Page:The New International Encyclopædia 1st ed. v. 01.djvu/362

ALCOHOLS. CH, — OH H — OH K — OH Water Pota&siuni Methyl hydroxide alcohol Again, a.s metallic hydroxides combine with acids to form salts, so alcohols combine with acids to form estei's (ethereal salts), which are perfectly analogous to the salts of inorganic chemistry. The following two equations repre- sent, respectively, the formation of a salt and of an ester : KOH + HCl = KCl + H,0 Potaspiiim Hydrochloric Potassium "Water hydroxide acid chloride CjH.OH + HC=H,0, = C,H,C2H,,02 + H,0 Ethyl Acetic Ethyl-acetic Water aJcohol acid ester The hydrogen of the hydroxyl group of an alcohol can be replaced either by metals or by hydrocarbon radicles. In the former case, a metallic alcoholate is obtained; in the latter, an ether. Thus, by the action of metallic sodium on ordinary (ethyl) alcohol, sodium alcoholate is obtained, according to the following chemical equation : C,H,OH + Na = C,H,Oya -f H Ethyl alcohol Sodium alcoholate On the other hand, by dehydrating ethyl alcohol, ordinary ether is obtained, as follows : C,H,OH + C,H,OH — H,0 = C.H.OCjH, molecules of ethyl alcohol Ethyl ether In this transformation (usually effected by the dehydrating action of sulphuric acid), the ethyl group of one molecule of alcohol evidently takes the place of the hydroxyl hydrogen of another molecule. An analogous reaction takes place when a mixture of two different alcohols is sub- jected to the dehydrating action of sulphuric acid: C.H.OH + CH.OH — H,0 = C.H.OCHj Ethyl alcohol Methyl alcohol Methyl-ethyl ether The chemical similarity between the alcohol- ates and the ethers is furtlicr sliown by the fact that the latter may be readily obtainetl from the former. Thus, methyl ether may be obtained by the action of methyl iodide on sodiuni-methj'l- ate (an alcoholate), according to the following chemical equation: CH^ONa -f CH3I = CH.OCHj + Nal Sodium Methyl Methyl Sodium methylate iodide ether iodide The chemical transformations characterizing the three sub-classes of the alcohols, viz., the pri- mary, secondary, and tertiary alcohols, may now be briefly considered. . It was mentioned above that primary alco- hols contain the group CH,OH. When they are oxidized, this group is changed into the group /H C. which is characteristic of the aldehydes — N another important class of organic compounds. Thus, when ethyl alcohol is oxidized with chromic acid, ordinary aldehyde is obtained, according to the following chemical equation: CH,CH,0H + O = CH.CIIO + ILO Ethyl alcohol Aldehyde By further combination with oxygen, aldehydes readily yield acids, the group CHO being ex- //O changed for the acid group C— OH. Thus, when ordinary aldehyde is oxidized, acetic acid is produced, as follows : CH3CHO + — CHjCOOH Aldehyde Acetic acid If the structural formulae of acetic acid and ethyl alcohol are compared, H H C=0 H— I -H H— C— H A i Acetic acid Ethyl alcohol it may be seen that the gradual oxidation result- ed in the substitution of one atom of oxygen for the two atoms of hydrogen linked to the same carbon atom to which the OH group of the alcohol is linked. If in the place of these hydro- gens, the alcohol molecule contained atomic groups like methyl, for instance, which could not be replaced by oxygen, the acid could evi- dently not be made by oxidizing the alcohol. In otiier words, unless an alcohol contains two hydrogens linked to the hydroxyl group OH through a carbon atom, it could not be trans- formed, by simple oxidation, into an acid con- taining the same number of carbon atoms ; only primary alcohols, characterized by the group CH;OH, are capable of this transformation. . When secondary alcohols are oxidized, their characteristic group CHOH is converted into the group CO, and as a result lactones are produced, thus, when iso-propyl alcohol is acted on by oxidizing agents, ordinary acetone (di-methyl- ketone) is produced, according to the following chemical equation: CH3 CHOH + O = / CH3 + H,0 Iso-propyl Acetone alcohol It is seen that the molecule of acetone contains the same number of carbon atoms as the molecule of iso-propyl alcohol. . Tertiary alcohols cannot be transformed by simple oxidation into a compound whose mole- cule contains tlie same number of carbon atoms. In the language of the structural theory, the (mly atomic group into which the characteristic COH group of the tertiary alcohols could be converted by sini])le loss of hydrogen tlirough oxidation, is tiie group CO. Now, the COH group is tri- valent, and is, in tertiary alcohols, combined with three radicles; thus, the simplest tertiary al- cohol, called tertiary butyl alcohol, is represented by the graphic formula: CH, CH,— C— 0— H CH,/ Tertiary butvl alcohol