CH1810 Lecture #6
Polymers, Carbonyl Compounds, and Chirality
Structure of the Carbonyl Group
C O
The carbonyl group is constructed in the same m a n n e r a s t h e c a r b o n -carbon double bond, from an sp2 hybridized carbon atom and an sp2 hybridized oxygen atom.
The angles between the three b o n d s i n v o l v e d a r e approximately 120º.
Nomenclature of Carbonyl Compounds
Ethanal
Propanone
Ethanoic Acid
Methyl ethanoate
Ethanamide
Nomenclature of Carbonyl Compounds
Aldehydes and Ketones
CH2OFormaldehyde
Common Aldehydes and Ketones
Physical Properties of Aldehydes and KetonesSummary of Important “Secondary Forces”
Which Contribute to boiling Points
Seco
ndar
y A
ttra
ctiv
e Fo
rces
London
Dipole-dipole
H-bonding
Increased Boiling Point
Hydrocarbons
Aldehydes and Ketones
Alcohols
Amines
240
200
160
120
80
40
-
-
-
-
-
-
Boili
ng P
oint
I I I I I 40 80 120 160 200 Molecular Mass
Alcohols
Aldehydes
Alkanes
Physical Properties of Aldehydes and Ketones
CO
H H
CO
CH3 H
CO
CH3CH2 H
CO
CH3CH2CH2 H
CH3CH2CH2CH2CO
H
Compound Boiling Point (ºC) Water solubility (g/100 mL H2O)
-21 very soluble
21 very soluble
49 16
76 7
103 1
Physical Properties of Aldehydes
Physical Properties of Ketones
H3CC
CH3
O
CCH3
O
CH3CH2
CCH3
O
CH3CH2CH2
CCH3
O
CH3CH2CH2CH2
CCH3
O
CH3CH2CH2CH2CH2
Compound Boiling Point (ºC) Water solubility (g/100 mL H2O)
56 very soluble
80 26
102 6
127 -
151 -
Carboxylic Acids and Derivatives
Metabolic Fate of Alcohols
CH3OH Methanol
CH3CH2OH Ethanol
CH2OFormaldehyde
HCOOH Formic Acid
CH3COOH Acetic Acid
Polymer (macromolecule) – a very large molecule with high molar mass formed by bonding together a large number of small molecules of low molecular mass.
Monomer – small molecule that bonds with others like it to form polymers.
Oligomer – molecule that contain a few monomers; the middle ground between
small molecules and polymers.
Polymers
Addition Polymerization
Condensation Polymerization
Monomers are joined by removing small molecules from combining units. Each monomer has two reactive ends.
Monomers are added to the growing chain in such a manner so that all the atoms in the original monomers wind up in the chain.
“Addition” Polymerization of Ethylenes Overall Reaction:
C=CA
B
X
YC=C
A
B
X
YC=C
A
B
X
YC=C
A
B
X
YC=C
A
B
X
Y
C CA
B
X
YC C
A
B
X
YC C
A
B
X
YC C
A
B
X
YC C
A
B
X
Y
Acid or “initiator”
C CA
B
X
Y( ) n n = number of individual units
a “polyethylene”
CH2 CH2
CH2 CH
CH3
CH2 CH
Monomer Polymer Uses
ethylene
(CH2 CH2 )n
polyethylene
(CH2 CH )n
CH3propylene polypropylene
(CH2 CH )n
styrene polystyrene
bottles, toys, housewares, wire cableinsulation, plastic sheeting
outdoor carpeting, food packagingappliance housings
styrofoam containers, food packaginghairbrush handles, toys
“Addition” Polymers from Ethylenes
CH2 CH
Cl
CH2 CH
CN
CF2 CF2
(CH2 CH )n
Cl
vinyl chloride polyvinylchloride (PVC)
(CH2 CH )n
CN
acrylonitrile polyacylonitrile
(CF2 CF2 )n
tetrafluoroethylene polytetrafluoroethylene
home siding, gutters, flooring, garden hose, PVC tubing
acrylic textile fibers
“Teflon”, mechanical parts, cookware, chemical resistant gaskets
Monomer Polymer Uses
polyacrylonitrile
“Addition” Polymers from Ethylenes
Condensation Polymers
Polyesters Polyamides
Condensation reaction – two molecules combining to form a larger molecule and a small molecule (typically water).
Condensation Reactions
Condensation reaction – two molecules combining to form a larger molecule and a small molecule (typically water).
Condensation Reactions
methyl butanoate
H3CCH2
CH2C
O
O CH3
butanamide
H3CCH2
CH2C
O
N H
H
+ H2O
H3CCH2
CH2C
O
O H H OCH3
butanoic acid methanol+
H3CCH2
CH2C
O
O HH N
H
H
butanoic acid ammonia+
+ H2O
Condensation Reactions
are also known by the term “Dehydration Synthesis”
Proteins
Polysaccharides
Nucleic Acids
Polyester Synthesis
etc.
“Polyesters”
Polyamide Synthesis
etc.
“Nylons”
13.8 Chirality
Stereoisomers
Isomers
Structural Isomers
Stereochemistry - Review of Isomerism
Stereochemistry - Review of Isomerism
Isomers
Structural Isomers Stereoisomers
Isomers with chiral centersCis-trans Isomers
Stereochemistry - “Handedness” in Everyday Objects
We can imagine the mirror image of an object.
In some cases, the mirror image and the original object are identical. In some cases, the mirror image and
the original object are not identical.
Stereochemistry - “Handedness” in Everyday Objects
Stereochemistry - “Handedness” in Organic Compounds
Enantiomers - compounds that have the following characteristics:
1) Molecules of two compounds are mirror images of each other.
2) Molecules of two compounds are nonsuperimposable.
The characteristics of enantiomers are often the
result of a single “chiral” carbon atom.
Stereochemistry - A Chiral Tetrahedral Carbon
1, 2, 3, and 4 must be different groups. What are “different” groups?
bromochlorofluoromethane
Stereochemistry - Examples of Enantiomers
2-bromobutane
Stereochemistry - Examples of Enantiomers
L-carvone D-carvone
Stereochemistry - Examples of Enantiomers
Optical Activity - The Polarimeter
Optical Activity of Enantiomers
Optical activity is the only property that distinguishes one enantiomer from the other. All other properties (MP, BP, solubility, etc.) are the same.
D-Lactic Acid L-Lactic Acid
m.p. 53 oC m.p. 53 oC
Very soluble in water Very soluble in water
[α] = - 2.6 o [α] = +2.6 o
Most processes in living cells are mediated by macromolecules referred to as “RECEPTORS.”
Chiral Recognition
Most receptors interact with small messenger molecules at “ACTIVE SITES”
For most receptors, THIS SITE IS CHIRAL.
Chiral active sites are often designed to interact strongly with one of two possible enantiomers, just as a left shoe interacts
strongly with a left foot, and more or less excludes a right foot.
This phenomenon is called CHIRAL RECOGNITION or CHIRAL DISCRIMINATION.
Chiral Recognition
𝞭+
𝞭+ 𝞭-
(-) epinephrine (natural epinephrine)
receptor active site
receptor neurotransmitter
complex
receptor response
OH
OH
C
HHO NH2
CH3CH2
𝞭-
𝞭-
Chiral Recognition
𝞭+
𝞭+ 𝞭-
(+) epinephrine (Unnatural epinephrine)
Chiral Recognition
receptor active site
No receptor neurotransmitter
complex forms
receptor responseX X
OH
OH
COH
HNH2
H3CCH2
𝞭-
𝞭-