AROMATIC ACID PPT.pptx
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1. Aromatic acids contain one or more carboxyl groups directly attached to an aromatic ring. The acidity of aromatic acids is influenced by electron withdrawing and donating groups on the ring through inductive or resonance effects. 2. Electron withdrawing groups increase the acidity of benzoic acid by stabilizing the anion through resonance. Electron donating groups decrease acidity by increasing the electron density of the aromatic ring. 3. Aromatic acids undergo various reactions including salt formation, esterification, acylation, reduction, decarboxylation, and electrophilic substitution.
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AROMATIC ACID PPT.pptx
- 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. COOH benzoic acid COOH OH COOH NH2 COOH COOH phthalic acid COOH CH3 2-methylbenzoic acid (toluic acid) COOH NO2 3-nitrobenzoic acid 2-aminobenzoic acid (anthranilic acid) 2-hydroxybenzoic acid (Salicylic 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 • 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 COOH C O O + H I II C III O O
- 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. COOH HNO3 benzoic acid H2SO4 COO NO2 H More acidic
- 5. Effect of withdrawing group on acidity of benzoic acid COOH NO2 NO2 C O O H NO2 C O O NO2 C O O NO2 C O O NO2 C O O Inductive effect N C O O O O I II III IV •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 NH2 CH3Cl Aniline AlCl3 NH2 CH3 NH2 COOH K2Cr2O7 Less acidic (Base) (Base)
- 7. Effect of electron withdrawing group on acidity of benzoic acid COOH C O O H C O O C O O C O O C O O Inductive effect NH2 NH2 NH2 NH2 H2N II I •Electron donating group reduces resonance structure and stability • Increases electron density hence decreases acidity of benzoic acid
- 8. COOH COOH COOH NH2 (Less acidic) NO2 > > Acid (More acidic) Benzoic acid m-nitro benzoic acid Para amino Benzoic acid Decreases PE Increases ionization H MORE ACIDIC Electron withdrawing group withdraws electron density from the benzene and hence lowers electron density of benzene Equilibrium shift to right side Increases PE Decreases Ionization H Less ACIDIC Electron donating group donates electron density to the benzene and hence increases electron density of benzene Equilibrium shift to left side Increases decreases Electron withdrawing group increases acidity of benzoic acid Electron donating Group decreases acidity of Benzoic acid Effect of substituents on acidity of benzoic acid
- 9. 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
- 10. 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
- 11. 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
- 12. 1.Oxidation of Benzyl chloride CH2Cl H2O CH2OH Oxidation of Benzyl chloride with acidic potassium permanganate or sodium dichromate COOH benzoic acid KMnO4 CH2Cl H OH CH2OH + HCl CH2OH + O O +H2O C O OH
- 14. 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
- 15. Mechanism MgBr phenylmagnesium bromide C O O C O O Mg Br H OH COOH Mg Br OH
- 16. 3.Acid hydrolysis of benzonitrile CN benzonitrile H2O COOH benzoic acid
- 18. 4.Basic hydrolysis of benzotrichloride CH3 toluene CCl3 NaOH H2O COONa H H2O COOH benzoic acid 3Cl2 -3HCl
- 20. 5. Hydrolysis of Phenyl benzoate C O O H2O C O OH OH Phenol Benzoic acid Phenyl benzoate
- 21. 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
- 22. Reactions of aromatic acid 1. Salt formation 2. Ester formation 3. Acyl halide formation 4. Reduction to benzyl alcohol 5. Decarboxylation 6. Electrophilic substitution
- 23. 1.Salt formation COOH benzoic acid NaOH COONa sodium benzoate Benzoic acid reacts with base to form salt
- 24. 2.Ester formation COOH benzoic acid C2H5OH H2SO4 COOC2H5 ethyl benzoate Benzoic acid undergoes esterification with ethanol and conc. Sulfuric acid to form ethyl benzoate
- 25. Mechanism COOH benzoic acid COO benzoic acid + H C2H5 OH C2H5 + OH COOC2H5 + H2O
- 26. 3.Acyl halide formation COOH benzoic acid PCl5 C O Cl benzoyl chloride POCl3 HCl Benzoic acid treated with phosphorous penta chloride to give benzoyl chloride
- 27. 4.Reduction to benzyl alcohol COOH benzoic acid LiAlH4 CH2OH Benzylalcohol Benzoic acid reduces to benzyl alcohol
- 28. 5. Decarboxylation COOH benzoic acid CaO NaOH CaCO3 When benzoic acid treated with soda lime and undergoes decarboxylation to give benzene
- 29. 6. Electrophilic substitution COOH benzoic acid HNO3 H2SO4 COOH NO2 3-nitrobenzoic acid a) Nitration: When benzoic acid treated with nitric acid and sulfuric acid to give m-nitro benzoic acid
- 30. Mechanism Step-I- Formation of Electrophile HNO3 + H2SO4 NO2 + H2O + HSO4 COOH Step-II- Formation of arenium ion NO2 + COOH NO2 H Step-III- Deprotonation COOH NO2 H HSO4 COOH NO2 + H2SO4
- 31. 6. Electrophilic substitution b) halogenation: When benzoic acid treated with bromine in acetic acid to give 3-bromo benzoic acid COOH + Br2 Acetic acid COOH Br benzoic acid 3-bromobenzoic acid
- 32. Mechanism Step-I- Formation of Electrophile Br2 + CH3COOH COOH Step-II- Formation of arenium ion Br + COOH Br H Step-III- Deprotonation COOH Br H CH3COO COOH Br + CH3COOH Br + CH3COO + HBr
- 33. 6. Electrophilic substitution c) Sulfonation: When benzoic acid treated with concentrated sulfuric acid to give 3-sulfo benzoic acid COOH + H2SO4 COOH SO3H benzoic acid 3-sulfobenzoic acid + H2O
- 34. Mechanism Step-I- Formation of Electrophile H2SO4 + H2SO4 COOH Step-II- Formation of arenium ion + COOH SO3H H Step-III- Deprotonation COOH SO3H H COOH SO3H + H2SO4 SO3H H2O + + HSO4 SO3H HSO4
- 35. Uses • Germicide-UTI(urinary tract infection) • Food preservatives