Chemistry Reactions PDF

51 CHEMISTRY REACTIONS You Can't Afford to MISS! 1. Aldol condensation 5. Clemmensen Reduction Two molecules of...

51 CHEMISTRY REACTIONS You Can't Afford to MISS! 1. Aldol condensation 5. Clemmensen Reduction Two molecules of aldehydes or ketones having a-hydrogen In this method, aldehydes and ketones are reduced with condense together in presence of base [dil. NaOH, Na2CO3, Zn - Hg amalgam and conc. HCl. Ba(OH)2] to form b-hydroxyaldehyde or b-hydroxyketone Zn – Hg/HCl CH3CHO + 4H CH3 – CH3 + H2O respectively which are collectively known as aldol. Zn – Hg/HCl O CH3COCH3 + 4H CH3 – CH2 – CH3 + H2O  dil. NaOH CH3 C H+H CH2 CHO 6. Corey-House synthesis Acetaldehyde In this reaction, an alkyl halide (1°, 2° or 3°) is first converted OH into lithium dialkyl copper and then reacted with another CH3 CH CH2 CHO alkyl halide (preferably 1°) to give corresponding alkane. 3-Hydroxybutanal Li CuI (-Hydroxybutanal or aldol) 2R – X 2R – Li R2CuLi + LiI Ether Alkyl halide Lithium dialkyl 2. Birch Reduction cuprate In case of disubstituted alkynes reduction with sodium in liq. ammonia gives trans-alkene predominantly. This type 7. Cope elimination of reduction is known as Birch-reduction. Tertiary amines are not oxidised by KMnO4. Their oxidation is carried out with Caro’s acid or ozone or hydrogen peroxide to form amine oxide. 3. Beckmann Rearrangement Oximes on treatment with catalyst such as conc. H2SO4, Tertiary amine oxide containing a -hydrogen atom forms β SOCl2, PCl5, etc. undergo rearrangement to form substituted an alkene. This reaction is called Cope reaction or Cope amides. Reaction is known as ‘Beckmann rearrangement’. elimination. 4. Balz-Schiemann’s reaction This is the method to prepare fluorobenzene from benzene 8. Carbylamine Reaction diazonium salt by first converting it to benzene diazonium Primary amines both aliphatic and aromatic on heating with tetrafluoroborate. chloroform and alcoholic solution of potassium hydroxide + + form isocyanides or carbylamines which have an extremely N NCl– – N NBF 4 F unpleasant odour. HBF 4 ∆ –HCl + N2 + BF 3 9. Claisen—Schmidt reactions CH2 It is a base catalyzed crossed aldol condensation in which CH2 CH CH2 CH an aromatic aldehyde condenses with aliphatic aldehyde  CH2 CH + or ketone. It is also known as simply Claisen reaction. CH2 CH CH2 O O CH2 CH2 dil. NaOH C6H5 C H + CH 3 C CH3 Buta-1, 3-diene Ethylene Cyclohexene Benzaldehyde Acetone 14. Etard Reaction OH O Aromatic hydrocarbons on treatment with mild oxidising C6H5 CH CH2 C CH3 agents such as chromyl chloride CrO2Cl2 yield aldehydes. CH3 CHO O CrO2Cl2 C6H5 – CHO C6H5 CH CH C CH3 + H2O dil. NaOH Toluene Benzaldehyde Benzylidene acetone O 15. Frankland Reaction C6H5 CH CH C CH CH C 6H5 This is similar to Wurtz reaction with the difference that Dibenzal acetone instead of sodium, zinc is used here in inert solvent. R – X + Zn + X – R R – R + ZnX2 10. Cannizzaro Reaction It is a self oxidation-reduction reaction in which Dialkyl zinc compounds react with tertiary alkyl halides aldehydes that do not have any a-hydrogen atom undergo to give hydrocarbons with quaternary carbon atoms only. disproportionation reaction (i.e. self-redox reaction) in the (CH3)2Zn + (CH3)3CCl (CH3)4C + CH3ZnCl presence of 50% aqueous or ethanolic solution of alkali in 16. Finkelstein reaction which one of the molecule being reduced to alcohol and Iodoalkanes can be conveniently prepared by treating alkyl other being oxidised to the salt of corresponding acid. chloride or bromides with sodium iodide in acetone or 2HCHO + NaOH CH3OH + HCOONa methanol. This is known as Finkelstein reaction. Formaldehyde 50% Methanol Sodium formate Acetone CH3Cl + NaI CH3I + NaCl Reduction Oxidation 17. Friedel-Crafts Reaction Simple aromatic hydrocarbons can be converted to 11. Claisen condensation substituted hydrocarbons by reaction with alkyl halide in Esters containing a-hydrogen atoms undergo self presence of Lewis acid like AlCl3 or FeCl3, etc. -condensation in presence of strong base like sodium ethoxide to give b-keto esters. 18. Fries Rearrangement Phenyl esters on heating with anhydrous AlCl3 undergo Fries rearrangement in which acyl group (acetyl, benzoyl, etc.) migrates from phenolic oxygen to ortho or para position of 12. Curtius rearrangement benzene ring resulting in the formation of mixture of o- and In this method an acyl azide (obtained from reaction of p-hydroxyketone. carboxylic acid chloride and sodium azide), on heating OCOC6H5 OH in acidic or alkaline medium yields primary amine. The OH COC6H5 reaction involves an intermediate isocyanate which is Anhyd. AlCl3 hydrolysed to give primary amine. ∆ + Phenyl benzoate o-Hydroxy benzophenone COC6H5 p-Hydroxy benzophenone 19. Gabriel phthalimide synthesis 13. Diels-Alder Reaction Phthalimide on reaction with caustic potash forms potassium This reaction involves the addition of a conjugated phthalimide which on treatment with alkyl halide gives diene (4p-electron system) to an unsaturated compound N-alkyl phthalimide. This N-alkyl phthalimide on hydrolysis called dienophile (2p-electron system) to yield a cyclic with hydrochloric acid yields primary amines. system.  25. Hell-Volhard-Zelinsky reaction (HVZ reaction - Halogenation) N Aliphatic carboxylic acids on reaction with bromine or chlorine in presence of small amount of red phosphorous 20. Gattermann-Koch reaction produce a-haloacids. Benzene on reaction with a mixture of CO + HCl in presence of AlCl3 forms benzaldehyde. CHO AlCl3 + CO + HCl + HCl 21. Hydroboration-Oxidation Alkenes react with diborane to give alkyl boranes which on oxidation with hydrogen peroxide in presence of hydroxide forms alcohol. B 2H6 26. Hofmann-bromamide reaction R – CH CH2 R – CH2 – CH2 – BH2 Primary amides on reaction with bromine in presence of RCH CH2 an alkali yield primary amine with one carbon atom less than the parent amide. RCH CH2 (RCH2CH2)3B (RCH2CH2)2BH Trialkyl borane 3H2O2/OH– 3RCH2CH2 – OH + B(OH)3 Alcohol Boric acid 27. Knoevenagel reaction 22. Hunsdiecker reaction In this reaction, aldehydes and ketones condense with This reaction involves the treatment of silver salt of carboxylic compounds containing active methylene group like acid (e.g. acid with bromine in refluxing CCl4 to yield alkyl bromide malonic acid), ester (e.g. acetoacetic ester, malonic ester) with one carbon atom less than the original acid used. or nitrile, etc. leading to the formation of a, b-unsaturated CCl4 CH3CH2COOAg + Br2 Reflux CH3CH2 compound. 2 CH3 COOH (i) Pyridine/ 23. Hofmann Mustard oil Reaction C O + H2C H COOH (ii) H3O+ This reaction is given by aliphatic and aromatic primary Acetaldehyde Malonic acid amines only, hence it can be used as a test for primary amines. H3C – CH CH – COOH + CO2 + H2O Crotonic acid 28. Kolbe’s Electrolytic Method In this method, a concentrated solution of sodium or potassium salt of a carboxylic acid is electrolysed to give higher alkanes. Alkyl isothiocyanates have a characteristic unpleasant smell RCOOK + RCOOK Electrolysis of mustard oil. Hence, this reaction is known as Hofmann R — R + 2CO2 + H2 + 2KOH mustard oil reaction. 29. Leuckart reaction 24. Haloform reaction An aldehyde or ketone on heating with ammonium formate Methyl ketones on oxidation with sodium hypohalite or ammonium formamide, undergoes reductive amination (NaOX i.e. NaOH + X2) yield haloform along with sodium to form formyl derivative of primary amine which on salt of carboxylic acid with one carbon atom less than the hydrolysis either with acid or base yields primary amine. starting ketone.  O H2 CH C CH3 COONa C6H5 CH O+ O Benzaldehyde CH3 C –H2 O, D O Acetic anhydride O 30 Meerwein-Ponndorf-Verley reduction H2 O C6H5 CH CH C In this reaction, ketones are reduced to secondary alcohols Hydrolysis O on heating with iso-propyl alcohol in presence of catalyst CH3 C aluminium isopropoxide. In the reaction iso-propyl alcohol O gets oxidised to acetone. R CH3 [(CH3)2CHO]3Al CH3COOH + C6H5 CH CH COOH C O+ CH OH Acetic acid Cinnamic acid R CH3 Ketone Iso -propyl alcohol 35. Reimer-Tiemann reaction R CH3 Concentrated solution of CHCl3 reacts with phenol in CH OH + C O presence of alc. KOH to yield salicylaldehyde. R CH3 OH OH 2° alcohol Acetone CHO 31. Ozonolysis KOH (alc.) + CHCl3 Ozone on passing through a solution of alkenes in an inert dil. HCl solvent like CCl4 or CHCl3 at low temperature oxidises the Salicylaldehyde alkene to a cyclic product called ozonide which is unstable 36. Reformatsky reaction and on reduction with reducing agents like zinc and water It involves the reaction of zinc and a-halogenated ester, or hydrogen in presence of palladium gives aldehydes and/ which add to carbonyl compound to yield b-hydroxy ester. or ketone depending upon structure of alkene, i.e., C O part of the alkene gets converted to C O.  Zn O CH3 – C – CH3 + BrCH2COOC2 H5 Zn/H2O C C + O3 C C 2 C O –ZnO O OH OZnBr O H2O/H+ CH3 – C – CH2COOC2H5 CH3 – C – CH2COOC2H5 32. Oppenauer’s oxidation In this reaction, secondary alcohols are oxidised to ketones CH3 CH3 in a good yield using aluminium tert- butoxide in excess Ethyl-3-hydroxy-3-methyl butanoate of acetone. O 37. Rosenmund’s reduction R Acid chlorides are reduced to aldehydes by palladised barium CH OH + CH3 C CH3 R [(CH3)3CO]3Al sulphate partially poisoned with sulphur or quinoline. 2° alcohol Acetone (—COCl is reduced to —CHO) OH R C O + CH3 CH CH3 R Ketone Iso- propyl alcohol 38. Sandmeyer’s reaction 33. Oxo process In this reaction Diazonium salttract with CuX/HX and In this process, an alkene on heating with water gas respective halide is formed. (CO + H2) under pressure in the presence of catalyst cobalt Cl carbonyl hydride [CoH(CO)4] yields aldehyde. + N NCl– CuCl/HCl [CoH(CO)4] + N2 C C + CO + H2 C C CHO 100°C, Pressure 34. Perkin condensation Br It is a condensation reaction in which an aromatic aldehyde CuBr/HBr condenses with aliphatic acid anhydride in presence of + N2 sodium salt of same acid to give a condensate which upon hydrolysis yields a,b-unsaturated acid. 39. Schotten-Baumann reaction  OH O 45. Williamson’s synthesis Metal alkoxides on treatment with alkyl halides yield ethers. Cl C NaOH The reaction is known as Williamson’s synthesis. + O O C + HCl 46. Wacker process Phenyl benzoate Alkenes are directly oxidised by the catalyst palladium Benzoylation of alcohols or phenols in presence of NaOH chloride-cupric chloride (PdCl2-CuCl2) in the presence is called Schotten-Baumann reaction. of air or oxygen. 1 PdCl2-CuCl2 40. Stephen’s reduction CH2 CH2 + O 2 CH3 CHO 2 air or O2 Ethene Ethanal In this reaction cyanides are reduced to aldehyde in pressure of SnCl2/H4 followed by hydrolysis. 47. Wolff-Kishner Reduction H SnCl2 + HCl + H2O In this method, aldehydes and ketones are reduced with R C N Ether R C NH2Cl¯ hydrazine (NH2–NH2) and KOH. Aldimine O CH3 hydrochloride NH2 – NH2 RCHO + NH4Cl R – C – CH3 R –C NNH2 Aldehyde KOH/glycol 41. Schmidt’s reaction or C2H5ONa Carboxylic acids on heating with hydrazoic acid (HN3) at 50-55°C in presence of conc. H2SO4 produce primary amines R–CH2– CH3 + N 2 with one carbon atom less than original carboxylic acid. 48. Wurtz Reaction In this reaction, ether solution of alkyl halide is treated with sodium to form alkane. Dry ether 42. Sabatier - Senderen’s reaction R –X + 2Na + X – R R– R + 2Na X The method involves the reduction of unsaturated hydrocarbons (alkenes and alkynes) with nickel catalyst. 49. Wittig Reaction Raney nickel is more reactive than supported nickel catalyst. It is an important reaction to change a carbonyl compound Ni RCH CH2 + H2 RCH2CH3 into alkene by treating carbonyl compound with a ylide. 200-300°C Alkene Alkane Ylides are the species which in their ground state have 43. Tischenko reaction negative carbon adjacent to a positive heteroatom like P, + – All aldehydes (with or without a-hydrogen atom) in As, Sb, etc. For example, phosphorus ylide, Ph3P – CHR. + – THF or presence of aluminium ethoxide, [Al(OC2H5)3] undergo RCH O + Ph3P – CHR dry ether RCH CHR + Ph 3PO simultaneous oxidation (to carboxylic acid) and reduction (to alcohol) to form an ester. 50. Wohler’s reaction Al(OC2H5)3 Acetylene is prepared by action of water on calcium carbide. 2RCHO RCH2OH + RCOOH This method is used for laboratory as well as industrial Aldehyde Alcohol Carboxylic acid preparation. CaC2 + 2H2O CH CH + Ca(OH)2 RCOOCH2 R Ester 51. Wurtz-Fittig Reaction 44. Ullmann Reaction When a mixture of aryl halide and alkyl halide reacts Aryl halides especially iodides on reaction with copper with sodium metal in dry ether, substituted arenes are metal yield biphenyls. obtained. Sealed Dry tube ether I + 2Cu + I + 2CuI Cl + 2Na + Cl CH3 CH3 + 2NaCl Biphenyl