Structure and Properties of Carbonyl Compounds
Capsaicin
Aldehydes and ketones
Carbonyl Compounds
Contain the carbonyl group
C=O
Aldehydes:
R may be hydrogen,
usually a carbon
containing group
Ketones:
R contains carbon
Short
forms
Structures of Aldehydes
and Ketones
13.1 Structure and Physical Properties
•
Aldehydes and ketones are polar compounds
•
The carbonyl group is polar
–
The oxygen end is electronegative
–
Can hydrogen bond to water
–
Cannot form intermolecular hydrogen bond
Hydrogen
bond
Hydrogen Bonding and dipole
association in Carbonyls
13.1 Structure and Physical Properties
Bonding with H
2
O dipole-dipole
Physical Properties
Carbonyls boil at
•
Higher temperatures than:
–
Hydrocarbons
–
Ethers
•
Lower temperatures than:
–
Alcohols
13.2 Nomenclature and Common
Names
Naming Aldehydes
•
Locate the parent compound
–
Longest continuous carbon chain
–
Must contain the carbonyl group
•
Replace the final
–e
of the parent with
–al
•
Number the chain with the carbonyl carbon as
1
•
Number and name all substituents
Naming Aldehydes
What is the name of this molecule?
1.
Parent chain – 5 carbons =
pentane
2.
Change suffix – pentan
al
3.
Number from carbonyl end – L to R
4.
Number / name substituents –
4-methyl
4
-
m
e
t
h
y
l
p
e
n
t
a
n
a
l
13.2 Nomenclature and Common Names
1
2
3
4
5
Common Names of Aldehydes
•
These names are taken from Latin roots as
are the first 5 carboxylic acids
•
Greek letters are used to indicate the
position of substituents with the carbon
atom adjacent or bonded to the carbonyl
carbon being the
carbon
13.2 Nomenclature and Common Names
-
c
h
l
o
r
o
v
a
l
e
r
a
l
d
e
h
y
d
e
IUPAC and Common Names With
Formulas for Several Aldehydes
13.2 Nomenclature and Common Names
Examples of Ketones
Simplest ketone MUST have 3 carbon atoms so that the carbonyl group is interior
•
Base name: longest chain with the C=O
•
Replace the –e of alkane name with –one
•
Indicate position of C=O by number on chain so that C=O has lowest possible number
IUPAC Naming of Ketones
Rules directly analogous to those for aldehydes
•
Base name: longest chain with the C=O
pent
•
Replace the –e of alkane name with –one
•
Indicate position of C=O by number on chain so that C=O has lowest possible number
2
4
-
c
h
l
o
r
o
-
2
-
p
e
n
t
a
n
o
n
e
13.2 Nomenclature and Common Names
1
2
3
4
5
Common Names of Ketones
•
Based on the alkyl groups that are bonded to
the carbonyl carbon
–
Alkyl groups are prefixes (2 words) followed by the
word ketone
–
Order of alkyl groups in the name
•
Alphabetical
•
Size – smaller to larger
M
e
t
h
y
l
e
t
h
y
l
k
e
t
o
n
e
o
r
E
t
h
y
l
m
e
t
h
y
l
k
e
t
o
n
e
13.2 Nomenclature and Common Names
D
i
m
e
t
h
y
l
k
e
t
o
n
e
13.3 Important Aldehydes and Ketones
•
Methanal (b.p. –21
o
C) is a gas used in aqueous
solutions as formalin to preserve tissue
•
Ethanal is produced from ethanol in the liver
causing hangover symptoms
•
Propanone (Acetone) is the simplest possible
ketone
–
Miscible with water
–
Flammable
–
Both acetone methyl ethyl ketone (MEK or butanone)
are very versatile solvents
Fragrant aldehydes
Oxidation
•
Tollens test
•
Benedict
Reduction of Carbonyls
•
Both aldehydes and ketones are readily
reduced to alcohols
–
Reduction occurs with hydrogen as the reducing
agent
•
Classical reaction is hydrogenation
–
React with hydrogen gas
–
Requires a catalyst – Ni, Pt, Pd
–
Occurs with heat and pressure
13.4 Reactions Involving Aldehydes and Ketones
Addition Reactions
•
Principal reaction is the addition reaction
across the polar C=O double bond
–
Very similar to the addition hydrogenation of
alkenes
–
Requires catalytic acid in the solution
•
Product of the reaction is a hemiacetal
–
Hemiacetals are quite reactive
–
Undergo a substitution reaction with the –OH
group of the hemiacetal is exchanged for another
–OR group from the alcohol
–
Reaction product is an acetal
–
This reaction is reversible
13.4 Reactions Involving Aldehydes and Ketones
Formation of Hemiacetal
or Hemiketal
•
Product of the addition reaction is a
hemiacetal
(above)
or a hemiketal
(below)
13.4 Reactions Involving Aldehydes and Ketones
Carbohydrates
Recognizing Hemiacetals, Acetals,
Hemiketals, and Ketals
13.4 Reactions Involving Aldehydes and Ketones
Keto-Enol Tautomers
•
Tautomers are isomers which differ in the
placement of:
–
A hydrogen atom
–
A double bond
–
The
keto
form has a C=O while the
enol
form has a
C=C.
•
The keto form is usually the most stable
13.4 Reactions Involving Aldehydes and Ketones
Aldol Condensation
•
Self-addition or condensation
•
Uses two molecules of the same aldehyde or
ketone
•
The
carbon of the second molecule adds to
the carbonyl carbon of the first molecule
•
Strong base such as hydroxide catalyzes the
reaction
•
Very complex reaction occurring in multiple
steps
13.4 Reactions Involving Aldehydes and Ketones
Condensation of an Aldehyde
•
An aldol has an –OH
to the carbonyl group
13.4 Reactions Involving Aldehydes and Ketones
Aldol Condensation: Aldolase
Dihydroxyacetone phosphate +
D-glyeraldehyde-3-phosphate
D-fructose-1,6-bisphosphate
carbon (
3
) adds to carbonyl carbon (
4
)
13.4 Reactions Involving Aldehydes and Ketones
Cats pea
Tautomerization
Reaction Schematic
Hemiketal - Ketal
Carbonyl
1
º
Alcohol
2
º
Alcohol
Hemiacetal - Acetal
If aldehyde
If ketone
If ketone
If aldehyde
Carboxylic
Acid
Oxidation
Reduction
Addition
Summary of Reactions
1. Aldehydes and ketones
a. Oxidation of an aldehyde
b. Reduction of aldehydes and ketones
c. Addition reactions
i. Hemiacetal and acetal
ii. Hemiketal and ketal
2. Keto-enol tautomerization
3. Aldol condensation
Summary of Reactions
Carbonyl compounds, such as aldehydes and ketones, exhibit unique structures and physical properties due to the presence of the carbonyl group. They are polar compounds capable of hydrogen bonding, impacting their boiling points and reactivity. Explore their nomenclature and common names.
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Presentation Transcript
Carbonyl Compounds Contain the carbonyl group C=O Short forms O Aldehydes: R may be hydrogen, usually a carbon containing group H RCHO R C O Ketones: R contains carbon R RCOR R C
Structures of Aldehydes and Ketones
13.1 Structure and Physical Properties 1 Aldehydes and ketones are polar compounds The carbonyl group is polar The oxygen end is electronegative Can hydrogen bond to water Cannot form intermolecular hydrogen bond Hydrogen bond - O O H O + C H C
Hydrogen Bonding and dipole association in Carbonyls 13.1 Structure and Physical Properties Bonding with H2O dipole-dipole
Physical Properties Carbonyls boil at Higher temperatures than: Hydrocarbons Ethers Lower temperatures than: Alcohols
13.2 Nomenclature and Common Names 1 Naming Aldehydes Locate the parent compound Longest continuous carbon chain Must contain the carbonyl group Replace the final e of the parent with al Number the chain with the carbonyl carbon as 1 Number and name all substituents
Naming Aldehydes What is the name of this molecule? 1. Parent chain 5 carbons = pentane 2. Change suffix pentanal 3. Number from carbonyl end L to R 4. Number / name substituents 4-methyl 13.2 Nomenclature and Common Names O 5 4 3 2 1 CH3CH CH2CH2CH CH3 4-methylpentanal
Common Names of Aldehydes These names are taken from Latin roots as are the first 5 carboxylic acids Greek letters are used to indicate the position of substituents with the carbon atom adjacent or bonded to the carbonyl carbon being the carbon 13.2 Nomenclature and Common Names O Cl CH3 CH CH2CH2CH -chlorovaleraldehyde
IUPAC and Common Names With Formulas for Several Aldehydes 13.2 Nomenclature and Common Names
Examples of Ketones Simplest ketone MUST have 3 carbon atoms so that the carbonyl group is interior Base name: longest chain with the C=O Replace the e of alkane name with one Indicate position of C=O by number on chain so that C=O has lowest possible number 2
IUPAC Naming of Ketones 2 Rules directly analogous to those for aldehydes Base name: longest chain with the C=O pent Replace the e of alkane name with one Indicate position of C=O by number on chain so that C=O has lowest possible number 2 13.2 Nomenclature and Common Names Cl O CH3CH CH2C CH3 3 4 5 2 1 4-chloro-2-pentanone
Common Names of Ketones Based on the alkyl groups that are bonded to the carbonyl carbon Alkyl groups are prefixes (2 words) followed by the word ketone Order of alkyl groups in the name Alphabetical Size smaller to larger O CH3 Methyl ethyl ketone or Ethyl methyl ketone 13.2 Nomenclature and Common Names O CH3C CH2 CH3C CH3 Dimethyl ketone
13.3 Important Aldehydes and Ketones 3 Methanal (b.p. 21oC) is a gas used in aqueous solutions as formalin to preserve tissue Ethanal is produced from ethanol in the liver causing hangover symptoms Propanone (Acetone) is the simplest possible ketone Miscible with water Flammable Both acetone methyl ethyl ketone (MEK or butanone) are very versatile solvents
Oxidation Tollens test Benedict
Reduction of Carbonyls 7 Both aldehydes and ketones are readily reduced to alcohols Reduction occurs with hydrogen as the reducing agent Classical reaction is hydrogenation React with hydrogen gas Requires a catalyst Ni, Pt, Pd Occurs with heat and pressure 13.4 Reactions Involving Aldehydes and Ketones O OH CH3CH2C CH3 CH3CH2CHCH3 H2 Pt, Pd, Ni O OH CH3CH2CH2CH CH3CH2CH2CH2
Addition Reactions 7 Principal reaction is the addition reaction across the polar C=O double bond Very similar to the addition hydrogenation of alkenes Requires catalytic acid in the solution Product of the reaction is a hemiacetal Hemiacetals are quite reactive Undergo a substitution reaction with the OH group of the hemiacetal is exchanged for another OR group from the alcohol Reaction product is an acetal This reaction is reversible 13.4 Reactions Involving Aldehydes and Ketones
Formation of Hemiacetal or Hemiketal Product of the addition reaction is a hemiacetal (above) or a hemiketal (below) 13.4 Reactions Involving Aldehydes and Ketones O OH H+ CH3CH2CH2CH CH3OH CH3CH2CH2CH + O CH3 Hemiacetal (ketal) carbons are part of both alcohol and ether functions and are a new functional group OH O H+ CH3CH2C CH3 CH3OH CH3CH2C CH3 + O CH3
Recognizing Hemiacetals, Acetals, Hemiketals, and Ketals 13.4 Reactions Involving Aldehydes and Ketones
Keto-Enol Tautomers 8 Tautomers are isomers which differ in the placement of: A hydrogen atom A double bond The keto form has a C=O while the enol form has a C=C. The keto form is usually the most stable H C R3 13.4 Reactions Involving Aldehydes and Ketones R1 OH O R1 C C C R2 R3 R2 H O OH H C C H C H C H H H
Aldol Condensation 9 Self-addition or condensation Uses two molecules of the same aldehyde or ketone The carbon of the second molecule adds to the carbonyl carbon of the first molecule Strong base such as hydroxide catalyzes the reaction Very complex reaction occurring in multiple steps 13.4 Reactions Involving Aldehydes and Ketones
Condensation of an Aldehyde An aldol has an OH to the carbonyl group 13.4 Reactions Involving Aldehydes and Ketones OH O O O OH- + CH3CH CH2CH CH3CH CH3CH C, 2nd molecule original C carbonyl carbon of first molecule becomes alcohol carbon in aldol
Aldol Condensation: Aldolase Dihydroxyacetone phosphate + D-glyeraldehyde-3-phosphate 2- 1 CH2OPO3 C C OH H 2- 1 CH2OPO3 C C OH C H O C H CH2OPO3 2 13.4 Reactions Involving Aldehydes and Ketones O 2 O 3 H 3 H aldolase Bond formed 4 H 4 5 H H C C CH2OPO3 O OH OH 5 2- 6 2- 6 D-fructose-1,6-bisphosphate carbon (3) adds to carbonyl carbon (4)
Reaction Schematic Carbonyl Oxidation Addition Carboxylic Acid Reduction If aldehyde If ketone If aldehyde Hemiacetal - Acetal 2 Alcohol 1 Alcohol If ketone Hemiketal - Ketal
Summary of Reactions 1. Aldehydes and ketones a. Oxidation of an aldehyde b. Reduction of aldehydes and ketones c. Addition reactions i. Hemiacetal and acetal ii. Hemiketal and ketal 2. Keto-enol tautomerization 3. Aldol condensation
