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Chemical properties of phenols
Source:www.chemjunchi.com issuing time:2017-04-12

The phenolic formula is ArOH, which is a kind of aromatic compound substituted by hydroxyl (- OH) hydrogen on the aromatic hydrocarbon ring. The simplest phenol is phenol. Phenolic compounds are compounds derived from hydroxyl radicals of aromatic hydrocarbons in benzene rings. They can be classified into single phenols and polyhydric phenols according to the number of hydroxyl groups in their molecules. The hydroxyl group of phenol is directly linked to the SP2 hybridized carbon atom of the benzene ring, which is similar to that in aliphatic compounds. In addition, because of the conjugated action of the non common electron atoms of the hydroxyl oxygen atoms of phenol with benzene rings, not only can the phenol be stabilized compounds, but also the dissociation of phenol is favorable. Notably, the phenolic hydroxyl oxygen atom hybrid type is unequal in SP2 hybridization and differs from the alcohol hydroxyl oxygen atom in the unequal SP3 hybridization. It is a weak acid, acid: > > > phenol carbonate bicarbonate water.

The acidity of phenolic alcohols is stronger because the O-H bond of phenolic hydroxyl group is easy to break, and the negative ion of phenoxy group is relatively stable, which makes the dissociation balance of phenol tend to the right side and show weak acidity. The addition of hydrogen to phenolic hydroxyl groups can be replaced by metals and can also produce salts and water with strong alkali solutions. If the carbon dioxide is injected into the aqueous solution of sodium phenol, the free phenol is precipitated. This is because the acidity of phenol is weaker than that of carbonic acid, so that the phenolic salts are broken down by carbonic acid. Because the acidity of phenol is weaker than that of carbonic acid, phenol can only be dissolved in sodium hydroxide and insoluble in sodium bicarbonate. The laboratory is often based on this characteristic of phenol, distinguished from carboxylic acids that are soluble in sodium hydroxide and soluble in sodium bicarbonate. This method can also be used for separation of phenolic compounds and carboxylic acids in Chinese herbal medicines.


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