Carbonyl Compounds

• Carbonyl compounds

  are chemicals that include a carbon-oxygen double bond.
• The polarity of the carbonyl group is stronger than that of molecules having carbon atoms connected to oxygen through a single bond.
• Physical Properties

  • Aldehydes and ketones, despite being extremely polar compounds, lack hydrogen atoms directly connected to oxygen and therefore cannot hydrogen bond with one another.
• Physical Properties

  • Due to hydrogen bonding, the lower members (up to 4 carbons) of aldehydes and ketones are soluble in water.
  • Water solubility decreases as the molecular weight or carbon number increases.
• Water solubility decreases as the molecular weight or carbon number increases.
• Chemical Properties

  • Carbonyl compounds are polar in nature.
  • They exhibit both positive and negative charges in slight form.
  • Insoluble in water but sometimes they dissolve other forms of polar molecules.
• Chemical Properties

  • Chemically reactive compounds, they undergo nucleophilic addition and substitution reactions.
• Aldehydes

  • are carbonyl compounds that contain a carbonyl group bonded to at least one hydrogen atom and one alkyl or aryl group.
  • are important intermediates in drug synthesis and are commonly used as reagents in organic chemistry.
• Ketones

  • carbonyl compounds that contain a carbonyl group bonded to two alkyl or aryl groups.
  • are important intermediates in drug synthesis and are commonly used to modify the properties of drugs.
• Carboxylic acids

  • are carbonyl compounds that contain a carbonyl group bonded to a hydroxyl group and an alkyl or aryl group.
  • are important in drug design because they can form esters and amides, which are common functional groups in drugs.
• Esters

  • carbonyl compounds that contain a carbonyl group bonded to an oxygen atom and an alkyl or aryl group.
  • are important in drug design because they are stable and can easily be hydrolyzed to form carboxylic acids and alcohols.
• Amides

  • carbonyl compounds that contain a carbonyl group bonded to a nitrogen atom and an alkyl or aryl group.
  • are important in drug design because they are stable and can easily be hydrolyzed to form carboxylic acids and amines.
• Carbonyl groups in aldehydes and ketones undergo addition reactions.

  • This is one of the most important reactions of the carbonyl group.
• Addition reactions occur by two different mechanisms:

  • Base-catalyzed addition (under basic or neutral conditions)
  • Acid-catalyzed addition (under acidic conditions)
• Carbonyl reduction

  • This reaction is a process in which the carbonyl groups are reduced by the hydride reagents such as the LiAlH4 and NaBH4 with baker’s yeast.
  • Or by the process of catalytic hydrogenation.
• Carbonyl alklylation

  • This is a process in which the carbonyl compounds are alkylated with the use of organometallic compounds like Grignard reagents, organolithium reagents, acetylides, etc.
• Carbonyl Substitution Reaction

  • The carbonyl here serves as the electrophile and “X” is a leaving group.
  • The ‘X’ group is replaced by the “Nu” group.
  • This is what we called substitution at an sp2 carbon.
  • This kind of substitution reaction involves the substitution of the atom of a hydrogen by an electrophile.
• Addition of water

  The formation of a hydrate is cause by the addition of water to an aldehyde.

  The formation of a hydrate proceeds via a nucleophilic addition mechanism
• • Water, acting as nucleophile is attracted to the partially positive carbon of the carbonyl group that generates an oxonium ion.
  • The oxonium ion liberates a hydrogen ion that is picked up by the oxygen anion in an acid-base reaction.
• Addition of alcohol

  • Reactions of aldehydes with alcohols produce either hemiacetals (a functional group consisting of one —OH group and one —OR group bonded to the same carbon) or acetals (a functional group consisting of two —OR groups bonded to the same carbon), depending upon conditions.
  • Hemiacetal is produced when the two reactants is mix together whereas, acetal is produced when the two reactants with hydrochloric acid is mixed.
• • This reaction is catalyzed by small amounts of acids and bases.
  • This occurs because the addition of acid causes a protonation of the oxygen of the carbonyl group, leading to the formation of a full positive charge on the carbonyl carbon, making the carbon a good nucleus.
  • Adding hydroxyl ions changes the nucleophile from water (a weak nucleophile) to a hydroxide ion (a strong nucleophile).
  • Ketones usually do not form stable hydrates.
• Addition of alcohol

  Reactions of aldehydes with alcohols produce either:

  • hemiacetals (a functional group consisting of one —OH group and one —OR group bonded to the same carbon)
  • acetals (a functional group consisting of two —OR groups bonded to the same carbon), depending upon conditions.
  • Hemiacetal is produced when the two reactants is mix together whereas,
  • acetal is produced when the two reactants with hydrochloric acid is mixed.