Acetyl Ferrocene (shown below) is an aromatic organometallic compound that can b

Question

Acetyl Ferrocene (shown below) is an aromatic organometallic compound that can be prepared using the reaction scheme shown below. Often time in this reaction two products form, acetyl ferrocene and diacetyl ferrocene. If a scientist wanted to synthesize in lab acetyl ferrocene using this reaction a purification technique such as column chromatography is usually employed to purify and isolate the desired product. The column chromatography typically used has alumina as the stationary phase and the mobile phase used has a gradient. First 100% hexanes is used to elute the first band then the mobile phase is changed to 50/50 mixture of dichloromethane and hexanes to elute the two remaining bands.

Assuming the reaction did not go to completion and starting material is present in addition to the two product, which fraction should the scientist keep if the desired compound is acetyl ferrocene? Explain your answer.

Explanation / Answer

order of polarity of ferrocene, acetyl ferrocene and diacetyl ferrocene are as follows,

ferrocene < acetyl ferrocene < diacetyl ferrocene
non-polar slightly polar more polar (because of the presence of two C=O group)

therefore, in 100% hexanes (non-polar solvent) only non-polar compound that is ferrocene will elute, so the first band is ferrocene. In 50/50 dichloromethane and hexanes polar compounds will elute according to the order of polarity. Being slightly polar acetyl ferrocene will elute second followed by more polar diacetyl ferrocene band

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