Enantiomeric excess question

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In summary, the percentages of each enantiomer in the mixture with an enantiomeric excess (ee) of 84% would be 92% for the major isomer and 8% for the minor isomer. The number of possible enantiomers is the same for any compound, and the pattern for determining the percentages of each enantiomer based on the excess is (100 - ee)/2 for the minor isomer and (100 + ee)/2 for the major isomer.
  • #1
uorganic
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If a natural product was isolated and was found to have an enantiomeric excess (ee) of 84% what would be the percentages of each enatiomer in the mixture?
 
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  • #2
Well, do you know the equation (or definition) of enantiomeric excess?
 
  • #3
uorganic said:
If a natural product was isolated and was found to have an enantiomeric excess (ee) of 84% what would be the percentages of each enatiomer in the mixture?

think about it...

how many possible enantiomers are there. hint: the number of possible enantiomers is the same for any compound.

so...let's say that the enantiomers were 50:50 in a mixture. then, the excess would be 0. if it were a 40:60 mixture, then one of the enantiomers would be in 10% excess. notice that (60 - (100 - 60) ) / 2 = 10

see the pattern here?
 
  • #4
Enantiomeric excess (ee) of 84%

Then major isomer % = (100+84)/2 = 92 %

%minor isomer = 100-92 = 8%

regards
kandasani
 
  • #5

Enantiomeric excess (ee) refers to the percentage difference between the two enantiomers in a mixture, with a maximum value of 100%. In this case, the natural product has an ee of 84%, indicating that one enantiomer is present in significantly higher quantities than the other.

To determine the percentages of each enantiomer in the mixture, we can use the following formula:

Percentage of one enantiomer = ee + (100-ee)/2
Percentage of other enantiomer = (100-ee)/2

In this case, the percentage of the enantiomer with higher quantity would be 84% + (100-84)/2 = 92%. The percentage of the other enantiomer would be (100-84)/2 = 8%.

It is important to note that the actual percentages of each enantiomer may vary depending on the specific compound and isolation method used. However, the ee value provides a useful indicator of the relative amounts of each enantiomer in the mixture.
 

1. What is enantiomeric excess (ee)?

Enantiomeric excess is a measure of the asymmetry of a mixture of enantiomers, which are molecules that are mirror images of each other but cannot be superimposed.

2. How is enantiomeric excess calculated?

Enantiomeric excess is calculated by subtracting the percentage of the minor enantiomer from the percentage of the major enantiomer, and then dividing by the total percentage of both enantiomers.

3. What is a good enantiomeric excess value?

A good enantiomeric excess value depends on the specific application, but generally an ee of 90% or above is considered excellent, while an ee of 50% or below is considered racemic (equal mixture of both enantiomers).

4. How can enantiomeric excess be determined experimentally?

Enantiomeric excess can be determined experimentally using techniques such as chiral chromatography, polarimetry, or NMR spectroscopy. These methods involve separating and analyzing the enantiomers to determine their relative quantities.

5. Why is enantiomeric excess important in organic chemistry?

Enantiomeric excess is important in organic chemistry because it can affect the properties and reactivities of chiral molecules. In addition, many pharmaceuticals and natural products are chiral, so having control over the enantiomeric excess is crucial in drug development and synthesis of natural compounds.

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