Faculty : Science Department : Chemistry Course : BSC SEM : IV Unit : VI (organic synthesis via enolates) Paper : II Teacher : Dr M Karunakar Topic brief description: EAA, ME –synthesis and their chemical properties ORGANIC SYNTHESIS VIA ENOLATES: ACTIVE METHYLENE COMPOUNDS O O- -CH2-EWG -CH C CH C α- hydrogens always in acidic nature α Base can abstract these protane to form a carbanion Active methylene group Enolate (stable)

Enolate = anion of enol

Active methylene group Enolates are imp compds in org. synthesis for new C-C bond formation EWG EWG

Carbonyl β α Ester

α -Active methylene carban

Ethyl Aceto Acetate (EAA) Acetyl Aceto Ester (AAE) β- keto ester imp

β- keto ester

Base abstract proton from ketone methyl group carbanion which generated attack upon ester carbonyl carbon

H- transferred to O- Cyclo addition

Ketene 2 moles

EAA H

Enol form

Important

Enol of EAA

v

Important 2 moles Enol and keto form of EAA

Pyrogallol OR Important 1,2,3-trihydroxy benzene Enol of EAA Vii

Viii

iX α α

α

R-X Mono alkylation ------> dialkyl

In this case act as strong base, alkyl halide undergo elimination

Mono Acyl------ Di acyl substituted Key thing to remember always in conversion

important

EAA Easy to remember imp

H shifted

OH H Easy to remember Applications

1. Synthesis of methyl ketones. Example: 2-butanone., 3-methyl-2-pentanone 2. Synthesis of 1, 3 di ketone(β-diketone) example: 2,4-pentanone Ketonic 1,4 diketone (γ -diketone) example: 2,5-hexadione hydrolysis

3.Synthesis carboxylic acid , mono alkyl substituted carboxylic acid, di carboxylic acid [succinic acid, glutaric acid, Adipic acid} , highter carboxylic acid 4. Synthesis of γ-Keto acid Acidic hydrolysis 5. Synthesis of α,β-unsaturated acid eg :crotonic acid hydrolysis

Note: in ketonic hydrolysis(dilute Aqueos alkali /acid): prouct formed is methyl ketone derivative in acidic hydrolysis ( Concentrated ethanolic aloholic KOH sol)produce acetic acid and its derivatives Application of EAA R = alkyl gp 1. Synthesis of Methyl Ketone *Mainly depends on R-X

Q: how will you synthesize 2- butanone(methyl ethyl ketone) from EAA …………………………………… 2-pentanone( methyl propyl ketone) ………. important 2-

2- butanone or Methyl ethyl ketone

or 2,4-pentanone(1, 3 di ketone/ β-diketone)

1 2 3 4 5

1 Carbanion of EAA I-I imp

How can be synthesize butyric acid from EAA

imp How can be synthesize 2-methyl pentanoic acid from EAA Succnic acid

α chloro ester

H Di iodo alkane

2moles of EAA with 2 moles of base + di iodo alkane

important

Di iodo methane

Glutaric acid(5C) Adipic acid(6C)

Q: How can be syntheise Succinic acid, methyl substituted succinic acid, glutaric acid, adipic acid fromEAA β α γ

Synthesis of α,β-unsaturated acid/ crotonic acid

Acetaldehyde + EAA Or M E

-COOH COOC2H5

α-halogenation α-Alkylation

Mono alkyl

di alkyl

hydrolysis