Reactions of Aldehydes and Ketones PDF

Chapter 12 Reactions of Aldehydes and Ketones More Reactions of...

Chapter 12 Reactions of Aldehydes and Ketones More Reactions of Carboxylic Acid Derivatives Paula Yurkanis Bruice University of California, Santa Barbara © 2016 Pearson Education, Inc. This chapter continues the discussion of the families of compounds in Group IV © 2016 Pearson Education, Inc.  Aldehydes and Ketones Carbonyl compounds with hydrogen and alkyl groups Formaldehyde: two hydrogens Aldehyde: a hydrogen and an alkyl group Ketone: two alkyl groups © 2016 Pearson Education, Inc.  Some Aldehydes and Ketones found in Nature © 2016 Pearson Education, Inc.  Biologically Important Ketones © 2016 Pearson Education, Inc.  Naming Aldehydes © 2016 Pearson Education, Inc.  Naming Ketones the carbonyl is assumed to be at the 1-position in cyclic ketones © 2016 Pearson Education, Inc.  Aldehydes and Ketones are attacked by Nucleophiles The partial positive charge on the carbonyl carbon causes it to be attacked by nucleophiles: © 2016 Pearson Education, Inc.  Aldehydes are more reactive than Ketones Electronic Reason: An aldehyde has a greater partial positive charge on its carbonyl carbon than does a ketone because a hydrogen is more electron withdrawing than an an alkyl group. © 2016 Pearson Education, Inc.  Aldehydes are more reactive than Ketones Steric Reason: The carbonyl carbon of an aldehyde is more accessible to the nucleophile. ketones with larger R groups are even less reactive © 2016 Pearson Education, Inc.  Aldehydes and Ketones are moderately reactive Carbonyl Compounds Aldehydes and ketones are less reactive than acyl halides and acid anhydrides. Aldehydes and ketones are more reactive than esters, carboxylic acids, amides, and carboxylate ions. © 2016 Pearson Education, Inc.  Aldehydes and Ketones react differently than do Carboxylic Acid Derivatives In a carboxylic acid derivative, Y– can leave. Nucleophilic acyl substitution is observed. In aldehydes and ketones, neither alkyl nor hydride groups can leave. Nucleophilic addition is observed. © 2016 Pearson Education, Inc.  Organometallic Compounds © 2016 Pearson Education, Inc.  Organometallic Compounds: Grignard Reagents Grignard reagents react as carbanions. They are strong bases and react vigorously with water. © 2016 Pearson Education, Inc.  Mechanism for the reaction of an Aldehyde or a Ketone with a Grignard Reagent Grignard reagents react with aldehydes, ketones, and carboxylic acid derivatives. Addition of dilute acid breaks up the complex. © 2016 Pearson Education, Inc.  Grignard Reagents are used to prepare alcohols © 2016 Pearson Education, Inc.  Grignard Reagents form Carboxylic Acids by reaction with Carbon Dioxide The carboxylic acid has one more carbon than the Grignard reagent. © 2016 Pearson Education, Inc.  Examples of reactions with Grignard Reagents The numbers above and below the arrows mean the acid is not added until the Grignard reagent has reacted with the carbonyl compound. The product of this reaction is a racemic mixture because a compound with an asymmetric center was created from a reactant without an asymmetric center. © 2016 Pearson Education, Inc.  Esters react with Grignard Reagents to form alcohols © 2016 Pearson Education, Inc.  Acyl Chlorides react with Grignard Reagents to form alcohols © 2016 Pearson Education, Inc.  Reactions of Aldehydes and Ketones with Hydride Ion © 2016 Pearson Education, Inc.  Strong Bases form Direct Addition products © 2016 Pearson Education, Inc.  Reactions of Acyl Chlorides with Hydride Ion © 2016 Pearson Education, Inc.  Reaction of an Ester with Hydride Ion © 2016 Pearson Education, Inc.  Mechanism for the reaction of an Ester with Hydride Ion © 2016 Pearson Education, Inc.  Reactions of Carboxylic Acids with Hydride Ion © 2016 Pearson Education, Inc.  The Reactions of Amides with Hydride Ion © 2016 Pearson Education, Inc.  Reaction of Aldehydes and Ketones with Cyanide Ion © 2016 Pearson Education, Inc.  Reactions of Cyanohydrins Hydrolysis to form an α-hydroxycarboxylic acid. Reduction to a primary amine with an OH group on the β-carbon. © 2016 Pearson Education, Inc.  Aldehydes and Ketones form Imines with Primary Amines © 2016 Pearson Education, Inc.  Imine Hydrolysis is Irreversible The amine is protonated in the acidic solution, so it is unable to react with the carbonyl compound. © 2016 Pearson Education, Inc.  Reductive Amination The unstable imine formed from ammonia is hydrogenated to an amine. © 2016 Pearson Education, Inc.  The reaction of an Aldehyde or Ketone with an alcohol © 2016 Pearson Education, Inc.  Acid-Catalyzed Hydrolysis of an Acetal © 2016 Pearson Education, Inc.