Benzoin condensation

A concise information on benzoin condensation

1. BENZOIN CONDENSATION PRESENTED BY: MR K V NANDA KUMAR ASSOCIATE PROFESSOR KRISHNA TEJA PHARMACY COLLEGE, TIRUPATHI-517506 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR 1

2. CONTENTS 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR 2

3. HISTORY 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR 3

4. GENERAL PRINCIPLE The benzoin condensation is the condensation between two molecules of benzaldehyde to form benzoin in the presence of a cyanide catalyst (e.g., NaCN and KCN) or thiamine (vitamin B). The structure of benzoin is that of a ketone. It consists of acetophenone bearing hydroxy and phenyl substituents at the alpha-position ( α‐ hydroxyl ketone). Its IUPAC name is 2-hydroxy-1,2-diphenylethanone with a molecular mass of 212.24 g/mol. A cyanide ion usually catalyzes benzoin condensation . 4 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR

5. REQUIREMENTS OF THE REACTION Two molecules of benzaldehyde A cyanide ion usually catalyzes benzoin condensation. Cyanide is used because it is a good nucleophile, can stabilize the intermediate ion, and is an excellent leaving group. 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR 5

6. MECHANISM OF THE REACTION 6/19/2020 6 PHARM D YEAR I POC - MR K V NANDA KUMAR STEP 1: The standard method for performing the benzoin condensation begins with benzaldehyde treated with a catalytic amount of sodium cyanide in the presence of a base. The cyanide ion forms a stable cyanohydrin intermediate

7. MECHANISM OF THE REACTION 6/19/2020 7 PHARM D YEAR I POC - MR K V NANDA KUMAR STEP 2: The second step is the condensation reaction that occurs between the cyanohydrin and the benzaldehyde.

8. MECHANISM OF THE REACTION 6/19/2020 8 PHARM D YEAR I POC - MR K V NANDA KUMAR STEP 3: In the third phase, rearrangement occurs and also the removal of the cyanide ions occurs resulting in the formation of benzoin.

9. USES AND APPLICATIONS OF BENZOIN CONDENSATION 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR 9

10. QUESTIONS What is benzoin condensation? Write the general principle involved in benzoin condensation. Explain the mechanism involved in benzoin condensation? What are the important applications of benzoin condensation? 6/19/2020 PHARM D YEAR I POC - MR K V NANDA KUMAR 10

11. PHARM D YEAR I POC - MR K V NANDA KUMAR 6/19/2020 11