Alcohols and theirs classification

                    Alcohols

Hydrocarbons are the parents of other organic compounds. When One or more hydrogen atoms are replaced by the different types of atoms or group of atoms from hydrocarbons then different types of organic compounds are formed .
           When hydrogen atoms are replaced from saturated aliphatic hydrocarbons by the hydroxyl group (-OH) ,then Alcohols are formed.
  For example-

                -H
  R-H ------------->    R-OH                                +OH

Where R is the alkAl group.

                   -H
 CH3-H ------------->     CH3-OH                         +OH              (Methanol)


So, Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols.



Classification of Alcohols-

Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols.
The general formula of the alcohols are R-OH. Where R is the Alkyl group.

Alcohols are classified on the basis of the number of the Hydroxyl groups (-OH) attached to the alkAl group.


(1) Monohydric Alcohols -

In the monohydric alcohols only one Hydroxyl group (-OH) attached to the alkAl group. The general formula of the monohydric alcohols are CnH2n+1OH or ROH.
   These are further classified as follows-

(A) Primary alcohols-

Those alcohols in which -OH group is attached to the 1° carbon atom is called primary alcohols.

For example-

           H

           |1°

      H-C-OH    (Methyl alcohol)

          |
          H

               H 

               |1°

      CH3-C-OH    (Ethyl alcohol)

               |
               H

(B) Secondary alcohols-

Those alcohols in which -OH group is attached to the 2° carbon atom is called secondary alcohols.

For example-

           CH3

           |2°

  CH3-C-OH    (Isopropyl alcohol)

           |
           H

  (C) Tertiary alcohols-

Those alcohols in which -OH group is attached to the 3° carbon atom is called tertiary alcohols.

For example-

           CH3

           |3°

  CH3-C-OH    (tert.butyl alcohol)

           |
           CH3

   

(2) Dihydric alcohols-

These are generally called as Glycol . The general formula of the Dihydric alcohols are (CH2)n(OH)2 , where n= 2,3,4 etc.
In this type of the alcohols 2--OH groups are attached to the two different carbon atoms.
For example-


  HO-CH2CH2-OH
 (Ethane-1,2-diol)


   CH3-CHOH-CH2-OH
  (Propane-1,2-diol)

(3) Trihydric alcohols-

In this type of the alcohols 3--OH groups are attached to the three different carbon atoms. In I.U.P.A.C. system these are known as alkanetriol.
For example-

     CH2-OH
     |
     CH-OH
     |
     CH2-OH
 
( Propane-1,2,3-triol)
Or Glycerol