Acidity continued malonic acid

This ester (70 g) and diethyl carbonate (250 mg) were stirred at 90°C to 100°C while a solution of sodium ethoxide [from sodium (7.8 g) and ethanol (1 54 ml)] was added over 1 hr. During addition, ethanol was allowed to distill and after addition distillation was continued until the column heat temperature reached 124°C. After cooling the solution to 90°C, dimethyl sulfate (33 ml) was followed by a further 85 ml of diethyl carbonate. This solution was stirred and refluxed for 1 hr and then, when Ice cool, was diluted with water and acetic acid (10 ml). The malonate was isolated in ether and fractionally distilled to yield a fraction boiling at 148°C to 153°C/0.075 mm, identified as the alpha-methyl malonate. This was hydrolyzed by refluxing for 1 hr at 2.5N sodium hydroxide (350 ml) and alcohol (175 ml), excess alcohol was distilled and the residual suspension of sodium salt was acidified with hydrochloric acid to give a precipitate of the alpha-methyl malonic acid. This was decarboxylated by heating at 180°C to 200°Cfor 30 minutes and recrystallized from petroleum ether (BP 80°C to 100°C) to give 2-(2-fluoro-4-biphenylyl)propionic acid, MP 110°C to 111°C. 

The dry calcium malonate is placed in a 3-I. round-bottomed flask with sufficient (750-1000 cc.) alcohol-free ether (Note 3) to make a paste which can be stirred. The flask is surrounded by an ice bath, and the well-stirred salt is treated with 1 cc. of 12 N hydrochloric acid for each gram of salt. After the acid has been added slowly through a dropping funnel, the solution is transferred to a continuous extractor (Note 4) and extracted with ether until no more malonic acid is obtained. The product, as obtained from the undried ether solution by concentration, filtration, and drying in the air, melts at 130° or higher and is sufficiently pure for most purposes. The yield is 415-440 g. (77-82 per cent of the theoretical amount). 

A typical chemical system is the oxidative decarboxylation of malonic acid catalyzed by cerium ions and bromine, the so-called Zhabotinsky reaction this reaction in a given domain leads to the evolution of sustained oscillations and chemical waves. Furthermore, these states have been observed in a number of enzyme systems. The simplest case is the reaction catalyzed by the enzyme peroxidase. The reaction kinetics display either steady states, bistability, or oscillations. A more complex system is the ubiquitous process of glycolysis catalyzed by a sequence of coordinated enzyme reactions. In a given domain the process readily exhibits continuous oscillations of chemical concentrations and fluxes, which can be recorded by spectroscopic and electrometric techniques. The source of the periodicity is the enzyme phosphofructokinase, which catalyzes the phosphorylation of fructose-6-phosphate by ATP, resulting in the formation of fructose-1,6 biphosphate and ADP. The overall activity of the octameric enzyme is described by an allosteric model with fructose-6-phosphate, ATP, and AMP as controlling ligands. 

The main processes occurring in this system are the following [219] bromate oxidizes trivalent cerium to tetravalent cerium Ce4+ oxidizes bromomalonic acid, and is reduced to Ce3+. The bromide ion, which inhibits the reaction, is isolated from the oxidation products of bromomalonic acid. During the reaction, the concentration of the Ce4+ ions (and Ce3+) oscillates several times, passing through a maximum and a minimum. The shape of the peaks of concentrations and the frequency depend on the reaction conditions. The autooscillation character of the kinetics of the cerium ions disappears if Ce4+ or Br are continuously introduced with a low rate into the reaction mixture. The autooscillation regime of the reaction takes place only in a certain interval of concentrations of the reactants [malonic... 

At the start, the cycle begins with a certain amount of Ce+4 ions. The second reaction provides Br- ions, which inhibit the first reaction. This leads to an increase in concentration of Ce+3. After reaching a certain amount of Ce+3, the oxidation reaction starts, since little Ce+4 remains. The system can no longer produce sufficient Br to inhibit the reaction, and Ce+3 decreases rapidly, producing Ce+4 until the cycle is completed. It is possible to maintain indefinite oscillations with constant frequency in a continuous flow stirred reactor into which bromate, malonic acid, and cerium catalyst are being supplied at a uniform rate. 

For weakly coordinating potassium K+ counter-ions, the acidity of diethyl malonate (24) (in DMSO) increased by increasing the fraction of ion pairing, as shown in Table 1 for three counter-ions in DMSO solution (Table 1). This trend also continued by increasing the coordinating ability of the metal counter-ions from sodium to lithium counterions. From this study, it appears the ( ,W)-confoimer (26 ) is more preferred over the (Z,U)-conformer (26) as the repulsion between the C—O bonds is more energetically unfavourable than chelate formation might be favourable. 

Anhydrides—Continued reduction to alcohols, 155 reduction to lactones, 535 Arenes, see Hydrocarbons, aromatic Amdt-Eistert reaction, 433, 487, 573 Aryl esters. Fries rearrangement, 344 hydrolysis, 169 preparation, 169 Aryl halides, see Halides Atyloxy acids, preparation, by aceto-acetic ester synthesis, 430 by malonic ester synthesis, 429 from atyloxy alcohols, 419 from atyloxy cyanides, 414 preparations listed in table 48, 460 Aryloxy acyl halides, preparation, 547 preparations listed in table 61, 553 Aryloxy esters, preparations listed in table 55, 516... 

Hydroxymercuri methyl malonic methyl ester, IIOlIg.CMe (C02Me)2.—The preparation is carried out in a similar manner to tlie above, using equal molecules of the ester and mercuric oxide and continuing the shaking for several days. It is a white amorphous solid, insoluble in the usual solvents. When saponified as above it gives an 85 per cent, yield of the anhydride of h droxymercuri-propionic acid. In a similar manner the methyl ester of ethylmalonic acid yields 80 per cent, of hydroxymercuribiityric acid anhydride. 

A rapid and linear conversion of succinic acid was observed with initial reaetion rates of 15 mol yf, h mol j and 61 mol,- h molR , resulting in complete eonversion within one hour. The intermediate produets detected were acrylic and acetic acids (maximum yields 10.5 and 2 mmol 1, respectively), which were then converted into carbon dioxide and water. Acrylic acid disappeared rapidly and completely during the first hour, but aeetic acid, known as a refractory molecule towards oxidation, was decomposed at a lower rate. There was a continuous TOC reduction throughout the course of oxidation with the rate of TOC removal progressively decreasing at the end of the reaction. Nevertheless, more than 99% of TOC removal was measured after 6 h of reaction - only traces of acetic acid were then detected (TOC < 9 mg 1, i.e. 0.4 pmol 1 ). Malonic acid, oxalic acid or formic acid were not detected by HPLC, probably due to their rapid oxidation. Indeed, separate experiments on the malonic acid vide infra) and previous results [9] have shown that these acids were oxidized to CO, and H,0 at a very high rate at the present reaction conditions. As expected, the acidity of the solution... 

Fairly high yields of coumarins are obtainable by irradiation for 4-6 h of methoxycinnamic acids in acetonitrile-water saturated with oxygen and containing naphthalene-1,4-dinitrile. Further routes to the flavone ring system continue to appear. Flavone-3-carboxylic acids are ao ssible from fi-phenoxybenzylidenemalonic acids and either sulphuric acid or trifluoroacetic acid-trifluoroacetic anhydride. Attempts to cyclize the malonic esters were less... 

Even more intriguing is the Belousov-Zhabotinskii class of oscillating reactions some of which can continue for hours. Such a reaction was first observed in 1959 by B. P. Belousov who noticed that, in stirred sulfuric acid solutions containing initially KBr03, cerium(IV) sulfate and malonic acid, CH2(C02H)2, the concentrations of Br and Ce" " underwent repeated oscillations of major proportions (e.g. tenfold changes on a time-scale which was constant but which could be varied from a few seconds to a few minutes depending on concentrations and temperature). These observations were extended by... 

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