Cannizzaro Reaction Lab

The Cannizzaro Reaction

Resources:

Mayo, Pike, Trumper, Strange de Soria. Microscale Organic Laboratory. New York: John

Wiley and Sons, 2002.

Strange de Soria, Luise. “Student Survival Guide”.

http://www.gpc.edu/~lstrange/2642lab/survivalguide/grignard2.pdf. 2004.

Purpose:

The purpose of this experiment is to oxidize and reduce an aromatic aldehyde to form benzoic acid and benzyl alcohol. We will also separate the layers into two products, a carboxylic acid and a neutral alcohol.

Summary of the Theory behind the Cannizzaro Reaction:

The Cannizzaro reaction consists of an oxidation-reduction reaction between a hydroxide ion and aldehydes without α-hydrogen atoms. With the presence of a strong base, the first aldehyde molecule reduces to a second aldehyde molecule and then becomes a primary alcohol. Within this process the molecule oxidizes itself to the corresponding carboxylate anion. If the aldehyde does possess an α-hydrogen atom, the α-carbon will deprotonate when there is a base present and the reaction will not go through this kind of reaction (an Aldol reaction will usually occur with the resulting enolate).

The mechanism of this reaction happens as follows…

Reaction Analysis:

Balanced Chemical Equation:

• (ClC7H5O)2 + KOH + H+ → ClC7H4OH + ClC7H4O2H

Theoretical yield:

Alcohol Layer

1) Take the amount of 4-chlorobenzaldehyde and divide it by its molecular weight

• 0.3g ÷ 140.57g/mol = 0.002mol

2) Take the value found in step 1 and multiply it by the molecular weight of the product

• 0.002mol x 144.52g/mol = 0.289g theoretical yield

Acid Layer

1) Take the value found in step 1 of alcohol layer and multiply it by the molecular weight of the product

• 0.002mol x 142.25g/mol = 0.285g theoretical yield

Potential side products:

• Leftover starting material

Procedure:

Add 150mg of 4-chlorobenzaldehyde and 0.4mL of methanol to a 5mL conical vial on a reflux condenser with a spin...