3. Alcohol.— In organic chemistry, a mem ber of a numerous class of compounds consist ing of carbon, hydrogen, and oxygen, and de rived from hydrocarbons containing an even number of hydrogen atoms by the substitution of one or more hydroxyl molecules (HO) for an equal number of hydrogen atoms. The alcohols, as thus defined, include the two sub stances described above, and also many others (such as glycerin) whose properties at first sight appear to be radically different from those of either ethyl or methyl alcohol. Alcohols are classified as monohydric, dihydric, trihydric, tetrahydric, pentahydric and hexahydric, ac cording as they contain one, two, three, four, five or six molecules of hydroxyl (OH). Thus ethyl alcohol, GH2OH, is monohydric, while glycerin, C,H,.(OH),, is trihydric. In the present article only the monohydric alcohols will be considered. These are divisible into five general series as follows: (a) Those hav ing the general formula Culis,+1.0H; they are derived from the paraffins, C,11,,±2, by the substitution of one molecule of OH for one atom of hydrogen and are known as the °fatty (b) Those having the formula CH„r-1.0H. Allyl alcohol is the most familiar member of this series. Its formula is C,H,.OH. (c) Those having the general formula C,112,--,.0H. No familiar example can be given. (d) Those having the general formula -1,11—r.OH. This series is derived from the aromatic series of hydrocarbons, just as the first series given above is derived from the paraffins. Thus, when hydrogen peroxide. 11,0,, acts upon benzene, Cale, we have the last expres sion in this equation being the formula of phenyl alcohol, or (as it is more familiarly known) carbolic acid. (e) Those having the general formula CH,,.--,.OH. Cholesterin be longs to this series. It will be evident that the complete discussion of even the monohydric alcohols would be impossible in the present place; hence in what follows attention will be confined to the fatty or paraffin series of mono hydric alcohols, having the general formula C,111,-Fa.OH. No less than 17 distinct mein hers of this series are known, the first five, when they are arranged in order according to the number of carbon atoms they contain, being: Methyl alcohol, CH,.OH.
Ethyl alcohol, C,H..OH.
Propyl alcohol, C,H,.OH.
Butyl alcohol, GH..OH.
Amyl alcohol, C,H,i.OH.
The first two members of this series do not admit of any isomeric modifications; but the third member admits of one such modification and the following members admit of more than one. For example, propane has the formula
Clia.C111.CH,, and an alcohol may be formed by substituting OH for any one of the H atoms in this formula. If a hydrogen atom at the end of the formula be replaced in this way, we shall obtain the same result whether the substitution be made at the right-hand end or the left; that much is evident from the symmetry of the formula. But if one of the hydrogen atoms in the central CH, be so replaced the alcohol thus formed may differ from the one previously ob tained by an end substitution; and in fact ex periment shows that two different alcohols do actually exist, both having the same formula C,H2OH. These are distinguished as "pri mary' and °secondary' respectively. In gen eral, an alcohol is called °primary' if the carbon atom to which the OH is attached is itself attached to only one other carbon atom; it is if the carbon atom to which the OH is attached is itself attached to two other carbon atoms; and it is if this car bon atom is attached to three other carbon atoms. If it is admitted that the quantivalence of carbon is never greater than four, it follows that no carbon atom can be attached to more than three other carbon atoms; hence every alcohol in the class under consideration must be either primary, secondary or tertiary. The various radicals with which hydroxyl (OH) is combined in the alcohols are collectively called alkyls. Thus CH, (methyl), C,H, (ethyl) and (propyl) are all ((alkyls,' and an alcohol may be briefly described as the hydrate of an alkyl. Other alkyl compounds are also known_ For example, hydrochloric, hydrobromic, by driodic or hydrofluoric acid, when allowed to act upon an alkyl hydrate, yields the chloride, bromide, iodide or fluoride of that alkyl. Thus: C11.0H+HC1=CHs.C1A-H20; and GHT.OH-FHI=C,111.IA-H2O. CH,.C1 is °methyl and GHT.I is °propyl iodide.' The oxides of alkyls are called °simple ethers.' (See ETHER ) . For example, (C211.02.0 is ethyl oxide (or ether), often erroneously called °sul phuric from the fact that sulphuric acid is used in preparing it. By the action of vari ous acids upon alkyl hydrates (or alcohols), salts of these alkyls, entirely analogous to the metallic salts, are obtained. Thus acetic acid and ethyl alcohol react according to the equa tion: Cans.0H+CHI.COOH=CHLCOO(C4H,)+H2O. Ethyl Acetic Ethyl Water hydrate acid acetate This reaction is entirely analogous to the fol lowing familiar one relating to potassium: K.OH+CH.8.COOH=CH&COOK+1130.
See ESTERS.