Methyl alcohol, absolute

Absolute methyl alcohol. The synthetic methanol now available is suitable for most purposes without purification indeed, some manufacturers claim a purity of 99 85 per cent, with not more than 0 1 per cent, by weight of water and not more than 0 02 per cent, by weight of acetone. Frequently, however, the acetone content may be as high as 0 1 per cent, and the water content 0-5-1 per cent. 

It is essential to use freshly recrystallised benzoyl peroxide. The commercial material usually gives poor results. Commercial benzoyl peroxide may bo recrystal, lised from a small amount of hot chloroform, or by dissolving in chloroform and precipitating with absolute methyl alcohol. 

Methyl crotonate. Purify commercial crotonic acid by distiUing 100 g. from a 100 ml. Claisen flask attached to an air condenser use an air bath (Fig. II, 5, 3). The pure acid passes over at 180-182° and crystallises out on cooling, m.p. 72-73° the recovery is about 90 per cent. Place 75 g. of absolute methyl alcohol, 5 g. (2 -7 ml.) of concentrated sulphuric acid and 50 g. of pure crotonic acid in a 500 ml. round-bottomed flask and heat under reflux for 12 hours. Add water, separate the precipitated ester and dissolve it in ether wash with dilute sodium carbonate solution until effervescence ceases, dry with anhydrous magnesium sulphate, and remove the ether on a water bath. Distil and collect the methyl crotoiiato at 118-120° the yield is 40 g. 

The alkah manganates(V) in strongly alkaline solution (45—50% at 0°C) are all blue. In water these manganate(V) compounds instantly disproportionate into manganate(VI) and Mn02. Lithium manganate(V), prepared by reaction of LiMnO and excess LiOH at 124°C, is an exception. This compound is relatively stable in 3% LiOH solution at 0°C and in absolute methyl alcohol. 

Absolute Methyl Alcohol, 7, 28, 29 Absorption trap for gases, 8, 26, 28 Acetal, 3,1 Acetaladon, 3,1... 

The apparatus consists of a 3-]. three-necked flask fitted with a mercury-sealed mechanical stirrer, a reflux condenser, a dropping funnel, and a thermometer which reaches almost to the bottom of the flask. Five hundred grams of potassium hydroxide pellets (85 per cent potassium hydroxide) (7.5 moles) and 750 cc. of commercial absolute methyl alcohol (free from acetone) are placed in the flask and stirring begun. The bulk of the alkali dissolves in a few minutes, with the evolution of heat. The flask is now surrounded by an ample cold-water bath, and, when the internal temperature drops to 6o°, addition of a mixture of 360 g. (353 cc., 3 moles) of -tolualdehyde (Note 1), 300 cc. of formalin (3.9 moles) (Note 2), and 300 cc. of absolute methyl alcohol is begun at such a rate that the internal temperature remains at 60-70°. This addition requires about fifteen minutes. The internal temperature is then maintained at 60-70° for three hours, after which the reflux condenser is replaced by a downward condenser, and the methyl alcohol distilled with the aid of a brine bath until the internal temperature reaches ioi°. Nine hundred cubic centimeters of cold water is then added to the warm residue, and the mixture cooled. The resulting two layers are separated at once (Note 3), and the aqueous layer extracted with three 200-cc. portions of benzene. The combined oil and extracts are washed with five or six 50-cc. portions of water (Note 4), and the combined washings extracted... 

A further quantity of arabinose may be isolated from the mother liquors by the use of diphenylhydrazine to a solution of 22 g. of diphenylhydrazine hydrochloride in 100 cc. of absolute methyl alcohol is added a solution of 3.3 g. of sodium in 50 cc. of methyl alcohol. After fifteen minutes standing the sodium chloride is removed by filtration and washed with methyl alcohol. The filtrate, which contains approximately 18 g. of free diphenylhydrazine, is added to the alcoholic mother liquor from the arabinose and the mixture is inoculated with diphenylhydrazone prepared from some of the crystalline arabinose. The mixture is allowed to stand overnight, and the crystalline diphenylhydrazone is filtered, washed with 95 per cent ethyl alcohol, and dried in a vacuum desiccator. In a preparation in which the yield of crystalline arabinose had been 23.5 g., the yield of diphenylhydrazone was 16.5 g., corresponding to 7.8 g. of the sugar. Arabinose can be recovered from the diphenylhydrazone by treatment with formaldehyde in aqueous solution. In view of the... 

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