Question

(a)Count the elements of unsaturation in cicutoxin, capillin, and panaxytriol.

(b) Draw structural formulas of at least two alkynes of each molecular formula.

(1) ${\mathbf{C}}_5{\mathbf{H}}_8$ (2) ${\mathbf{C}}_8{\mathbf{H}}_{10}$ (3) ${\mathbf{C}}_9{\mathbf{H}}_{12}$

Short answer

(a) The element of unsaturation in cicutoxin, capillin, and panaxytriol is 5, 4 and 4 respectively.

(b) The structural formulas for the given alkynes are:

(1) ${\text{C}}_{\text{5}}{\text{H}}_{\text{8}}$

${\mathrm{CH}}_3-\mathrm{C}\equiv \mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_3$

Pent-2-yne

$\mathrm{CH}\equiv \mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_3$

Pent-1-yne

(2) ${\text{C}}_{\text{8}}{\text{H}}_{\text{10}}$

Meta-xylene

Ethylbenzene

(3) ${\text{C}}_{\text{9}}{\text{H}}_{\text{12}}$

Cumene

(Isopropyl benzene)

Cumene

(Propyl benzene)

Step-by-step solution

Step-by-Step SolutionStep 1: Counting the elements of unsaturation

Each pi-bond has one element of unsaturation and each ring has one element of unsaturation. The pi- bond comprises of one double bond and the triple bond comprises of two double bonds.

Step 2: Structures of given compounds

The structures of cicutoxin, capillin, and panaxytriol are represented as:

• Cicutoxin has 2 triple bonds + 3 double bonds = 5 elements of unsaturation.

Cicutoxin

• Capillin has 2 triple bonds and one ring = 4 elements of unsaturation.

Capillin

• Panaxytriol ha 3 triple bond and one double bond = 4 element of unsaturation.

Panaxytriol

The structural formula of alkynes

The two structural formulas for ${\text{C}}_{\text{5}}{\text{H}}_{\text{8}}$are:

${\mathrm{CH}}_3-\mathrm{C}\equiv \mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_3$

Pent-2-yne

$\mathrm{CH}\equiv \mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_3$

Pent-1-yne

The two structural formulas for ${\mathrm{C}}_8{\mathrm{H}}_{10}$are:

Meta-xylene

Ethyl benzene

The two structural formulas for ${\mathrm{C}}_9{\mathrm{H}}_{12}$ are:

Cumene

(Isopropyl benzene)

Cumene

(Propyl benzene)