1. SODIUM BOROHYDRIDE REDUCTION OF A KETONE
Experiment 20
SODIUM BOROHYDRIDE REDUCTION OF A KETONE

2. Objectives:
To synthesize a tertiary alcohol from a ketone using a sodium borohydride reduction.
To purify the product using fractional distillation.
To analyze the purity of the product using GC.
To characterize the reactants and products using NMR and IR spectroscopy.

3. Before coming to lab… Review these techniques: Fractional distillation
Vacuum filtration
GC Analysis

4. REDUCTION USING NaBH4
NaBH4 (sodium borohydride) is a versatile and useful reducing agent in organic chemistry.
A reducing agent causes a reaction (a reduction) in which the product has more bonds from carbon to hydrogen (or fewer bond to oxygen)

5. MECHANISM The oxygen anion eventually removes a proton from water.
NaBH4 transfers a hydride ion to the carbonyl carbon.

6. TODAY’S REACTION Pinacolone is reduced using sodium borohydride.
Note that 1 mole of NaBH4 will reduce 4 moles of ketone.

7. EXPERIMENTAL PROCEDURE (Synthesis)
Add 3,3-dimethyl-2-butanone and methanol to 100 mL beaker.
Place in ice water bath.
Add NaBH4 while stirring with glass rod.
Continue to react at 0oC for 5min, then 10 min more at RT.
Add 6M HCl dropwise.
Suction filter to remove separate solid from liquid filtrate.
Transfer to 50 mL round bottom flask.
100 mL
50 mL

8. EXPERIMENTAL PROCEDURE (Purification and GC Analysis)
Set up fractional distillation apparatus.
Apply heat and collect distillate below 70oC in a small flask.
Switch to 25 mL round bottom flask and collect distillate between 70-85oC.
Cool flask, reweigh.
Prepare GC sample.

9. Distillation Range (oC)
Table 20.1
Theoretical yield (g)
Calculated based on limiting reactant
Actual yield (g)
Percent yield
(Actual yield/Theoretical yield)
X 100
Distillation Range (oC)
Give Ti-Tf of distillate collected in 25 mL round bottom flask
Product Appearance
Give physical state and color of product

10. Table 20.2 Review Experiment 13 for calculations!
Atom Economy (%)
Calculate based 3,3-dimethyl-2-butanone and sodium borohydride ONLY!
Experimental
Review Experiment 13 for calculations!
“Eproduct”
Cost per synthesis ($)
Cost per gram ($/g)

11. WASTE MANAGEMENT
Place the solid boric acid waste from the filtration into the container labeled “SOLID WASTE” located in the waste hood.
Place all liquid waste into the container labeled “LIQUID WASTE”.

12. SAFETY CONCERNS
3,3-dimethyl-2-butanone, 3,3-dimethyl-2-butanol, methanol and sodium borohydride are all FLAMMABLE materials.
Methanol and sodium borohydride are TOXIC in large concentrations.
Hydrochloric acid is CORROSIVE.