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Chapter 11: ALDEHYDES-KETONES

Common names: carboxylic acid - “aldehyde” is substituted for “ic acid”. Lower priority than ester - “oxo” group. Derived names: alkyls + ketone. IUPAC names: hydrocarbon + one. | ORGANIC CHEMISTRY Dr Nam T. S. Phan Faculty of Chemical Engineering HCMC University of Technology Office: room 211, B2 Building Phone: 8647256 ext. 5681 Email: ptsnam@hcmut.edu.vn Chapter 11: ALDEHYDES-KETONES C=O C=C SP2 carbon NOMENCLATURE OF ALDEHYDES IUPAC names: hydrocarbon + al Common names: carboxylic acid “aldehyde” is substituted for “ic acid” Lower priority than ester “oxo” group NOMENCLATURE OF KETONES Derived names: alkyls + ketone IUPAC names: hydrocarbon + one PREPARATION OF ALDEHYDES & KETONES Aldehydes & ketones from alkenes In the presence of an oxidizing agent, the products will be ketones / carboxylic acids Aldehydes & ketones from alkynes Markovnikov’s rule Anti-Markovnikov Aldehydes & ketones from alcohols Can NOT be isolated PCC: pyridinium chlorochromate Aldehydes from esters, acyl chlorides Note: LiAlH4 alcohols Preparation of aromatic ketones Gatterman-Koch synthesis of benzaldehyde Can NOT be prepared & isolated REACTIONS OF ALDEHYDES & KETONES I The partial positive carbon can be attacked by nucleophiles The addition of nucleophiles to the carbon atom of the carbonyl group in nucleophilic addition reactions Reactions with Grignard reagents Only for the reaction of HCHO Numbers 1 & 2 are used to indicate that the acid is not added until the reaction with the Grignard reagent is complete Reactions with acetylide ions Weak acid, will NOT react with the triple bond Reactions with hydrogen cyanide Converted back to carbonyl in basic solutions Nitriles carboxylic acids Nitriles amines Reactions with primary amines Reaction mechanism: Reactions with secondary amines Reaction mechanism: Reactions with water Reactions with alcohols Reaction mechanism: Reactions with sulfur nucleophiles Reduction reactions – with hydride ion NaBH4 can reduce aldehyde, ketones, acyl chlorides, but NOT alkenes & alkynes LiAlH4 is a stronger reducing agent than NaBH4, but NOT safe to use for aldehydes & ketones Reduction reactions to hydrocarbons NOTE: Oxidation reactions Aldehydes are generally easier to oxidize than primary alcohols Tollens reagent Too weak to oxidize an alcohol or any other functional groups Should be used when oxidizing aldehydes containing double bond REACTIONS OF ALDEHYDES & KETONES II – REATIONS AT a-C Aldol additions Reaction mechanism: Aldol additions occur more slowly with ketones Nucleophilic additions Aldol condensations = Additions + dehydrations Easier to dehyrate than other alcohols because the double bond is conjugated with the carbonyl group Aldol condensations sometimes occur under the aldol addition conditions without additional heating NOT isolated Mixed / crossed Aldol additions 4 addition products NOT useful Very strong base Halogenations at a-C Only 1 hydrogen is replaced in acidic solution The haloform reactions Only for methyl ketones