ii2 PRACTICAL ORGANIC CHEMISTRY distinctly acid to litmus-paper) in a distilling-flask and distil off about 5 ml. through a water-condenser. Then apply to the filtrate the tests for acetic acid given on p. 347. Oxalic Acid. COOH 9 2O 2 O. COOH Certain aliphatic compounds are oxidised by concentrated nitric acid, the carbon atoms being split off in pairs, with the formation of oxalic acid. This disruptive oxidation is shown by many carbohydrates, e.g., cane sugar, where the chains of secondary alcohol groups, -CH(OH)-CH(OH)-CH(OH)-CH(OH)-, present in the molecule break down particularly readily to give oxalic acid. It should be noted that aliphatic compounds (except the paraffins) are usually oxidised by concentrated nitric acid, whereas aromatic compounds (including the hydrocarbons) are usually nitrated by the concentrated acid (in the presence of sulphuric acid) and oxidised by the dilute acid. As an example of the latter, benzaldehyde, C 6 H 6 CHO, when treated with concentrated nitric acid gives
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