Tri -chlor aldehyde

The tri-chlorine substitution product of methane is the common and very important anesthetic chloroform. It may be made by the method referred to, viz., by the direct chlorination of methane. This method is not, however, a practical one. The industrial preparation is from alcohol or acetone, by treatment with chlorine and an alkali. In the reaction with alcohol the chlorine acts, first, as an oxidizing agent, oxidizing the alcohol to aldehyde. The chlorine then acts as a substituting agent forming a tri-chlorine substitution product of the aldehyde. This tri-chlor aldehyde is then decomposed by the alkali and chloroform results. The steps in this reaction have been definitely proven, as follows ... 

Ethylidene Chloride.—CH3—CHCI2 is a colorless liquid boiling at 57.7°. It does not mix with water and possesses anesthetic properties, though it has no general use as such. It is a by-product in the manufacture of chloral, tri-chlor aldehyde (p. 226). 

C. SUBSTITUTED ALDEHYDES AND KETONES I. HALOGEN ALDEHYDES Tri-chlor Aldehyde CCI3—CHO Chloral... 

This reaction of oxidation often takes place, as has been referred to in the case of tri-chlor aldehyde, or chloral, which yields tri-chlor acetic acid on oxidation. But this is not the ordinary method of preparation of the halogen acids. The commoh method of preparing these compounds is by the direct halogenation of the acids themselves. 

When aldehydes are directly halogenated the halogen enters a carbon group other than the one containing the aldehyde group. In the case of acet-aldehyde chlorine may be substituted for all three of the hydrogens in the methyl radical and we obtain, tri-chlor acetaldehyde ... 

In the preparation of chloroform the tri-chlor acet-aldehyde then reacts with an alkali present yielding chloroform and the alkali-metal salt of formic acid, as follows ... 

Chloral.—Chloral, or tri-chlor acet-aldehyde, was first prepared by Liebig in 1832 by the chlorination of alcohol as above. It may also be obtained by the direct action of chlorine upon acet-aldehyde. It is an oily liquid with a sweet suffocating odor. It boils at 97.7°. It does not mix with water but on boiling with water it forms a hydrated compound which crystallizes in large clear crystals, readily soluble in water. This is known as chloral hydrate. The structure of chloral hydrate is probably that of an addition product, viz., a, chlorinated di-hydroxy alcohol. In this compound we have an exception to the general rule that two hydroxyl groups can not be linked to the same carbon atom. 

It reduces ammoniacal silver nitrate solution. It is oxidizable to tri-chlor acetic acid and, by the action of zinc and hydrochloric acid, is reduced to acet-aldehyde. Chloral is a most important soporific and is used in certain cases for anesthetic purposes. In this latter use it is always the readily soluble form of chloral hydrate which is employed. Its anesthetic action was, at first, attributed to the probable formation of chloroform but this is now doubted. 

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