Methyl acetate, atmosphere

Acetyl-2-Dimethylsulfamylthioxanthene A suspension of 2-dimethylsulfamylthioxanthene (12.22 grams, 0.04 mol) in 60 ml of dimethoxymethane is cooled to 0°C and 17.2 ml of a 2.91 M solution of n-butyl lithium in heptane is added slowly in a nitrogen atmosphere while the temperature is maintained below 10°C. After an additional 10 minutes of stirring, the cooling bath is removed and a solution of 2.96 grams of methyl acetate in 20 ml of di-methoxyethane is added during % hour and then the mixture is stirred at 25°C for an additional 3 hours. The reaction mixture is then treated with 60 ml of ethyl acetate and with 60 ml of a 10% aqueous ammonium chloride solution. The layers are separated and the ethyl acetate layer is washed once with water (25 ml) and then the solvent is removed by distillation. 

Acetic acid is formed when methane reacts with CO or C02 in aqueous solution in the presence of 02 or H202 catalyzed by vanadium complexes.327 A Rh-based FeP04 catalyst applied in a fixed-bed reactor operating at atmospheric pressure at 300-400° C was effective in producing methyl acetate in the presence of nitrous oxide.328 The high dispersion of Rh at sites surrounded by iron sites was suggested to be a key factor for the carbonylation reaction. 

The low equilibrium constant and the strongly nonideal behavior that causes the forming of the binary azeotropes methyl acetate/methanol and methyl acetate/ water make this reaction system interesting as a possible RD application (33). Therefore, methyl acetate synthesis has been chosen as a test system and investigated in a semibatch RD column. Since the process is carried out under atmospheric pressure, no side reactions in the liquid phase occur (146). 

Figure A.6 Comparison of computed (solid line) and experimentally measured equilibrium reactive RCM for the methyl acetate system at atmospheric pressure [3],...

The Kinetics of Methanol Carbonylation Over RhX, RhY and IrY zeolites Carbonylation of methanol proceeds readily at atmospheric pressure under mild temperature conditions 150°-180°C. This reaction ZCH OH + CO - CH COOCH + HjO produces mainly methyl acetate and water. Acetic acid was detected at high conversions and high temperatures. Traces of dimethyl ether could also form. In most cases the selectivity to methyl acetate was at least 90% in presence of the iodide promotor. 

The test solution should not contain more than 5 per cent (v/v) concentrated hydrochloric acid and must have a pH < 2. It is spotted on a paper strip and allowed to evaporate for 10-15 minutes. Diffusion of the solvent takes place in an atmosphere saturated with respect to the vapour of a saturated solution of methyl acetate in water, and the temperature is maintained constant at 22°. The solvent moves sufficiently far in 20-30 minutes to effect a complete separation. After evaporation of the solvent, the strip is made alkaline by exposure to ammonia vapour and then sprayed with a 1 per cent solution of diphenyl-carbazide in alcohol. Mercury is indicated by a narrow blue band in the dry solvent front. 

The ammines of cobalt(II) are much less stable than those of cobalt(III) thermal decomposition of [Co(NH3)6]Cl2 is characterized by reversible loss of ammonia, whereas that of [Co(NH3)6]Cl3 is not. In his classic dichotomy of complexes, Biltz regarded [Co (NH 3)3] Cl 2 as the prototype of the normal complex and [Co(NH3)6]Cl3 as that of the Werner or penetration complex. Hexaamminecobalt-(II) chloride has been prepared by the action of gaseous ammonia on anhydrous cobalt (II) chloride or by displacing water from cobalt(II) chloride 6-hydrate with gaseous ammonia. It may also be synthesized in nonaqueous solvents by passing dry ammonia through solutions of cobalt(II) chloride in ethanol, acetone, or methyl acetate. Syntheses in the presence of water include heating cobalt(II) chloride 6-hydrate in a sealed tube with aqueous ammonia and alcohol and the treatment of aqueous cobalt(II) chloride with aqueous ammonia followed by precipitation of the product with ethanol. The latter method is used in this synthesis. Inasmuch as the compound is readily oxidized by air, especially when wet, the synthesis should be performed in an inert atmosphere. 

B. a-Bromoheptaldehyde dimethyl acetal. A solution of 156 g. (177 ml., 1 mole) of the enol acetate and 200 ml. of carbon tetrachloride is placed in a l-l. flask and cooled in an ice-water bath. A mixture of 160 g. (51 ml., 1 mole) of bromine and 50 ml. of carbon tetrachloride is added slowly through a buret, the flask being constantly shaken and the rate of addition so controlled as not to allow the temperature of the brominated mixture to rise above 10° (Note 6). The addition of bromine takes from 20 minutes to 1 hour, and the end point is reached when the calculated amount is absorbed and the bromine is no longer decolorized. The brominated mixture is added to 600 ml. of anhydrous methanol (Note 7) and allowed to stand for 48 hours or longer. At the end of this period the mixture is diluted with 2 1. of water and the separated oil (lower layer) is washed with 1 1. of water and finally with 1 1. of 5% sodium carbonate (Note 8). The carbon tetrachloride and methyl acetate are removed by distillation at atmospheric pressure. The residual oil is then distilled under reduced pressure in the presence of a small amount of sodium carbonate. The fraction boiling at 117-119°/17 mm. is collected as pure a-bromoheptaldehyde dimethyl acetal, 1.4510-1.4520 df 1.180-1.195. The yield is 191-203 g. (80-85%) (Note 9). 

The esters RC(0)0R again react essentially totally with the OH radical under atmospheric conditions (Atkinson, 1989). Figure 6 gives the methyl acetate-OH mechanism. 

The chief pathways to account for the disappearance of MTBE in the environment are atmospheric reactions and biodegradation. By virtue of its sterically hindered structure, MTBE has lower reactivity than other hydrocarbons in gasoline. The atmospheric half-life of MTBE has been estimated at 4 toll days (Carter et al., 1991). MTBE will react with hydroxyl (OH) radicals in the atmosphere. The rate of atmospheric reactivity of hydroxyl radicals with MTBE has been determined to be close to 2.8 x 10 cm molecule sec . While the ultimate product of degradation of MTBE is carbon dioxide and water, in laboratory experiments, observed products are tertiarybutyl formate, formaldehyde, methyl acetate, and acetone. Organic nitrate has also been noted when nitrogen oxides are present. 

Nagata, I. Vapor-liquid equilibrium at atmospheric pressure for the ternary system, methyl acetate -chloroform - benzene. J. Chem. Eng. Data 1962, 7, 360-366. 

Kushner, T. M. Tatsievskaya, G. L Babich, S. V Serafimov, L. A. Liqnid-vapor phase equilibrinm in the acetone - methyl acetate - ethyl acetate system at atmospheric pressure [Russ]. Zh. Prikl. Khim. (Leningrad) 1969, 42, 100-103. 

Tu, C.-H. Wu, Y.-S. Liu, T.-L. Isobaric vapor-liquid equilibria of the meflianol, methyl acetate and methyl acrylate system at atmospheric pressure. Fluid Phase Equilib. 1997, 135, 97-108. 

The acid anhydrides, compounds of general formula RC(=0)0C(=0)R, are formed in the atmosphere from the atmospheric degradation of esters see chapter vn. For example, formic acetic anhydride, CH3C(0)0CH0, is a product of methyl acetate oxidation (Christensen et al., 2000) ... 

Esters are emitted directly into the atmosphere from both natural and anthropogenic sources and are produced during the atmospheric oxidation of ethers. Methyl acetate and ethyl acetate have found widespread use as solvents. Vegetable oils and animal fats are esters. Transesterification of vegetable oils and animal fats with methanol gives fatty acid methyl esters (FAMEs) which are used in biodiesel. Many esters have pleasant odors and are present in essential oils, fruits, and pheromones, and are often added to fragrances and consumer products to provide a pleasant odor. Table VII-A-1 provides a list of common esters and their odors. 

Methyl acetate has a Henry s law constant of approximately 10 M atm (Sander, 1999). Loss of methyl acetate by dissolution into cloud-rain-sea-water will not be of atmospheric significance. Combining (0H CH30C(0)CH3) = 3.46 x 10 cm molecule" s" at 298 K with a diurnal average of [OH] 1.0 x 10 molecule cm gives an estimate of 33 days for the atmospheric lifetime with respect to reaction with OH radicals. Reaction with OH radicals dominates the atmospheric fate of methyl acetate. 

B-Apo-8 -carotenoic acid methyl ester [16266-99-2] M 512.7, m 136-137°, A2575 at 446nm and 2160 at 471nm, in pet ether. Crystd from pet ether or pet ether/ethyl acetate. Stored in the dark in an inert atmosphere at -20°. 

Ergometrine crystallises, with solvent, from benzene in needles or from methyl ethyl ketone in prisms both forms have m.p. 162-3° (dec.). From ethyl acetate it crystallises at — 4° in thin, solvent-free plates, m.p. 160-1° (dec.), and at atmospheric temperature on concentration in vacuo in diamond-shaped plates, B.0-5EtAc, m.p. 130-2° (dec.), from which the combined solvent is not removed at 100° in vacuo. By crystallisation from acetone, Grant and Smith obtained a second form in long needles, m.p. 212° (dec.), which appears to be the more stable, since the form, m.p. 162-3°, tends to pass into it on keeping. Ergometrine has [o]d — 44° (CHCI3) - - 42-2° or + 62-6° (c = 1-7, EtOH) or... 

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