Organic Chemistry
Unit 10
What is Organic chemistry?
• What does organic mean to you?
• The name organic was given to molecules
found in living organisms
• Now, organic chemistry refers to the chemistry
of carbon compounds
– Carbon is important to life because of its ability to
form an endless number of molecules
• CH4 – methane gas
• Proteins
• Cotton, wool, silk
• CH3CH2OH - Ethanol
Organic Compounds
Typically, organic compounds
 Contain carbon.
 Have covalent bonds.
 Have low melting points.
 Have low boiling points.
 Are flammable.
 Are soluble in nonpolar
solvents.
Bonding in Organic Compounds
• Carbon has 4 valence electrons (lone
electrons)
•
•
C•
•
• This means there are four places for it to
bound to other atoms in order for carbon
to achieve an octet
•4
1•
•
C
•
3
2
Bonding with Hydrogen

Carbon has 4 lone electrons; hydrogen has 1.
•
•
C•
H•
•

To achieve an octet, carbon forms four bonds.
H
H
••
|
HCH
H—C—H
CH4 , methane
••
|
H
H
Tetrahedral Nature of Carbon
• When carbon forms four bonds to other
atoms, the bonds are situated 109.5o apart
from each other.
• This arrangement is a
tetrahedral arrangement.
Organic Molecules
• In organic molecules, valence electrons
form covalent bonds between carbon
atoms
• Molecules consisting of only carbon and
hydrogen are call hydrocarbons
H
••
HC 
••
H
H
••
CH
••
H
H H
| |
H—C—C—H
| |
H H
Ethane,CH3CH3
Other Elements
• Carbon in organic compounds also
commonly forms covalent bonds with N,
O, S, and halogens (Cl, Br)
Learning Check
• Complete the structure of the organic
molecule by adding the correct number
of hydrogen atoms.
C—C—C
Learning Check
• Complete the structure of the organic
molecule by adding the correct number
of hydrogen atoms.
H H H
|
| |
H—C—C—C—H
|
| |
H H H
Alkanes
• Hydrocarbons that contain only carbon-carbon single
bonds
• General formula = CnH2n+2
– n = number of carbons
Uses of Alkanes
• Small number of carbons (1 – 4
carbons)
– gases
– Heating fuels – propane, butane
• 5 – 8 carbons
– Liquids
– Fuels – gasoline, kerosene, diesel,
jet fuel
• 18 + carbons
– Waxy solids
– Waxes (paraffins), Vaseline
Conformation of Alkanes
• Because of the tetrahedral shape of carbon bonds,
carbon bonds are in a zigzag pattern
• Atoms can rotate around a single carbon-carbon bond
– Different arrangements that can occur because of this
are called conformations
Expanded and Condensed
Formulas
• Expanded structural formula = all individual
bonds (indicated with dashes) and atoms are
drawn
• Condensed structural formula =each carbon
atom is grouped with its bonded hydrogen
atoms. Subscripts are used to indicate number
of H’s and bonds are indicated with dashes
• Skeletal Formula= only carbons and bonds(as
dashes) are represented- Hydrogens are
implied
Expanded and Condensed
Formulas
• Line bond formulas = lines represent
carbon-carbon bonds. No individual atom
is indicated. Hydrogens and Carbons are
implied.
• Molecular Formula= Atoms are
represented and subscripts are used to
indicate the number of each atom. No
bonds are drawn.
• Geometric Formula= Similar to line bond
formulas, but used for cyclic compounds.
IUPAC
• International Union of Pure and Applied
Chemistry
• Determined protocol for naming organic
compounds
• Pentane
– Prefix states number of carbons
• Pent - = five carbons
– Suffix shows kind of compound
• -ane = alkane, only single carbon bonds
Prefixes (Table 11.2)
Cycloalkanes
• Hydrocarbons do not need to be in a chain, they
can also form circular structures
Cycloalkanes
• Cycloalkanes:
• Are rings of carbons that can be drawn as
geometric figures.
• Have a general formula of CnH2n or 2 H less
than the alkane.
•
propane C3H8
cyclopropane C3H6.
•
butane C4H10
cyclobutane C4H8.
• Are named with the prefix cyclo- in front of
the corresponding alkane name.
Table 11.4
LINE BOND FORMULAS FOR SOME CYCLOALKANES
Cyclopropane
Cyclobutane
Cyclopentane
Cyclohexane
C3H6
C4H8
C5H10
C6H12
Naming Alkanes
• Molecular formulas do not tell us the structure
– constitutional isomers
• Carbon compounds can be continuous-chain or
branched-chained
Substituents
• Substituents are groups of atoms that
replace a hydrogen on a carbon chain
– Blue flashcards! *need to know!!*
• If the substituent is a hydrocarbon, it is
called an alkyl group
– The alkyl group is named by replacing the –
ane with -yl
Some of these included in Table 11.5
Steps for naming alkanes
1. Name the longest continuous chain of
carbons as the main chain
2. Number the carbon atoms in the main
chain starting on the end nearest a
substituent
-Where there are 2 or more substituents, the
main chain should be numbered to give the lowest
possible number set
Naming Alkanes Cont.
3. Give the location and name of each alkyl
group in front of the name of the main
chain
- use prefixes (di-, tri-) if a group appears more
than once
4. List the substituents in alphabetical order
Naming
CH3-CH-CH2-CH-CH2-CH3
CH3
CH2CH3
• 1. Name Longest Chain First= hexane
• 2. Number Carbons from the end with the
nearest substituent.
1
2
3
4
5
6
CH3-CH-CH2-CH-CH2-CH3
CH3
CH2CH3
3. Give the location and name of each alkyl
group in front of the name of the main
chain
2-methyl-4-ethylhexane
4. List substituents in alphabetical order.
4-ethyl-2-methylhexane
Naming
CH3-CH-CH2-CH2-CH-CH3
CH3
CH2CH3
• 1. Name Longest Chain First= heptane
• 2. Number Carbons from the end with the
nearest substituent.
1
2
3
4
5
CH3-CH-CH2-CH2-CH-CH3
CH3
6 CH2CH3
7
3. Give the location and name of each alkyl
group in front of the name of the main
chain
2,5-dimethylheptane
4. List substituents in alphabetical order.
Fine as is!
Try a Few!
• On board exercise!
Drawing Structural Formulas
Step 1 – Draw the main chain of carbon
atoms
Step 2 – Draw the substituents on the main
chain in the positions indicated by the
location numbers
Step 3 – Fill in the correct number of
hydrogen atoms to give four bonds to each
carbon atom
Draw 2,3-dimethylpentane
1. Draw Main Chain of Carbon atoms
C-C-C-C-C
2. Draw the substituents on the main chain
in the positions indicated by the location
numbers
C-C-C-C-C
C C
3. Fill in the correct number of hydrogen
atoms to give four bonds to each carbon
atom
CH3-CH-CH-CH2-CH3
CH3 CH3
Try a few!
• 2,3,5-trimethylhexane
• 3-ethylpentane
• 4-isopropyloctane
Isomers
• Molecules with the same molecular
formula but different structural formula
• Example: C5H12
CH3-CH2-CH2-CH2-CH3
CH3-CH-CH2-CH3
C H3
C H3
CH3-C-CH3
C H3
Constitutional Isomers
• Most organic compounds have structural
isomers and their number increases as the
number of atoms increases
Physical Properties of Constitutional
Isomers

Different structural arrangement can result in
very different physical properties
Drawing Isomers
• Step 1 – Draw the longest continuous
chain
• Step 2 – Remove one carbon from the
chain and attach it as a methyl group in as
many locations as possible
• Step 3 – Remove another carbon atom
from the main chain and attach as another
alkyl group
Try Some
• Draw isomers for C4H10
– Practice Naming!!
Haloalkanes
• An alkane in which halogen atoms replace
one or more hydrogens
• Used as solvents and anesthetics
• CFC’s (chlorofluorocarbons) were used a
propellants in aerosols
– React with ozone in the upper
atmosphere
– Resulted in ozone depletion
over the Antarctic
Naming Haloalkanes
• IUPAC names for halogen substituents
are:
•
•
•
•
Fluorine = fluoroChlorine = chloroBromine = bromoIodine = iodo-
• The halo-substituents are numbered and
arranged alphabetically, like we did before
Other substituents
• Use the same naming rules
– Number position on the parent chain
– Put in alphabetical order
CH3-CH-CH2-CH3
Cl
CH3-CH-CH-CH2-CH3
Cl Br
Naming Cycloalkanes
A cycloalkane with:
 One substituent is named by placing the
name of the substituent in front of the
cycloalkane name.
 Two or more substituents is named by
numbering the ring in the direction that
gives the lower numbers to the
substituents.
Cycloalkanes with Side Groups
CH3
methylcyclopentane
CH3
CH3
1,2-dimethylcyclopentane
CH3
CH3
1,2,4-trimethylcyclohexane
CH3
Try Some!
• On Board Exercise
Worksheet 1
• You can now complete worksheet 1.
Chemical Properties of Alkanes


Alkanes are typically not very reactive due
to strong C-C single bonds.
The most typical reaction is combustion,
where an alkane reacts with oxygen to
produce carbon dioxide, water, and energy.
alkane + O2
CO2 + H2O + energy
Combustion
A fuel such as propane reacts
with oxygen and burns,
producing CO2 and H2O.
 Propane is burned to obtain
energy and heat for cooking
or warming a room.
C3H8 + 5O2
3CO2 + 4H2O

Incomplete combustion
• It is dangerous to burn fuels in a closed room
• With limited amounts of oxygen, incomplete
combustion occurs
– This produced carbon monoxide, which is a toxic
gas
2CH4(g) + 3O2(g)
2CO(g) + 4H2O(g) + heat
Classifying Carbon Atoms
• Primary Carbons (1o)- Bonded to only one
other carbon atom
• Secondary Carbons (2o)- Bonded to two
other carbon atoms
• Tertiary Carbons (3o)- Bonded to three
other carbons
Functional Groups
• Millions of compounds possible
• However, certain structures behave in
similar manners
• These are called functional groups
• For now:
• Alkanes
– Saturated Hydrocarbons
• Alkenes, Alkynes, Aromatics
– Unsaturated Hydrocarbons
Background: Double Bonds
• Two nonmetal atoms can share more than
one set of electrons
• Sharing four electrons = double bond
H
H
H
H
•• •• ••
• •C • • •C•
Background: Triple Bonds
• Two nonmetals can also form triple bonds
= sharing 6 electrons
Alkenes, Alkynes and Aromatics
• Alkanes contain only single bonds
• Alkenes contain one or more double
bonds
• Alkynes contain one or more triple bonds
• Aromatic ring (benzene) is 6 carbons
cyclized with alternating double bonds
Ch. 12-Unsaturated Hydrocarbons
Unsaturated
hydrocarbons:
 Have fewer hydrogen
atoms attached to the
carbon chain than
alkanes.
 Are alkenes with
double bonds or
alkynes with triple
bonds.
Alkenes
• Contain at least one
double bonds
• Important in
manufacturing and in
human and plant
functioning
– Hormones
– Ripening fruit
– Ethene used to make
polymers
Naming Alkenes and Alkynes
 In the IUPAC system, the –ane ending of the
corresponding alkane is changed to –ene for
alkenes and to –yne for alkynes.
Naming Alkenes and Alkynes
When the carbon chain has 4 or more C
atoms, the chain is numbered to give the
lowest number to the double or triple bond.
1
CH2=CH—CH2—CH3
1-butene
2
CH3—CH=CH—CH2—CH3
2-pentene
3
CH3—CH2—CC—CH2—CH3 3 -hexyne
More Naming
• If you have more than 1 double or triple
bond:
– Name them as dienes or diynes
• CH2=CH—CH2—CH2=CH3
1
2
3
4
1, 4 - pentadiene
5
• CHC—CH2—CC—CH2—CH3
????
More Naming
• If you have more than 1 double or triple
bond:
– Name them as dienes or diynes
• CH2=CH—CH2—CH2=CH3
1
2
3
4
1, 4 - pentadiene
5
• CHC—CH2—CC—CH2—CH3
1, 4 - heptadiyne
Alkenes and Alkynes with
Substituents
• 1. Name the longest carbon chain that
contains the double or triple bond
• 2. Number the chain starting at the end
nearest the double or triple bond.
4-methyl-1-pentene
Try One!
Naming Cyclic Alkenes and
Alkynes
• Use –ene instead of -ane
• The double bond of a cycloalkene is
understood to be between Carbon 1 and
Carbon 2. Number from there to get the
lowest possible number set.
Practice!
• On Board Exercise
Cis-Trans Isomers
Double Bonds do not rotate freely!
Introducing a new type of isomer!
Cis-Trans Isomers
 Two isomers are possible
when groups are attached
to the double bond.
 In a cis isomer, groups are
attached on the same side
of the double bond.
 symmetrical
 In the trans isomer, the
groups are attached on
opposite sides.
 unsymmetrical
Naming Cis-Trans Isomers

The prefixes cis or trans are placed in front of the
alkene name when there are cis-trans isomers.
Br
Br
C C
H
H
Br
C C
H
cis-1,2-dibromoethene
H
Br
trans-1,2-dibromoethene
Worksheet 2
• You can now complete worksheet 2.
Addition Reactions
 Double and triple bonds are
weaker than single bonds
 More reactive
 In the addition reaction, reactants
are added to the carbon atoms in
the double or triple bond.
Addition Reactions
• H2C=CH2 + A—B  H2C—CH2
A B
Hydrogenation
 In hydrogenation, hydrogen atoms add to
the carbon atoms of a double bond or
triple bond.
 A catalyst such as Pt or Ni is used to
speed up the reaction.
H H
H2C CH2 + H2
Pt
H2C CH2
H H
HC CH + 2H2
Ni
HC CH
H H
Hydrogenation of Oils
 When hydrogen
adds to the
double bonds in
vegetable oils,
the products
are solids at
room
temperature.
Halogenation
• In halogenation, halogen atoms add to
the carbon atoms of a double bond or
triple bond.
Br Br
H2C CH2 +
Br2
H2C CH2
Cl Cl
HC C CH3 + 2Cl2
H C C CH3
Cl Cl
Testing for Double and Triple
Bonds
• When bromine (Br2) is
added to an alkane,
the red color of
bromine persists.
• When bromine (Br2) is
added to an alkene or
alkyne, the red color
of bromine
disappears
immediately.
Hydrohalogenation
• In hydrohalogenation, the atoms of a
hydrogen halide add to the carbon atoms
of a double bond or triple bond.
H
CH3 CH CH CH3 + HCl
+ HBr
Cl
CH3 CH CH CH3
H
Br
Markovnikov’s Rule
• When an unsymmetrical alkene undergoes
hydrohalogenation, the H in HX adds to
the carbon in the double bond that has the
greater number of H.
H
Cl
CH3 CH CH2 Does not form
CH3 CH CH2 + HCl
C with the most H
Cl
H
CH3 CH CH2
Product that forms
Hydration Adds Water
• In hydration, H and OH from water add to
the carbon atoms of a double bond or
triple bond to form alcohols (OH).
• The reaction is catalyzed by acid H+.
+
H
CH3 CH CH2 + HOH
CH3 CH CH2
H+
+ HOH
OH H
H
OH
Worksheet 3
• You can now complete worksheet 3.
Aromatic Compounds
Benzene is
 An aromatic compound.
 A ring of 6 C atoms and 6 H atoms.
 Alternating single and double bonds
 Aromatic compounds often have fragrant
odors
Aromatic Compounds in Nature and
Medicine
Naming Aromatic Compounds

A benzene with a single substituent is often named
as a benzene derivative.
CH3

Cl
Methylbenzene
Chlorobenzene
A benzene ring as a substituent is called a phenylgroup
Some Common Names

Some substituted benzene rings have common
names that have been in use for many years.
CH3
Toluene
(Methylbenzene)

NH2
Aniline
(Benzenamine)
Also, know naphthalene (2 fused rings)
OH
Phenol
(Hydroxybenzene)
Naming Aromatic Compounds


A benzene ring with two or more substituents
is numbered to give the lowest numbers to the
side groups.
Common names use the prefixes ortho- (1,2-),
meta- (1,3-) and para- (1,4-).
CH3
Br
Cl
Br
Cl
1,2-dimethylbenzene
(o-dibromobenzene)
1,3-dichlorobenzene
(m-dichlorobenzene)
Cl
4-chloromethylbenzene
(p-chlorotoluene)