Chapter 17, Problem 17.76P

Interpretation Introduction

(a)

Interpretation:

The differences in the structural formula of testosterone and methandrostenolone should be determined along with functional groups present in the structure.

Concept Introduction:

Steroids are the third major class of lipids. These are the compounds containing the following ring system:

Answer to Problem 17.76P

Both methandrostenolone and testosterone hormone contains hydroxyl functional group (alcohol) and carbonyl functional group (kentone).

In the structural formula of testosterone hormone, there is only one double bond and it has only one methyl group attached to cyclopentane ring whereas in methandrostenolone there are two double bonds and two methyl groups are attached to the cyclopentane ring.

Explanation of Solution

Testosterone and methandrostenolone both the hormones contain one −OH group attached to cyclopentane ring and one >C=O group in cyclohexene ring. Therefore both alcoholic and ketone functional groups present in both hormones.

In the structure of testosterone there is only a double bond in cyclohexene ring having ketonic group and no methyl group is present on the carbon of cyclopentane ring having alcoholic group as shown:

In the structure of methandrostenolone, there are two double bonds in cyclohexene ring having ketonic group and one methyl group attached on the carbon of cyclopentane ring having alcoholic group as shown:

Interpretation Introduction

(b)

Interpretation:

In both the given hormones mark all the stereocenters and state the number of stereoisomer possible for each.

Concept Introduction:

Stereoisomers are the compounds that are differ only in the spatial arrangement of their atoms. Each stereoisomer has at least one stereocenter. A stereocenter is a tetrahedral carbon atom that has four different groups bonded to it. For a molecule with n sterocenters, a maximum of $2^n$ stereoisomers are possible.

Answer to Problem 17.76P

Stereocenters in testosterone:

Since testosterone has six stereocenters therefore it has 64 possible stereoisomers.

Stereocenters in methandrostenolone:

Since methandrostenolone has six stereocenters therefore it has 64 possible stereoisomers.

Explanation of Solution

A stereocenter is a tetrahedral carbon atom that has four different groups bonded to it.

Stereocenters in testosterone:

In testosterone there are six stereocenters.

For a molecule with n stereocenter, a maximum of $2^n$ stereoisomers are possible. Therefore.

$\begin{array}{l}Numb\text{e}rofst\text{e}r\text{e}\text{O}\text{i}s\text{O}m\text{e}rsoft\text{e}st\text{O}st\text{e}r\text{O}n\text{e}=2^n\\ \text{H}\text{e}r\text{e},n=6\\ \therefore numb\text{e}rofst\text{e}r\text{e}\text{O}\text{i}s\text{O}m\text{e}rsoft\text{e}st\text{O}st\text{e}r\text{O}n\text{e}=2^6\\ =64\end{array}$

Stereocenters in methandrostenolone:

In methandrostenolone there are six stereocenters.

For a molecule with n stereocenter, a maximum of $2^n$ stereoisomers are possible. Therefore.

$\begin{array}{l}Numb\text{e}rofst\text{e}r\text{e}\text{O}\text{i}s\text{O}m\text{e}rsofm\text{e}t\text{H}\text{a}ndr\text{O}st\text{e}n\text{O}\text{l}\text{O}n\text{e}=2^n\\ \text{H}\text{e}r\text{e},n=6\\ \therefore numb\text{e}rofst\text{e}r\text{e}\text{O}\text{i}s\text{O}m\text{e}rsofm\text{e}t\text{H}\text{a}ndr\text{O}st\text{e}n\text{O}\text{l}\text{O}n\text{e}=2^6\\ =64\end{array}$.