AROMATIC ACID PPT.pptx

Aromatic acids

1. Aromatic Acids Mr.P.S.Kore Assistant Professor(Research Scholar) Pharmaceutical Chemistry Department RCP, Kasegaon

2. Aromatic acid The compounds in which one or more carboxyl groups are attached directly to the aromatic ring.

3. Acidity of aromatic acids The π electron plays important role in acidity of carboxylic acid. The negative charge of the carboxylate ion is shared by the two carboxylate oxygen atoms cannot be effectively delocalized by aromatic ring. Acidity influence by inductive effect According to lowery-bronsted theory, it is acid because it proton donor. According Arrhenius theory it is acid because it give H+ ion in water

4. Factor affecting on acidity of benzoic acid The electron withdrawing group increases the acidity of a benzoic acid. The electron deficient atom stabilizes anion Ortho substitution by electrophilic group increases acidity due to steric effect.

5. Effect of withdrawing group on acidity of benzoic acid Electron withdrawing group increases resonance structure and stability. Reduces increases electron density on the hence increases acidity of benzoic acid

6. Factor affecting on acidity of benzoic acid Electron donating group adds electron density on the benzene. It increases electron density and decreases acidity of benzoic acid

7. Effect of electron withdrawing group on acidity of benzoic acid Electron donating group reduces resonance structure and stability Increases electron density hence decreases acidity of benzoic acid

8. Why Aromatic carboxylic acid is meta director? Ortho and Para positions in benzoic acid resonating structure carry positive charge . Hence an electrophile can not attack these positions(repulsion). Thus the carboxyl group directs all electrophile to the meta positions.

9. Why carboxylic acid is called as deactivating? Benzoic acid undergoes electrophilic substitution is more slowly than benzene because carboxyl group withdraws electron from the ring by resonance. It decreases electron density of the ring and makes it less attractive to an incoming electrophile. hence electrophilic substitution is slow It requires vigorous reagent and condition

10. Preparation of aromatic acid Oxidation of benzyl chloride Reaction of phenyl magnesium bromide with carbon dioxide Acid hydrolysis of benzonitrile Basic hydrolysis of benzotrichloride Hydrolysis of phenyl benzoate

11. 1.Oxidation of Benzyl chloride Oxidation of Benzyl chloride with acidic potassium permanganate or sodium dichromate

12. Mechanism

13. 2.Reaction of phenyl magnesium bromide with carbon dioxide The reaction of phenyl magnesium bromide with carbon dioxide followed by acid hydrolysis.

14. Mechanism

15. 3.Acid hydrolysis of benzonitrile

16. Mechanism

17. 4.Basic hydrolysis of benzotrichloride

18. Mechanism

19. 5. Hydrolysis of Phenyl benzoate

20. Aromatic acid derivatives Benzoyl chloride Benzamide Benzoic anhydride Benzoyl peroxide Benzonitrile Toluic acid Anthranilic acid Salicylic acid Benzene dicarboxylic acid Phthalic acid Phthalic anhydride Phenyl acetic acid Cinnamic acid

21. Reactions of aromatic acid Salt formation Ester formation Acyl halide formation Reduction to benzyl alcohol Decarboxylation Electrophilic substitution

22. 1.Salt formation Benzoic acid reacts with base to form salt

23. 2.Ester formation Benzoic acid undergoes esterification with ethanol and conc. Sulfuric acid to form ethyl benzoate

24. Mechanism

25. 3.Acyl halide formation POCl3 HCl Benzoic acid treated with phosphorous penta chloride to give benzoyl chloride

26. 4.Reduction to benzyl alcohol Benzoic acid reduces to benzyl alcohol

27. 5. Decarboxylation When benzoic acid treated with soda lime and undergoes decarboxylation to give benzene

28. 6. Electrophilic substitution a) Nitration: When benzoic acid treated with nitric acid and sulfuric acid to give m-nitro benzoic acid

29. Mechanism

30. 6. Electrophilic substitution b) halogenation: When benzoic acid treated with bromine in acetic acid to give 3-bromo benzoic acid

31. Mechanism

32. 6. Electrophilic substitution c) Sulfonation: When benzoic acid treated with concentrated sulfuric acid to give 3-sulfo benzoic acid

33. Mechanism

34. Uses Germicide-UTI(urinary tract infection) Food preservatives