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Experiment 20:. REDUCTION OF 9-FLUORENONE. Objectives:. To synthesize a secondary alcohol from a ketone using a sodium borohydride reduction. To purify and isolate the product using recrystallization. To analyze the purity of the product using TLC, HPLC and melting point analysis.

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experiment 20

Experiment 20:

REDUCTION OF 9-FLUORENONE

objectives
Objectives:
  • To synthesize a secondary alcohol from a ketone using a sodium borohydride reduction.
  • To purify and isolate the product using recrystallization.
  • To analyzethe purity of the product using TLC, HPLC and melting point analysis.
  • To characterize the reactants and products using NMR spectroscopy.
before coming to lab
Before coming to lab…
  • Review these techniques:
    • Fractional distillation
    • Vacuum filtration
    • GC Analysis
slide4

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 bonds to oxygen)
slide5

MECHANISM

NaBH4 transfers a hydride ion to the carbonyl carbon.

The oxygen anion eventually removes a proton from water.

experimental procedure synthesis
EXPERIMENTAL PROCEDURE(Synthesis)
  • Weigh 9-fluorenone into 50 mL flask with stir bar.
  • Dissolve in ethanol.
  • Add NaBH4 slowly. Stir 20 minutes.
  • Add deionized water.
  • Add 0.1 M HCl dropwise until pH = 7.
experimental procedure purification
EXPERIMENTAL PROCEDURE(Purification)
  • Suction filter.
  • RINSE SOLID WITH 10 ML COLD WATER!
  • Prepare TLC and HPLC samples.
  • Place product in warm oven for 10 minutes on a preweighed watch glass.
  • Obtain final product yield, calculate % yield.
  • Proceed to PRODUCT ANALYSIS.
experimental procedure product analysis
EXPERIMENTAL PROCEDURE(Product Analysis)
  • TLC analysis
    • Identify components present in product solution and determine purity.
  • HPLC analysis
    • Identify components present in product solution and determine purity.
  • MP analysis
    • Compare to literature value of melting point to determine purity.
  • NMR analysis
    • Characterize reactant and product using spectra on page 169.
nmr spectroscopy 9 fluorenone
NMR Spectroscopy9-fluorenone

Aromatic protons

Aromatic carbons

NMR

solvent

194d

nmr spectroscopy 9 fluorenol
NMR Spectroscopy9-fluorenol

Aromatic protons

5.54d

TMS

1.75d

Aromatic carbons

NMR

solvent

75d

safety concerns
SAFETY CONCERNS
  • All compounds used in today’s experiment are FLAMMABLE
  • and TOXIC! Use extreme caution when in use!
slide15

WASTE MANAGEMENT

  • Place aqueous filtrate from suction filtration in container labeled “AQUEOUS WASTE (Ketones)”.
  • Place TLC solvent in container labeled “ORGANIC WASTE (Ketones)”.
  • Place MgSO4, filter papers, and used TLC plates in yellow “SOLID WASTE” can.
  • Place used TLC and melting point capillaries in BROKEN GLASS CONTAINER.
  • Place product in container labeled “9-FLUORENOL (Student Prep).
cleaning
CLEANING
  • Clean all glassware with soap, water, and a brush if necessary.
  • Rinse all glassware with wash acetone before returning it to the lab drawer!
  • DO NOT return glassware to lab drawer dirty or wet!