Organic Chemistry
Chapter 9
Part I
Carbonyl Group (I)
Aldehydes and Ketones
Nanoplasmonic Research Group
Carbonyl Group (I)
• Carbonyl Compounds
• The alpha hydrogens of a carbonyl compounds
are much more acidic than a typical C-H bond.
Carbonyl Group (II)
• Oxygen is more electronegative than
carbon. Therefore, the carbonyl carbon
becomes electrophilic, and thus more
reactive with nucleophiles. The oxygen can
react with an electrophile such as a proton
and other Lewis acids
Nomenclature of Aldehydes
• Acyclic aliphatic aldehydes are named as
derivatives of the longest chain containing
the aldehyde group by changing the suffix –
e of the parent alkane to –al.
• -CHO group is attached to a ring, the suffix
–carbaldehyde may be used.
methanal
(formaldehyde)
ethanal
(actaldehyde)
propanal
(propionaldehyde)
butanal
n-butyraldehyde
Nomenclature of Ketones
• Ketones are named using IUPAC
nomenclature by changing the suffix –e of
the parent alkane to –one.
2
propanone
(acetone)
3
2-butanone
(ethyl methyl ketone)
3-pentanone
(diethyl ketone)
1
2
3
cyclohexanone
2-metjhylcyclopentanone
2
3-buten-2-one
(methyl vinyl ketone)
Synthesis of Aldehydes and Ketones
• Aldehydes can be prepared by reacting a
primary alcohol with an oxidizing agent (an
chromium (VI) oxidizing agent)
• Ketones can be created by oxidation of
secondary alcohol
oxidizing
agent
Reactions of Aldehydes and Ketones
• Let’s focus on the reactivity of the carbonyl
group!!!
• Nucleophilic Addition
• Ketones are less reactive than aldehydes
• Reduction and Oxidation
• Keto-Enol Tautomerism
• The Aldol Condensation
Nucleophilic Addition to Carbonyl
Groups (oxygen (I))
• Addition of Alcohols: Formation of
Hemiacetals and Acetals
Nucleophilic Addition to Carbonyl
Groups (oxygen (II))
• Formation of a cyclic hemiacetal: Generally
unstable compounds, in some cases,
however, stable cyclic hemiacetals can be
readily formed when 5- and 6-membered
rings are possible.
• Acetal are used as a protecting group for
carbonyl groups since they are stable with
respect to hydrolysis by bases.
Nucleophilic Addition to Carbonyl
Groups (carbon (I))
• Nucleophilic Carbon: Grignard Reagents
• Nucleophilic Carbon: Acetylides
• A metal acetylide is an alkyne for which the
terminal proton has been replaced by a
metal such as sodium or an organolithium
Nucleophilic Addition to Carbonyl
Groups (carbon (II))
• Nucleophilic Carbon: Addtion of Hydrogen
Cyanide
• Hydrogen cyanide has no lone pair electron
on carbon. The base can converts to cyanide
ions which then can act as a carbon
nucleophile since it is weakly acidic.
Nucleophilic Addition to Carbonyl
Groups (nitrogen)
• The tetrahedral addtion of ammonia and
amines: similar to a hemiacetal
• These addition products are unstable. They
can readily eliminate water to form imines!!!
-HOH
primary
amine
tetrahedral
Addition product
imine