We did Friedel-Crafts Acylation on ferrocene and got a mixture; unreacted ferroc

Question

We did Friedel-Crafts Acylation on ferrocene and got a mixture; unreacted ferrocence, acetylferrocene and diacetylferrocene of products of which we separated using column chromatography. The first solvent we used was 90/10 hexane/acetone. This is mostly hexane so the solvent is more polar than it is nonpolar and will push the least polar of the products (unreacted ferrocene) down the column which makes ferrocene the first to be eluted. We changed the solvent to 80/20 hexane/acetone which increased the polarity enough to move acetylferrocene down the column since this compound is polar itself. For the last compound, we changed the solvent to 50/50 hexane/acetone and diacetylferrocene eluted last.

I don't really understand how we increased the polarity of the solvent and had a nonpolar solvent such as diacetylferrocene elute. Can someone help me understand?

Explanation / Answer

Polarity order of reaction mixture; ferrocene < acetylferrocene < diacetylferrocene.

When the first solvent was used 90/10 hexane/acetone, it is mostly non-polar so only least non-polar Ferrocene elute first as like dissolves like and least non-polar dissolves in 90/10 hexane/acetone.

When we increased the  polarity to  80/20 hexane/acetone, it was enough to move intermediate polar acetylferrocene down the column but the highest polar diacetylferrocene eluted last with 50/50 hexane/acetone.

All this observation are based on the principle of like dissolves like. As we increased the polarity of eluting solvent more and more higher polar elutant gets elute according to polarity of solvent .

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