Cyclohexane equatorial hydrogens

FIGURE 1.6 The two chair conformations of cyclohexane a = axial hydrogen atom and e = equatorial hydrogen atom. 

Figure 4.8 Axial (red) and equatorial (blue) positions in chair cyclohexane. The six axial hydrogens are parallel to the ring axis, and the six equatorial hydrogens are in a band around the ring equator.

For example, cyclohexane gives a single averaged resonance in the H NMR at room temperature, but separate signals are seen for the axial and equatorial hydrogens when spectra are acquired at very low temperature. 

FIGURE 1.7 The two chair conformations of cyclohexane a = axial hydrogen atom and e = equatorial hydrogen atom. The middle and bottom panels show methylcyclohexane in the chair form with the methyl group equatorial (middle) and axial (bottom). 

In the space provided on the Report Sheet (2e), draw the structure of cyclohexane in the chair conformation with all 12 hydrogens attached. Label all the axial hydrogens, Ha, and all the equatorial hydrogens, He. How many hydrogens are labeled Ha (2f) How many hydrogens are labeled He (2g) ... 

Draw a chair cyclohexane. Show the axial and equatorial hydrogens. 

This principle is illustrated by the cyclohexane spectrum. In the chair conformation, there are two kinds of protons the axial hydrogens and the equatorial hydrogens. The axial hydrogens become equatorial and the equatorial hydrogens become axial by chair-chair interconversions. These interconversions are fast on an NMR time scale at room temperature. The NMR spectrum of cyclohexane shows only one sharp, averaged peak (at S 1.4) at room temperature. 

Each cyclohexane carbon atom has one axial and one equatorial hydrogen. 

Ring-flipping interconverts axial and equatorial hydrogens in cyclohexane... 

Each carbon atom on a cyclohexane ring has one axial and one equatorial hydrogen. Ring-flipping converts axial H s to equatorial H s, and vice versa. 

After inversion of chair cyclohexane, axiai hydrogens have become equatorial and vice versa this inversion is rapid at room temperature. 

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