Thalidomide was used to treat morning sickness in the late 1950s, but was soon discovere...

Thalidomide was used to treat morning sickness in the late 1950s, but was soon discovered to have caused a number of birth defects. For a time it was believed that the birth defects were due to one enantiomer of this drug and that the other enantiomer was harmless. However, it was later found that either enantiomer will racemize under the acidic conditions of the stomach so the harmless enantiomer is converted to the harmful one. Suggest a mechanism for this racemization.