Q10-34E-a - Organic Chemistry (Mcmurry)

Question

Sort the radicals below from most stable to least stable.

Step-by-Step Solution

Answer

The order of radical stability is: 3 > 2 > 1

Step 1: Free radical

These molecular species have at least one unpaired electron. Molecules normally consist of pairs of electrons. These are electron-deficient species.

Step 2: Stability of free radical

• As radicals are electron deficient species. Their stability Increases with number of alkyl groups present on carbon bearing the free radical. So, radical stability increases in the order vinyl < methyl < primary < secondary < tertiary < allyl radical. 
• Radicals Are Stabilized by resonance.

Step 3: Stability of radical 1

As the radical cannot move from its place due to no conjugation present on the adjacent position of the double bond .

RADICAL 1

It is a vinyl radical so least stable. 

Step 4: Stability of radical 2

The radical cannot move from its position, since there is no conjugation at the adjacent position of the double bond.

RADICAL 2

      It is a primary radical so less stable

Step 5: Stability of radical 3

The radical cannot move from its place since there are no conjugations present on the adjacent positions of the double bond.

RADICAL 3

 

It is secondary radical so among all three most stable