Download 11.1 Organic Chemistry

Organic Chemistry
Organic Chemistry: Carbon Compound
Chemistry
• Organic chemistry is the chemistry of carbon compounds.
Originally these were compounds that were studied from
organisms.
An Early Perspective on Organic Chemicals
• In Organic chemistry’s early stages, chemists wondered if
chemicals from living things had some special properties
or life force associated with them.
• The compound, urea , was isolated from human urine. To
show it was just a regular chemical without special life
properties, Wohler (a German chemist) made urea from
scratch in a chemical laboratory.
Hydrocarbons
• Hydrocarbons are compounds of just carbon and
hydrogen.
Hydrocarbons
• Many hydrocarbons
are produced by
fractional distillation
of crude oil.
Alkanes: Single Bonds
• Hydrocarbons with only single bonds between all carbon
atoms are called alkanes.
Alkanes: General Formula
• The general formula for alkanes is CnH2n+2 .
Bond Number in Hydrocarbons
• In any organic compound, every C atoms always has 4
bonds, every H atom always has 1 bond, every O atom
always has 2 bonds, every halogen atom (F, Cl, Br, I)
always has 1 bond and every N atom always has 3 bonds.
Alkane Nomenclature
Alkane Boiling Points
• As the hydrocarbon chains gets longer, the boiling points
increase due to increasing London forces between the
increasingly longer molecules.
Branched Alkanes
• Alkanes can have many branches coming off a main chain.
Side Chain Groups
• If a hydrogen atom is detached from an alkane chain, it
becomes a group that can be attached to another alkane
chain.
• A methyl group is a methane minus a hydrogen atom.
• An ethyl group is an ethane minus a hydrogen atom.
Alkane Nomenclature
1.
2.
Number the longest carbon chain so that side groups get
the lowest numbers.
Use numbers followed by commas and dashes to
indicate group locations and names.
Below is 3,3,6-trimethylheptane :
Alkane Nomenclature
1.
2.
Number the longest carbon chain so that side groups get
the lowest numbers.
Use numbers followed by commas and dashes to
indicate group locations and names.
The left structure is 1,3-dichlorohexane
The right structure is 2,3-dichloropentane
Alkane Nomenclature
1.
2.
Number the longest carbon chain so that side groups get
the lowest numbers.
Use numbers followed by commas and dashes to
indicate group locations and names. The side groups
are listed alphabetically: ethyl before propyl.
Below is 3-ethyl-4,5-dipropyloctane.
Alkane Nomenclature
1.
2.
Number the longest carbon chain so that side groups get
the lowest numbers.
Use numbers followed by commas and dashes to
indicate group locations and names (alphabetic order).
Below is 4,6-diethyl-4,6,7-trimethyl-5,5-dipropyldecane
Not 5,7-diethyl-4,5,7-trimethyl-6,6-dipropyldecane
Isomers
• Isomers are organic compounds which have the same
chemical formula but have different structures and
properties.
• The isomers of C5H12 are shown
Isomers
• Isomers are organic compounds which have the same
chemical formula but have different structures and
properties.
• The isomers of C6H14 are shown
Cycloalkanes
• Alkane rings are called cycloalkanes. Their general
formula is CnH2n .
Cycloalkanes
• Cycloalkanes can have groups and are numbered so that
the groups get the lowest numbers as with alkane chains.
Alkenes
• Alkenes are hydrocarbons
with one or more double
bonds.
• Alkenes are named by the
numbers of carbon atoms
like alkanes but with an
“ene” ending.
• The last three structures
to the right shown require
an extra H at the rt. End of
the molecule.
• Alkenes have a general
formula, CnH2n .
Alkene Nomenclature
Some alkenes can have their double bonds in numerous
positions so their naming system accounts for the double
bond placement.
The Geometry of Alkenes
• Unlike alkanes in which atoms can freely rotate, in
alkenes the double bond rigidly fixes atoms on either
side of the double bond.
Cis-Trans Isomers
• In alkenes with groups other than hydrogen, two
different molecules are possible with the same
formulas. Trans isomers have the groups diagonally
opposite while cis isomers have the groups on the
same side of a molecular axis.
Cis and Trans 2-Pentene
• The groups on opposite sides of the double bond in 2pentene are in different positions so these molecules
are isomers
Alkene Nomenclature
Some alkenes can have their double bonds in numerous
positions so their naming system accounts for the double
bond placement. But-1-ene can be called n-butene or 1butene.
Alkynes
• Alkynes have one or more triple bonds. They are named
by using the standard alkane root and applying a “yne”
ending rather than the “ane” ending.
Triple Bond Position Alters an Alkyne’s Name
Like alkenes,
alkynes need to
have their triple
bond position
notated in their
name.
General Formula for an Alkyne
The general formula for an alkyne is CnH2n-2 .
The Geometry of Alkynes
• The triple bond of an alkyne is very rigid. Parts of
alkynes with repeating triple bonds form straight,
needle-like molecules.
Comparison of Single, Double and Triple Bonds
• The length of a bond shortens from single to double to
triple bonds.
Benzene – A Ring Compound
• Benzene, C6H6 , is a common organic molecule.
Benzene’s Bond Lengths
• Although benzene can be constructed with alternating
double and single bonds, every bond between the
carbons is midway between a single and a double
bond.
Explaining Benzene’s Intermediate Bond Length
• A concept called resonance is used to explain the
intermediate bond length of benzene’s bonds.
• Resonance is the idea that the double bonds alternate
between the atoms which evens out the sharing of
electrons, bonds of intermediate length.
Resonance
in Benzene
• Different
resonance
structures
show
alternating
double
bonds.
Ways of Representing Benzene
Aromatic Compounds
• Any compound incorporating the benzene ring is
called an aromatic compound.
Many Aromatic Compounds have Aromas
• Spearmint smell
Steroid Molecules are Aromatics
Functional Groups
• A functional group is a specific group of atoms on a
molecule that gives it specific properties.
Alcohols
• All alcohols have one or more hydroxyl groups (-OH)
• The General Form of an alcohol is R-OH, where R
stands for any organic chain or ring.
Naming Alcohols
• The molecule above is 3-methyl-2-pentanol
• Alcohols take the longest chain name, replacing the
regular ending with an –ol ending.
Properties of Alcohols
• Alcohols have an –OH group (polar character) that
makes them more soluble in water but they may also
have longer hydrocarbon chains (nonpolar character)
which make them less soluble in water.
Review of Polar Molecules
• Water is a polar molecule (develops + and – poles)
because the oxygen atom attracts shared electrons
more than hydrogen does.
Polar Water Molecules
Attract Polar Substances
• Water, a polar
substance will
dissolve other
polar substances
or substances
with charged
particles.
The “Like Dissolves Like” Rule
• Nonpolar substances (like gasoline) dissolve and mix
with (are soluble in) nonpolar substances while polar
substances are soluble with polar substances.
Polar and Nonpolar Substances are
Immiscible (Do Not Mix)
Properties of Alcohols
• If the –OH group is more prominent than the carbon
chain, the alcohol is soluble (methanol, ethanol and
propanol). If the chain is more prominent, the alcohol
resists dissolving in water (butanol, pentanol etc.)
Other Alcohol Properties
• All alcohols are poisonous
• Ethanol (in beer, wine and spirits) is less poisonous but
slows down the nervous system and shut down the brain
and breathing. When drunk persons pass out, they may
stop breathing. The liver detoxifies ethanol.
The Aldehyde and Ketone Functional Group
• The carbonyl
group converts an
organic compound
into either an
aldehyde or a
ketone, depending
on whether the
group is on an end
carbon or a carbon
within a chain.
A Carbonyl Group on an End Carbon, makes
an Aldehyde
• An aldehyde changes the root name to –al.
• Methanal (commonly called formaldehyde), ethanal, and
propanal are three aldehydes.
An Aromatic Aldehyde
• Benzylaldehyde is formed from benzene and an
attached carbon with carbonyl group.
Ketones Made by Internal Carbonyl
• Ketones have a carbonyl group on a carbon not on the
end of a molecule.
• Ketones change the regular chain ending to -one
Naming Ketones
• Besides changing the
ending to –one, the
position of the carbonyl
group must be indicated.
• 3-pentanone
The Organic Acid Group
• Carboxyl groups (-COOH) attached to an organic
molecule give the molecule an acidic character.
Naming Organic Acids
• Organic Acids change the root name ending to –oic
acid. (methanoic, ethanoic, propanoic acids)
Methanoic Acid (Formic Acid)
• Ants use formic acid as a defense or stunning
chemical against predators or prey.
Ethanoic Acid (Acetic Acid)
• The active ingredient of vinegar is acetic acid, usually
present in about 5% by volume.
• Vinegar is often manufactured from ethyl alcohol in
wines or ciders.
Other Organic Acids with COOH Group(s)
The Ether Linkage
• The oxy group makes ethers of organic compounds.
Naming Ethers
• The shortest hydrocarbon chain prefix is used with oxy
followed by the longer chain hydrocarbon name
unchanged.
• Methoxypropane
Branched Chain Ethers
• When naming branched chained ethers, the carbons
on the chains are numbered from the oxy group.
• The formula for 1-methoxy-3,3-dimethylbutane
is
CH3OCH2CH2C(CH3CH3)CH3
Properties of Ethers
• Ethers have low boiling points, evaporating readily.
• Ethers have anaesthetic properties, rendering higher
organisms unconscious, “quieting” lower organisms.
The NH2 Group and Amines
• An amine is an organic compound containing an NH2
group.
• Amines often have “fish-like” odour.
Amino Acids
• Amino acids have an amine group and an acid group.
Amino Acids
• Living things
make and use
amino acids.
There are 20
naturallyoccuring amino
acids.
• A
Amino Acids
• Amino acids link together to form long chains that
become proteins, very important compounds in living
things.
Bonding of Amino Acid
• When amino
acids are
bonded
together, they
lose a water
molecule, so
this type of
reaction is
called a
condensation
synthesis
Amino Acids
• The bond between amino acids is called a peptide
bond and a chain of amino acids is called a
polypeptide
Amino Acid Bonding
• The linkage between amino acids (peptide bond) is
generally known as an amide linkage
• The oxygen in the above structure should have a
double bond !
Amides
• Amides have the amide group, CONH2
• Amide chains are numbered from the amide group
• A
The Ester
• An ester is an organic compound in which a COO
group joins two hydrocarbon chains.
The Ester
• Esters often have distinct aromas and flavours.
Alcohols and Acids React, Forming Esters
• In naming
an ester,
the alcohol
chain is
given a –yl
ending
followed by
the acid
chain name
whose
ending
becomes –
ate.
Examples of Esters
• Rum is isobutyl propionate
• Apple is methyl butyrate
• Banana is 3-methyl butylacetate
Pear is propyl formate
Orange is octyl acetate
Triglycerides (Fats) and the Ester Linkage
• Fatty acids are linked to glycerol by means of
ester linkages.
Summary of
Functional
Groups
• Groups not
represented
include esters
and ethers
• A
Summary of Functional Groups
Organic Reactions: Oxidation and Reduction
• Organic molecules are oxidized if they have oxygen
added to the molecule or if they have hydrogen
removed from the molecule
• Alcohol in wine is oxidized to ethanal and then to
acetic acid (Wine in air or acted on by aerobic bacteria
turns to vinegar).
Substitution Reactions
Substitution reactions occur with alkanes. One
atom or group on a chain is substituted with
another.
+
Cl-Cl

+
H-Cl
Multiple Substitutions
When chlorine gas is reacted with methane, Cl
atoms can substitute up to four hydrogens.
+
Cl-Cl
chloroform

+
H-Cl
Displacement Reactions
One group can take the place of another and this is
called a displacement reaction.
+ NH3

+
H-Cl
Addition Reactions
In alkenes, a double bond can be opened, leaving
two sites for the parts of another substance to
bond to. Alkenes are more reactive than alkanes.
+
H-O-H 
Examples of Other Addition Reactions
Polymerization Reaction (Forming Plastics)
A monomer is a repeating unit found within a larger
molecule. A polymer is a molecule made up of
similar repeating monomers. Polymerization is
the reaction in which monomer link together to
form polymers.
Addition Polymerization Reactions
Addition polymerization involves the bonding of polymers
without the elimination of atoms. Molecules with double
bonds open one of the bonds which allows them to link
together in a long chain. The monomer ethene opens one
of its double bonds to form a long polymer, polyethylene.
+

Addition Polymerization Reactions
Addition polymerization involves the bonding of polymers
without the elimination of atoms. Molecules with double
bonds open one of the bonds which allows them to link
together in a long chain. The monomer ethene opens one
of its double bonds to form a long polymer, polyethylene.
Teflon Addition Polymer
Teflon is a plastic (polymer) used for valves and
non-stick surfaces.
Saran Addition Polymer
Lucite Addition Polymer
Plexiglass Addition Polymer
A
PVC Addition Polymer
A
Styrofoam Addition Polymer
A
Condensation Polymerization Reactions
Condensation polymerization results in the
elimination of atoms, often water molecules.
Protein
Dacron (A Polyester) :Condensation
Polmerization
Elastomers
A
Thermoplastic Plastics
A
Thermosetting Plastics
A
A
A
A
A