous Solution (25 C, 0.1 M NaClO )... 

Cyclopropanation of Cjq with diethyl bromomalonate in toluene with NaH as auxiliary base proceeds smoothly at room temperature (Scheme 3.5). By-products are unreacted Cjq and higher adducts. The formahon of higher adducts is discussed in detail in Chapter 10. The monoadduct can be isolated easily from the reach on mixture by column chromatography. Saponificahon of such di(efhoxycarbonyl)-methylene adducts of Cgg is achieved by treatment with NaH in toluene at elevated temperatures and subsequent quenching with methanol (Scheme 3.6) [32], This method provides easy access to defined water-soluble fullerenes and can also be applied to higher adducts. These malonic acid derivatives of are very soluble in polar solvents, for example acetone, THF or basic water, but insoluble in aqueous acids. 

Elemental composition C 52.96%, 0 47.04%. It may be analyzed by treatment with water. The product malonic acid formed may be measured quantitatively by direct injection of aqueous solution into a GC for FID detection. Alternatively, the aqueous solution may be evaporated and the residue may be derivatized to methyl ester and identified by mass spectrometry. Also, the gas may react with ammonia or an amine, and the amide derivative may be identified and quantitatively determined by GC-FID, GC-NPD, GC/MS or infrared techniques. 

Ice-acetone bath. The bottle is closed with a rubber stopper which is clamped or wired securely in place (Note 3) and is shaken mechanically at room temperature until the suspended malonic acid dissolves (Note 4). The bottle is chilled in an ice-salt bath and opened then the contents are poured into a separatory funnel containing 250 ml. of water, 70 g. of sodium hydroxide, and 250 g. of ice. The mixture is shaken (carefully at first), the layers are separated, and the aqueous portion is extracted with two 75-ml. portions of ether. The organic layers are combined, dried over anhydrous potassium carbonate, and filtered into a dropping funnel attached to the neck of a 125-ml. modified Claisen flask (Note 5). The flask is immersed in an oil bath at about 100°, and the excess isobutylene and ether are removed by flash distillation effected by allowing the solution to run in slowly from the dropping funnel. The dropping funnel is then removed, and the residue is distilled at reduced pressure. The fraction boiling at 112—115°/31 mm. is collected. The yield of colorless di-tert-butyl malonate is 60.0 62.0 g. (58-60%), 1.4158-1.4161,... 

Beside this basic method of manufacturing mercury fulminate, which is widely practised, there are alternate processes. Angelico [11] recognized that mercury fulminate is formed by treating a mercury solution in an excess of nitric acid with a concentrated aqueous solution of malonic acid in the presence of a small amount of sodium nitrate. The reaction results in a considerable rise of temperature, C02 evolution and the precipitation of the fulminate (L. W. Jones [12]). 

In a 1-1. round-bottomed flask fitted with a reflux condenser are placed 192 g. (166 ml., 2 moles) of freshly distilled furfural (Note 1), 208 g. (2 moles) of malonic acid (Note 2), and 96 ml. (1.2 moles) of pyridine (Note 3). The flask is heated on a boiling water bath for 2 hours, and the reaction mixture is cooled and diluted with 200 ml. of water. The acid is dissolved by the addition of concentrated aqueous ammonia, the solution is filtered through a fluted filter paper, and the paper is washed with three 80-ml. portions of water. The combined filtrates are acidified with an excess of diluted (1 1) hydrochloric acid with stirring. The mixture is cooled by running water and then allowed to stand in an ice bath for at least 1 hour. The furylacrylic acid is filtered, washed with four 100-ml. portions of water, and dried. The yield of practically colorless needles melting at 141° is 252-254 g. (91-92%). If a purer product is desired, recrystallization is best effected from dilute alcohol (Note 4). On slow cooling of the solution, needles melting at 141° separate. 

In reactions where nitriles are prepared from halogen compounds by double decomposition with alkali cyanide in alcoholic or aqueous alcoholic solution, the latter is usually added in solution or as a powder (cf. Preparations 77,78,79), otherwise the alkali halide which separates forms a coating round the cyanide and hinders further action. If the reaction is performed in aqueous solution, as in the preparation of malonic acid (p. 125), this precaution is not so necessary the alkali halide, when formed, remains in solution. 

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