1 Based on your knowledge of the mechanism involved in the n

1. Based on your knowledge of the mechanism involved in the nitration of methyl benzoate, what role(s) would you expect sulfuric acid to play in the nitration of benzaldehyde?

2. During the purification of acetyl ferrocene by column chromatography, hexanes are used to elute the unreacted ferrocene first. Upon subsubsequent elution with (1:1) hexane/Ch2Cl2 the acetyl ferrocene starts to move down the column. Explain the theoretical principle underlying this purification method.

Solution

1. Sulfuric acid reacts with HNO3 to form (+NO2) electrophile which undergoes electrophilic aromatic substitution over phenyl ring of benzaldehyde.

2. . Ferrocene is a nonpolar compound therefore gets easily eluted with nonpolar hexane.

Acetylferrocene is a polar compound as in this case COCH3 (acetyl) group makes the compound more polar. Thus acetylferrocene is retained in the column when we use hexane as a mobile phase.

However, on increasing the polarity of the mobile phase by using (1:1) hexane/Ch2Cl2 (remeber CH2Cl2 is a polar compound) the acetyl ferrocene starts to move and gets eluted.