Note 45 — Chapter VIII · CARBON AND THE HYDROCARBONS

The following are the most generally known of the oxygenised but non-nitrogenous hydrocarbon derivatives. (1) the alcohols. These are hydrocarbons in which hydrogen is exchanged for hydroxyl (OH). The simplest of these is methyl alcohol, CH3(OH), or wood spirit obtained by the dry distillation of wood. The common spirits of wine or ethyl alcohol, C2H3(OH), and glycol, C2H4(OH)2, correspond with ethane. Normal propyl alcohol, CH3CH2CH2(OH), and isopropyl alcohol, CH3CH(OH)CH3, propylene-glycol, C3H6(OH)2, and glycerol, C3H3(OH)3 (which, with stearic and other acids, forms fatty substances), correspond with propane, C3H8. All alcohols are capable of forming water and ethereal salts with acids, just as alkalis form ordinary salts. (2) Aldehydes are alcohols minus hydrogen; for instance, acetaldehyde, C2H4O, corresponds with ethyl alcohol. (3) It is simplest to regard organic acids as hydrocarbons in which hydrogen has been exchanged for carboxyl (CO2H), as will be explained in the following chapter. There are a number of intermediate compounds; for example, the aldehyde-alcohols, alcohol-acids (or hydroxy-acids), &c. Thus the hydroxy-acids are hydrocarbons in which some of the hydrogen has been replaced by hydroxyl, and some by carboxyl; for instance, lactic acid corresponds with C2H6, and has the constitution C2H4(OH)(CO2H). If to these products we add the haloid salts (where H is replaced by Cl, Br, I), the nitro-compounds containing NO2 in place of H, the amides, cyanides, ketones, and other compounds, it will be readily seen what an immense number of organic compounds there are and what a variety of properties these substances have; this we see also from the composition of plants and animals.