By methylation we should evidently obtain from marsh gas, ethane, CH3CH3 = C2H6.
By methylenation—that is, by substituting group CH2 for H2—methane forms ethylene, CH2CH2 = C2H4.
By acetylenation—that is, by substituting three atoms of hydrogen, H3, in methane—by the remnant CH, we get acetylene, CHCH = C2H2.
If we have applied the principles of Newton correctly, there should not be any other hydrocarbons containing two atoms of carbon in the molecule. All these combinations have long been known, and in each of them we can not only produce those substitutions of which an example has been given in the case of methane, but also all the phases of other substitutions, as we shall find from a few more instances, by the aid of which I trust that I shall be able to show the great complexity of those derivatives which, on the principle of substitution, can be obtained from each hydrocarbon. Let us content ourselves with the case of ethane, CH3CH3, and the substitution of the hydrogen by hydroxyl. The following are the possible changes:—
1. CH3CH2(OH): this is nothing more than spirit of wine, or ethyl alcohol, C2H5(OH) or C2H6O.
2. CH2(OH)CH2(OH): this is the glycol of Würtz, which has shed so much light on the history of alcohol. Its isomeride may be CH3CH(OH)2, but as we have seen in the case of CH(OH)2, it decomposes, giving off water, and forming aldehyde, CH3CHO, a substance capable of yielding alcohol by uniting with hydrogen, and of yielding acetic acid by uniting with oxygen.
If glycol, CH2(OH)CH2(OH), loses its water, it may be seen at once that it will not now yield aldehyde, CH3CHO, but its isomeride, CH2CH2/O, the oxide of ethylene. I have here indicated in a special manner the oxygen which has taken the place of two atoms of the hydrogen of ethane taken from different atoms of the carbon.
3. CH3C(OH)3 decomposed as CH(OH)3, forming water and acetic acid, CH3CO(OH). It is evident that this acid is nothing else than formic acid, CHO(OH), with its hydrogen replaced by methyl. Without examining further the vast number of possible derivatives, I will direct your attention to the circumstance that in dissolving acetic acid in water we obtain the maximum contraction and the greatest viscosity when to the molecule CH3CO(OH) is added a molecule of water, which is the proportion which would form the hydrate CH3C(OH)3. It is probable that the doubling of the molecule of acetic acid at temperatures approaching its boiling-point has some connection with this power of uniting with one molecule of water.
4. CH2(OH)C(OH)3 is evidently an alcoholic acid, and indeed this compound, after losing water, answers to glycolic acid, CH2(OH)CO(OH). Without investigating all the possible isomerides, we will note only that the hydrate CH(OH)2CH(OH)2 has the same composition as CH2(OH)C(OH)3, and although corresponding to glycol, and being a symmetrical substance, it becomes, on parting with its water, the aldehyde of oxalic acid, or the glyoxal of Debus, CHOCHO.