The pyrolysis of (-)-(S)-nicotine: racemization and decomposition

The pyrolytic behaviour of (-)-(S)-nicotine in methanol was investigated using on-line pyrolysis GC/MS to establish whether racemization to the R(+) antipode occurs and to identify other products of pyrolysis. The conditions used included pyrolysing the sample for 15 seconds in an atmosphere of 9% oxygen in nitrogen (275 ml/min total flow) across the temperature range of 200 degrees C-1000 degrees C. A chiral Cyclodex-B analytical column (30 m x 0.25 mm i.d. x 0.25 microm film thickness) was used to separate the enantiomers of nicotine, although the two enantiomer peaks were not baseline resolved. The results of the experiment shows that there is no increase in (+)-(R)-nicotine levels across a wide temperature range. This suggests that the elevated levels of (+)-R-nicotine observed in tobacco smoke (compared to tobacco leaf material) are not due to the pyrolytic auto-racemization of (-)-(S)-nicotine but are a result of more complex interactions between (-)-(S)-nicotine and other smoke components. The pyrolysis of isotopically labelled nicotine established that nicotine undergoes thermal decomposition to beta-nicotyrine which in turn may decompose to other products.