# Is it possible for a group to substitute itself?

When I first learned about substitution reactions, I started wondering something that I never ended up figuring out:

Suppose you have a strong nucleophile which is also a good leaving group, such as I$^{-}$. Can such a group substitute itself using the SN1 mechanism? If so, would that mean if such a group were bonded to a chiral carbon, an enantiomerically pure solution could spontaneously racemize?

• Very short answer: Yes. Possibly also via SN2. Jul 6 '15 at 1:28
• Has spontaneous racemization been observed? Jul 6 '15 at 1:36
• see this and this
– ron
Jul 6 '15 at 1:41
• The reaction you refer to has been done and racemisation observed, however I don't have the reference Apr 2 '16 at 13:07