Chemistry of Aromatic acid
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Definition, Acidity, Substituents effects on acidity, Carbxyl group meta director, Deactivating group, Preparation, reaction and uses
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Chemistry of Aromatic acid
- 1. Aromatic acid Mr. Mote G.D. Annasaheb Dange College of B.Pharmacy, Ashta
- 2. Aromatic acid • The compounds in which one or more carboxyl group are attached directly to the aromatic ring. COOH benzoic acid COOH OH COOH NH2 COOH COOH phthalic acid COOH CH3 2-methylbenzoic acid COOH NO2 3-nitrobenzoic acid 2-aminobenzoic acid2-hydroxybenzoic acid
- 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
- 4. Factor affecting on acidity of benzoic acid • The electron withdrawing group increases the acidity of a benzoic acid. • The electronegative atom stabilizes anion • An electron releasing on meta or para position decreases acidity of benzoic acid. • Ortho substitution by electrophilic or nucleophilic group increases acidity due to steric effect. COOH HNO3 benzoic acid H2SO4 COO NO2 H
- 5. 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. C HO O C O- HO C HO O CH HO O
- 6. 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 COOH HNO3 benzoic acid H2SO4 COOH NO2
- 7. Preparation of aromatic acid 1. Oxidation of benzyl chloride 2. Reaction of phenyl magnesium bromide with carbon dioxide 3. Acid hydrolysis of benzonitrile 4. Basic hydrolysis of benzotrichloride 5. Hydrolysis of phenyl benzoate
- 8. 1.Oxidation of Benzyl chloride CH2Cl H2O CH2OH Oxidation of Benzyl chloride with acidic potassium permanganate or sodium dichromate COOH benzoic acid KMnO4
- 10. 2.Reaction of phenyl magnesium bromide with carbon dioxide • The reaction of phenyl magnesium bromide with carbon dioxide followed by acid hydrolysis. MgBr phenylmagnesium bromide CO2 COO- magnesium benzoate bromide H2O COOH benzoic acid
- 11. 3.Acid hydrolysis of benzonitrile CN benzonitrile H2O COOH benzoic acid
- 13. 4.Basic hydrolysis of benzotrichloride CH3 toluene 3Cl2 CCl3 NaOH H2O COONa H H2O COOH benzoic acid
- 15. 5. Hydrolysis of Phenyl benzoate C O O H2O C O OH OH PhenolBenzoic acidPhenyl benzoate
- 16. 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
- 17. Reactions of aromatic acid 1. Salt formation 2. Ester formation 3. Acyl halide formation 4. Reduction to benzyl alcohol 5. Decarboxylation 6. Electrophilic substitution
- 18. 1.Salt formation COOH benzoic acid NaOH COONa sodium benzoate
- 20. 3.Acyl halide formation COOH benzoic acid PCl5 C O Cl benzoyl chloride PCl3 HCl
- 21. 4.Reduction to benzyl alcohol COOH benzoic acid LiAlH4 CH2OH Benzylalcohol
- 23. 6. Electrophilic substitution COOH benzoic acid HNO3 H2SO4 COOH NO2 3-nitrobenzoic acid
- 24. Uses • Germicide-UTI(urinary tract infection) • Food preservatives