Question

Nepetalactone is the active ingredient of catnip. It is isolated as an oil from the plant Nepata cataria. Show that it is a terpene (i.e., that its carbon skeleton can be divided into isoprene units). Is the molecule chiral? How many stereoisomers are possible?

Short answer

Answer: Yes, nepetalactone is a terpene as its carbon skeleton can be divided into isoprene units. It is chiral, having one chiral center, and there are two possible stereoisomers.

Step-by-step solution

Examining the structure of nepetalactone

First, we need to examine the structure of nepetalactone molecule. The molecular formula of nepetalactone is C10H14O2. The structural formula is given by: [](https://en.wikipedia.org/wiki/Nepetalactone) In this structure, the dashed line represents a single bond between two carbon atoms and the bold wedges represent the orientation of the bond (in this case, it is coming out towards you).

Dividing the carbon skeleton into isoprene units

Now that we have the structure, we will divide the carbon skeleton into isoprene units. The carbon skeleton can be divided into two isoprene units as shown below: [](https://i.imgur.com/h6k6gkg.png) Each isoprene unit contains 5 carbon atoms, and since the total number of carbon atoms in nepetalactone is 10, the carbon skeleton can indeed be divided into isoprene units.

Checking for chirality

A molecule is considered chiral if it cannot be superimposed on its mirror image (a requirement for chirality is the presence of a chiral center, which is defined as a carbon atom with four different substituents). In nepetalactone's structure, there is one chiral center: [](https://i.imgur.com/F2rnzF2.png) The chiral center is marked with an asterisk. Therefore, nepetalactone is indeed a chiral molecule.

Calculating the number of stereoisomers

Since nepetalactone has one chiral center, we can calculate the number of possible stereoisomers using the formula 2^n, where n is the number of chiral centers: Number of stereoisomers = 2^n Number of stereoisomers = 2^1 Number of stereoisomers = 2 So, there are two possible stereoisomers for nepetalactone. To summarize our findings: 1. Nepetalactone is indeed a terpene because its carbon skeleton can be divided into isoprene units. 2. The molecule is chiral because it has one chiral center. 3. There are two possible stereoisomers for nepetalactone.