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Victor- Meyer’s method and Lucas test are two famous methods for the distinction of Primary (10) , Secondary (20) and Tertiary(30) alcohols. Lucas test can be done by using two chemicals only ,i.e. ZnCl2 and HCl . So it is an easiest method to distinguish different types of alcohols.


What are Primary (10) , Secondary (20) and Tertiary(30) alcohols ?


  1. Alcohol in which the carbon atom bonded with –OH group is further bonded with one or non other carbon atom is called primary alcohol. Eg. methanol, ethanol, etc.
  2. Alcohol in which the carbon atom bonded with –OH group is further bonded with two other carbon atoms is called secondary alcohol. Eg. propan-2-ol.
  3. Alcohol in which the carbon atom bonded with –OH group is further bonded with three other carbon atoms is called tertiary alcohol. Eg. 2-methyl propan-2-ol.


Methods for the distinction of primary (10) , secondary (20) and tertiary(30) alcohols :



Victor Meyer’s method to distinguish alcohols :


In Victor Meyer’s method, alcohol is first treated with P and I2 to get iodoalkane , which is then treated with AgNO2 ( silver nitrate) to get nitroalkane. The nitroalkane thus obtained is treated with nitrous acid ( a mixture of NaNO2 and dil. HCl) and the resulting solution is finally made alkaline with KOH and the colour is observed. If the colour obtained is :

Red Colour = Primary alcohol

Blue Colour = Secondary alcohol

No colour = Tertiary alcohol.

victor meyers method to distinguish alcohols

Victor Meyer's method to distinguish alcohols

Note :  Don’t be confused on third step i.e. reaction of nitroalkane with HNO2 ( HONO). Just try to remove water molecule as by-product.

Q. How would you distinguish ethanol and propan-2- ol using Victor Meyer’s method?

Ethanol is a primary alcohol while propan-2-ol is a secondary alcohol.

In Victor Meyer’s method, alcohol is first treated with P and I2 to get iodoalkane , which is then treated with AgNO2 ( silver nitrate) to get nitroalkane. The nitroalkane thus obtained is treated withnitrous acid ( a mixture of NaNO2 and dil. HCl) and the resulting solution is finally made alkaline with KOH and the colour is observed. If the colour obtained is :

Red Colour = Primary alcohol

Blue Colour = Secondary alcohol

Hence, ethanol and propan-2-ol can be distinguished by observing colour in Victor- Meyer’s method as ethanol gives red colour while propan-2-ol gives blue colour .

How would you distinguish ethanol and propan-2- ol using Victor Meyer’s method?


Lucas test for the distinction of alcohols:


The Lucas reagent is an equimolar mixture of ZnCl2 and HCl.

In this method, few drops of Lucas reagent is added to the given sample of alcohol in a test tube and the speed of reaction(reactivity of alcohol) is observed.

This is done by measuring the time taken for the clear solution of alcohol to turn turbid.

  1. Tertiary Alcohol : The solution turns turbid and forms an oily layer immediately. Example: 2-hydroxy-2-methyl propane.
  2. Secondary alcohol : The solution turns turbid and forms an oily layer in three to five minutes (varies based on the solubility). Example: propan-2-ol.
  3. Primary alcohol : The solution remains colourless unless it is subjected to heat. The solution forms an oily layer when heated. Example: ethanol.

i.e Reactivity of alcohols : 30 alcohol > 20 alcohol > 10 alcohol

Lucas test


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