Question

Pyrethrins, such as jasmolin II (below), are a group of natural compounds synthesised by flowers of the genus Chrysanthemum (known as pyrethrum flowers) to act as insecticides.

(a) Circle and name the functional groups in jasmolin II.

(b) What is the hybridization of the numbered carbons?

(c) Which, if any, of the numbered carbons are chiral centers?

Short answer

a. Jasmolin II has two ester groups (R-CO-O-R’) and one ketone group in the ring

b. Hybridisation of Carbon 1,4,7and 6 has and Carbon2,3 and five have

c. Chiral centres are carbon 2,3,5

Step-by-step solution

Functional group

The group is different from the rest of the molecule and has different chemical properties irrespective of the other atom of a molecule like a hydroxyl group (OH) etc.

In jasmolin II, there are two different functional groups present

1. Two ester group (R-CO-O-R’)
2. Ketonic group present in between the ring (CO)

Jasmin II

Hybridisation

In a given jasmoline II hybridisation of each carbon is:

Carbon 1, 4, 7 and 6 has because carbon forms three bonds and bonds are not included in hybridisation.

Carbon 2, 3 and 5 have formed four sigma bonds.

Chiral centers

These are the carbon centre in which carbon forms four bonds with distinct atoms. They are optically active in jasmolin II carbon 2,3,5 are the chiral centres as the four forms formed by carbon are distinct forms.

Jasmin II