PERKIN REACTION BY PROF R P S CHAUHAN HOD DEPTT OF CHEMISTRY - PowerPoint PPT Presentation

PERKIN REACTION BY PROF R P S CHAUHAN HOD DEPTT OF CHEMISTRY MAGADH UNIVERSITY BODH GAYA

INTRODUCTION • THIS REACTION INVOLVE TREATMENT OF AROMATIC ALDEHYDE WITH THE ANHYDRIDE OF AN ALIPHATIC ACID CONTAINING AT LEAST TWO ALPHA HYDROGEN ATOM IN PRESENCE OF ANHYDROUS SODIUM SALT OF THE SAME ACID. • THE PRODUCT OF THIS REACTION IS ALPHA BETA UNSATURATED ACIDS.

REACTION

MECHANISM

MECHANISM • ACETATE ION ABSTRACT ALPHA HYDROGEN ATOM FROM ACETIC ANHYDRIDE TO FORM A CARBANION (1). • THIS CARBANION COMBINES WITH CARBONYL GROUP OF THE ALDEHYDE FORMS OXYANION (II), WHICH FORMS A CYCLIC INTERMEDIATE (III). • A MOLECULE OF ACETIC ACID IS LOST FROM CYCLIC INTERMEDIATE (III) BY E2 ELIMINATION TO GIVE PRODUCT.

IMPORTANT POINTS • AROMATIC ALDEHYDE HAVING ELECTRON WITHDRAWING GROUPS AT PARA POSITION GIVES BETTER YIELD, WHEREAS ELECTRON DONATING GROUP SLOW DOWN THE REACTION. • THE STEREOCHEMISTRY OF THE ALKENE FORMED IS TYPICAL E.

FEW EXAMPLES

REFERENCES • REACTION MECHANISM IN ORGANIC CHEMISTRY BY SUBRATA SEN GUPTA. • SOME STRUCTURE AND REACTIONS ARE COPIED FROM INTERNET.