Section 1 Compounds of Carbon
• Explain the unique properties of carbon that make the formation of organic molecules possible.
• Relate the structures of diamond, graphite, and other allotropes of carbon to their properties.
• Describe the nature of the bonds formed by carbon in alkanes, alkenes, alkynes, aromatic compounds,
and cyclic compounds.
• Classify organic compounds such as alcohols, esters, and ketones by their functional groups.
• Explain how the structural difference between isomers is related to the difference in their properties.
Properties of Carbon
• Carbon atoms nearly always form covalent bonds.
• Three factors make carbon-carbon bonds unique:
• First, carbon-carbon bonds are quite strong
• Second, carbon compounds are not very reactive.
• Third, carbon can form up to four single covalent bonds, so a wide variety of compounds is
possible.
Carbon Exists in Different Allotropes
• As an element, carbon atoms can form different bonding arrangements, or allotropes.
• The different allotropes have properties that differ due to the different arrangements of the carbon bonds.
Other Carbon Allotropes Include Fullerenes and Nanotubes
• Besides diamond and graphite, carbon allotropes include buckminsterfullerene, and nanotubes.
Organic Compounds
• Organic compounds contain carbon, and most also contain atoms of hydrogen.
• They can contain other elements, such as oxygen, nitrogen, sulfur, phosphorus, and the halogens.
• Chemists group organic compounds with similar characteristics into classes.
• The simplest class of organic compounds, hydrocarbons, contain only carbon and hydrogen.
Alkanes Are the Simplest Hydrocarbons
• Alkanes are hydrocarbons with carbon atoms that are connected only by single bonds.
• Three alkanes are methane, ethane, and propane.
• The formulas of the alkanes fit the general formula CnH2n+2, where n is the number of carbon atoms.
• For example, if an alkane has 30 carbon atoms, then its formula is C30H62.
Many Hydrocarbons Have Multiple Bonds
• Alkenes are hydrocarbons that contain at least one double bond between two carbon atoms.
• Alkenes with one double bond have a general formula that is written CnH2n.
• Alkynes are hydrocarbons that contain at least one triple bond between two carbon atoms.
• An alkyne with one triple bond is written as CnH2n−2.
Carbon Atoms Can Form Rings
• Carbon atoms that form covalent bonds with one another can be arranged in a straight line or in a
branched arrangement.
• Carbon bonds can also be arranged in a ring structure.
• The prefix cyclo- is added to the name of an alkane to indicate that it has a ring structure.
Benzene Is an Important Ring Compound
• An important organic ring compound is the hydrocarbon benzene, C6H6.
• Benzene is the simplest aromatic hydrocarbon.
• It can be drawn as a ring with three double bonds.
• Experiments show that all the carbon-carbon bonds in benzene are the same, so it is a molecule with
resonance structures.
Other Organic Compounds
• Other classes of organic compounds contain other atoms such as oxygen, nitrogen, sulfur, phosphorus,
and the halogens along with carbon and hydrogen.
• The word organic originally described only compounds made by living things. Now chemists can make
organic compounds from inorganic substances.
Many Compounds Contain Functional Groups
• A typical organic compound has a group of atoms that is responsible for its chemical properties.
• This a group of atoms is known as a functional group.
• Organic compounds are commonly classified by the functional groups they contain.
• Because single bonds between carbon atoms rarely react, functional groups are often responsible for
how an organic compound reacts.
Functional Groups Determine Properties
• The presence of a functional group causes an organic compound to have properties that differ greatly
from those of the corresponding hydrocarbon.
• The structural formulas of butane and 1-butanol both have 4 carbon atoms joined by single bonds
in a line.
• Butane is a gas at room temperature, but 1-butanol is a liquid and has a greater density and
higher melting and boiling points than butane.
• The only difference between butane and 1-butanol is the presence of the functional group —OH
on one of the carbon atoms in 1-butanol.
Different Isomers Have Different Properties
• Both molecules below are alcohols and have the same molecular formula: C4H10O.
• The molecules of 1-butanol and 2-methyl-1-propanol differ in the way in which their atoms are
arranged.
• Isomers are compounds that have the same formula but differ in their chemical and physical properties
because of the difference in the arrangement of their atoms.
• The greater the structural difference between two isomers, the more they will differ in their properties.
Section 2 Names and Structures of Organic Compounds
Objectives
• Name simple hydrocarbons from their structural formulas.
• Name branched hydrocarbons from their structural formulas.
• Identify functional groups from a structural formula, and assign names to compounds containing
functional groups.
• Draw and interpret structural formulas and skeletal structures for common organic compounds.
Naming Straight-Chain Hydrocarbons
• Inorganic carbon compounds are named by using a system of prefixes and suffixes.
• Organic compounds have their own system of prefixes and suffixes that denote classes.
• For example, the names of all alkanes end with the suffix -ane.
• For alkanes that consist of five or more carbon atoms, the prefix comes from a Latin word that indicates
the number of carbon atoms in the chain.
Naming Short-Chain Alkenes and Alkynes
• A saturated hydrocarbon is one in which each carbon atom forms four single covalent bonds.
• The alkanes are saturated hydrocarbons.
• An unsaturated hydrocarbon is one in which not all carbon atoms have four single covalent bonds.
• Alkenes and alkynes are unsaturated hydrocarbons.
• The rules for naming an unsaturated hydrocarbon with fewer than four carbon atoms are similar to those
for naming alkanes.
• A two-carbon alkene is named ethene, with the suffix -ene indicating that the molecule is an
alkene.
• A three-carbon alkyne is named propyne, with the suffix –yne indicating that the molecule is an
alkyne.
Naming Long-Chain Alkenes and Alkynes
• The name for an unsaturated hydrocarbon containing four or more carbon atoms must indicate the
position of the double or triple bond within the molecule.
• First number the C atoms in the chain so that the first C atom in the double bond has the lowest number.
• If there is more than one multiple bond in a molecule, number the position of each multiple bond, and
use a prefix to indicate the number of multiple bonds.
• The molecules on the left is correctly numbered from left to right because the first carbon atom with the
double bond must have the lowest number.
•
For example, the following molecule is called
1,3-pentadiene.
• (Note the placement of the prefix di-.)
Naming Branched Hydrocarbons
• When a hydrocarbon is not a simple straight chain, first count the carbon atoms in the longest chain.
• The named is based on the corresponding alkane. The compound below has a “parent” chain that
contains 7 carbon atoms, so it is heptane.
• Next, number the C atoms so that any branches on the chain have the lowest numbers possible.
Name the Attached Groups and Indicate Their Positions
• The third carbon atom has a —CH3 group attached. This group is known as a methyl group.
• Because the methyl group is attached to the third C, the complete name is 3-methylheptane.
• You can omit the numbers if there is no possibility of ambiguity.
• For example, a propane chain can have a methyl group only on its second carbon.
• If the methyl group were on the first or third carbon of propane, the molecule would be butane.
• So, 2-methylpropane is called methylpropane.
• With unsaturated hydrocarbons that have attached groups, the longest chain containing the double bond
is considered the parent compound.
• In addition, if more than one group is attached to the longest chain, the position of attachment of each
group is given.
• Prefixes are used if the same group is attached
more than once.
•
•
The chain with the double bond has 5 C atoms, so the compound is a pentene.
The 1st C atom has a double bond, so it is 1-pentene. Two methyl groups are attached to the third carbon
atom, so the name is 3,3-dimethyl-1-pentene.
Naming a Branched Hydrocarbon
Sample Problem A
Name the following hydrocarbon.
Names of Compounds Reflect Functional Groups
• Names for organic compounds with functional groups are based on the same system for branched
chains.
• First, the longest chain is named.
• Then a prefix or suffix indicating the functional group is added to the hydrocarbon name.
• When necessary, the position of the functional group is noted just as with hydrocarbon branches.
Naming Compounds with Functional Groups
• A prefix or suffix can indicate a functional group.
• Because the longest chain in the structure below has three C atoms, the name is based on propane.
• The —OH functional group classifies it as an alcohol.
• Because the —OH is attached to the second C atom, the correct name for this compound is 2-propanol.
Sample Problem B
Name the following organic compound.
Representing Organic Molecules
• There are many ways of depicting organic molecules.
• Each type of model used to represent an organic compound has both advantages and disadvantages.
• They can highlight different features such as the number and kinds of atoms or the three-dimensional
shape of the space-filling model.
• A model cannot fully show the true three-dimensional shape of a molecule or show the motion within a
molecule caused by the atoms’ constant vibration.
Structural Formulas Can Be Simplified
• Structural formulas are sometimes represented by skeletal structures, which show bonds, but leave out
some or even all of the carbon and hydrogen atoms.
• Skeletal structures usually show the carbon framework only as lines representing bonds.
• These lines form a zigzag pattern to indicate the tetrahedral arrangement of bonds.
• Atoms other than C and H are always shown.
• In structural formulas, C and H atoms are not shown unless they are part of functional groups.
Sample Problem C
Draw both the structural formula and the skeletal structure for 1,2,3-propanetriol.
Section 3 Organic Reactions
Objectives
• Describe and distinguish between substitution and addition reactions.
• Describe and distinguish between condensation and elimination reactions.
Substitution and Addition Reactions
• Organic compounds participate in a variety of chemical reactions.
• A substitution reaction is a reaction in which one or more atoms replace another atom or group of
atoms in a molecule.
• An addition reaction is a reaction in which an atom or molecule is added to an unsaturated molecule
and increases the saturation of the molecule.
Halogens Often Replace Hydrogen Atoms
• One substitution reaction occurs when a halogen, such as a chlorine atom, replaces a hydrogen atom on
an alkane molecule, such as methane.
• The substitution reactions can continue, replacing the remaining H atoms in methane one at a time.
• The products are dichloromethane, trichloromethane, and tetrachloromethane (commonly known as
chloroform).
Hydrogenation Is a Common Addition Reaction
• One addition reaction is hydrogenation, in which H atoms are added to an unsaturated molecule.
• The product of the reaction contains fewer double or triple bonds than the reactant.
Making Consumer Products by Hydrogenation
• Another kind of hydrogenation is the manufacture of cyclohexane from benzene as shown below.
• Over 90% of the cyclohexane that is made is used in the manufacture of nylon.
Some Addition Reactions Form Polymers
• Some addition reactions involve joining smaller molecules together to make larger ones.
• The smaller molecules are known as monomers.
• The larger molecule that is made by the addition reaction is called a polymer.
• Polyethylene is a strong but flexible plastic that is made from ethane monomers, C2H4.
• Because ethene is commonly known as ethylene, the polymer it forms is often called polyethylene.
• The following equation shows how a portion of the polymer forms.
Monomers Can Be Added in Different Ways
• Polyethylene is a very long alkane polymer chain.
• The chains form a product that is strong yet flexible.
• Monomers can be added so that a chain branches.
• For example, an ethene monomer is sometimes added to form a side chain.
• A polymer with many side chains remain flexible.
Condensation and Elimination
• Polymers can also be formed by a condensation reaction in which two molecules combine, usually
accompanied by the loss of a water molecule.
• The formation of water as a reaction product is the reason for the name of this type of reaction.
• An elimination reaction is a reaction in which a simple molecule is removed from adjacent carbon
atoms on the same organic molecule.
• An elimination reaction also produces water.
Condensation Reactions Produce Nylon
• Nylon is formed in a condensation reaction.
• The reaction takes place between an amine group on hexanediamine and a carboxyl group on adipic
acid.
• A water molecule is eliminated when an H atom from the amine group and an —OH group from the
carboxyl group are removed.
• This reaction repeats, linking hundreds of reactantsto form the synthetic polymer called nylon 66.
Many Polymers Form by Condensation Reactions
• The polymer polyethylene terephthalate, abbreviated PET, is formed when two monomers are combined
in the following condensation reaction.
•
The functional group present in the product shown above classifies this molecule as an ester, so PET
is a polyester.
Elimination Reactions Often Form Water
•
The acid catalyzes a reaction that eliminates water from ethanol, which leaves a double bond.