PHASE TRANSFER CATALYSIS [PTC]

PTC IS THE PHASE TRANSFER CATALYSIS HERE TYPES OF PTC ARE DISCUSSED , THEORIES OF CATALYSIS AND MECHANISM OF PTC, ADVANTAGES OF PTC, APPLICATION OF PTC

1. PHASE TRANSFER CATALYSIS

2. CONTENTS Introduction Mechanism of PTC reaction Theories of PTC Types of phase transfer catalyst Advantages of phase transfer reaction Application of phase transfer catalysis References 19-12-2019 2

3. Introduction Catalysis :- Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst. Definition :- Phase transfer catalysis (PTC) refers to reaction between two substances located in different immiscible phases in the presence of catalyst. Heterogenous catalysis. It facillate the migration of a reactant from one phase into another phase where reaction occurs. 19-12-2019 3

4. Following three factors plays important role in the successful use of phase transfer catalyst reaction :- Influence of solvent :- Solvent should be aprotic and immiscible with water to avoid strong interaction with ion pairs. Influence of cation :- The large number of carbon atom around the central N atom in the PTC. Salt effect :- Addition of sodium hydroxide and potassium carbonate increases the extraction coefficient many times and thus increases the rate of reaction. 19-12-2019 4

5. Theories of catalysis Intermediate Compound formation theory (Homogenous catalyst reaction ) Adsorption theory ( Heterogenous catalyst reaction ) 1) Intermediate compound formulation theory: According to this theory one of the reactants combines with catalyst to form intermediate product, which carries out the reaction, E.g. A + C = AC AC + B =AB + C A + B + C = AB + C where A and B are reactants, C is the catalyst and AC is the intermediate product. 19-12-2019 5

6. 2) Adsorption Theory: In general adsorption theory applies to heterogeneous catalytic reactions. The catalyst functions by the adsorption of the reacting molecules on its surface. The adsorption reaction undergoes four types of steps. ( i ) Adsorption of reactant molecule: The reactant molecules A and B strike the surface of the catalyst. The reaction molecules held up by the partial chemical bond. ii ) Formation of intermediate complex: The reactant molecule adjacent one another join to form an intermediate complex ( A-B ). The intermediate complex is unstable. 19-12-2019 6

7. ( iii ) Decomposition of intermediate complex: The intermediate complex breaks to form the products C and D. The product molecules hold to the catalyst surface by partial chemical bond. 19-12-2019 7 ( iv ) Release of product: The product particles are released from the surface .

8. Mechanism of PTC Reaction 19-12-2019 8

9. Types of phase transfer catalyst Quaternary ‘Onium’ salts such as ammonium, phosphonium , antimonium and tertiary sulphonium salts. Some of the PTC’s normally used are:- 1) Aliquat 336 : N+CH3(C8H17)3 Cl Methyl trioctylammonium chloride 2) Benzyl trimethylammonium chloride or bromide (TMBA) N+(CH3)3 CH2 C6H5 X- 3) Benzyl triethylammonium chloride N+(C2H5)3 CH2 C6H5 X- 4) Cetyl trimethylammonium chloride or bromide (CTMAB) N+ (CH3)3 (CH2)15 CH3 X- 19-12-2019 9

10. Types of phase transfer catalysed reactions Phase transfer reactions 19-12-2019 10 Liquid-Liquid phase transfer reaction Solid-Liquid phase transfer reaction Solid-gas phase transfer reaction Triphase catalyst Insolubilized ammonium and phosphonium salts Insolubilized crown ethers and cryptands Insolubilized cosolvents

11. Advantages of PTC Do not require vigorous conditions and the reaction are fast. Do not require expensive aprotic solvents. Do not require high temperature ; the reaction usually occur at low temperature. There is no need for anhydrous conditions since water is used as one of the phases. With the help of PTC , the anion is available in organic solvent and so its nucleophilicity increases. 19-12-2019 11

12. Applications of phase transfer Catalysis 1 ) Nitriles From Alkyl Halides :- R-X + NaCN RCN + NaX 2 ) Benzoyl Cyanides from Benzoyl Chloride:- PTC Organic Aqueous 19-12-2019 12 Bu4 N +X- Benzoyl cyanide Benzoyl chlolride Sodium cyanide Nitrile

13. 3 ) Aryl Ethers/Thioethers :- 4) Benzoin Condensation :- 19-12-2019 13 ArOH + RX ArOR NaOH Phenol Aryl ether Benzaldehyde

14. 4) Esterification :-Carboxylic acids can be esterified with alkyl halides in the presence of triethylamine. RCO 2 Na + RX RCO 2 R + Na X 5)In the field of Pharmaceuticals like Synthesis of various drugs like dicyclomine, phenoperidine , oxaladine , ritaline ,etc. 6) Williamson Ether Synthesis :- C 8 H 17 OH + C 4 H 9 Cl C 8 H 17 OC 4 H 9 + C 8 H 17 OC 8 H 17 PTC 19-12-2019 14 Alcohol Alkyl halide Ether By-product Carboxylic acid as sod. salt Alkyl halide Ester

15. THANK YOU……..!!!!! 19-12-2019 15