Cyclohexanes conformation isomerisms twist boat

This boat-chair difference is not immediately obtainable from experiment, e.g. the high-temperature conformational isomerization—and then quenching—of cyclohexane does not result in a chair — boat interconversion, but rather chair — twist-boat M. Squillacote, R. S. Sheridan, O. L. Chapman and F. A. L. Anet, 7. Am. Chem. Soc., 97, 3244 (1975). 

In general, things are simpler than that, much to our advantage. Within the limits set by the precision of the present estimates, structural features like the chair, boat, or twist-boat conformations of cyclohexane rings, as well as the butane-gawc/ze effects or the cis-tmns isomerism of ethylenic compounds leave no recognizable distinctive trace in zero-point plus heat content energies. Indeed, whatever residual, presently... 

The chair conformer can undergo conformational isomerism to a second chair conformer which is degenerate in energy with the first. Cyclohexane is thus a dynamic molecule which exists largely in one of two chair isomers. These are the lowest energy conformations. Other higher energy conformations of cyclohexane include the boat form, which is 10.1 kcal/mol (42.3 kJ/mol) above the chair form, and the twist boat form, which lies 3.8 kcal/mol (15.9 kJ/mol) above the chair form. 

Conformational isomerism in cycloalkyl and cycloheteroalkyl structures is characterized by several different conformational extremes. For example, cyclohexane systems can exist in three distinct conformations boat, twist boat, and chair. Of these, the chair form is the most stable conformation because steric... 

On each carbon, one bond is directed up or down and the other more or less in the plane of the ring. The up or down bonds are called axial and the others equatorial. The axial bonds point alternately up and down. If a molecule were frozen into a chair form, there would be isomerism in monosubstituted cyclohexanes. For example, there would be an equatorial methylcyclohexane and an axial isomer. However, it has never been possible to isolate isomers of this type at room temperature.219 This proves the transient existence of the boat or twist form, since in order for the two types of methylcyclohexane to be non-separable, there must be rapid interconversion of one chair form to another (in which all axial bonds become equatorial and vice versa) and this is possible only through a boat or twist conformation. Conversion of one chair form to another requires an activation energy of about 10 kcal/mol (42 kJ/mol)220 and is very rapid at room temperature.221 However, by... 

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