Higher Halogen Ethanes

The hexa-halogen ethanes, CX3—CX3, or per-halogen ethanes, are known in both the chlorine and the bromine compounds. Per-chlor ethane, CCI3—CCI3, hexa-chlor ethane is a colorless, crystalline substance with a camphor-like odor and which melts at 184°. Per-brom ethane, CBr3—CBr3, hexa-brom ethane is also a colorless, crystalline substance. 

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Any condensation of methane to ethane and subsequently to higher hydrocarbons must overcome the unfavorable thermodynamics. This can be achieved in condensation processes of oxidative nature, where hydrogen is removed by the oxidant. SbF5- or FS03H-eontaining superacid systems also act as oxidants. The oxidative condensation of methane was subsequently found to take place with more economical cooxidants such as halogens, oxygen, sulfur, or selenium 91... 

The present authors question whether these results prove that the alkyl bromides (particularly methyl bromide) actually underwent condensa -tion with the butanes. In most of the experiments no data are given to show how much methane or ethane was formed. For none of the experiments is the amount of unreacted methyl or ethyl bromide recorded. It is quite possible that hydrogen-halogen exchange occurred and that the isopentane and the higher-boiling paraffins were formed entirely from the butane. 

Reactions of zinc or aluminum with organic halogen compounds as used in certain white smoke formulations also fall into the intermediate (0.5—1.0 kcal/g) range. In order to present meaningful figures, the considerable heat of vaporization of the aluminum (III) chloride (Aids) and the still higher one of zinc chloride (ZnClj must be considered. The reaction of aluminum with hexachloro-ethane (CaClg) furnishes 0.98 kcal/g in standard states but only 0.88... 

No methylene chloride or chloroform was observed in the reaction. Under the used stable ion conditions, dimethylchloronium ion formation (equation 61) also occurs. This is, however, a reversible process and helps to minimize competing alkylation of methane to ethane (and higher homologs) which becomes more predominant when methyl fluoride is formed via halogen exchange. 

Higher alkanes react with halogens by the same kind of chain mechanism as those that we have just seen. Ethane, for example, reacts with chlorine to produce chloroethane (ethyl chloride). The mechanism is as follows ... 

Halogen derivatives are increasingly reactive towards aluminium, the lower the molecular mass of the product. Aluminium will be less resistant in contact with methane derivatives (Cl) and ethane derivatives (C2) than with higher homologues (C5 and higher). 

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