Acid continued formation

Dutcher et al 54 used 40% sulphuric acid to produce an acid concentration of 37% in the solution for hydrolysis and obtained maximum formation of furfural after 1 hrs reflux. Morgan et al 59 however, used 70% sulphuric acid to produce a 25% acid concentration in the hydrolysis solution and obtained maximum formation of furfural after one hour. Ivashkivl O has evaluated the use of both hydrochloric and sulphuric acids and found up to four times more furfural to be produced by sulphuric acid, the yield being extremely sensitive to the concentration of acid employed. Continuing further work with sulphuric acid, the formation of furfural as a function of neomycin concentration was examined and the conclusion reached that better yields of furfural are obtained at low concentrations of the antibiotic. Heyesl has shown a constant amount of furfural to be produced on hydrolysis with 27-28% sulphuric acid, refluxing for 1 hour. This makes it unnecessary to accurately... 

Process (12). The reactor is a horizontal pressure vessel called Contactor and containing an inner circulation tube, a heat exchanger tube bundle to remove the heat of reaction, and a mixing impeller in one end. The hydrocarbon feed and recycle acid enter on the suction side of the impeller inside the circulation tube. This design ensures the formation of a fine acid-continuous emulsion. The high circulation rate prevents significant temperature differences within the reactor. The reactor is shown schematically in Fig. 11. 

Photolytic. Methyl formate, formed from the irradiation of dimethyl ether in the presence of chlorine, degraded to carbon dioxide, water, and small amounts of formic acid. Continued irradiation degraded formic acid to carbon dioxide, water, and hydrogen chloride (Kallos and Tou, 1977 Good et al, 1999). 

Evidence of Two Enzymatic Activities. We found no formation of NADH spectrophotometrically during decomposition of malic acid by cell-free extracts of L. oenos ML 34. However, using a more sensitive fluorometric technique to search for NADH (88), we found a small, continual formation of NADH (about 5 nmoles NADH/min/mg extract protein) as an end product (89,90). Thus, in addition to the decarboxylation of malic acid to lactic acid, there is another reaction that gives... 

Since in the citric acid cycle there is no net production of its intermediates, mechanisms must be available for their continual production. In the absence of a supply of oxalacetic acid, acctaic" cannot enter the cycle. Intermediates for the cycle can arise from the carinxylation of pyruvic acid with CO, (e.g., to form malic acid), the addition of CO > to phosphcnnlpyruvic acid to yield oxalacetic acid, the formation of succinic acid from propionic acid plus CO, and the conversion of glutamic acid and aspartic acid to alpha-ketoglutaric acid and oxalacetic acid, respectively. See Fig. 3. 

For amino acids (continued) Ammonium formate 4.10 138 ml 2 M Formic acid 200 ml 1 M NH4OH (H13)... 

These results indicate that the solvent removal process in poly(amic acid) film formation is dependent on the residual stress level. Solvent evaporation creates volume changes which in turn generate shrinkage stresses ( 8 MPa at room temperature). This will continue until there is a balance between the internal stress and the driving forces for solvent removal. Further solvent may be removed if this balance is altered by a change in stress or temperature. 

The measurement of circular dichroism is an especially sensitive and excellent method for studying the reactions of 34. A freshly prepared solution of 34 at pH 7.8 contains no 33 or 22 after several hours, a Cotton effect is observable, and it attains a maximum after two days. Thus, the equilibrium 34 33 has been established. The position of the equilibrium is dependent on the pH at pH 7.8, the content of 33 is 3—6%, on the assumption that 33 has a molar extinction coefficient of circular dichroism similar to that found for other cyclic azomethines. On treatment of the solution with carbon dioxide to pH 6.8, the Cotton effect disappears immediately, because the acid-catalyzed Amadori rearrangement of 33(= 16) —> 22 is accelerated. Compound 22 is, however, a secondary amine, and is a stronger base than 33 and 34, so that the continued formation of 22 causes ftie pH to rise. Thereby, the acid-catalyzed Amadori rearrangement is slowed down so much that the equilibrium 33 34, with its high Cotton... 

Although interesterification will occur in the absence of added catalysts at sufficiently high temperatures, catalysts are employed by industry to speed this reaction, reducing reaction time and the sample degradation that occur at elevated temperatures. The most commonly used inorganic catalysts are alkaline ones such as sodium methoxide, sodium ethoxide, sodium or potassium metal, and alloys of sodium and potassium. Catalyst concentrations of 0.05% to 0.1% are employed. As the catalysts will react with water, free fatty acids, and oxidized compounds, it is important to use clean, dry feedstocks. Reaction temperatures are generally kept below 100°C. The reactions can be mn in batch or continuous formats. In batch mode, the reaction times are typically less than an hour. 

Chemistry of the Tricyclic Diterpenoids.—The addition of chlorosulphonyl isocyanate to the methyl esters of levopimaric and neoabietic acids with the formation of C-12 carboxyamides has been described.63 The well documented aromatic substitution reactions of dehydroabietic acid continue to be examined,64 together... 

Several hypotheses have been propounded to explain the continued formation of urea. One of the first was the suggestion that to the synthesis of urea there was a pathway alternative to the Krebs-Henseleit one (L7). Evidence for such a pathway had earlier been adduced by Bach (Bl), who concluded that, in the liver, glutamine formed from glutamic acid and ammonia could combine further with ammonia and... 

Some oxidoreductases require nicotine adenine dinucleotide (NADH) as a cofactor.146 To use them in organic synthesis, as in the reduction of a ketone to an alcohol, it is necessary to have an efficient system to continuously regenerate them. A common way is to include in the same reaction formic acid and formate dehydrogenase, the byproduct being carbon dioxide.147 The regeneration of the cofactor can also be done electrochemically with or without the addition of a hydrogenase.148 The use of whole organisms eliminates this need. 

The olefin formation is influenced very much by the presence of other substances which act as catalysts. Sulfuric acid is one of those most commonly used in this reaction. The efficiency of the sulfuric acid in this reaction is often connected with its tendency to combine with water, or its dehydrating property. In the final products, it is true that the elements of water have been removed from the alcohol, but the mechanism of the reaction is unquestionably not so simple. The continuous formation of ethylene by running ethyl alcohol into warm sulfuric acid the formation of alcohol from an olefin and dilute sulfuric acid [A. Butleroff, Lieb. Ann. 180, 245 (1876)] the formation of alcohol from olefin and concentrated sulfuric... 

The total hydrocarbon yield exhibits a maximum at 330-360°C and decreases above those temperatures due to severe cracking (gas formation). The Pr/Ph ratio increases with temperature to a maximum at 330°C and above that temperature the isoprenoid hydrocarbons are destroyed. The 17a-hopane biomarkers are still relatively immature in the unheated samples. They show no further maturation and are destroyed above 360°C. Alkanoic acids have a maximum yield at 330-360°C and are present over the complete temperature range. This indicates continual formation from kerogen and cracking of the products. PAHs increase in concentration with increasing temperature and the alkyl PAHs concomitantly decrease. At 500°C essentially only the parent PAHs remain in the extractable bitumen. 

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