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  Halogenation in acid (23.7A) The reaction occurs via enol intermediates. Monosubstitution of X for H occurs on the carbon.  Halogenation in base (23.7B) The reaction occurs via enolate intermediates. Polysubstitution of X for H occurs on the carbon.  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  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  follows an SN2 mechanism.  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  follows an SN2 mechanism.  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  follows an SN2 mechanism.
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