358 



NATURE 



[August 8, 18S9 



of carbon to the molecule, as in acetic acid, and proceed to 

 evolve them from methane by the principle of substitution. 

 This principle declares at once that methane can only be split 

 up in the four following ways : — 



( i) Into a group CFT3 equivalent with H. Let us call changes 

 ■of this nature methylation. 



(2) Into a group CH^ and H^- We will call this order of 

 •substitutions methylenation. 



(3) Into CH and H3, which coiniutations we will call acetyl- 

 enation. 



(4) Into C and II4, which may be called carbonization. 



It is evident that hydrocarbon compounds containing two 

 atoms of carbon can only proceed from methane, CH4, which 

 ■contains four atoms of hydrogen by the first three methods of 

 •substitution : carbonizing would yield free carbon if it could 

 take place directly, and if the molecule of free carbon — which 

 is in reality very complex, that is to say, strongly polyatomic, 

 as I have long since been proving by various means — could 

 contain only C.j like the molecules O2, Ho, Nj, and so on. 



By methylation, we should evidently obtain from marsh gas, 

 €thane, CHaCHa = CgHg. 



By methylenation, that is, by substituting group CHj for H_,, 

 methane forms ethylene, CH.^CHo = C2H4. 



By acetylenation, that is, by substituting three atoms of hy- 

 •drogen, M3, in methane, by the remnant CH, we get acetylene 

 €HCn - 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. AH these combinations have long been 

 known, and in each of them we can not only produce those sub- 

 stitutions 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 deriva- 

 tives 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 

 hydroxy!. The following are the possible changes : — 



(i) CH.,CH.,(OH) : this is nothing more than spirit of wine, 

 •or ethyl alcohol, CoHglOH), or C.^HeO. 



(2) CH.2(OH)CH2(OH): this is the glycol of Wartz, which 

 ■has shed so much light on the history of alcohol. Its isomer 

 may be CH3CH(OH)2, but as we have seen in the ca;e of 

 CH(0H)2, it decomposes, giving off water, and forming alde- 

 hyde, CH3CHO, a body capable of yielding alcohol by uniting 

 ■with hydrogen and of yielding acetic acid by uniting with 

 oxygen. 



If glycol CH2(OH)CH.2(OH) loses its water, it may be seen at 

 •once that it will not now yield aldehyde, CH3CHO, but its 



isomer, ?^ *, 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 alojas of 

 the carbon. 



(3) CH3C(OH)3 dec-imposed as CHvOH)3, forming water and 

 acetic acid, OH3CO(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 

 •CH3C0(0H) is added a molecule of water, which is the pro- 

 portion 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) CH-(OH)C(OH)-* is evidently alcoholic acid, and indeed 

 this compound, after losing water, answers to glycolic acid, 

 CH2(0H)C0(0II). Without investigating all the possible iso- 

 mers, 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, aldehyde of oxalic acid, or 

 theglyoxalof Debus, CHOC HO. 



(5) CH(OH)2C(OH3), from the tendency of all the preceding, 

 coresponds to glyoxylic acid, aldehyde acid, CHOCO(OH), 

 because the group CO(Ofl), or carbaxyl, enters into the compo- 

 sitions of organic acids, and the group C HO defines the aldehyde 

 /■unction. 



(6) C,0M)aC(0H)3, thrjugh the loss of 2H2O, yields the 



bibasic oxalic acid CO(OH)CO(OH), which generally crystallizes 

 with 2lI.jO, following thus the normal type of hydration charac- 

 teristic of ethane.^ 



Thus, by appl)ing the principle of sub-titution, we can, in 

 the simplest manner, derive not only every kind of hydrocarbon 

 compound, such as the alcohols, the aldehyde alcohols, alde- 

 hydes, alcohol acids, and the acids, but also combinations 

 analogous to hydrated crystals which usually are disregarded. 



Bit even th se unsaturated substance-', of which ethylene, 

 CH2CH2, and acetylene, CHCH, are types, may be evolved 

 with equal simplicit)'. With respect to the phenomena of iso- 

 merism, there are many possibilities among the hydrocarbon 

 compounds containing two atoms of carbon, and without going 

 into details it will be sufficient to indicate that the following 

 formulas, though not identical, will be isomeric substantially 

 among themselves: CH3CHX0 and CH„XCH,X, although 

 both contain C2H4X2, or CH.,CX2 and CHXCHX, although 

 both contain CjHgXg, if by X we indicate chlorine or gene- 

 rally an element capable of replacing one atom of hydrogen, 

 or capable of uniting with it. To isomerism of this kind belongs 

 the case of aldehyde and the oxide of ethylene, to which 

 we have already referred, because both have the composition 

 C2H4O. 



What I have said appears to me sufficient to show that the 

 principle of substitution adequately explains the composition, 

 the isomerism and all the diversity of combination of the hydro- 

 carbons, and I shall limit the further development of these views 

 to preparing a complete list of every possible hydrocarbon com- 

 pound containing three atoms of carbon in the molecule. There 

 are eight in all, of which only five are known at present. - 



Among tho^e possible for Cgllg there should be two isomers, 

 propylene and trimethylene, and they are both already known. 

 For C3H4 there should be three i omers : allylene and allene 

 are known, but the third has not yet been discovered ; and for 

 C3H2 there should be two isomers, though neither of them are 

 known as yet. Their composition and structure is easily deduced 

 from ethane, ethylene, and acetylene, by methylation, methylen- 

 ation, by acetylenation and by carbonization. 



(i) CsHg = CH3CII2CH3 out of CH3CH3 by methylation. 

 This hydrocarbon is named propane. 



(2) CjHe = CH3CHCH2 out of CHjCHaby methylenation. 

 This substance is propylene. 



(3) CgHfi = CHoCHjCHo out of CH3CH3 by methylenation. 

 This substance is trimethylene. 



(4) C3H4 = CH3CCH out of CH3CH3 by acetylenation or 

 from CHCH by methylation. This hydrocarbon is named 

 allylene. 



(5) C3H4 = CHCH out of CH3CH3 by acetylenation, or 



CH. 

 from CHoCHj by methylenation, because CHjCH — CHCH. 



CH CH2 



This body is as yet unknown. 



(6) C3H4 = CH0CCH2 out of CHjCH2 by methylenation. 

 This hydrocarbon is named allene, or iso-allylene. 



(7) C3H2 = CHCH out of CH3H3 by symmetrical carboniza- 



C 

 tion, or out of CH2CH2 by acetylenation. This compound is 

 unknown. 



(8) C3H2 — CC out of CH3CH3 by carbonization, or out of 



CHo 

 CHCH by methylenation. This compound is unknown. 



' One more Isomer, CH2CH(0H', is possible, that is secondary vinyl 

 alcohol, which is related to ethylene, CHoCHo, but derived by the principle 

 of substitution from CH4. Other isomers of the composition C2H4O, such, 

 for example, as CHCH3(OH), are impossible, because it would correspond 

 to the hydrocarbon CHCHg = C2H4, which is isomeric with ethylene, and 

 it cannot be derived from methane. If such an isomer existed, it would be 

 derived f'om CH-j, but such products are up to the present unknown. In 

 su h ca^ es the insufficiency of the points of departure of the statical struc- 

 tural teaching is shown. It first admits constant atomicity, and then rejects 

 it, the facts serving to establish either one or the other view ; and therefore, 

 it seems to nie that we must come to the conclusion that the structural 

 method of reasoning, having done a service to science, has outlived the age, 

 and must be regenerated, as, in their time, was the teaching of the electro- 

 chemists, the radicalists, and the adherents of the doctrine of types. As we 

 cannot now lean on the views above stated, it is time to abandon the struc- 

 tural theory. They w.ll all be united in chemical mechanics, and the prin- 

 ciple of substitutif^n must be lo jked upon only as a preparation for the 

 coming epoch in chemistry, where such cases as the isomerism of fumaric 

 and maleic acids, when explained dynamically, as proposed by Le Bel and 

 Van 't Hoff, nay yield points if departure. 



2 Conced.ng variable atomicity, the structurists must expect an incom 

 parably larger number of isomers, and they cannot now decline to ackm-w. 

 lede"" ih^ change of atO'iiicity, were it cnly for the examples HgCl and 

 HgCli, CO and CO., PCI3 and PCI5. 



