Basic concepts
It can be regarded as formic acid The univalent group (- CHO) remains after the hydroxyl group is removed from the molecule. Actually Aldehyde group (aldehyde group)。 Benzoyl group benzoyl group Formyl group pyridine There are three isomers of benzoylpyridines. All have the general properties of aromatic ketones. 2-formylpyridine: boiling point 317 ℃, melting point 42~44 ℃; Soluble in chloroform ； Its main derivatives are oxime (Z) - (melting point 150.5~152.5 ℃), oxime (E) - (melting point 165~167 ℃), phenyl hydrazone (melting point 137~138 ℃). 3-formylpyridine: boiling point 307 ℃, melting point 39 ℃; Its main derivatives are oxime (Z) - (melting point 142 ℃), oxime (E) - (melting point 162 ℃) and phenylhydrazone (melting point 143.5 ℃).
4-formylpyridine: boiling point 315 ℃, melting point 71.5-72.5 ℃; Soluble in ethanol 、 Ether And benzene; Its main derivatives are oxime (Z) - (melting point 152 ～ 155 ℃), oxime (E) - (melting point 176 ～ 177 ℃, decomposition), phenyl hydrazone (melting point 181 ～ 182 ℃). Use benzene with pyridine Friedel Crafts acylation of carbonyl chloride or potassium permanganate Oxidation corresponding benzyl Pyridine and corresponding cyanopyridine react with Grignard reagent. 
