Challenges
- Despite numerous studies, shape theory has yet to discover shape-odor relations with great predictive power. .
- Similarly shaped molecules with different molecular vibrations have different smells (metallocene experiment and deuterium replacement of molecular hydrogen).
- Differently shaped molecules with similar molecular vibrations have similar smells (replacement of carbon double bonds by sulfur atoms and the disparate shaped amber odorants).
- Hiding functional groups does not hide the group's characteristic odor.
- Very small molecules of similar shape, which seem most likely to be confused by a shape-based system, have extremely distinctive odors, such as hydrogen sulfide.
- Some studies seem to show that human beings and animals can distinguish between isotopes by smell, despite their identical shapes .
- Odor descriptions in the olfaction literature correlate more strongly with their vibrational frequencies than with their molecular shape .
Read more about this topic: Shape Theory Of Olfaction
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