Question

why reactivity order for alchohols is 3°>2°>1° in alkyl chains
no wrong answer plzzzzz

Answer 1

Tertiary alcohols are more stable because of the three alkyl groups. 

First of all, the three alkyl groups prevent the tertiary alcohol from being oxidised because there's no hydrogen bonded to the carbon atom with hydroxyl group, which means that no hydrogen will be lost from the alcohol. An experimental evidence is that tertiary alcohols do not change the orange-looking potassium dichromate (VI) solution into a green solution on heating, but primary alcohols do.  

Secondly, nucleophilic substitutions on tertiary alcohols are very slow compared to that on primary alcohols, since the three alkyl groups sterically prevent the attacking nucleophile from being bonded to the carbon atom. The experiment for this is that tertiary alcohols react with PCl5 or PI3 more slowly under reflux, compared with when primary alcohols react with these reagents.  

Answer 2

Reactivity of Alcohols:

Understanding :

Reactivity depends on :

1) Steric factors :
Steric is considered to be size when other molecules attacks substrate for reaction.

For example, size of 3° alcohol more than 1° alcohol.
And it will be more crowded and hence it will
hinder the molecules which help in the reaction.


So, There may be more repulsion of C groups with other molecules which may hinder the reaction in case 3°

In this case ,
Reactivity :
1°>2°>3°.

This happens in reactions called SN 2.

2) Formation of stable compounds in between the reaction.

In reaction where formation of carbonation takes place in place of carbon which is attached to Oxygen, there reactivity of 3 ° alcohols will be more.

As, 3° carbonation is more stable than 1,2 degrees.

This happens in reactions called S N 1.

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Overall, when we are finding reactivity of molecules then all these and other factors like temperature, pressure are considered.

By taking consideration of all these, we can say about reactivity of Alcohols.