Specific Rotation of Chiral Molecules

[Cyberchicken]

Homework Statement

Why may the specific rotation of a sample of (R)-(+)-limonene be less than the literature value of (R)-(+)-limonene. Assume that there are so (S) enantiomers present.

Homework Equations

The Attempt at a Solution

There are no (S) enantiomers, but there are some molecules of methylene chloride mixed into the sample that was analyzed. But since these are achiral, I don't understand why they should affect the rotation of the limonene.

 

[Ygggdrasil]

When you calculate the specific rotation of a sample, what values do you need to know? Would the presence of solvent affect any of those values?

 

[Cyberchicken]

When you calculate the specific rotation of a sample, what values do you need to know? Would the presence of solvent affect any of those values?

The solvent used was ethanol, so that should not affect the optical activity. Are there any other factors which would affect it? Like the presence of methylene chloride perhaps? And why would it affect it?

 

[Ygggdrasil]

Again, think about how you calculate the specific rotation of a sample. You place your sample in the polarimerter and obtain the angle by which your sample rotated the light. How do you calculate the specific rotation from that value?

 

[DeeNos]

Could you clarify the question and provide more information about the specific conditions and methods used to determine the specific rotation of the sample? Without this information, it is difficult to provide a specific answer. However, in general, there are a few reasons why the specific rotation of a sample of (R)-(+)-limonene may be less than the literature value.

Firstly, it is possible that the sample was not pure and contained impurities or other chiral molecules that may have affected the specific rotation. This could be due to errors in sample preparation, contamination during the analysis process, or the presence of other compounds in the sample.

Additionally, the specific rotation of a molecule can vary depending on the conditions under which it is measured. Factors such as temperature, solvent, and concentration can all influence the specific rotation value. If the conditions used in the literature value are different from those used in the analysis of the sample, this could explain the difference in the specific rotation values.

Furthermore, the specific rotation of a chiral molecule is also affected by the length of the light path through the sample. If the sample was not measured under the same conditions as the literature value, for example, if the sample was measured in a shorter light path, this could result in a lower specific rotation value.

In conclusion, there are several reasons why the specific rotation of a sample of (R)-(+)-limonene may be less than the literature value. It is important to carefully consider the experimental conditions and potential sources of error when analyzing chiral molecules to ensure accurate results.