Question

Differentiate between primary, secondary and tertiary alcohol using Victor Meyer method.

Answer 1

Hint: Victor Meyer's method is used to differentiate between the different types of alcohol. In this the alcohols are treated with different chemicals producing different colors, differentiating the alcohols.

Complete step by step answer:
-When an -OH group is attached to a hydrocarbon then it is known as an alcohol. Alcohols can be of three types: primary, secondary and tertiary alcohol.
-Primary alcohol is the one which is attached to the primary carbon atom of the hydrocarbon. Secondary alcohol is the one which is attached to the secondary carbon atom of the hydrocarbon. And tertiary alcohol is the one which is attached to the tertiary carbon atom of the hydrocarbon.
-A test or method known as Victor Meyer method is used to differentiate between primary, secondary and tertiary alcohols.
-In Victor Meyer's Method,
The given alcohol is made to react with conc. HI or red phosphorus and iodine to form the corresponding alkyl iodide.
-Then this produced alkyl iodide is treated with silver nitrate to produce the corresponding nitroalkane.
-This nitroalkane is then treated with nitrous acid which is $NaN{O}_{2} + {H}_{2}S{O}_{4}$ and then excess of caustic soda is added to make the solution alkaline.
-After this process, if a blood red color is obtained, then it indicates that the original reactant was a primary alcohol.
$\underset { Primary\quad alcohol }{ R-C{ H }_{ 2 }OH } \quad \xrightarrow [ P/{ I }_{ 2 } ]{ \quad } \quad R-C{ H }_{ 2 }I\quad \xrightarrow [ AgN{ O }_{ 2 } ]{ \quad } \quad R-C{ H }_{ 2 }N{ O }_{ 2 }\quad \xrightarrow [ HN{ O }_{ 2 } ]{ \quad } \quad \underset { Nitrolic\quad acid }{ R-C(NOH)-N{ O }_{ 2 } } \quad \xrightarrow [ NaOH ]{ \quad } \quad Blood\quad Red\quad Color$
- If a blue color is obtained, then it indicates that the original reactant was a secondary alcohol.
$\underset { Secondary\quad alcohol }{ { R }_{ 2 }-C{ H }OH } \quad \xrightarrow [ P/{ I }_{ 2 } ]{ \quad } \quad { R }_{ 2 }-CHI\quad \xrightarrow [ AgN{ O }_{ 2 } ]{ \quad } \quad { R }_{ 2 }-CHN{ O }_{ 2 }\quad \xrightarrow [ HN{ O }_{ 2 } ]{ \quad } \quad \underset { Pseudonitrol }{ { R }_{ 2 }-C(NO)-N{ O }_{ 2 } } \quad \xrightarrow [ NaOH ]{ \quad } \quad Blue\quad Color$
-If no color is obtained, then it indicates that the original reactant was a tertiary alcohol.
$\underset { Secondary\quad alcohol }{ { R }_{ 3 }-C-OH } \quad \xrightarrow [ P/{ I }_{ 2 } ]{ \quad } \quad { R }_{ 3 }-C-I\quad \xrightarrow [ AgN{ O }_{ 2 } ]{ \quad } \quad { R }_{ 3 }-C-N{ O }_{ 2 }\quad \xrightarrow [ HN{ O }_{ 2 } ]{ \quad } \quad No\quad Reaction\quad \xrightarrow [ NaOH ]{ \quad } \quad Colorless$

This is how Victor Meyer's method is used to differentiate between the three alcohols.

Note:
The Victor Meyer' test is only shown by primary, secondary and tertiary alcohols. It is not given by phenols. This is because in the first step R-OH is converted to R-I but the procedure involves breaking of the OH bond with carbon but in phenol as we know the carbon–oxygen bond is much stronger, and even the formation of the transition state will completely rupture the aromaticity this compound making the it unstable.