Harjinder Kaur
8 hours ago
What are enantiotropic and diastereotropic protons? Illustrate your answer with examples.
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ChatGPT
8 hours ago
Enantiotropic protons are protons that can exist in two different chemical environments, resulting in two distinct chemical shifts in the NMR spectrum. These protons are in equilibrium between two different conformations or isomers. An example of enantiotropic protons is found in the compound 1,2-dichloroethane. In this compound, the two hydrogen atoms on the carbon atoms adjacent to the chlorine atoms can exist in two different chemical environments due to the rotation around the C-C bond, resulting in two distinct chemical shifts in the NMR spectrum.
Diastereotropic protons, on the other hand, are protons that are not equivalent due to the presence of chiral centers or other asymmetric elements in the molecule. These protons will have different chemical shifts in the NMR spectrum due to their unique chemical environments. An example of diastereotropic protons is found in the compound 2,3-dichlorobutane. In this compound, the two hydrogen atoms on the carbon atoms adjacent to the chlorine atoms are diastereotopic due to the presence of the chiral center at the second carbon atom, resulting in different chemical shifts in the NMR spectrum.
Diastereotropic protons, on the other hand, are protons that are not equivalent due to the presence of chiral centers or other asymmetric elements in the molecule. These protons will have different chemical shifts in the NMR spectrum due to their unique chemical environments. An example of diastereotropic protons is found in the compound 2,3-dichlorobutane. In this compound, the two hydrogen atoms on the carbon atoms adjacent to the chlorine atoms are diastereotopic due to the presence of the chiral center at the second carbon atom, resulting in different chemical shifts in the NMR spectrum.
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Google Gemini AI
8 hours ago
Enantiotropic Protons:
- Protons in a chiral molecule that are made equivalent by a symmetry operation (e.g., reflection through a plane of symmetry).
- They have identical chemical shifts and coupling constants.
- Example: The methylene protons in ethane (CH3-CH3) are enantiotropic. Rotation around the C-C bond interconverts the protons, making them chemically equivalent.
Diastereotropic Protons:
- Protons in a chiral molecule that are not made equivalent by any symmetry operation.
- They may have different chemical shifts and coupling constants.
- Example: The two methyl protons in 2-butanol (CH3-CHOH-CH2-CH3) are diastereotropic. Rotation around the C-C bond does not interconvert the protons, so they remain chemically distinct.
Additional Examples:
- Enantiotropic:
- The two hydrogen atoms on the terminal carbon in propene (CH3-CH=CH2)
- The two hydrogen atoms on the same carbon in cyclohexane (C6H12)
- Diastereotropic:
- The two hydrogen atoms on the adjacent carbon atoms in butene (CH3-CH=CH-CH3)
- The three hydrogen atoms on the same carbon in 2-methylpropane (CH3-CH(CH3)-CH3)
- Protons in a chiral molecule that are made equivalent by a symmetry operation (e.g., reflection through a plane of symmetry).
- They have identical chemical shifts and coupling constants.
- Example: The methylene protons in ethane (CH3-CH3) are enantiotropic. Rotation around the C-C bond interconverts the protons, making them chemically equivalent.
Diastereotropic Protons:
- Protons in a chiral molecule that are not made equivalent by any symmetry operation.
- They may have different chemical shifts and coupling constants.
- Example: The two methyl protons in 2-butanol (CH3-CHOH-CH2-CH3) are diastereotropic. Rotation around the C-C bond does not interconvert the protons, so they remain chemically distinct.
Additional Examples:
- Enantiotropic:
- The two hydrogen atoms on the terminal carbon in propene (CH3-CH=CH2)
- The two hydrogen atoms on the same carbon in cyclohexane (C6H12)
- Diastereotropic:
- The two hydrogen atoms on the adjacent carbon atoms in butene (CH3-CH=CH-CH3)
- The three hydrogen atoms on the same carbon in 2-methylpropane (CH3-CH(CH3)-CH3)
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