The secondary and tertiary amides of the types (RCO) 2 NH and (RCO) 3 N may be prepared by heating the primary amides or the nitriles with acids or acid anhydrides to 200° C. Thiamides of the type R.
Williamson showed how alcohol and ether were to be regarded as derived from water by substituting one or both hydrogen atoms by the ethyl group; he derived acids and the acid anhydrides from the same type; and from a comparison of many inorganic and the simple organic compounds he concluded that this notion of a " water-type " clarified, in no small measure, the conception of the structure of compounds.
Considering derivatives primarily concerned with transformations of the hydroxyl group, we may regard our typical acid as a fusion of a radical R CO - (named acetyl, propionyl, butyl, &c., generally according to the name of the hydrocarbon containing the same number of carbon atoms) and a hydroxyl group. By replacing the hydroxyl group by a halogen, acid-haloids result; by the elimination of the elements of water between two molecules, acid-anhydrides, which may be oxidized to acid-peroxides; by replacing the hydroxyl group by the group. SH, thio-acids; by replacing it by the amino group, acid-amides (q.v.); by replacing it by the group - NH NH2, acid-hydrazides.
They are neutral to litmus and do not combine with dilute acids or bases; strong bases, such as lime and baryta, yield saccharates, whilst, under certain conditions, acids and acid anhydrides may yield esters.
Primary alcohols are obtained by decomposing their sulphuric acid esters (from sulphuric acid and the olefines) with boiling water; by the action of nitrous acid on primary amines; or by the reduction of aldehydes, acid chlorides or acid anhydrides.