Download Organic Chemistry Lecture Outline Carbonyl

Organic Chemistry
Lecture Outline
Carbonyl-Containing Functional Groups
FUNCTIONAL GROUPS CONTAINING CARBONYL GROUPS
A carbonyl group has a carbon atom doubly bonded to an oxygen atom.
1. The carbon atom of a carbonyl group is sp2 hybridized.
2. A carbonyl group is polarized with the oxygen atom bearing a partial negative and the carbon bearing a partial positive charge.
3. The carbon atom of a carbonyl group is electrophilic.
The following functional groups contain a carbonyl group.
ALDEHYDES
AMIDES KETONES ESTERS IMIDES
ACID CHLORIDES
ANHYDRIDES
CARBOXYLIC ACIDS
GENERAL TYPES OF REACTIONS CARBONYL GROUPS UNDERGO
1. NUCLEOPHILIC ADDITION REACTIONS: Occurs with all types of carbonyls
2. NUCLEOPHILIC ACYL SUBSTITUTIONS: Occurs with acids, acid chlorides,amides, esters, anhydrides, imides
3. ALPHA-SUBSTITUTION REACTIONS: Occurs with all carbonyls that bear an alpha hydrogen atom
4. CARBONYL CONDENSATION REACTIONS: Occurs between two carbonyl groups
ALDEHYDES AND KETONES
Aldehydes and ketones are carbonyl-containing functional groups. The structures and reactivity of these functional groups are similar.
Aldehydes have a hydrogen atom and a carbon atom bonded to the carbonyl carbon. Ketones have two carbon atoms bonded to the
carbonyl carbon. The carbonyl carbon of both aldehydes and ketones is electrophilic.
Aldehyde
Ketone
O
O
δ
δ
H
H atom
C atom
C atom
C atom
NOMENCLATURE OF ALDEHYDES AND KETONES
IUPAC
The parent of an aldehyde or ketone is the longest, continuous carbon chain that contains the carbonyl carbon of the functional group.
The parent name reflects the total number of carbon atoms in the chain (2 carbons = ethan, 3 carbons = propan, etc..). The parent
chain is numbered from one end of the chain, so as to give the carbonyl carbon the lowest possible number. For aldehydes, this means
the carbonyl carbon will always be the number 1 carbon. Substituents are assigned a number to indicate their position on the parent
chain. Substituents are named to reflect the number of carbon atoms of the substituent. Substituents are placed in alphabetical order.
The “-AL” suffix is used for aldehydes, the “–ONE” suffix is used for ketones.
O
O
O
CH3
H
3-methylbutanal
4-methylhexanone
Cl
4-chloro-2-methylcyclohexanone
Organic Chemistry
Lecture Outline
Carbonyl-Containing Functional Groups
COMMON
There are many common names that are used to describe aldehydes and ketones. Some of these are:
O
O
O
CH3
H
O
H
methylethyl ketone
Acetophenone
Benzaldehyde
O
O
H
H3C
Formaldehyde
H
CH3
Acrolein
Acetone
REACTIONS TO PREPARE ALDEHYDES & KETONES
ALDEHYDES
1. Oxidation of Alcohols
O
PCC
H
OH
O
Jones Reagent
2.
OH
Reduction of Esters
DIBAL is used to reduce esters to aldehydes
Ester
Aldehyde
O
O
O
DIBAL
R
R
OR
OR
+
OR
R
H
H
HOH
H
3.
Tetrahedral
Intermediate
ROH
Hydration of Terminal Alkynes
H2B
H
C
C
CH3
=
H
H2B
H
BH3
H
CH3
H
CH3
Transition State
O
H
H2O2
NaOH
HO
H
H
H
CH3
Aldehyde
H
CH3
Enol
Organic Chemistry
Lecture Outline
Carbonyl-Containing Functional Groups
KETONES
1. Oxidation of Alcohols
O
PCC
O
OH
Jones Reagent
O
Na2Cr2O7
2.
Friedel-Crafts Acylation
Cl
Cl
Al
Cl
Al
O
Cl
O
Cl
X
R
X
R
AlX3
O
O
H
R
3.
R
Hydration of Terminal Alkynes
H
H
+
H
C
C
CH3
H3O
H
CH3
H
Most Stable Carbocation
H
OH2
CH3
Oxonium ion
O
H
OH
H
H
CH3
Ketone
H
CH3
Enol
CARBOXYLIC ACIDS, ESTERS AND AMIDES
Carboxylic acids, esters and amides are carbonyl-containing functional groups. The structures and reactivity of these functional
groups are similar. Carboxylic acids have a hydroxyl group (-OH) and a carbon atom bonded to the carbonyl carbon. Esters have an
alkoxide group (-OR) and a carbon atom bonded to the carbonyl carbon. Amides have an amino group (-NH2, -NHR, -NR2) and a
carbon atom bonded to the carbonyl carbon. The carbonyl carbon of all of these functional groups is electrophilic, but not as
electrophilic as aldehydes and ketones.
Organic Chemistry
Lecture Outline
Carbonyl-Containing Functional Groups
Ester
Carboxylic Acid
O
O
HO
hydroxyl
group
Primary Amide
δ
RO
Secondary Amide
O
H2N
amino
group
Alkoxide
group
C atom
δ
C atom
Tertiary Amide
O
O
δ
RHN
C atom
amino
group
δ
R2N
C atom
amino
group
δ
C atom
STERIC AND ELECTRONIC EFFECTS OF CARBONYL COMPOUNDS
Steric Effects
Steric effects influence the reactivity of the electrophilic carbonyl carbon in nucleophilic acyl addition and nucleophilic acyl
substitution reactions. Carbonyl groups bonded to large, bulky substituents (eg., tertiary carbons) react slower with nucleophiles than
carbonyl groups with smaller, less bulky substituents.
Electronic Effects
Electronic effects influence the reactivity of the electrophilic carbonyl carbon in nucleophilic acyl addition and nucleophilic acyl
substitution reactions. Substituents with lone pair electrons assiociated with them can donate electrons into the pi system, making the
electrophilic carbonyl carbon less positive and less reactive with a nucleophile. Carbonyl-containing functional groups like carboxylic
acids, esters and amides that have substituents with lone pairs (O or N atoms) react slower than aldehydes and ketones due to this
electronic effect.