Page:The New International Encyclopædia 1st ed. v. 01.djvu/363

ALCOHOLS. If its COH proup were oonvertcd into CO, a eom- pouiul would be obtained in wliifh carbon would exist in the peuta-valent form, as shown by the fornnda : CH,, CH3— C=0 CH,/ Neither this, nor any other compound containing jjenta-valent carbon, is known. In reality, when a tertiary alcohol is oxidized, it breaks up into various compounds, each containing less carbon atoms than the alcohol. The three sub-classes of alcohols can thus be readily distinguished from one another by their behavior toward oxidizing agents. Primary alcohols may be transformed into corresponding secondary or tertiary alcohols with the aid of sulphuric acid. As an example may be mentioned the conversion of normal jjropyl alcohol (primarj-) into iso-propyl alcohol (secondary). (1) Hy the dehydrating action of sulphuric acid on normal propyl alcohol, the hydrocarbon propylene is obtained, according to the following equation: CH.CH.CH.OH — H,0 = CHjCHiCHj Normal propyl alcohol Propylene (2) When propylene is dissolved in fuming sul- pliuric acid and the compound thus obtained is boiled with water, iso-propyl alcohol is obtained : CH;,CH:CH., -f H„0 = CH3CH(0H)CH, Propylene Water Iso-propyl alcohol In this manner a hydroxyl group can be made to change its position in the molecule by simple laboratory methods. The di-h.vdrie alcohols, as the name indicates, contain two hydroxyl groups. Glycols is the name usually applied by chemists to the di- hydric alcohols. The simplest glycol, derived from methane (CHj) — the simplest hydrocarbon — should be represented by the formul.a CH, (OH);. But though certain compounds of this glycol have been obtained, the glycol itself could not be prepared in the free state. Expe- rience shows, in general, that the formation of a compound in which two hydroxyl groups might be attached to one carbon atom is almost invariably accompanied by a loss of the elements of water. The imaginary compound CH. (OH), is thus split up, according to the following equa- tion: CH,(OH)„ = CH,0 -f H.O The compound CH^O (formaldehyde) is there- fore obtained in reactions which might be expected to result in the formation of the glycol CH2(0H).. The simplest glycol actually pre- pared is a derivative of ethane (C2H,,), one hydroxyl group being attached to each of the two carbon atoms of ethane, and its formula CH.OH therefore being |. This glycol evidently CH.OH contains two primary .alcohol groups (.CH2OH), by the oxidation of one or both of which a series of interesting compounds is obtained, including: CH..OH CHO CHO COOH COOH GlycocoUic acid CHO C
 * )H0

Glyosal OOH Glyoxylic acid COOH Oxalic .acid Glycols containing two tertiary-alcohol groups (COil) are usually called phtacuncs, the sim- plest pinacone known being represented by the following graphic formula: ch:)c-o-h Ordinary pinacone The simplest and best known tri-Iiydric alco- hol is the well-known glycerin (q.v.), which may be considered as derived from propane (CH3 CHoCHa) by the substitution of hydro.xyl groups for three hydrogens attached to three different carbon atoms : the constitutional formula of glycerin is CH,(OH) . CH(OH) . CH,(OH) . Among the few other poly-hydric alcohols known may be mentioned the hexa-hydric alco- hol inniinitol. which is found in iiiuiina (q.v.). The poly-Iiydric alcolmls generally possess a sweet taste and are insoluble in ether. They mostly occur ready formed in nature. The mono-hydrie alcohols are rarely found in nature in the free state: in the forni of esters, however, i.e., in combination with acids, they occur largely in the vegetable kingdom. The for- mation of alcohols from the sugars through fermentation is described elsewhere. (See Alco- hol and Ferme.xtation.) It remains to mention here a few of the general chemical methods by which alcohols are made artificially. . Many alcohols are prepared from the corre- sponding h_ydrocarbons by substituting halogens for part of their hydrogen, and treating the halo- gen derivatives thus obtained with dilute aque- ous alkalis or with moist silver oxide. The fol- lowing equations represent examples of the for- mation of alcohols from halogen-substitutive- products of hydrocarbons: CH3Br H Mono-bromo- metliane KOH I Potaflsium hydroxide CH.OH + KBr Methyl alcohol Potaj-sinm bromide C^HjI + AgOH Moiio-iodo Silver propane hydroxide = C,H;OH -f Agl Propyl alcohol Silver iodide . Since aldehydes are produced by the oxida- tion of primary alcohols, the latter may be. obtained, conversely, by reducing aldehydes. Thus, ethyl alcohol may he obtained by the action of nascent hydrogen upon ordinary aldehyde, according to the following equation:" CH3CHO + 2H Aldehyde = CHjCH.OH Ordinary alcohol . Since ketones are produced by the oxidation of secondary alcohols, the latter may, conversely, be prepared from ketones by reduction. Thus, secondary propyl alcohol may be obtained by the action of nascent hydrogen on acetone (di-methyl- ketone), according to the following equation: CH..CO.CH3 + 2H = CH3CH(0H)CH, Acetone Iso-propyl alcohol . Tertiary alcohols may be prepared from chlorides of acid radicles with the aid of com- pounds of zinc and Iiydrocarbon radicles. Thus, tertiary butyl alcolinl is obtained according to the following equation: