Experiment 8: Multistep synthesis

Experiment 8: Multistep synthesis

Benzoin Condensation

O

H

+ CN- /H2O

OH OH H CN

O H

OH O H

OH CN

H

OHOH CN -

+ CN-

Since cyanide is quite toxic, we will use thiamine as our catalyst to replace cyanide

CH3

N

N

NH2 S

N +

CH3

ClOH

Thiamine is heat sensitive so the addition of 5 M NaOH needs to be added slowly (3 to 5 min) to the thiamine hydrochloride in an ice bath with constant swirling and maintain the temperature below room temperature.

Once the benzaldehyde is added, the reaction flask, an Erlenmeyer flask, is sealed with a cork and sealed with Parafilm to keep out air. Place in your drawer until next week.

How do I go about figuring out what my unknown is?

1. From your solubility measurements, you should be able to classify your unknowns according to the solubility classes discussed.

2. Complete and hand in your preliminary report if you haven't done so.

3. From your solubility measurements and you physical properties, make a list of the possible compounds.

4. Look up some reference IR spectra in your manual that have the possible functional groups present in your unknown.

5. Begin to analyze your NMR spectrum. If you have an carboxylic acid as an unknown, consider titrating it to determine its equivalent weight.

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