Glacial acetic acid advantages

The solvent used is an important factor influencing the rate of reduction 34 and no generalization can be made beyond the one that alcohol, either 95 per cent or absolute has proved to be the best solvent for most of the compounds thus far studied. Ethyl acetate and glacial acetic acid may be used to advantage in some cases. 

A mixture of 50 per cent sulphuric acid and glacial acetic acid may be used with advantage in the case of diflicultly-hydrolysable aromatic nitriles. The reaction product is poured into water, and the organic acid is separated from any unchanged nitrile or from amide by means of sodium carbonate solution. 

The qualitative analysis of trityl compoimds takes advantage of the orange-yellow color of the halochromic salt formed when a trityl com-poimd is treated with a solution of concentrated sulfuric acid in glacial acetic acid. 

Carnoy fluid consisting of 6 parts absolute alcohol, 3 parts formaldehyde and i part of glacial acetic acid, can also be used for fixing small objects. It has the advantage of fixing these in about 10 minutes. Moreover the objects can be carried directly to absolute alcohol, thence to Paraffin and imbedded. 

It will be noted that the hydroxy compounds yield esters and the amines yield substituted amides. Acid anhydrides may be used as the acylating agent (see page 175). For acetylation of amines, heating with glacial acetic acid may be used advantageously. 

Treatment of the Mother-Liquor.—The mother-liquor filtered off from crystals still contains more or less of the substance, in proportion to its solubility at the ordinary temperature in many cases it is advantageous to extract the last portions remaining in solution. A second crystallisation is obtained by distilling or evaporating off a portion of the solvent. The mother-liquor may also be diluted with a second liquid, in which the dissolved substance is difficultly soluble e.g. a solution in alcohol or glacial acetic acid may be diluted with water, or a solution in ether or benzene with ligroin. 

Noble-metal catalysts are highly efficient and permit hydrogenations to be carried out at room temperature. That is especially important when the starting materials or the products are unstable at higher temperatures. A further advantage is the insensitivity of platinum and palladium catalysts to acids, wherefore hydrogenations can also be effected in acid solution (glacial acetic acid). Alcohols, ethyl acetate, ether, and water are also used as solvent. 

In broad terms it is only in special cases that the oxidation of hydrocarbons to primary or secondary alcohols is of practical importance. One such case is oxidation of toluene and its derivatives to the corresponding benzyl alcohols, by e.g., manganese dioxide, lead dioxide, lead tetraacetate, or Caro s acid. It is advantageous to use lead tetraacetate in glacial acetic acid solution since then the alcohol formed is protected by esterification against further oxidation. 

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