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Chemistry of Aromatic acid
The document discusses aromatic acids, particularly their structure, acidity, and preparation methods, highlighting the role of electron withdrawing and releasing groups on acidity. It outlines several methods for preparing aromatic acids and their derivatives and describes various reactions involving these compounds. Additionally, it mentions uses for aromatic acids, such as in germicides and food preservatives.
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Chemistry of Aromatic acid
- 1. Aromatic acid Mr. MoteG.D. Annasaheb Dange College of B.Pharmacy, Ashta
- 2. Aromatic acid • Thecompounds 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 aromaticacids • 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 onacidity 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 carboxylicacid 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 acidis 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 aromaticacid 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 Benzylchloride CH2Cl H2O CH2OH Oxidation of Benzyl chloride with acidic potassium permanganate or sodium dichromate COOH benzoic acid KMnO4
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- 10. 2.Reaction of phenylmagnesium 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 ofbenzonitrile CN benzonitrile H2O COOH benzoic acid
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- 13. 4.Basic hydrolysis ofbenzotrichloride CH3 toluene 3Cl2 CCl3 NaOH H2O COONa H H2O COOH benzoic acid
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- 15. 5. Hydrolysis ofPhenyl 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 aromaticacid 1. Salt formation 2. Ester formation 3. Acyl halide formation 4. Reduction to benzyl alcohol 5. Decarboxylation 6. Electrophilic substitution
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- 20. 3.Acyl halide formation COOH benzoicacid PCl5 C O Cl benzoyl chloride PCl3 HCl
- 21. 4.Reduction to benzylalcohol COOH benzoic acid LiAlH4 CH2OH Benzylalcohol
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- 23. 6. Electrophilic substitution COOH benzoicacid HNO3 H2SO4 COOH NO2 3-nitrobenzoic acid
- 24. Uses • Germicide-UTI(urinary tractinfection) • Food preservatives