CHE 252
Laboratory: Sodium Borohydride Reduction of Benzophenone
Spring 2011
Reminder: This lab is tentatively worth 18 points. Your lab report’s results section
should include all TLCs (scaled reproductions of your actual TLCs drawn into the results
section) with their Rf values.
Introduction:
2 pts.
Results:
TLC slides reproduced in the results section
Table of Rf values
Melting point
Percent yield calculation
Sample appearance
Labeled 1H and 13C NMR spectra of product and starting material
Discussion:
Writing/Format
Questions
1 pt.
1 pt.
1 pt.
2 pts.
1 pt.
2 pts.
3 pts.
2 pts.
3 pts.
Questions:
1. (1 pt) If the rate of heating is too high while heating the reaction mixture under reflux,
what will happen to the solvent?
2. (2pts) In the reduction of an acyclic aldehyde or ketone (e.g. benzophenone) the
hydride ion can attack from either side of the planar carbonyl unit with equal probability.
When 4-tert-butylcyclohexanone (a monocyclic ketone) reacts with NaBH4 in methanol
two alcohol stereoisomers are possible. The reaction seems to be influenced by
thermodynamic factors. Draw the structures of the two stereoisomers and circle the
isomer that will be in the greater amount due to being thermodynamically more stable.