Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone

2857 words 12 pages
Megan Entwistle, Maria Amos, and Paul Golubic
CHEM 0330 Organic Lab 1
Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone


Redox (shorthand for REDuction-OXidation) reactions are chemical reactions in which the oxidation state (or oxidation number) of atoms has changed. Oxidation can be observed through the loss of electrons or an increase in oxidation state by an atom, ion or molecule. Reduction describes the gain of electrons or decrease in oxidation state of an atom, ion or molecule. However, there are many processes that are classed as redox even though no electron transfer occurs, for example those reactions that involves covalent bonds.
Reduction reactions can be determined through three
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This process only works for carbonyl groups. Carbonyl groups are functional groups that have a carbon atom and double-bonded oxygen attached to it (C=O). Carbonyl groups can be reduced by reacting them with hydride reagents. There are two types of hydride reagents, NaBH4 and LiAlH4. However, carbonyl can also be reduced by hydrogen as well, but with the presence of catalysts. Examples of catalysts are copper, chromite, Raney nickel, rhenium, ruthenium and rhodium.
Mechanism for hydride transfer reagent:

The borohydride anion delivers a hydride ion to the carbonyl compound at the same time that a proton is transferred from the solvent to the carbonyl oxygen. As the B-H bond breaks, a new bond between the boron and, the oxygen atom of the solvent is formed. An important thing to note is the hydrogen atom that ends up bonded to the carbonyl carbon comes from the NaBH4 while the hydroxyl hydrogen is derived from the solvent.

Many reaction mixtures require heat in order to perform reactions at a reasonable rate. Reflux is a heating process that involves the boiling of reaction mixtures in solution. In reflux, a solvent is chosen so that its boiling point coincides with a reaction temperature that is ideal. Heating a reaction mixture to reflux assures chemists of a constant, appropriate temperature. Reflux is the process of boiling reactants while continually cooling the vapor returning