Cleaning Up of α-Methylstyrene by Flash Chromatography

The Application Notebook

The Application Notebook, The Application Notebook-02-11-2011, Volume 0, Issue 0

The isolation of α-Methylstyrene from the crude reaction mixture seems easy. However the reaction mixture contains some dimethyl sulfoxide and the oily wetting agent from the sodiumhydride.

A. Talamona, BÜCHI Labortechnik AG

The isolation of α-Methylstyrene from the crude reaction mixture seems easy. However the reaction mixture contains some dimethyl sulfoxide and the oily wetting agent from the sodiumhydride. Both of them are not UV-active and therefore invisible in the TLC.

TLC of the crude reaction mixture

TLC on silica gel Si60F254, developed in n-hexane/ethyl acetate 90:10, detection UV 254 nm.

Figure 1: Chromatogram of α-Methylstyrene crude reaction mixture.

TLC of the the separated fractions

TLC on silica gel 60F254, developed in n-hexane-ethyl acetate 9:1, detection UV 254 nm.

Figure 2: TLC of crude reaction mixture and pooled fractions 14–18.

Recovery

Fraction 11–12: 0.4 g colorless oily liquid.

Figure 3: TLC of crude reaction mixture and pooled fractions 11–12.

Sepacore configuration

Cartridge 40 × 150 mm, prepacked with silica gel 60, 40–63 µm

2 Pump Modules C-605

Fraction Collector C-660

Control-Unit C-620 with Sepacore Control software

UV Photometer C-635

Separation conditions

Eluent: n-hexane with 0%, 2%, and 15% ethyl acetate, step gradient

Flow rate: 100 mL/min

Sample: 3 g crude mixture, dissolved in toluene

Injection volume: 4.5 mL (although the mixture is liquid, the sample is not fully miscible with n-hexane and must be dissolved in toluene and injected directly onto the cartridge).

Fractions

2–10: mainly toluene and wetting agent

11–12: α-Methylstyrene

14–18: Acetophenone (reactant)

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