Organic Synthesis

Synthesis of 9-fluorenone and 9-fluorenol

Theory:

Fluorene is a hydrocarbon with a formula C13H10. It is a white solid crystallizing in plates from alcohol. The compound is well soluble in acetic acid [1], carbon disulfide, ether and benzene. It is insoluble in water. Different melting points were found for the compound ranging from 113°C up to 118°C. Well purified fluorene has a melting point of 114.2 °C [2]. Fluorene can be isolated from coal-tar fractions [3]. The compound can be prepared in laboratory by numerous ways. P. Adam described a reaction between biphenyl and methylene dichloride yielding fluorene [4] . Upon oxidation, fluorenone is obtained as a beautiful yellow crystalline material [5]. Oxidation is done in sodium hydroxide solution/toluene mixture by air oxygen. Reduction of fluorenone leads to 9-fluorenol that was first obtained by Barbier [6]. This reaction is accomplished by reducing the compound with sodium borohydride in methanol.

fluorene

Two step synthesis of 9-fluorenol

 

Procedure:

  1. Synthesis of 9-fluorenone

The reaction was carried out at laboratory temperature. Fluorene (70 mg, 0.4 mmol) was weighted and placed into a  50 mL round bottom flask. Under constant stirring 5 mL of 10M NaOH water solution was added dropwise. To the mixture 5 mL of toluene was added and the mixture was stirrred until all fluorene has dissolved. Tetraybutylammonium iodide (30 mg) in a solid state was added to the mixture.  The reaction progress was tested by TLC. TLC plates were developed in a mixture of hexene/ethyl acetate (6:1). 1% fluorene standard was used for a comparison. The reaction was quit after 45 minutes. The aqueous layer was separated from the organic layer in a separatory funnel. The organic layer was washed three times with 5 mL of 1.5M hydrochloric acid and then with three portions of water (5 mL). The organic layer was dried over anhydrous sodium sulfate. The drying agent was filtered off and washed with another 10 mL of toluene. The solvent was distilled off using RVE.

  1. Synthesis of 9-fluorenol.

9-fluorenone prepared in the previous step was dissolved in 2 mL of methanol and to the solution sodium borohydride (3.4 mg, 0.1 mmol) was added under constant stirring. The solution was stirred until the yellow color disappeared. 20 mL of water was then added and the suspension was heated on a hot water bath for two minutes. The final product was filtered with suction and washed thorougly with cold water. The product was dried in the air.  Yield: Not known.

platnicky

1. synthesis of fluorenone – a) after 10 minutes, b) after 45 minutes, 2. synthesis of 9-fluorenol – c) after 5 minutes

product

Literature:
[1] HODGKINSON and MATTHEWS: J. Chem. Soc. Vol. 43, p. 163 (1883).
[2] MORTIMER and MURPHY: Ind. Eng. Chem. Vol. 16, p. 1140 (1923).
[3] German patent 130, 679; British patent 5047-1 (German patent 124,150).
[4] ADAM, P.: Compt. rend. Vol. 103, p. 207 (1886).
[5] HUNTRESS, HERSCHBERG, and CLIFF: J. Am. Chem. SOC. Vol. 63, p. 2720 (1931).
[6] BARBIER: Compt. rend. 80, 1396 (1875).