Question

4-hydroxypentanal reacts with one equivalent of methanol to form a cyclic acetal.

Draw curved arrows to show the movement of electrons in this step of the reaction mechanism.

Answer 1

Step-by-step explanation:

The equation is given as:

CH3CHOHC2H4CHO + CH3OH --> CYCLIC ACETAL + H2O

This above equation is carried out in the presence of a strong acid. There are five mechanisms employed and they are:

Step 1:

Initial formation of the hemiacetal which takes several steps

Step 2:

Addition of a proton. The hemicetal is protonated on the hydroxyl group (-OH group)

Step 3:

As seen a bond is broken to give the H2O molecule and a resonance stabilized cation.

The carbonyl group on the cation is enriched with the oxygen-18 got from the H2O molecule as seen in the mechanism.

Step 4:

An attraction occurs between electrophile and nucleophile i.e the stabilised cation and the lone paids of the methanol.

Step 5:

Finally, a proton (+) is removed from the molecule by a lone pair of electron on the methanol.

Attached are the Steps 1 - 5 mechanism below