ALDEHYDES  , a class of chemical compounds of the

general formula R•CHO (R = an alkyl or an aryl group) . The name is derived from alcohol dehydrogenatum in allusion to the fact that they may be prepared by the oxidation of alcohols . The lower members of the series are neutral liquids possessing a characteristic smell; they are soluble in water and are readily volatile (formaldehyde, however, is a gas at ordinary temperatures) . As the carbon content of the molecule increases; they become less soluble in water, and their smell becomes less marked with the increase in boiling point, the highest members of the series being odourless solids, which can only be distilled without decomposition in vacuo, CRRI CRR' [ --> 0< CH•COOC2H6 CH.000H CO2+CHRR'•CHO .