What is the impurity that must be removed from the benzaldehyde reagent before it can be used in this experiment?
this is from are Benzil lab
in this lab, benzoin condensation of benzaldehyde will be carried out with a biological coenzyme, thiamine hydrochloride, as the catalyst:
Procdure.
Reaction Mixture-Add 0.3 g of thiamine hydrochloride to a erlenmeyer flask. Dissolve the solid in 0.45 mL of water by swirling the flask. Add 3.0 mL of 95% ethanol, and swirl the solution until it is homogeneous. To this solution add 0.9 mL of an aqueous sodium hydoxide solution and swirl the flask until the bright yellow color fades to a pale yellow color. Weigh the flask and solution, add 0.9 mL of benzaldehyde, and reweigh the flask to dtermine an accurate weight of benzaldehyde introduced to the flask. swirl the contents of the flask until it is homogeneous. Stopper the flask, and let it stand in a dark place for at least 2 days.
Isolation of crude Benzoind-allow about 5 minutes for the crystals of benzoin to form fully. place the flask, with crystals, into an ice bath for 5-10 minutes.
Break up the crystalline mass with a spatula, swirl the flask rapidly and quickly transfer the benzoin to a hirsch funnel under vacuum. Was the crystals with three 1.0 mL portions of ice cold wateer. allow the benzoin to dry in the hirsch funnel by drawing air through the crystals for about 5 mins. Transfer the benzoin to a watch glass and allow it to dry in air for one day. The product may be dried in a few minutes in an oven set at about 100 C
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