Question

Give the IUPAC name (including any E,Z designation) for each unsaturated aldehyde. Neral is obtained from lemon grass, and cucumber aldehyde (Problem 1.30) contributes to the aroma of a fresh mango.

a.

b.

Short answer

a. (Z)-3,7-dimethylocta-2,6-dienal

b. (2E,6Z)-nona-2,6-dienal

Step-by-step solution

E and Z configurations

E and Z configurations are assigned to compounds when they have a double bond and different substituents attached to the carbon atoms involved in the bond.

IUPAC names of a and b

a. The given compound has eight carbon atoms in a chain in which methyl groups are attached to C-3 and C-7 atoms, respectively.

The double bond is present on C-2 and C-6 atoms, respectively. At the C-2 atom, the high priority groups are present on the same side, so it is assigned Z configuration.

The IUPAC of the given compound is shown below:

(Z)-3,7-dimethylocta-2,6-dienal

b. The given compound has nine carbon atoms in a chain. The double bond is present on C-2 and C-6 atoms, respectively. At the C-2 atom, the high priority groups are present on opposite sides; that’s why it is assigned E configuration.

At the C-6 atom, the high priority groups are present on the same side; that’s why it is assigned Z configuration.

The IUPAC name of the given compound is shown below:

(2E,6Z)-nona-2,6-dienal