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Substitution reactions of Carbonyl Compounds at the

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					                                                             Substitution Reactions of Carbonyl Compounds 23–1

Chaptterr 23:: Substtiittuttiion Reacttiions off Carrbonyll Compounds att tthe  Carrbon
Chap e 23 Subs u on Reac ons o Ca bony Compounds a he  Ca bon

 Kiinettiic verrsus ttherrmodynamiic enollattes ((23..4))
 K ne c ve sus he modynam c eno a es 23 4

               O
                             Kinetic enolate
                     R
                              The less substituted enolate
                              Favored by strong base, polar aprotic solvent, low temperature:
        kinetic enolate         LDA, THF, –78 oC
                O
                     R  Thermodynamic enolate
                            The more substituted enolate
                            Favored by strong base, protic solvent, higher temperature:
        therm odynam ic      NaOCH2CH3, CH3CH2OH, room temperature
              enolate

 Hallogenattiion att tthe  carrbon
 Ha ogena on a he  ca bon
[1] Halogenation in acid (23.7A)


                                                                  The reaction occurs via enol intermediates.
                                                                  Monosubstitution of X for H occurs on the 
                                                                   carbon.



[2] Halogenation in base (23.7B)

                                                                  The reaction occurs via enolate
                                                                   intermediates.
                                                                  Polysubstitution of X for H occurs on the 
                                                                   carbon.


[3] Halogenation of methyl ketones in base—The haloform reaction (23.7B)

                                                                  The reaction occurs with methyl ketones, and
                                                                   results in cleavage of a carbon–carbon 
                                                                   bond.
Chapter 23–2

 Allkyllattiion rreacttiions att tthe  carrbon
 A ky a on eac ons a he  ca bon
[1] Direct alkylation at the  carbon (23.8)

                                                          The reaction forms a new C–C bond to the
                                                            carbon.
                                                          LDA is a common base used to form an
                                                           intermediate enolate.
                                                          The alkylation in Step [2] follows an SN2
                                                           mechanism.

[2] Malonic ester synthesis (23.9)

                                                           The reaction is used to prepare 
                                                            substituted carboxylic acids with one or
                                                            two alkyl groups on the  carbon.
                                                           The alkylation in Step [2] follows an SN2
                                                            mechanism.




[3] Acetoacetic ester synthesis (23.10)

                                                                    The reaction is used to prepare 
                                                                     substituted ketones with one or
                                                                     two alkyl groups on the  carbon.
                                                                    The alkylation in Step [2] follows
                                                                     an SN2 mechanism.

				
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