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The detailed mechanism of the chair-to-chair interconversion has been the subject of much study and debate. [9] The half-chair state (D, in figure below) is the key transition state in the interconversion between the chair and twist-boat conformations. The half-chair has C 2 symmetry. The interconversion between the two chair conformations ...
The chair and twist-boat are energy minima and are therefore conformers, while the half-chair and the boat are transition states and represent energy maxima. The idea that the chair conformation is the most stable structure for cyclohexane was first proposed as early as 1890 by Hermann Sachse, but only gained widespread acceptance much later.
The chair conformation minimizes both angle strain and torsional strain by having all carbon-carbon bonds at 110.9° and all hydrogens staggered from one another. [2] The conformational changes that occur in a cyclohexane ring flip take place over several stages. Structure D (10.8 kcal/mol) is the highest energy transition state of the process.
The interconversion of equivalent chair conformers of cyclohexane (and many other cyclic compounds) is called ring flipping. Carbon–hydrogen bonds that are axial in one configuration become equatorial in the other, and vice versa. At room temperature the two chair conformations rapidly equilibrate.
They have been used as models for analyzing the effects of different geometric positions of the large atoms with dipolar bonds on the stability of the cyclohexane conformation. [1] The isomers are poisonous, pesticidal, and persistent organic pollutants, to varying degrees. Hexachlorocyclohexane was dimerized to produce mirex, a banned pesticide.
Similarly, cis-1,2-dichlorocyclohexane consists of chair conformers that are nonidentical mirror images, but the two can interconvert via the cyclohexane chair flip (~10 kcal/mol barrier). As another example, amines with three distinct substituents (R 1 R 2 R 3 N:) are also regarded as achiral molecules because their enantiomeric pyramidal ...
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A Newman projection is a drawing that helps visualize the 3-dimensional structure of a molecule. [1] This projection most commonly sights down a carbon-carbon bond, making it a very useful way to visualize the stereochemistry of alkanes.