Experiment 8: Multistep synthesis. Benzoin Condensation. Since cyanide is quite toxic, we will use thiamine as our catalyst to replace cyanide.
Since cyanide is quite toxic, we will use thiamine as our catalyst to replace cyanide
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.
Classification test should only be run to confirm your suspicions regarding the presence of a functional group suggested by your solubility tests or IR. Always run a blank and a known at the same time you run your unknown so that you know what a positive test looks like and that you performed the classification test properly.
A derivative should be chosen whose melting temperature will allow you to differentiate between possible compounds. If you have a carboxylic acid or an amine, a titration can be substituted for a derivative providing that the molecular weights of other possible compounds in your possibility list can be excluded on the basis of your titration results.
C14H10O2 C14 -6
2HNO3 + C14H12O2 C14H10O2 + 2NO2 + 2H2O
Recrystallization of benzil: be sure that the benzil does not oil out first before solidifying. When a matrial oils out, any impurites will also disolve in the oil and subsequently when everything solidifies, your material will remain impure.