Transcript Organic Chemistry & Polymers

ORGANIC CHEMISTRY
Organic chemistry is the study of carbon chemistry and the
compounds of carbon.
Majority of chemical compounds on earth are organic.
The main elements involved in organic chemistry are C, H, O,
& N; shorthand notation: HC = hydrocarbon
Organic chemistry reminds us of plants and animals but is not
limited to such.
Natural medicines: penicillin, cortisone, streptomycin
Manmade medicines: novocaine, sulfa drugs, aspirin.
Natural textile fibers: nylon, Dacron, latex, rayon
Polymers: saran, Teflon, Styrofoam, plastics, polyethylene,
PBC’s
CLASSIFICATION OF HYDROCARBONS
HYDROCARBONS
ALIPHATIC HYDROCARBONS
SATURATED
HYDROCARBONS
AROMATIC HYDROCARBONS
(unsaturated hydrocarbons)
UNSATURATED
HYDROCARBONS
BENZENE AND
DERIVATIVES
alkenes
(CnH2n)
Alkanes
(CnH2n + 2)
Cycloalkanes
(CnH2n)
alkynes
(CnH2n - 2)
FUSED-RING
AROMATIC
HYDROCARBONS
Combustion of Hydrocarbons
• Hydrocarbons combine with oxygen to produce
carbon dioxide and water.
• All the products are gases:
– Carbon dioxide (CO2)
– Water (H2O)
• No solid residues.
• Maximize pressure to perform mechanical work.
Theory and Reality
• Combustion equations are expressions of
ideal combustion where only CO2 and H2O
are products.
• In limited oxygen incomplete combustion
occurs:
– Carbon monoxide is also produced.
– (21 O2 compared with 25 O2 with complete
combustion).
Fractional Distillation
• Crude oil is a fossil fuel –
organic matter
decomposed over time.
• Complex mixture of
different sized
hydrocarbons.
• Refinement is achieved by
distillation.
• Lighter fractions condense
higher up the fractionating
column.
Emissions and the Environment
•
•
•
•
Typical car engine results in about 5 % CO.
CO2 and CO are both greenhouse gases.
CO is also a health hazard.
Catalytic converters convert CO into CO2.
What Makes a Good Fuel?
• In the combustion process:
– C-C and C-H bonds are broken.
– C-O and H-O bonds are made.
• The bonds that are made are stronger than those that
are broken – energy is released – exothermic
reaction.
Checking the Ratings
• Molecular structure
affects combustion.
• Octane number
describes combustion
efficiency.
• Straight chain is
worse than branched:
– 2,2,4-trimethylpentane
has octane rating 100.
– n-heptane has rating 0.
• Gasoline is a complex
mixture of different
hydrocarbons and
additives with octane
ratings from 85 – 97.
I Hear You Knocking
• For efficient operation,
combustion must
occur at the right
moment to drive the
piston up and move
the crankshaft.
• Premature combustion
is inefficient and
results in “knocking.”
GASOLINE
The combustion engine operates:
1. Gasoline is allowed into the cylinder
2. Compression concentrates the gasoline and
air (mixes)
3. Spark plugs ignite the mixture producing gas
(pressure/volume) work.
The compression step causes ignition.
Knocking is pre-mature ignition of the more volatile
components of the gasoline/air mixtures.
GASOLINE
ANTI-KNOCKING AGENTS
1. Pb(C5H5)4 tetra ethyl lead 1920’s
2. MTBE methyl-tert butyl ether 1990’s
& EtOH ethanol (oxygenated)
3. Reformulated Gas (RFG)
- contains less volatile hydrocarbons like
benzene (C6H6) 1995 (note: volatile
hydrocarbons contribute to O3 production
in troposphere)
Cleaning Up Our Act
• The Clean Air Act of 1991 introduced
new standards to reduce hazardous
exhaust emissions – maximize
conversion of CO to CO2.
• Oxygenates: Adding O to the fuel
before combustion rather than
afterwards.
• Two options:
– Ethanol – expensive to produce
– Methyl tert-butyl ether (MTBE)
Unwanted Consequences of MTBE
• Ethers are more polar
than hydrocarbons and
dissolve slightly in
water.
• Gasoline containing
MTBE poses
environmental hazard:
– MTBE is carcinogenic.
– MTBE does not
degrade.
• MTBE contamination of
water supplies is a major
health issue.
• Ethanol poses a safer,
but a more expensive
alternative.
ORGANIC NOMENCLATURE REVIEW
1. NAMING BASED ON # OF CARBONS IN THE
MOLECULE
#C NAME (prefix)
1 meth
2 eth
3 prop
4 but
5 pent
#C
6
7
8
9
10
NAME (prefix
hex
hept
oct
non
dec
2. NAMING BASED ON CARBON-CARBON BONDING.
single bond – ane ending
double bond – ene ending
triple bond – yne ending
ORGANIC NOMENCLATURE
3. FUNCTIONAL GROUPS containing oxygen
R - OH
-ol
alcohol
R-O-R
ether
ether
R- HC = O
-al
aldehyde
R-C=O
l
R
-one
ketone
R - C - O-H
ll
O
-oic acid
carboxylic acid
R-C-O-R
ll
O
-oate
ester
carbonyl C=O
ORGANIC NOMENCLATURE
3. FUNCTIONAL GROUPS containing nitrogen
R – NH2
-amine
amine
R – C=O
l
NH2
-amide
amide
ALCOHOL
MeOH – wood alcohol – methanol CH3OH
- oxidized in body to formaldehyde
- 1oz MeOH causes blindness
EtOH – grain alcohol – ethanol C2H5OH
- not poisonous in low concentrations
- 500 mL 200 proof rapidly ingested will kill
IPA – Isopropyl alcohol (rubbing alcohol)
- C3H7OH 2-propanol
-toxic (dosage) causes nerve damage, blindness and/or
death, it’s a poison.
- FAS
- depressant
- heavy drinking alter brain cell functions, causes nerve
damage, shortens life span
ETHERS
- solvent
- flammable
- react w/O2 to form unstable peroxides
- Diethyl ether  anesthetic 1842; side
effects include nausea & vomiting.
- MODERN ANESTHETICS include methy
propyl ether (Neothyl) and methoxyflurane
(penthrane; CHCl2CF2OCH3)
- MTBE (methyl tert-butyl ether) –
reduce CO emissions in automobiles but is a
suspected carcinogen.
- ethylene oxide (C2H4O; cyclic) is used to make
ethylene glycol which in turn is used to make polyester
fibers and antifreeze.
The Ether
• Molecules beside hydrocarbons function as fuels.
• Ether contains two hydrocarbon groups separated
by an O atom.
• General formula is: R-O-R'
Naming Ethers
• When the hydrocarbon groups are different,
the name orders the two group
alphabetically and ends in ether.
– Butyl methyl ether: H3CCH2CH2CH2-O-CH3
• When the groups are the same the prefix diis used.
– Dimethyl ether: H3C-O-CH3
ALDEHYDES/KETONES
- formaldehyde
- makes plastic
- embalming
- disinfectant
- benzaldehyde (oil of almond)
- maraschino cherry flavor
- perfume, flavoring
- acetone C3H6O
- nail polish remover; common solvent for
fats, rubber, plastics, & varnishes. Used in
paint and varnish removers.
- MEK – methyl ethyl ketone – solvent in oil
paints and glues. Also formed in the blood
stream in ketosis (a problem in diabetes).
Ketone functional group
• Ketone functional
group is basis for soft
contact polymer
• Carbonyl group is
C=O
• Ketone contains two
hydrocarbon chains
attached to carbonyl
group
Naming ketones
• Obtain root name
– Count total number of
C atoms
• Remove –e and
replace with –one
• Location of carbonyl
group
– Count carbon atoms
from shortest end
CABOXYLIC ACIDS
- carboxylic acids are polar and form hydrogen
bonds thus leading to higher boiling points. (formic acid;
46 g/mol has bp of 101oC whereas ethanol; 46 g/mol has
bp of 78oC). They are weak acids and react with bases
to form salts.
-formic acid – methanoic acid - ant sting - CH2O2
-acetic acid – ethanoic acid - vinegar - CH3COOH
-butyric acid – butanoic acid – rancid butter
-benzoic acid – Listerine
-citric acid – sour flavor in oranges, lemons, &
limes
-lactic acid – imparts tartness to pickles,
sauerkraut, & sweat. -cause of muscle pain &
sorenss after exercise.
Carboxylic Acids Are Acidic
• The –COOH group loses protons “easily.”
– Prostaglandin is ionized and is partly soluble in water.
Naming Carboxylic Acids
•
Replace terminal “e”
by “-oic acid.”
a) Seven carbon atoms:
– heptanoic acid.
b) Ten carbon chain and
ethyl group on C-7:
7-ethyldecanoic acid.
ESTERS
carboxylic acid + alcohol  ester + H2O
- sodium benzoate - preservative
- fragrances
- pineapple = ethyl butyrate
- rum = ethyl formate
- wintergreen = methyl salicylate
- oil of jasmine = has benzyl acetate
(C6H6)-CH2-O-CO-CH3
-rose = benzyl butanoate
Ester group
• Ester functional group
• Esters have flavor and
fragrance
• Esters and their uses
as flavoring agents and
perfumes
The name game
• Ester contains two
name parts
– First: attached to O
atom in main chain
– Second: all C atoms in
main chain, subtract -e
and add -oate
AMINES/AMIDES
Organic bases – similar to ammonia NH3 in odor
and basicity. Many amines have unpleasant
odors like trimethylamine (smell of rotting fish)
& putrescine (component of decaying animal
flesh) H2N-(CH2)4-NH2
Amines are biologically important for example
some illicit drugs like amphetamine &
methamphetamine are amines and amino acids &
proteins contain amines/amides. Nylon is a
polyamide.
Carboxylic acid + amine = amide + H2O
Amide groups
• Amide group contains carbonyl group
– Hydrocarbon group attached to C atom
– Nitrogen atom attached to C atom
• Rotation about C-N bond is not possible
Functional group review
Functional group review
Penicillin G shown below, a drug that inhibits the
production of bacterial cell walls:
H H
O
O
S
N
CO2H
Functional group review
derivative of Neomethymycin,
synthetic analog of bryostatin, a
natural anticancer agent:
an antibiotic
H
O
O
O
O
O
O
HO
HO O
N(CH3)2
OH
O
H3C
O
O
OCH3
O
HO
O
HO
O
O
The polymer century
• Polymers came of age in the 20th century
• Plastics became stronger, lighter, more
flexible, more rigid, more colorful, more
durable
• Disposal becomes a major issue
• Future challenge is to meet dual demands
of high performance and biodegradability
Poly = many
• Chemical names that begin with
poly- mean big molecules
• Polymers are made up of monomers
– small molecules connected
together
• Polymer chains:
– Long or short
– Straight or branched
– Hydrophilic or hydrophobic
– Flexible or rigid
POLYMERS
Polymers are macromolecules
Polymers are composed of monomers: smallest unit
Polymers are long chains of monomers
Polymerization: the process by which monomers are
converted to polymers.
Natural Polymers: starch, protein, cotton, wool
Synthetic Polymers
-
Polyethylene – bags, squeeze bottles, films
Polypropylene –carpeting, fabrics, battery cases
Polystyrene - styrofoam cups, building insulation
Polyvinyl chloride - PVC pipes, floor tile, raincoats
polytetrafluoroethylene – Teflon, gasket & pan coating
Some historical polymers
• Shell lacca (from insect secretions) was used as a
varnish
• Rubber (natural from Hevea brasiliensis tree, C5H8)
emulsion of rubber particles in water; elastic, waterrepellent, & sticky.
• Vulcanized rubber (short chains of sulfur bonded to
natural rubber) reduces stickiness, increases elasticity
of material. 1839 Charles Goodyear
• Frankincense and myrrh (from tree resins) were used
as incense and perfumes
• Gutta-percha was used a coating
20th century and the polymer age
• New synthetic materials:
rubber, polystyrene,
polyethylene,
polyvinylchloride,
polyesters, nylon
• World polymer
consumption is now vast
• Disposal presents
environmental challenge
Models for polymer growth
a) Polymer grows by adding units on end of a chain
b) Polymer grows by linking of shorter chains
Two routes to a polymer
• Addition
polymerization: add
monomers to one end
• Condensation
polymerization:
joining of longer
chains is possible
Structure is function
• Monomer for rubber is
cis-isoprene
• Rubber is cispolyisoprene
• Each double bond has
a cis- orientation
• Chains are curvy and
intertwined – allows
stretching
Dacron polymerization
• First monomer has ester
group on each end: diester
• Second monomer has
alcohol group on each
end: dialcohol
• End of first monomer
reacts with end of second
monomer
– Ester group is slightly
positive, alcohol group is
slightly negative
Sweet smell of esters
•
•
•
•
Individual ester molecules are fragrant
Polyesters are fragrance-free
Dacron® is most widely used polyester in fabrics
Dacron® is a copolymer polymer containing 2 or more
monomers
Nylon and Polyamides
• Amide group is formed
when an amine group
and a carboxylic acid
group combine and
eject H2O
(condensation).
Cutting the suit to fit the cloth