ch1810 lecture #6 polymers, carbonyl compounds, and...

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).


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


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


L-carvone D-carvone


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-

ch1810 lecture #6 polymers, carbonyl compounds, and...

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