Compounds obtained by the replacement of hydrogen atoms of aliphatic and aromatic hydrocarbons by hydroxyl (-OH) group are called alcohols and phenols respectively.
Alcohols and phenols are very important to our daily life and industries, such as food sugar, paper and cotton are all made of compounds containing -OH group.
Ethanol (C₂H₅OH) is used to polish wooden furniture.
In alcohol the –OH group is attached directly to the carbon of the aliphatic group and in phenol –OH group is attached directly to the carbon of the aromatic group.
Therefore, alcohols are called R-OH and phenols are called Ar-OH.
When the hydrogen atom of hydrocarbon is replaced by alkoxy or aryloxy (RO/ARO) the compounds formed are called ethers.
Alcohols are classified on the basis of the number of hydroxyl (OH) groups present in it.
one (mono-), two (di-), three (tri) or more hydroxyl (OH) groups respectively as mono hydric, di hydric, tri hydric or polyhydric.
In dihydric, trihydric and polyhydric alcohols -OH groups are attached to different carbons because compounds containing two or three -OH groups on the same carbon, are temporary.
And by the removal of water from them, respectively, carbonyl compounds and carboxylic acids are obtained.