Question

Reduction of Ketones using Sodium Borohydride Virtual Lab CHE242----Prelab OH 1) NaBH4/CH3OH Olescente del Conte CH2CH3 Olan.com CH2CH3 2) NaOH Names Pre-Lab Questions 1. How many moles of propiophenone and sodium borohydride will you use in your experi- ment (show calculations)? Which of these two is the limiting reagent? For full credit, you must explain why it is limiting. 2. Draw a detailed reaction mechanism for the reaction (Make sure your mechanism includes the role of the boron species). 3. Does your product have a chiral center? If so, how many stereo-isomers of the product are possible? Will the product produced by this reaction be racemic? Explain why or why not.

0.25 g of propiophenone

100mg of sodium borohydride

Answer 1

1. + NaBH 0.25 g 100 mg MW: 134 g/mol MW: 37 g/mol MW: 136 g/mol moles = moles = — MW MW 0.25 g moles =- moles =- 0.1g 37 g/mol 134 g/mol moles = 0.00187 moles = 0.0027 Limiting reagent The limiting reagent is the one in the least amount. Determine the total amount of the product formed

2) Mechanism: Attack of the hydride from the reducer on carbonyl carbon O Na + BH Nucleophilic attack Nat H-B-H Hydride anion source o Na H CH3 + CH3ON The solvent protonates the oxygen from the alkoxide

3. The product has a chiral center: ОН If a molecule has n asymmetric carbon atoms, it will have a total of 2n optical isomers. Two stereoisomers are possible In this case a racemic product can be obtained. H 50% 50%