Finding stereoisomers....confused

In summary, the conversation discussed the number of distinct stereoisomers for hexadecanoic acid (palmitic acid) and oleic acid. It was confirmed that there is only 1 stereoisomer for hexadecanoic acid, as it does not have any stereocenters. On the other hand, oleic acid has 2 stereoisomers due to the presence of a double bond that can have two different arrangements, cis and trans. The conversation also clarified that stereoisomerism is not limited to chirality, as it can also refer to other types of isomerism.
  • #1

Homework Statement


[/B]
How many distinct stereoisomers exist for the hexadecanoic acid and oleic acid, respectively?
Please choose from one of the following options.
  • 1, 1
  • 1, 2
  • 2, 2
  • 2, 4

Homework Equations


None

The Attempt at a Solution



If you look at the following images of hexadecanoic (palmitic) acid, and oleic acid, respectively, I cannot find how they arrive at their answer.
https://upload.wikimedia.org/wikipedia/commons/b/ba/Palmitic_acid.svg

Oleic-acid-based-on-xtal-1997-2D-skeletal.png


The correct answer is B.

In palmitic acid...where is the stereoisomer? I would be looking for something that is either cis/trans or R/S...and none of the sp3 carbons have a stereocenter (they all have at least two H's), and the only double bond is on the carboxylic oxygen. Even if you assume that it is resonant with the hydroxyl group, the CH2 group will freely rotate and not cause any fixation. So I do not see where the stereocenter is..

In oleic acid, I can see that there is one cis/trans site, but otherwise I have the same issue.

Why is the carboxylic acid counting as a stereocenter...?
 
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  • #2
Must be some error, no stereoisomers here.
 
  • #3
Borek said:
Must be some error, no stereoisomers here.
Thanks, that's what I wanted to confirm. Thanks Khan Academy...
 
  • #5
Strange, I was always under impression stereoisomerism is other name for chirality. Seems I was wrong.
 

1. What are stereoisomers?

Stereoisomers are molecules that have the same molecular formula and connectivity, but differ in the spatial arrangement of their atoms. This means that they have the same number and types of atoms, but the atoms are arranged differently in space.

2. How do you find stereoisomers?

To find stereoisomers, you need to identify the chiral centers in a molecule. These are carbon atoms that have four different groups attached to them. Then, you can use the principles of stereoisomerism, such as mirror images and rotations, to generate the different possible arrangements of the molecule.

3. What is the difference between enantiomers and diastereomers?

Enantiomers are stereoisomers that are non-superimposable mirror images of each other. This means that they have the same molecular formula and connectivity, but they are arranged differently in space. Diastereomers, on the other hand, are stereoisomers that are not mirror images of each other and have different physical and chemical properties.

4. Why is it important to consider stereoisomerism in chemistry?

Stereoisomerism is important in chemistry because it can significantly affect the physical and chemical properties of a molecule. For example, enantiomers can have different biological activities and medicinal effects, while diastereomers can have different melting points and boiling points. Understanding stereoisomerism is crucial in drug design, material science, and other areas of chemistry.

5. Can stereoisomers be separated?

Yes, stereoisomers can be separated using various techniques such as chromatography, distillation, and crystallization. These methods take advantage of the differences in physical and chemical properties between stereoisomers to separate them. However, some stereoisomers may be difficult to separate due to their similar properties, and advanced methods such as chiral chromatography may be required.

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