CH243 Thompson Organic Chemistry Laboratory

Working Notes Experiment 15: Carbonyl Chemistry: Thiamine-Mediated Benzoin

Condensation of Furfural Introduction

In this reaction two benzaldehyde molecules will react (condensation) to form benzoin using vitamin B1 (thiamine) as a catalyst. Condensation reactions like this have high atom economy, but have traditionally required highly toxic cyanide salts as catalysts. Replacing dangerous cyanide salts with the safe, biologically derived thiamine is a significant green enhancement to the reaction. Note that this is a two-week experiment as the reaction rate is slow so we will start the reaction week one and do the workup and purification week two. Techniques

Melting Point Determination (Chapter 12) Recrystallization (Chapter 13)

Reading Notes • Prepare the reaction in the mini-hoods to minimize exposure. • The product will be characterized by melting point and infrared

spectroscopy.

Experiment Report For this experiment I would like you to create a summary report. The

report should be a typed one-page narrative and should include: A brief summary of your results including

o Percent yield of furfural product. o Atom economy for this reaction o Yield economy (% yield * atom economy)

Analyze the quality end error of your experiment. o Melting point (or range) of your product. o Did the experiment go well or poorly and can you explain what went

wrong? Do you find your results to be reliable? Evaluate this experiment in terms of its greenness.

o Give a brief overall analysis of the greenness of this reaction o What recommendations do you have to improve the green

character of this reaction? Attach a copy of your IR (another copy should be taped in your

notebook).

Working Notes Experiment 15

CH243 Name____________________ Organic Chemistry Laboratory

Experiment 15: Carbonyl Chemistry: Thiamine-Mediated Benzoin Condensation of Furfural

Pre-laboratory Questions 1. Give the balanced equation for this reaction. 2. Describe the role of sodium hydroxide in this reaction? 3. Complete the following tables of chemical data:

Compound M.M. (g/mol)

Sol. m.p. (°C)

b.p. (°C)

D (g/mL)

Thiamine hydrochloride

Water

Ethanol

Sodium hydroxide

Furfural

Furoin

4. Consider the chemicals used for this experiment. What realistic

hazards are present? What safety procedures are necessary beyond wearing goggles and gloves?

Working Notes Experiment 15