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PLZ NAMES TYPES OF CONFERMATIONAL ISOMER.....
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Rotation about single bond of butane to interconvert one conformation to another. The gaucheconformation on the right is a conformer, while theeclipsed conformation on the left is a transition state between conformers. Above: Newman projection; below: depiction of spatial orientation.
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Conformational isomers are thus distinct from the other classes of stereoisomers (i. e.configurational isomers) where interconversion necessarily involves breaking and reforming of chemical bonds.[3] For example, L/D- and R/S- configurations of organic molecules have different handedness and optical activities, and can only be interconverted by breaking one or more bonds connected to the chiral atom and reforming a similar bond in a different direction or spatial orientation. They also differ from geometric (cis/trans) isomers, another class of stereoisomers, which require the π-component of double bonds to break for interconversion. (Although the distinction is not always clear-cut, since certain bonds that are formally single bonds actually have double bond character that becomes apparent only when secondary resonance contributors are considered, like the C–N bonds of amides, for instance.)
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The types of conformational isomers are related to the spatial orientations of the substituents between two vicinal atoms. These are eclipsed and staggered. The staggered conformation includes the gauche(±60°) and anti (180°) conformations, depending on the spatial orientations of the two substituents.
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Ring conformationCyclohexane conformations, including with chair and boat conformers among others.Carbohydrate conformation, which includes cyclohexane conformations as well as other details.Allylic strain – energetics related to rotation about the single bond between an sp2carbon and an sp3 carbon.Atropisomerism – due to restricted rotation about a bond.Folding, including the secondary and tertiary structure of biopolymers (nucleic acids and proteins).
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Rotation about single bond of butane to interconvert one conformation to another. The gaucheconformation on the right is a conformer, while theeclipsed conformation on the left is a transition state between conformers. Above: Newman projection; below: depiction of spatial orientation.
=========================================
Conformational isomers are thus distinct from the other classes of stereoisomers (i. e.configurational isomers) where interconversion necessarily involves breaking and reforming of chemical bonds.[3] For example, L/D- and R/S- configurations of organic molecules have different handedness and optical activities, and can only be interconverted by breaking one or more bonds connected to the chiral atom and reforming a similar bond in a different direction or spatial orientation. They also differ from geometric (cis/trans) isomers, another class of stereoisomers, which require the π-component of double bonds to break for interconversion. (Although the distinction is not always clear-cut, since certain bonds that are formally single bonds actually have double bond character that becomes apparent only when secondary resonance contributors are considered, like the C–N bonds of amides, for instance.)
=========================================
The types of conformational isomers are related to the spatial orientations of the substituents between two vicinal atoms. These are eclipsed and staggered. The staggered conformation includes the gauche(±60°) and anti (180°) conformations, depending on the spatial orientations of the two substituents.
=======≠=================================
Ring conformationCyclohexane conformations, including with chair and boat conformers among others.Carbohydrate conformation, which includes cyclohexane conformations as well as other details.Allylic strain – energetics related to rotation about the single bond between an sp2carbon and an sp3 carbon.Atropisomerism – due to restricted rotation about a bond.Folding, including the secondary and tertiary structure of biopolymers (nucleic acids and proteins).
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The types of conformational isomers are related to the spatial orientations of the substituents between two vicinal atoms. These are eclipsed and staggered. The staggered conformation includes the gauche(±60°) and anti (180°) conformations, depending on the spatial orientations of the two substituents.
For example, butane has three conformers relating to its two methyl (CH3) groups: two gauche conformers, which have the methyls ±60° apart and are enantiomeric, and an anti conformer, where the four carbon centres are coplanar and the substituents are 180° apart (refer to free energy diagram of butane). The energy difference between gauche and anti is 0.9 kcal/mol associated with the strain energy of the gauche conformer. The anti conformer is, therefore, the most stable (≈ 0 kcal/mol). The three eclipsed conformations with dihedral angles of 0°, 120°, and 240° are not considered to be conformers, but are instead transition states between two conformers.[4]Note that the two eclipsed conformations have different energies: at 0° the two methyl groups are eclipsed, resulting in higher energy (≈ 5 kcal/mol) than at 120°, where the methyl groups are eclipsed with hydrogens (≈ 3.5 kcal/mol).[7]
While simple molecules can be described by these types of conformations, more complex molecules require the use of the Klyne–Prelog system to describe the different conformers.[4]
More specific examples of conformational isomerism are detailed elsewhere:
Ring conformation
Cyclohexane conformations, including with chair and boat conformers among others.
Carbohydrate conformation, which includes cyclohexane conformations as well as other details.
Allylic strain – energetics related to rotation about the single bond between an sp2 carbon and an sp3carbon.
Atropisomerism – due to restricted rotation about a bond.
Folding, including the secondary and tertiary structure of biopolymers (nucleic acids and proteins).
Akamptisomerism – due to restricted inversion of a bond angle.
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For example, butane has three conformers relating to its two methyl (CH3) groups: two gauche conformers, which have the methyls ±60° apart and are enantiomeric, and an anti conformer, where the four carbon centres are coplanar and the substituents are 180° apart (refer to free energy diagram of butane). The energy difference between gauche and anti is 0.9 kcal/mol associated with the strain energy of the gauche conformer. The anti conformer is, therefore, the most stable (≈ 0 kcal/mol). The three eclipsed conformations with dihedral angles of 0°, 120°, and 240° are not considered to be conformers, but are instead transition states between two conformers.[4]Note that the two eclipsed conformations have different energies: at 0° the two methyl groups are eclipsed, resulting in higher energy (≈ 5 kcal/mol) than at 120°, where the methyl groups are eclipsed with hydrogens (≈ 3.5 kcal/mol).[7]
While simple molecules can be described by these types of conformations, more complex molecules require the use of the Klyne–Prelog system to describe the different conformers.[4]
More specific examples of conformational isomerism are detailed elsewhere:
Ring conformation
Cyclohexane conformations, including with chair and boat conformers among others.
Carbohydrate conformation, which includes cyclohexane conformations as well as other details.
Allylic strain – energetics related to rotation about the single bond between an sp2 carbon and an sp3carbon.
Atropisomerism – due to restricted rotation about a bond.
Folding, including the secondary and tertiary structure of biopolymers (nucleic acids and proteins).
Akamptisomerism – due to restricted inversion of a bond angle.
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