Question

What is the evidence that your product is a single geometric dibenzalacetone isomer and not a

mixture of isomers? Can the evidence be from an IR spectrum or the melting point or both ? And why ?

Answer 1

Answer will depend on your result. A mixture of isomers , like any impurity, will cause a lower broader melting point range while a single isomer will produce a higher sharper melting point range.

A sharp melting point suggests one pure geometric isomer.

If you have the literature values, the melting point should also let you determine which geometric isomer you have. The trans, trans is usually the major isomer produced in this Aldol, and a careful recrystallization should give you fairly pure trans, trans.

Trans trans isomer will have 110-111 melting point.

In mixed aldol dibenzalacetone get different geometrical isomers cis and trans.and they have different melting point.