ORGANIC EMISTRY II. CARBOXYLIC ACIDS Saturated mono carboxylic s are called fatty s. group is COOH which is made up of carbonyl and hydroxy groups. General molecular formula is CnH n O or C n H n+1 COOH. General representation is R COOH Most of these fatty s are derived from fats. NAMING OF CARBOXYLIC ACIDS : STRUCTURE COMMON NAME IUPAC NAME HCOOH Formic Methanoic COOH Acetic Ethanoic COOH Propionic (or) Methyl acetic Propanoic COOH Butyric (or) Ethyl acetic Butanoic β α Cl COOH β chloro--α - methyl butyric -chloro -methyl Butanoic HOOC COOH Oxalic Ethanedioic HOOC - - COOH Succinic Butanedioic HOOC COOH Malonic Propanedioic HOOC = COOH Maleic (or) Fumaric But ene dioic COOH α - Hydroxy propionic (or) Lactic OH Hydroxy propanoic ISOMERISM IN FATTY ACIDS : The molecule formula C n H n O permits the existence of chain, functional, and metamerism. Mono carboxylic s will exhibit chain and functional isomerism. They don t exhibit position isomerism COOH group is at chain terminal position. Carboxylic s and esters having same molecular formula are functional isomers. Example : 1) C H O : COOH HCOO ) C H 6 O : COOH 1 as
COO ) C H 8 O : COOH COOH COOH COO COOC H 5 C H 5 COO Chain isomers Metamers Acetic (or) Ethanoic ( COOH) Methods of preparation of Acetic : - - OH OH + CO KMnO or K Cr O 7 - O KMnO or K Cr O 7 Co or Rh Pressure, Δ O COOH ½ O Mn( COO) CO -NH HO CN - OH,HO Micoderma aceti OH + air HO, H + COOMgBr Primary alcohols on oxidation give aldehydes which are easily oxidised to carboxylic s in presence of ified K Cr O 7 or KMnO. MgBr on addition of CO gives an intermediate which on hydrolysis gives acetic. Alkyl cyanides on hydrolysis give carboxylic s. Methyl cyanide or Acetonitrile on hydrolysis gives acetic and NH. The intermediate is acetamide. Acetic is mostly prepared from OH and CO in presence of Co or Rh catalyst. Commercially, acetic is prepared by the oxidation of ethanal with air in presence of Mn + catalyst. MgBr + CO
Biochemical oxidation of ethylalcohol inpresence of Micoderma aceti bacteria yield 6 to 10% acetic, called vinegar. Physical properties : It is colorless liquid with pungent smell. It is corrosive liquid It s boiling point is higher than even H O due to formation of stronger hydrogen bonds [118 C]. It s b.p. is higher than the b.p of corresponding alcohols, ethers, alkylhalides, alkanes, alkenes, alkynes. It is miscible with H O, alcohol, ether. Due to hydrogen bonding it exists as dimer in vapour state or in aqueous solution and polymer in liquid state. EMICAL PROPERTIES : - COCl+SO +HCl - ( CO) O COCl+POCl +HCl HI + RedP H+Ni P O -H O 10 SOCl Na PCl5 CN+H O PO, 5 Δ CONH +H O Δ COONH NH Na CO COOH Cl Cl Cl Red P Red P Red P COONa + NaHCO NaHCO NaOH COONa + CO +H O PCl C H OH H Oxidation LiAlH C H -OH 5 5 + CO+H O COONa + H O COCl + H PO COOC H + H O 5
Reactions of salts of acetic : 1) De carboxylation : COONa+NaOH CaO + Na CO electrolys is ) Kolbe s electrolysis : COONa + H OH C H 6 + CO + NaOH + H (anode) (cathode) ) Dry distillation of calcium acetate : i) ( COO) Ca Δ CO + CaCO ii) ( COO) Ca+ (HCOO) Ca Δ O + CaCO With any active metal like Na, K, Zn it liberates H gas. It neutrlises bases basic salts NaOH, Na CO, NaHCO. With ethyl alcohol, it forms fruity smelling ester. With chlorinating agents like PCl, PCl 5, SOCl it gives ethanoyl chloride. With ammonia it first gives ammonium acetate and on heating it gives acetamide. With excess of Cl and in presence of red P it gives trichloro acetic. It is α - chlorination and is called HVZ reaction. In the reaction of COOH with metals, bases, metal carbonates and bicarbonates and NH, O H bond is cleaved. In the reaction of COOH with alcohol, PCl, PCl 5, SOCl C OH bond is cleaved. PREPARATION OF BENZOIC ACID FROM AMIDES : Benzamide FROM ESTERS : Ethyl benzoate FROMCO AND GRIGANARD REAGENT : FROM ALKYL BENZENE : Aromatic carboxylic s can be prepared by vigorous oxidation of alkyl benzenes with chromic (or) ic (or) alkaline potassium permaganate. The entire side chain is oxidised to the carbonyl group irrespecitve of length of the side chain. Primary (or) secondary alkyl groups are oxidised in this manner tertiary group is not effected.
a) Toluene b) Propylbenzene Uses of acetic : As solvent in industry For curing meat and fish As vinegar in food stuffs In the Preparation of perfumes, dyes and drugs. In the preparation of acetone, ester, acetic anhydride, acetamide etc 5