text: Racemization can be achieved by simply mixing equal quantities of two pure enantiomers.  Racemization can also occur in a chemical interconversion.  For example, when (R)-3-phenyl-2-butanone is dissolved in aqueous ethanol that contains NaOH or HCl, a racemate is formed.  The racemization occurs by way of an intermediate enol form in which the former stereocenter becomes planar and hence achiral. An incoming group can approach from either side of the plane, so there is an equal probability that protonation back to the chiral ketone will produce either an R or an S form, resulting in a racemate.
  Racemization can occur through some of the following processes:
  * Substitution reactions that proceed through a free carbocation intermediate, such as unimolecular substitution reactions, lead to non-stereospecific addition of substituents which results in racemization. 
  * Although unimolecular elimination reactions also proceed through a carbocation, they do not result in a chiral center.  They result instead in a set of geometric isomers in which trans/cis (E/Z) forms are produced, rather than racemates.
  * In a unimolecular aliphatic electrophilic substitution reaction, if the carbanion is planar or if it cannot maintain a pyramidal structure, then racemization should occur, though not always. 
  * In a free radical substitution reaction, if the formation of the free radical takes place at a chiral carbon, then racemization is almost always observed.
  The rate of racemization (from -forms to a mixture of -forms and -forms) has been used as a way of dating biological samples in tissues with slow rates of turnover, forensic samples, and fossils in geological deposits. This technique is known as amino acid dating.