8.4 Question 8.4.E.2 PASS - enantiomers, diastereomers, identical
- Page ID
- 452335
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For the following compounds, identify whether they are enantiomers, diastereomers, or the same compound.
- Answer
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a) Enantiomers
b) Diastereomers
c) Diastereomers
d) Same compound
See LibreText 8.1 Types of Isomers (Optical Isomers)
- Strategy Map
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Step Hint 1. Use your knowledge on compound sketches to “flip” one of the compounds. When we say “flip” a compound, we are referring to rotating its orientation. This causes atoms that are dashed back to become wedged forward and vice versa. From this, we can see if the two compounds are the same and how they differ.
2. Identify if both compounds have the same shape or are optical isomers. See LibreText 8.1 Types of Isomers (Optical Isomers) 3. If they are optical isomers identify if they are mirror images of each other.
- Solution
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a) Enantiomers
These compounds are mirror image optical isomers.
b) Diastereomers
These compounds are non-mirror image optical isomers.
c) Diastereomers
These compounds are non-mirror image optical isomers.
d) Same compound
These compounds have the same chemical formula and connectivity.
- Guided Solution
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Download Guided Solution as a pdf
Guided Solution Hint This is a theory type problem that requires you to identify if two compounds are optical isomers and what type. See LibreText 8.1 Types of Isomers (Optical Isomers) Question - For the following compounds, identify whether they are enantiomers, diastereomers, or the same compound.
Recall what these terms mean:
- Enantiomer
- Diastereomer
Enantiomers are non-superimposable mirror images. A common example of a pair of enantiomers is your hands. Your hands are mirror images of one another but no matter how you turn, twist, or rotate your hands, they are not superimposable.
Diastereomers are non-mirror image optical isomers. Diastereomers have a different arrangement around one or more atoms while some of the atoms have the same arrangement.
Recall how you know if the two compounds are the same. If two compounds are the same, they will have the same formula and connectivity. When you “flip” the compound it should be superimposable with the other. Recall how to “flip” the compound.
When we say “flip” a compound, we are referring to rotating its orientation. This causes atoms that are dashed back to become wedged forward and vice versa. From this, we can see if the two compounds are the same and how they differ. Complete Solution:
a) These compounds are mirror image optical isomers. These compounds are nonsuperimposable. The two methane groups have opposing orientations (on one compound, the first methane group is wedged and the second is dashed; on the other compound the first methane group is dashed and the second is wedged).
answer Enantiomers
b) These compounds are non-mirror image optical isomers. These are nonsuperimposable compounds, on one compound, the chlorine is dashed back; on the other, the chlorine is wedged forwards. All other connectivity is the same.
answer Diastereomers
c) These compounds are non-mirror image optical isomers. These are nonsuperimposable compounds, on one compound, the hydroxyl group is dashed back; on the other, the hydroxyl group is wedged forwards. All other connectivity is the same.
answer Diastereomers
d) These compounds have the same chemical formula and connectivity. They are superimposable.
answer same compound
Check your work!
The easiest way to check optical isomers is to imagine yourself trying to superimpose them (or doing so with a molecular model kit). This will allow you to see which bonds are different.
Why does this answer make chemical sense?
Enantiomers are mirror image optical isomers, and diastereomers are non-mirror image optical isomers. If you flip a compound by rotating its orientation you will end up with superimposable structures if they are the same compound.
Refer to the flowchart Figure 8.11 to check your process.
(question source from page titled 6.14: Additional Exercises https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_Chem_420_-_Organic_Chemistry_I/Text/06%3A_Stereochemistry_at_Tetrahedral_Centers/6.14%3A_Additional_Exercises, shared under a CC BY-NC-SA 4.0 license, authored, remixed, and/or curated by Libretexts)