Editing Rotamer (section)

===Spectroscopy===
Conformational dynamics can be monitored by variable temperature [[NMR]] spectroscopy. The technique applies to barriers of 8–14&nbsp;kcal/mol, and species exhibiting such dynamics are often called "[[Fluxional molecule|fluxional]]". For example, in [[Cyclohexane|cyclohexane derivatives]], the two chair conformers interconvert rapidly at room temperature. The ring-flip proceeds at a rates of approximately 10<sup>5</sup>&nbsp;ring-flips/sec, with an overall energy barrier of 10 kcal/mol (42 kJ/mol).  This barrier precludes separation at ambient temperatures.<ref name="eliel"/> However, at low temperatures below the [[Coalescence (chemistry)|coalescence]] point one can directly monitor the equilibrium by NMR spectroscopy and by dynamic, temperature dependent NMR spectroscopy the barrier interconversion.<ref>{{Cite journal|last1=Jensen|first1=Frederick R.|last2=Bushweller|first2=C. Hackett|date=1969-06-01|title=Separation of conformers. II. Axial and equatorial isomers of chlorocyclohexane and trideuteriomethoxycyclohexane|journal=Journal of the American Chemical Society|volume=91|issue=12|pages=3223–3225|doi=10.1021/ja01040a022|bibcode=1969JAChS..91.3223J |issn=0002-7863}}</ref>

Besides NMR spectroscopy, [[IR spectroscopy]] is used to measure conformer ratios. For the axial and equatorial conformer of bromocyclohexane, ν<sub>CBr</sub> differs by almost 50&nbsp;cm<sup>−1</sup>.<ref name="eliel">{{cite book|last1=Eliel|first1= E. L.|last2= Wilen|first2= S. H.|last3= Mander|first3= L. N. |title=Stereochemistry Of Organic Compounds|publisher= J. Wiley and Sons|date= 1994 |isbn=978-0-471-01670-0}}</ref>