Question

Alcohols react with active metals e.g. Na, K, etc. to give corresponding alkoxides. Write down the decreasing order of reactivity of sodium metal towards primary, secondary, and tertiary alcohols.

Answer 1

Hint: Think about why metals react with alcohol. Which property of alcohol is responsible for the reaction of alcohols and metals? Think about the electron density on the oxygen of the alcohol group in primary, secondary, and tertiary alcohols.

Complete step by step solution:
We know that alcohols react with active metals e.g. Na, K, etc. to give corresponding alkoxides. Alcohols contain hydrogen attached to oxygen. Compounds containing hydrogen attached more electronegative elements such as oxygen are acidic. Alcohols are acids but their acidic strength is very less. So, alcohol does not take place in the reactions in which acids take place.
Sodium metal reacts with alcohol and liberates hydrogen. But the order of reactivity depends on the acidic strength of the alcohol. Acids with higher acidic strength react with sodium faster than weaker acids. We need to identify the acidic strength of primary, secondary, and tertiary alcohols.
In tertiary alcohols connected alkyl groups pump the electron density towards the oxygen of alcohol this reduces the acidic strength of alcohol. So, as the alkyl groups on carbon connected to the alcohol group increases the acidic strength of that alcohol decreases. So, the reactivity of sodium towards alcohol will be primary > secondary > tertiary alcohols.

Note: Na, K are highly electropositive metals which react with acids and liberate hydrogen. Though alcohols are weak acids, the strong electropositive character of Na, K allows them to react with alcohol and release hydrogen gas.