Chapter U2.20, Problem 9E

(a)

Interpretation Introduction

Interpretation: The molecular formulas for citronellol and geraniol needs to be determined.

Concept Introduction: Chemical compounds with same molecular formula having different structure are known as isomers. Isomers having same number of atoms of each type but bonded together in a different sequence (spatial arrangement) are known as stereoisomers.

There are two kinds of stereo isomers- Geometrical and optical.

Explanation of Solution

The given structures are as follows:

From the above structures, molecular formula of the compounds can be determined as follows:

C₁₀H₂₁O −Citronellol

C₁₀H₁₈O- Gerniol

(b)

Interpretation Introduction

Interpretation: The two distinct smells of the molecule citronellol needs to be explained.

Concept Introduction: Chemical compounds with same molecular formula having different structure are known as isomers. Isomers having same number of atoms of each type but bonded together in a different sequence (spatial arrangement) are known as stereoisomers.

There are two kinds of stereo isomers- Geometrical and optical.

Explanation of Solution

The formula of citronellol is C₁₀H₂₁O. The structure is represented as follows:

There are two optical isomers which are non-superimposable mirror image of each other.

Isomer of Citronellol

Thus, the two different smells are due to two different optical isomers of citronellol.

(c)

Interpretation Introduction

Interpretation: The reason for only one smell of geraniol smell needs to be explained.

Concept Introduction: Chemical compounds with same molecular formula having different structure are known as isomers. Isomers having same number of atoms of each type but bonded together in a different sequence (spatial arrangement) are known as stereoisomers.

There are two kinds of stereo isomers- Geometrical and optical.

Explanation of Solution

The molecular formula of geraniol is C₁₀H₁₈O. The structure is represented as follows:

Geraniol

It can show geometrical isomerism. The E-isomer and Z-isomer are as follows:

Trans-Form Cis-Form

Due to absence of optical isomerism, there is only one smell of the molecule.