Mono chlor ethane

The next question which arises in regard to ethane is is ethane like methane in being symmetrical, i.e.y are all of the hydrogen atoms alike in their relation to the carbon atoms and to each other The same kind of facts which established this point in regard to methane are also true of ethane, viz., only one mono-chlor ethane is known. We thus conclude that all six hydrogen atoms in ethane are alikey and no matter which one is substituted by chlorine the product is always the same. We may write the structural formula for mono-chlor ethane then ... 

Isomerism of Di-chlor Ethanes.—When, however, we study the constitution of the poly-halogen ethanes we find that isomerism occurs just as in the case of the propyl iodides and of the hydrocarbons above propane. In the case of ethane it is a fact that only one mono-substitution product of any type is known, thereby proving the symmetry of the ethane molecule and the like character of all six of the hydrogen atoms. When two hydrogen atoms are substituted by two chlorine atoms two dif event compounds are produced both having the composition C2H4CI2. From the constitution of the ethane molecule, that has been established by its synthesis from methane (p. 16), we can readily see how this may be explained as we may have two hydrogen atoms replaced by two chlorine atoms in two different ways, as follows ... 

This reaction is entirely different from that of phosphorus penta-chloride on alcohol, in which the hydroxyl of the alcohol is replaced by one chlorine, and the mono-halogen substitution product of the hydrocarbon results (p. 81). If our ideas in regard to the constitution of aldehyde are correct, this reaction must mean, that, in the di-chlor ethane formed in this way, the two chlorine atoms are linked to the same carbon atom. Such a structure represents a compound which is plainly unsymmetricaL... 

The ethylidene, or unsymmetrical di-halogen substitution products of ethane, are not of much importance, because they do not easily undergo reaction. They are prepared by the reactions just described, viz., from aldehyde by the action of phosphorus penta-chloride, -bromide, or -iodide. Also by the action of phosphorus chlor-bromide, PCl3Br2, or of carbonyl chloride (phosgene), COCI2. They may also be made by the further halogenation of the mono-halogen ethanes ... 

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