Transcript Slide 1

Organic Chemistry
Saturated Hydrocarbons
Petroleum
Reactions of Alkanes
Unsaturated Hydrocarbons
Aromatic Hydrocarbons
Alcohols
Aldehydes and Ketones
Carboxylic Acids
Esters
Polymers
Saturated Hydrocarbons
• Hydrocarbons are molecules of carbon
and hydrogen, like methane.
• Methane
– Formula: CH4
- When carbon has
four bonds, it has a
tetrahedral
arrangement.
Saturated Hydrocarbons
• Alkanes are hydrocarbons with only single
bonds.
– A straight-chain alkane has a long chain of
carbons bonded to each other with hydrogen
atoms around the outside.
• Example: propane has three carbon atoms and 8
hydrogen atoms:
H
H
H
H
C
C
C
H
H
H
H
Saturated Hydrocarbons
– Formulas: For each carbon that is added in an
alkane, there are two more hydrogen atoms in
the compound.
• A CH2 group is added from one compound in the
series to the next.
CH3 – (CH2) m – CH3
– Memorize the first ten prefixes for naming
alkanes: meth, eth, prop, but, pent, hex, hept,
oct, non, dec
Saturated Hydrocarbons
• Branched-Chain Alkanes
– A substituent is an atom or group that
attaches to a carbon.
• Name alkyl groups by removing “-ane” and adding
“-yl”
• Methyl group: CH3
• An alkane substituent is an alkyl group.
• A chain with one or more substituent is
CH CH
branched.
3
CH3
C
CH3
3
CH
CH2
CH3
Saturated Hydrocarbons
• Naming alkanes with the IUPAC rules.
• Step 1. Find the longest continuous
chain of carbons (it doesn’t have to be
straight). (Draw a line through these
carbons if it’s helpful.) Assign an “alkane”
name according to the number of carbons
in this chain.
Saturated Hydrocarbons
• Step 2. All carbons not in this main chain
are “branches” connected to the main
chain. Name each branch using the
corresponding prefix with a “–yl” ending.
1 carbon - “methyl”
2 carbons - “ethyl”
3 carbons - “propyl”
Saturated Hydrocarbons
• Step 3. Number the carbons in the main
chain so that the branch(es) have the
lowest possible numbers assigned to
them. Assign each branch a number
corresponding to where it attaches to the
main chain.
CH3 CH3
CH3
“2, 2, 3 – trimethyl pentane”
C
CH3
CH
CH2
CH3
Petroleum
• Petroleum and natural gas were formed from
decayed plants over 500 million years old.
• It is called “buried sunshine” because the energy
in it originally came from the sun.
– Plants used photosynthesis to store energy.
• Petroleum contains hydrocarbons with chains
containing 5-25 carbon atoms.
• Natural gas contains methane,
ethane, propane and butane.
Combustion Reactions
• In a combustion reaction, a hydrocarbon
(or another fuel) reacts with O2 to make
CO2 and H2O.
• 2C4H10 + 13O2  8CO2 + 10H2O
Combustion Reactions
• Write the balanced equation for the
combustion of propane:
• C3H8 + 5 O2  3 CO2 + 4 H2O
• 1. Write O2 on the left
• 2. Write CO2 and H2O on the right.
• 3. Balance.
Substitution Reactions
• In substitution reactions, hydrogen
atoms are replaced by different atoms.
hv
CH4 + Cl2
CH3Cl + HCl
• The hv represents ultraviolet radiation.
Dehydrogenation Reactions
• In a dehydrogenation reaction, hydrogen
atoms are removed and a double or triple
bond forms.
Cr2O3
H
H
• CH3CH3
+ H2
500 °C
C
H
C
H
Unsaturated Hydrocarbons
• Alkenes have double bonds.
– Naming: add “-ene”
– Example: “ethene”
H
H
C
H
C
H
Unsaturated Hydrocarbons
– Naming alkenes: Name them like alkanes, but
use a number to show the location of the
double bond.
– Because there’s only one place for the double
bond on ethene and propene, you don’t need
a number.
– Example: 2-butene
H
H
H
H
H
C
C
C
C H
H
H
H
H
Unsaturated Hydrocarbons
• Alkynes have triple bonds.
– Naming: add “-yne”
– Example: C2H2 “ethyne”
CH
CH
Unsaturated Hydrocarbons
• In addition reactions, atoms are added
across a double or triple bond.
– Hydrogenation is an addition reaction. H2 is
added.
Pt Catalyst
CH2
CH
CH3
+ H2
CH3CH2CH3
– Halogenation is an addition reaction. A
halogen (group 7A) is added.
CH2
CH
CH3
+ Br2
Aromatic Hydrocarbons
• Aromatic hydrocarbons smell nice, like
wintergreen and cinnamon.
• Most aromatic hydrocarbons contain a
benzene ring.
H
• Benzene is a 6-carbon
H
H
C
ring with three double
C
C
bonds (C6H6).
C
C
H
C
H
H
Aromatic Hydrocarbons
• When two or more structures can be
drawn for a molecule, resonance occurs.
Aromatic Hydrocarbons
• In reality, there are no double bonds in
benzene. The electrons are shared evenly
around the ring.
• This is a more accurate way to represent
benzene:
Aromatic Hydrocarbons
• Benzene is called a “phenyl” group when it
is a side group on an alkane.
– Example: 3-phenylnonane
CH3
CH2
CH
CH2
CH2
CH2
CH2
CH2
CH3
Aromatic Hydrocarbons
• Naming benzene with one side group:
“Benzene” + “Side group name”
– Example: Methylbenzene
Aromatic Hydrocarbons
• Naming benzene with two side groups:
Name them like alkanes, but assign one
group the #1:
– Example: 1,3-dimethyl benzene
CH3
CH3
Aromatic Hydrocarbons
• Common names for disubstituted benzenes:
– 1, 2 position is “orotho” (o)
– 1, 3 position is “meta” (m)
– 1, 4 position is “para” (p)
Systematic Name
1, 2-dichlorobenzene
1, 3-dichlorobenzene
1, 4-dichlorobenzene
Common Name
o-dichlorobenzene
m-dichlorobenzene
p-dichlorobenzene
Alcohols
• Functional groups are groups of atoms
that are capable of characteristic chemical
reactions.
– For example, the functional group of a
carboxylic acid is circled below, a COOH
group.
– The “R” stands for the “rest” of the molecule.
O
R
C
O
H
Alcohols
• An alcohol is an organic compound with
an “-OH” group.
– The “-OH” group is called a hydroxyl group.
– There are three kinds of alcohols:
1). Primary alcohol – one “R” group attached
to the C-OH
2). Secondary alcohol – two“R” groups
attached to the C-OH
3). Tertiary alcohol – three “R” groups
attached to the C-OH
Alcohols
• Primary
• Secondary
• Tertiary
Alcohols
• Naming alcohols: Drop the “e” from the
alkane name and “-ol”
– Example: Methanol.
CH3
O
H
Alcohols
• Properties
– Ethanol is produced by fermentation, which
is the digestion of sugar by yeast. Alcoholic
beverages such as beer are made by this
process.
– Methanol is used to make many materials—
plastics, fibers, etc.
Aldehydes and Ketones
• A carbonyl group is a functional group
with a C
O group.
• An aldehyde has a carbonyl group, where
the carbon is bonded to one or two
hydrogen atoms. It has the general
formula: RCHO.
Aldehydes and Ketones
• A keytone has a carbonyl group on a
carbon that is bonded to two other
carbons. General formula: RCOR
Aldehydes and Ketones
• IUPAC Naming:
• Aldehydes: alkane name minus “e” plus
“al”:
– Methane  Methanal
• Keytones: alkane name minus “e” plus
“anone.” Write the number of the carbon
that has the carbonyl group first:
“2-pentanone”
O
CH3
C
CH2
CH2
CH3
Carboxylic Acids
• Carboxylic acids have the general
formula RCOOH
• They ionize slightly when dissolved in
water:
Carboxylic Acids
• IUPAC Naming:
• Add “-oic acid”
– “Ethanoic acid”
• Carboxylic acids don’t smell good.
• Vinegar contains ethanoic acid.
Esters
• Esters
• Esters have the general formula RCOOR
Esters
• Esters can be made by a reaction between
a carboxylic acid and alcohol.
“Methyl ethanoate”
H
H
o
C
C
H
H
O
H
+
H
O
C
H
H
H
H
o
C
C
H
H
H
O
C
H
H
• Esters smell good, and make the smells in
bananas, oranges and other fruits and
flowers.
Polymers
• Polymers are made from small molecules,
called monomers.
– Ethene can react with itself, creating an
addition polymer.
– This reaction is called an addition reaction.
Many ethene add onto the growinig polymer
chain to make a very long molecule.
Polymers
Ethene
H
H
C
H
Growing polymer chain
C
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
Polyethylene
(
H
H
C
C
H
H
)n