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  1. Hydroxy derivatives of hydrocarbons are called alcohols.
  2.   These are obtained by the replacement of one, two or three hydrogen atoms by -OH (hydroxyl ) groups from different carbon atoms. These are classified as-
  3. a) Monohydric  Alcohol (Alc.) –

                When One-OH group  is present in the molecule,then alcohol  is Monohydric alc.

        b) Dihydric Alc. –

               When two -OH groups  are  present in the molecule,then alcohol is Dihydric alc .

      c) Trihydric Alc.-

             When three -OH groups  are  present in the molecule,then alcohol is Trihydric alc .

4)   Monohydric alcohols are again of three types depending on the  position of -OH group –

    a)   Primary Alc.-

         In primary  alc.  -OH group  is attached to the primary carbon atom or  -CH2OH                                group is present in the molecule.

     b) Secondary Alc.-

        In secondary  alc.  -OH group  is attached to the secondary  carbon atom  or >CHOH group             is present in the molecule.

    c)  Tertiary Alc. –

      In tertiary Alc.  -OH group  is attached to the tertiary carbon atom  or  group  is present in the molecule.

5)  The general formula of monohydric Alc.  is CnH2n+1OH

6)  Their Suffix is ‘ol’.

7) Their  IUPAC  name is written as Alkane- e+ol = Alkanol.

source : Silverbullet

Dihydric & Trihydric Alcohol-

The suffix used for dihydric Alc. is ‘diol’ &  for trihydric alc.  is ‘triol’.