198 Mr. M. M. Piittison Muir on Chemical Classification. 



can have (according to our theory) but one constitutional 

 formula, viz. CH3 — CHg CI. Inasmuch as this body has been 

 produced by removing OH and putting CI in its place, we 

 conclude that the position originally occupied by the OH 

 group was the same as that now occupied by the Cl*. 



The reactions of alcohol then lead us to adopt the constitu- 

 tional formula CH3 — CHg — — H for this body, ^e know 

 of another compound, viz. methylic ether, having the same 

 empirical formula as alcohol: the general reactions of this com- 

 pound point to the constitutional formula CH3 — — CH3. 

 These two forms of the formula C2 Hg exhaust the list of 

 possible modifications deduced from the valency of the consti- 

 tuent atoms. We actually know of but two bodies having the 

 empirical formula C2 Hg 0. 



What is the constitutional formula of acetic acid, C2 H4 O2 ? 

 Theory points to the possibility of the existence of unsaturated 

 compounds, with two free affinities, having this empirical for- 

 mula. Inasmuch, however, as acetic acid shows no tendency 

 to form additive compounds, inasmuch as fresh atoms can 

 only be caused to enter the molecule by substitution, it pro- 

 bably does not belong to the group of unsaturated compounds. 

 Ten isomers of the formula C2 H4 O2, all of them saturated 

 compounds, are theoretically possible: two have actually been 

 prepared, viz. acetic acid and the methylic ether of formic 

 acid. 



Acetic acid may be prepared from common alcohol by oxi- 

 dation, two hydrogen atoms being replaced by one oxygen 

 atom. But we have seen that the constitutional formula of 

 common alcohol is almost certainly CH3 — CH2 — — H. 

 When this molecule is oxidized to acetic acid, which hydrogen 

 atoms are replaced by oxygen ? The H in the OH group is 

 in all probability not replaced. The chief reasons for this 

 statement are the facts : — that acetic acid, like alcohol, readily 

 parts with one atom of hydrogen, and with one atom only, in 

 exchange for metal, or for hydrocarbon radicles such as CHg, 

 C2 H5, &c. ; and that acetic acid and alcohol are evidently of 

 very similar constitution, as is shown by such reactions as 

 these : — 



C2HeO +PCl5 = C2H5Cl +POCI3 + HCI. 



C2 H4 O2 + PCI5 = C2 H3 OCl + POCI3 + HCl. 



If alcohol be represented by the formula C2 Hg (OH), acetic 

 acid may be represented by a formula constructed on the same 



* Tlie compound produced by the action of chlorine upon 63 Hg, viz. 

 C2H5 Cl, has been shown by Schorlemmer to be identical with the chlo- 

 rine compound obtained from alcohol by the reaction formulated above. 



