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					                              Haloform Reaction
                                      base
                         -
                 CH3 + OH + X2                               CX3 + X- + H2O
            ║                                         ║
            O                                         O
       Methyl Ketone                              Α-Halo ketone


 • In the presence of a base methyl ketones undergo this reaction


       Halogenation of aldehydes and ketones

                                H+ or OH-
                       + X2                               + HX
           ║                                     ║
      H    O                                 X   O
      Ketone                                 Α-Halo ketone

• Aldehydes and ketones having α hydrogen react readily with halogens

• Rates of the reactions increase with the addition of acids or bases
                      Base Promoted Halogenation

                H          O                                O δ-                       OH




                ― ―
Step 1                         slow                    δ-           fast
         B:- + ―C―C                      B:H + C―C                             C―C         + B:-
                                                 Enolate anion
                      O-                     O                             X     O
                                  -                          fast
Step 2        C―C                ―C―C             + X-X                ―C―C           + X-




                                  ―




                                                                           ―
          Enolate anion

                       Acid Catalyzed Halogenation

                                         B:- H              +
                                                            OH                        OH
                                                 ― ―
                                 fast                           slow
Step 1   ―C―C         + H:B                  ―C―C                             C―C      + H:B
          ―




                                                                               Enol
                OH                                     X     O+H
                                      fast
Step 2    C―C         + X-X                      ―C―C                  + X-
                                                   ―




          X     O+H                               X         O
                                      fast
Step 3   ―C―C          + X-                  ―C―C                   + HX
                                                  ―
         ―
                                  Analysis
• Aldehydes and ketones react with 2,4-dinitrophenylhydrazene to form an insoluble
  yellow or red solid




• Aldehydes are characterized by their ease of oxidation, they give a positive test with
  Tollen`s reagent

• Aldehydes give positive Schiff test, by reacting with fuschin-aldehyde reagent to form
  magenta colour




• Aliphatic aldehydes and ketones having α-hydrogen react with Br2in CCl4 with the
  liberation of HBr
                                    Analysis
                Methyl ketones are characterized through idoform test

                              Idoform test

The methyl ketone is treated with iodine and sodium hydroxide a methyl ketone yields
a yellow precipitate of idoform (CH3I)

            R—C—CH3
              ║               R is H or alkyl or aryl
              O


        R—C—CH3 + 3NaOI                R—C—CI3 + 3NaOH
          ║                              ║
          O                              O

        R—C—CH3 + NaOH                    RCOO-Na+ + CHI3
          ║
          O                                                Yellow
                                                           precipitate

                                               (for details read section 18.1-18.15, 18.20-18.21 Chapter 18
                                               “Organic Chemistry”, Morrison and Boyd)
                                    Carboxylic Acid
                         O                  O                O
                  H     C             R     C           Ar   C
                              OH                 OH              OH


  Common name: generally derived from the source rather than chemical structure
                                    δ γ βα
                  Numbering         C-C-C-C-COOH

 IUPAC: suffix -oic acid is used            5 4 321
                                            C-C-C-C-COOH

 HCOOH                 CH3COOH       CH3(CH2)10COOH              CH2=CHCOOH
 Formic acid           Acetic acid   Lauric acid                 Acrylic acid
 Methanoic acid        Ethanoic acid Dodecanoic acid             Propeonoic acid
     COOH                    COOH
                                                CH3CH(OH)COOH
                                                Lactic acid
                             NO2                1-Hydroxypropionoic acid
Benzoic acid          p-Nitrobenzoic acid
                             Dicarboxylic Acids
   They are named as alkanedioc acids


   HOOCCH2COOH             HOOCCH2CH2COOH               HOOCCH2CH2CH(Cl)COOH
   Malonic acid            Succinic acid                α-Chloroglutaric acid
   Propanedioic acid       Butanedioic acid             2-Chloroptanedioic acid



                           Salt of carboxylic acid

Name of a salt of carboxylic acid : name of the cation followed by the name of the acid
ending with -ate

                  COONa
                               (CH3COO)2Ca          HCOONH4

            Sodium benzoate Calcium acetate         Ammonium formate
                            Physical properties

• Molecules are polar, can form hydrogen bonds



• Aliphatic acids: first four are miscible with water, five carbon acid is partly soluble,
  higher acids are insoluble

• Boiling points are very high, higher than alcohols because carboxylic molecules
  are held together by two hydrogen bonds

• The acids are soluble in less polar solvents like ether, alcohol, benzene etc
                                 Industrial source


Acetic acid has been prepared chiefly by
i) catalytic air oxidation of various hydrocarbons or acetaldehyde
                       O2                                     O2

      hydrocarbons              CH3COOH              CH3CHO                   CH3COOH
                     catalyst                                      catalyst




i)    Reaction between methanol and carbon monoxide in presence of iodine-rhodium
      catalyst
                                   Rh-I2
                CH3OH + CO                 CH3COOH


iii) Large amounts of acetic acid is produced as dilute aqueous solution called vinegar
      Ethyl alcohol is oxidized to yield acetic acid and the catalyst used are bacterial
      (Acetobacter) enzymes.


     Aliphatic carboxylic acids are prepared from animal and vegetable fats
                                         Preparation
Oxidation of Primary alcohol
                          KMnO4
      R-CH2OH                        R-COOH


                                         KMnO4
   CH3CH2CH(CH3)CH2OH                                 CH3CH2CH(CH3)COOH
        2-Methyl-1-butanol                                   2-Methylbutanoic acid




 Hydrolysis of nitriles

      R—                               Acid or base   R—COOH
            or            + H2O                          or                  + NH3
     Ar—                                              Ar—COOH




           CH2Cl   NaCN
                                        CH2CN         70% H2SO4
                                                                               CH2COOH
                                                                                         + NH4+

Benzyl chloride               Phenylacetonitrile                     Phenylacetic acid
     Carbonation of Grignard reagents


                 Mg                    CO2                       H+
     R—X                   R—MgX              R—COOMgX                  R—COOH
      or                                                                  or
     Ar—X                                                               Ar—COOH




                          Mg                          CO2   H+
C2H5C(CH3) (CH3)Cl             C2H5C(CH3) (CH3)MgCl              C2H5C(CH3) (CH3)COOH
2-Methyl-2-chlorobutane                                          2,2-Dimethylbutanoic acid
  tert Pentyl chloride                                             Ethyldimethyl acetic acid
                                        Reactions

  Substitution in alkyl group

 Halogenation of aliphatic acids ( Hell-Volhard-Zelinsky reaction)

The presence of small amount of phosphorus causes halogenation to take place exclusively
at the alpha position



        RCH2COOH + X2             P         RCHCOOH + HX                         X2 : Cl2, Br2
                                               X
                                            An α-halo acid


                    Cl2,P                   Cl2,P                     Cl2,P
     CH3COOH                ClCH2COOH               Cl2CHCOOH                 Cl3CCOOH
      Acetic acid            Chloroacetic            Dichloroacetic           Trichloroacetic
                                acid                    acid                      acid
                Substitution in alkyl or aryl group

  P + X2                    PX3                                                     X2 = Cl2, Br2

  RCH2COOH + PX3                          RCH2COX

   RCH2COX + X2                        RCHCOOH + HX
                                         │
                                         X

   Phosphorous converts a little of the acid into acid halide


                                             Reduction

                   LiAlH4
 R—COOH                      R—CH2OH
                             Primary alcohol


4R—COOH + 3 LiAlH4                           (RCH2O)4AlLi + 4H2 + 2LiAlO2

                                      H2O/H2SO4
                                                                4R—CH2OH + Al2(SO4)3 + Li2SO4
                                 Carboxylic acid derivatives
The carboxylic acid derivatives are a family of closely related functional groups containing C=O
         O                                                         O
          ║                                                        ║
         C                 Acyl or acid chloride                   C
     R           Cl                                        R           NH2
          O
             ║
                                                                   O
          C           R’                                           ║
                 O               Ester
     R                                                             C                  Amide
                                                           R           NHR’
         O            O
         ║            ║
         C            C
    R            O         R’    Acid anhydride                O
                                                               ║
                                                               C
                                                       R           NR’R”
          R—C≡N                  Nitrile
                         Conversion into functional derivatives
                 O                     O
                                                              Z: Cl2, OR`, NH2
        R       C                R     C
                      OH                    Z


    i) Conversion into esters

•The names are derived from the names of the alcohol ( ending with –yl) and the acid ( ending with –ate or -oate)

• The portion of the name derived from the alcohol comes first



          (A)       O                                     O
                                           H+
            R     C          + R`OH               R      C              + H2O
                        OH                                    OR`
                                                   An ester
                        COOH                             COOCH3
                                            H+
                             + CH3OH                                + H2O

                Benzoic acid    Methanol              Methyl benzoate
                   Conversion into functional derivatives

    (B)       O                             O                                O
                           SOCl2                       R`OH
    R     C                            R   C                         R     C
                  OH                              Cl                             OR`
                                       An acid                       An ester
                                       chloride


                       SOCl2                               C2H2OH
(CH3)3CCOOH                        (CH3)3CCOCl                           (CH3)3CCOOC2H5
 Trimethylacetic                                                           Ethyl trimethyl
     acid                                                                     acetate


ii) Conversion into acid chlorides

          O                    SOCl2                          O
    R     C            +       PCl3                    R      C
                  OH           PCl5                                 Cl


Acyl chlorides are the most reactive of the acid derivatives
             Conversion into functional derivatives

iii) Conversion into acid anhydrides



RCOOH + R’COCl +                          RCOOCOR’+         Cl-
                                                        +
                                                       H
        Acyl chloride   Pyridine




iv) Conversion into nitriles

             P4O10 or (CH3CO)2O
  RCONH2                          R—C≡N + H3PO4 or CH3CO2H
                    heat
                    (-H2O)


                                                      (CH3CO)2O : Acetic anhydride
                                                           P4O10 : Phosphorus pentoxide
                Conversion into functional derivatives
 v) Conversion into amides

          O                                 O                          O
                     SOCl2                           NH3
    R    C                           R    C                       R    C
              OH                                Cl                           NH2
                                     An acid                      An amide
                                     chloride




                             SOCl2                               NH3
   C6H5CH2COOH                           C6H5CH2COCl                       C6H5CH2CONH2

      Phenylacetic acid                  Phenylacetyl chloride               Phenylacetamide




Alkyl groups on the nitrogen atoms of amides are named by adding preface N or NN

 CH3COONH2                                  CH3COON(CH2) (CH2)                     CH3COONH(C2H5)
 Acetamide or ethaneamide                   N,N-Dimethylacetamide                  N-Ethylacetamide
                      Acidity of Carboxylic acids

RCOOH + H2O             RCOO- + H3O+
                                                Acetic acid   Water                 Hydronium
                                                                      Acetate
                                                                       ion           ion




                                                                      HA        A− + H+
                                                                      acid      Conjugate
Acid strength is characterized in terms of acidity constant Ka                   base




 Relative acidities
                 RCOOH >H2O > ROH > HC≡CH > NH3 > RH

 Relative basicities
      RCOOH < OH- < OR- < HC≡C- < NH2- < R-


Certain substituted acids are stronger or weaker than a typical acid like acetic acid
                       Acidity of Carboxylic acids

       Carboxylic acids have greater acidity than alcohols


                  Acetic acid acting as an acid
        CH3COOH + H2O               RCOO-      +       H3O+

        Acetic acid                Acetate ion     Hydronium ion

                       Ethanol acting as an acid
        CH3CH2OH + H2O              CH3CH2O-       +     H3O+
           Ethanol                 Ethoxide ion Hydronium ion


• Focusing on the relative stability of the conjugate bases: greater stabilization of
 the negative charge takes place in the carboxylate ion in comparison to alkoxide ion

• This is due to i) delocalization of charge ii) an inductive electron withdrawing effect
                  Acidity of Carboxylic acids




                                        Carboxylate ions
                                      Resonance stabilized

      • Negative charge is distributed to both oxygen atoms

      • No resonance structure possible for alkoxide ion

                     Electrostatic potential




Acetic acid (ethanoic acid)
                                             Acetate ion (ethanoate ion)

             The more red an area is, the higher the electron density
             The more blue an area is, the lower the electron density.
                                            Acetate ion (ethanoate ion)
       Acetic acid (ethanoic acid)


• There is low electron density (blue) on H atom of the -CO2H group alcohol.
• The H atom of the RCO2H is acidic (pKa ~ 5).
• There is high electron density (red) on both O atoms in the acetate ion
  of the -CO2- group alcohol, i.e. resonance and basic or nucleophilic behaviour




                                                           Ethoxide anion




                                                             Acetate anion
                              Inductive effect



• The electron cloud in a σ-bond between two unlike atoms is not uniform
and is slightly displaced towards the more electronegative of the two atoms.

• A permanent state of bond polarization occurs where more electronegative atom
  has (δ-) and the other atom has a (δ+).

• If the electronegative atom is then joined to a chain of atoms, usually carbon, the
  positive charge is relayed to the other atoms in the chain.
           Inductive effect

• Electron withdrawing groups such as halo group( -NO2, -CN etc)
 increase the acidity

• They stabilize the carboxylate anion by dispersal of
the negative charge and increase the strength of the acid


• Electron releasing groups (like alkyl groups) cause
 concentration of negative charge.

• They destabilize the carboxylate anion and decrease the strength of
  the acid.




           O
          <




    CH3    C                 CH3―CH2―O―H
                                      <
               < O―H
                  <
         Acetic acid               Ethanol
       (stronger acid)           (weaker acid)
                                    Amides
Preparation
               O                     O                          O
                        SOCl2                   NH3
        R    C                  R   C                     R    C
                   OH                      Cl                        NH2
                                An acid                   An amide
                                chloride




Ammonolysis of acid anhydrides


  (CH3CO)2O + 2NH3              CH3CONH2 + CH3COO-NH4+

   Acetic anhydride             Acetamide             Ammonium acetate
                      Reactions of Amides
1. Hydrolysis

2. Conversion into imides

3. Hofmann degradation of amides

                                 Hydrolysis


                                          O
                            H+
                                    R    C         + NH4+
                                              OH
    O
R   C         + H2O
        NH2

                             OH-
                                        R—COO- + NH3
    Acidic conditions
                                                              OH                              +
                                       OH

R    C
      O
                    H+
                           R       C
                                        NH2
                                            }ө    H2O         │
                                                        R—C—OH2+
                                                              │
                                                                                       R    C
                                                                                              OH

                                                                                                   OH
                                                                                                         + NH3
             NH2
                               Protonated amide               NH2                      Protonated
                                                                                       Carboxylic acid




                                                                                  O
                                                                          R       C               + NH4+
                                                                                       OH



    Alkaline conditions

                                          O-                         O-
               O
                         OH-                │           OH-          │
         R     C                       R—C—OH                      R—C—O-         Dianion looses a molecule of
                                                                                  ammonia
                   NH2                      │                        │            A proton is transferred from water
                                          NH2            OH―H        NH2
                                                                              O
                                                                     R     C          + NH3 + OH-
                                                                                  O-
                              Conversion into imides


Imide is a functional group containing two carbonyl groups
 bound to nitrogen




Common imides are prepared by heating dicarboxylic acids or their anhydrides and
ammonia or primary amines



                       (RCO)2O + R'NH2 → (RCO)2NR' + H2O
               Hofmann degradation of amides
                                       OBr -
       R—CONH2 or Ar—CONH2                     R—NH2 or Ar—NH2 + CO3 2-
                                                    Primary amine



                                       H2O
      R—CONH2 + Br2 + 4NaOH                    RNH2 + 2NaBr + Na2CO3 + 2 H2O



Proposed mechanism
                     O        Halogenation of amides
                                                           O
 1.            R    C    ..
                         NH2 + OBr
                                  -
                                                 R      C          ..    + OH-
                                                                N—Br
                                                                │
                O
                                                                H
                                                       O
 2.        R   C    ..
                    N—Br + OH-                  R      C       ..       +H2O
                    │                                          N—Br
                                                               ..
                    H                                          -
               O
                                                       O
3.        R   C     ..
                    N—Br                         R    C    .. + Br-



4.              R
                    ..
                    -
                         O
                         C   ..
                             N
                                                       ..
                                                           N
                                                           ..


                                                     R—N=C=O
                                                                      }   Simultaneous



                             ..
                                                     Isocyanate
                         Hydrolysis of isocyanates

       ..                           H2O         ..
5.   R—N=C=O + 2OH-                           R—NH2 + CO3 2-




• Hofmann rearrangement involves a 1,2-shift

• A group migrates to the electron defecient nitrogen while in carbocation
  rearrangement the group migrates to electron – deficient carbon

• Special feature is the product contains one less carbon than the starting material
                        Lactams




    A β-lactam      A γ-lactam        A δ-lactam


• Cyclic amides are called lactams

• Penicillin antibiotics contain a β-lactam ring


                                          R = C6H5CH2 —   Penicillin G
                                          R = C6H5CH—     Ampicillin
                                                   │
                                                  NH2
                                          R = C6H5OCH2— Penicillin V
                                    Lactones

• Carboxylic acids whose molecules have a OH group on a γ or δ carbon
   undergo intramolecular esterification to give cyclic esters known as
  γ- or δ- lactones                                              δ γ βα
                                                               R- C-C-C-C-COOH
                                                                  ‫׀‬
                                                                  OH
• The reaction is acid catalysed                               A δ-hydroxy acid

• Many lactones occur in nature like vitamin C.

• Some antibiotics such as erythromycin and nonactin are lactones with large rings




                           Vitamin C
                        ( ascorbic acid)
Intramolecular esterification
                                    OH                      OH
                                                              O―H
  δ γ βα                              OH                       +
R- C-C-C-C-COH                       OH                      O H
   ‫׀‬       ║                         +
   OH      O
                   H―A              R                       R
A δ-hydroxy acid

           +
           OH                           O

        O       + H2 O               O        + H3O+ + A-

       R                            R
                                A δ-lactone
                             Esters
 Preparation
Esters from acyl chloride

                               -HCl
              RCOCl + R’OH            RCOOR




Esters from carboxylic acid anhydride

              (RCO)2O + R’OH          RCOOR’ + RCOOH
                                               Esters
   Preparation
Esterification
                           O                                 O
                                                HA
                   R      C         + R’―OH          R      C             + H2O
                               OH                                   OR’



                                                HA
                 CH3COOH + CH3CH2OH                  CH3COOCH2CH3 + H2O
                 Acetic acid         Ethanol                Ethyl acetate


       • Acid catalyzed esterification are called Fischer esterifications



                   O                                             O
                                      18        HA
         C6H5     C            + CH3―O―H             C6H5       C    18      + H2O
                          OH                                          OCH3
           Benzoic acid
                             Acid catalyzed esterification
                     O                                 O
                                            HA
             R       C            + R’―OH          R   C         + H2O
                             OH                            OR’


      Mechanisms
      • The forward reaction is acid catalysed esterification of the acid
      • The reverse reaction is acid catalyzed hydrolysis of an ester
 Acid catalyzed ester hydrolysis

                         O                                            O
                                            H3O+
                 R       C          + H2O          R’―OH + R         C
                              OR’                                           OH




•The amount of esters formed is controlled by the position of the equilibrium
• If esterification of acid is required then excess of the alcohol is used and if possible
 H2O is removed as it is formed
• If ester hydrolysis is required then excess of H2O is used
                     Acid catalyzed esterification
Reactivity in esterification
     CH3OH > 1° > 2° > 3°
     HCOOH > CH3COOH > RCH2COOH > R2CHCOOH > R3CCOOH


                 O                                     O
                                     HA
            R   C         + R’―OH                R    C           + H2O
                     OH                                     OR’



                                          H                              HHO
                                               +
    O                                         O                        │ |+
R   C           H―O+―H               R       C
                                                           + R’―OH
                                                                     R—C—O―R’
        O―H                                          O―H                   │
                                                           - R’―OH
                    H                                                      O―H
                                 H―O
                                                 H
                                                  +                        HO
            O                        H           O
                             +H3O+                                             │
        R   C                            R       C                        R—C—O―R’
                O―R’         -H3O+                    O―R’                     │+
                                         Protonated ester                 H―O―H
                  Base promoted ester hydrolysis
                                 Saponification

                   O                                              O
                                         H2O
              R   C           + NaOH             R’―OH + R        C
                       OR’                                         O-Na+
                                                        Sodium carboxylate



Mechanism involves a nucleophilic addition-elimination reaction at the acyl carbon


     O                              O-
                                    │                   O
R    C          O-―H   slow
                                R—C—OH              R   C
         O―R’                        │                       O―H       + -O―R’
                                    O―R’
                               An alkoxide ion

                                                              O
                                                         R    C            + H―O―R’
                                                                      O-

				
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