Lauricella et al. [44] tried to analyse the conformers of limonene
by studying the temperature dependence of the optical rotation at
589 nm. Interestingly, the authors explained the variation of
rotivity in vacuo (U0; the rotivity is defined as U ¼ [a]/(n2 þ 2), with
[a] as measured optical rotation, and n as refractive index of the
sample) at different temperatures with a shift in the population
mix: increasing the temperature resulted in decreased rotivities in
vacuo. Using our population mix based on experimental 13C resonances,
we can support this view: increasing the temperature increases
the populations of conformer 2 and 3 which have calculated
negative optical rotation values so that the decrease of the experimental
values with increased temperature is explained.