56 - Organic Chemistry

Question

What is the major Hofmann elimination product formed from each amine?

a

b

c

Step-by-Step Solution

Answer

a

                                    Major product of a.

b

                                 Major product of b.

c

                                    Major Pproduct of c.

Hofmann elimination

It is the only possible way of converting  $1^{°}$ amines into a better leaving group. The  $1^{°}$ amine is converted into a quaternary ammonium salt before undergoing  $\beta$-elimination. 

Conditions for Hofmann elimination reaction

The reaction consists of 3 steps, all of which take place in one single step.

The reaction takes place via an anti-periplanar geometry, according to which the hydrogen atom and the amine group should be present on the opposite sides of the molecule.

 

Mechanism of the given reaction

The C-C bonds are rotated in the given molecules to obtain the anti geometry of the hydrogen atom and the amine group. 

a

The given structure already has hydrogen and amine group anti to each other. Hence, the product of the reaction is given hereunder.

                                       Product of a.

b

The C-C bond is rotated ${120}^{°}$  counterclockwise. The product of the reaction is given hereunder.

                                   Product of b.

c

The C-C bond is rotated ${120}^{°}$ counterclockwise. The product of the reaction is given hereunder.

                                   Product of c.