Question

Write a mechanism for the acid–catalysed condensation of acetone. Looking at the structure of this product, and of ethylenediamine, suggest how the macrocyclic ligand might form.

Can you provide answer for this question, the macro ligand was prepared from ethylenediamine, 50% tetrafluoroboric acid.

Answer 1

The the acid–catalysed condensation of acetone is known as Aldol-type condensation reaction. The reaction mechanism for the acid–catalysed condensation of acetone is written as Scheme 1. The reaction between the product obtained from the Scheme 1 and ethylendiamine in presence of 50% tetrafluorboronic acid is shown in the Scheme 2 in the below second image.

Scheme 1.: Highlights the following steps

1. The acid acts as a proton donor and activates the carbonyl oxygen into a protonated form.

2. The formation of enol by conjugate base of acid to abstract proton from acetone.

3. The enol react with the another potonated molecule of acetone to give ketol as product.

4. The ketol undergo the dehydration ( elimination of water) in presence of base, here iwater act as base to form the alpha beta unsaturated acetone as final product.

Scheme 2: Macro ligand formation

The alpha beta unsaturated acetone as final product. react with ethylenediamine in prsence of 50% HBF4 to form the cyclic product as shown in the Scheme 2 (second image)

Mechamsn of aend cadalysid andensalan OF Acetore Scheme 1 polanulhay End Keld H-Ot pehy draters Bunsateradid tare Produet Aldd tyre ooancalich

Sdreme 2 unsatuorated Ketore Repehan dignnem Macro lgand И Prtoraton tautomenzn 2 Enat foomatn