How can we distinguish between
a) CH3OH and CH3CH2OH
b) 1-propanol and 2-propanol

(a)Ethanol contains the group CH3CHOH, therefore it gives a positive iodoform test, whereas methanol doesnot give iodoform test.

The reaction is as follows:

CH3CH2OH + 4I2+ 6 NaOH → CHI3 + HCOONa + 5 NaI + 5 H2O

                                                Yellow ppt.

 

CH3OH + I2 + NaOH →  no reaction

 

(b) 2-propanol contains CH3CHOH unit, so it will give positive iodoform test whereas 1-propanol will not give this test.The reaction is as follows:

CH3CH(OH)CH3 + 4I2+ 6 NaOH → CHI3 + CH3COONa + 5 NaI + 5 H2O

  2-propanol                                     Yellow ppt.

 

CH3CH2CH2OH + I2 + NaOH →  no reaction

  1- propanol

 

 

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