Question

Write the chemical test to distinguish between Propan-1-ol and Propan-2-ol.

Give one chemical test to distinguish between the following pair of compounds:

Propan-1-ol and propan-2-ol

Answer 1

1. Lucas reagent is used to distinguish between primary, secondary, and tertiary alcohols based on their reactivity. Primary alcohols react slowly or not at all, while secondary alcohols react quickly to form an immediate turbid solution due to the formation of the corresponding alkyl chlorides.
2. Propan-1-ol (1-propanol) is a primary alcohol that reacts slowly with Lucas reagent, forming a turbid solution or precipitating over time.
3. Propan-2-ol (2-propanol) is a secondary alcohol and reacts rapidly with Lucas reagent, forming an immediate turbid solution.

Answer 2

Propan-2-ol, also known as isopropyl alcohol, will produce a yellow iodoform precipitate (CHI₃) and result in a positive iodoform test. This indicates that a secondary alcohol is present.

\[\ce{\underset{Propan-2-ol}{CH3 - CH(CH3) - OH} ->[I2][NaOH] \underset{(Yellow ppt)}{\underset{Iodoform}{CHI3}} + CH3COONa}\]

As propan-1-ol (n-propyl alcohol) is a primary alcohol and does not produce iodoform in these conditions, it will not result in a positive iodoform test.

\[\ce{\underset{Propan-2-ol}{CH3 - CH2 - CH2 - OH} ->[I2][NaOH] No reaction}\]