4 . Melting points of aliphatic monocarboxylic acids shows alternation or oscillation effect , i . e ., the m . p . of an acid with even number of carbon atoms is higher than the next lower and next higher homologue containing odd number of carbon atoms . This is because , in case of acids with even number of carbon atoms , the terminal -CH3 and -COOH groups lie on the opposite sides of the zig-zag chain . As a result , they get closely packed in the crystal lattice .
5 . Glacial acetic acid is completely pure acetic acid and represents the solid state of acetic acid . Below 16.6 ° C temperature pure acetic acid is converted into ice like solid hence it is called glacial acetic acid .
Chemical Properties of Carboxylic Acids
Carboxylic acids do not give reactions of carbonyl groups as it enters into resonance with lone pair of O of -OH group .
( i ) Acidity
Above reactions are used to detect the presence of carboxyl group Ul an organic compound ,
Carboxylic acids dissociate in water to give resonance stabilised carboxylate anions and hydronium ion .