Methyl methanol concentration effect

The only dependencies noted in the kinetic studies were first-order dependencies on iodide promoter and rhodium concentrations. Thus there was no observed effect of varying methanol concentration, and the partial pressure of carbon monoxide had no effect on the reaction rate. Similarly, the concentration of the products, methyl acetate and acetic acid, has no effect on the reaction rate. Thus we have the unusual situation of a reaction, CH3OH + CO — CH3COzH, in which the concentrations of the reactants and product have no kinetic influence. 

Human exposure to 10,000 ppm for a short period of time resulted in eye, nose, and throat irritation, which persisted after cessation of exposure. In a man exposed to unmeasured concentrations, effects were general central nervous system depression, headaches, and dizziness, followed by blindness of both eyes caused by atrophy of the optic nerve. The toxic action on the optic nerve is possibly related to the presence of methanol after hydrolysis of methyl acetate. ... 

TABLE 4 Effect of Methanol Concentration on the Chiral Resolution of Amino Acids on Cu(II)-L-Hydroxypropyl)methyl-Silica Gel... 

Hg.3. Effect of methanol concentration on acyltransferase activity of lipolytic acyl hydrolase. Amounts of free fatty acids (circles) and fatty acid methyl esters formed (triangles) or lyso-phosphatidylcholine deacylated (squares) in 10-min incubations at 2S°C are given as percentage of substrate (lysophosphatidylcholine) added. (Reproduced from Galliard and Dennis, 1974, by permission.)... 

Lewis (74f) reports the observation by Ijewis and Farrissey of a 7% increase in rate of the reaction between triethylamine deuterated in one ethyl group and methyl brosylate The effect is comparable to those observed on the base strength of a-deuterated amines (Table VII). It is less easy to understand Simon and Palm s (118) observation that introduction of tritium into methanol reduces the rate of its reaction with 2,4-dinitrobenzoyl chloride by 12%. To be sure, the reaction was carried out in alkaline solution, so that it may involve a pre-equilibrium. If so, the increased reactivity of tritiated methoxide ion should be offset by its smaller equilibrium concentration. Still the net effect is uncomfortably large. 

With aldehydes, primary alcohols readily form acetals, RCH(OR )2. Acetone also forms acetals (often called ketals), (CH2)2C(OR)2, in an exothermic reaction, but the equiUbrium concentration is small at ambient temperature. However, the methyl acetal of acetone, 2,2-dimethoxypropane [77-76-9] was once made commercially by reaction with methanol at low temperature for use as a gasoline additive (5). Isopropenyl methyl ether [116-11-OJ, useful as a hydroxyl blocking agent in urethane and epoxy polymer chemistry (6), is obtained in good yield by thermal pyrolysis of 2,2-dimethoxypropane. With other primary, secondary, and tertiary alcohols, the equiUbrium is progressively less favorable to the formation of ketals, in that order. However, acetals of acetone with other primary and secondary alcohols, and of other ketones, can be made from 2,2-dimethoxypropane by transacetalation procedures (7,8). Because they hydroly2e extensively, ketals of primary and especially secondary alcohols are effective water scavengers. 

Other companies (e.g., Hoechst) have developed a slightly different process in which the water content is low in order to save CO feedstock. In the absence of water it turned out that the catalyst precipitates. Clearly, at low water concentrations the reduction of rhodium(III) back to rhodium(I) is much slower, but the formation of the trivalent rhodium species is reduced in the first place, because the HI content decreases with the water concentration. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilization of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives.8 The kinetics of the title reaction with respect to [MeOH] change if H20 is used as a solvent instead of AcOH.9 Kinetic data for the Rh-catalyzed carbonylation of methanol have been critically analyzed. The discrepancy between the reaction rate constants is due to ignoring the effect of vapor-liquid equilibrium of the iodide promoter.10... 

Because of the diaphoretic and laxative effects, the composition of Sambuci flos (Sambucus negra L., black elder) has been extensively investigated by TLC. Samples for TLC analysis were preparated by refluxing 1.0 g of air-dried, powdered flowers of Sambucus negra with 10 ml of methanol for 30 min. The suspension was filtered, and the filtrate was concentrated and redissolved in 5 ml of methanol. Separation was performed on silica layers using 10 different mobile phases 1 = ethyl acetate-formic acid-acetic acid-water (100 11 11 27, v/v) 2 = ethyl acetate-formic acid-water (8 1 1, v/v) 3 = ethyl acetate-formic acid-water (88 6 6, v/v) 4 = ethyl acetate-methyl-ethyl ketone-formic acid-water (50 30 10 10, v/v) 5 = ethyl acetate-methyl-ethyl ketone-formic acid-water (60 15 3 2, v/v) 6 = ethyl acetate-formic acid-acetic acid-methyl-ethyl... 

Catalytic Cycle. Attempts to determine the reasons for the improved activity of the base on alumina reagents followed two paths. Being as solubility of base in methanol appeared to greatly effect the production of methyl benzyl ether, we compared the amount of extractable base with selectivity to ester. This concentration of base, presumably alkoxide, was determined by stirring the base in methanol, filtering, and titrating the filtrate with acid. This comparison is given as Table VII. 

The maximum observed rotation for the 2-amino-2-methyl-1-propanol salt of levopimaric acid is [a] n —218°. Methanol and ethanol solutions give the same specific rotations, but methanol is the preferred solvent because the time required to effect solution in ethanol is longer. If pure levopimaric acid, m.p. 151-153°, [a] D —276° is desired, the salt with —210° rotation should be dissolved in 8 parts of boiling methanol, the solution concentrated to the point of incipient crystallization, cooled, and filtered. The yield in this recrystallization is about 70%. 

The concentration of HNO2 had little effect on CE, but increased concentrations of methanol up to 0.8 M increased the CE until it reached a plateau. The rate of disappearance of Craq002 + and formation of CH20 decreased as [CH3OH] was increased in the range 0.007-2 M. This kinetic effect is caused by the formation of the inactive methyl nitrite, Eq. (70), which has -Krqno = 3.5 M-1 (229). 

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