Organic
Chemistry
Organic and Inorganic Chemistry
Organic Chemistry
•The study of
hydrocarbons
(compounds of
Carbon and
Hydrogen) and
their derivatives.
Inorganic Chemistry
•The study of all
substances other
than hydrocarbons
and their
derivatives.
Bonding
Characteristics
of Carbon Atom
• Carbon atoms have the unique ability to bond to
each other in a wide variety of ways that involve
long chains of carbon atoms or cyclic
arrangements (rings) of carbon atoms
• Carbon is a member of Group IVA of the periodic
table (four valence electrons) In compound
formation, four additional valence electrons are
needed to give carbon atoms an octet of valence
electrons.
• The sharing of four valence electrons requires
the formation of four covalent bonds.
Four-bond requirement of Carbon
HYDROCARBONS
AND
HYDROCARBON
DERIVATIVES
Hydrocarbon - is a compound
that contains only carbon
atoms and hydrogen atoms.
Hydrocarbon Derivative - is a
compound that contains
carbon and hydrogen and one
or more additional elements.
2 Classes of Hydrocarbons
Saturated Hydrocarbons
• is a hydrocarbon
in which all
carbon–carbon
bonds are single
bonds.
Unsaturated Hydrocarbon
• is a hydrocarbon in
which one or more
carbon–carbon
multiple bonds
(double bonds, triple
bonds, or both) are
present.
2 Categories of Hydrocarbons Arrangements
•Acyclic Carbon Atom
•Cyclic Carbon Atom
Saturated Hydrocarbon
(Alkanes)
Alkanes: Acyclic Saturated Hydrocarbons
• is a saturated hydrocarbon in which the carbon atom arrangement is
acyclic.
• General molecular formula of Alkane: 𝐶𝑛 𝐻2𝑛+2
• 𝑛 =number of carbon atoms present.
• number of Hydrogen atoms present in an alkane is always
twice the number of carbon atoms plus two more.
• Example: CH₄ - Methane
C₂H₆ - Ethane
C₃H₈ - Propane
Practice: Identify if the following molecular
formula is an Alkane
1.
2.
3.
4.
5.
C₅H₁₂ - Alkane
C₄H₁₀ - Alkane
C₆H₁₂ - NOT Alkane
C₉H₂₀ - Alkane
C₁₀H₂₄ - NOT Alkane
Structural Formulas (2-D)
• A two-dimensional structural representation that shows how the various
atoms in a molecule are bonded to each other
1. Expanded structural formula – shows all atoms in a molecule and all bonds connecting
the atoms.
METHANE
ETHANE
PROPANE
2. Condensed structural formula – uses groupings of atoms in which central atoms and the
atoms connected to them are written as a group, to convey molecular structural
information.
Structural Formulas
• The condensed structural formulas of hydrocarbons in which a long chain of
carbon atoms is present are often condensed even more. The formula
can be further abbreviated as
where parentheses and a subscript are used to denote the number of —CH2—
groups in the chain.
Structural Formulas
3. Skeletal structural formula – is a structural formula that shows the
arrangement and bonding of carbon atoms present in an organic
molecule but does not show the hydrogen atoms attached to the
carbon atoms.
Structural Formulas
4. Line-angle structural formula – is a structural representation in
which a line represents a carbon–carbon bond and a carbon atom is
understood to be present at every point where two lines meet and at
the ends of lines.
Alkane Isomerism
• Isomers are compounds that have the same molecular formula (that is, the
same numbers and kinds of atoms) but that differ in the way the atoms are
arranged.
Ex: Four-carbon alkane isomers: (molecular formula C₄H₁₀)
Five-carbon alkane isomers: (molecular formula C₅H₁₂)
IUPAC Nomenclature for Alkanes
• International Union of Pure and Applied Chemistry (IUPAC) –
formulated systematic rules for naming Organic compounds known as
“IUPAC rules”.
• The advantage of the IUPAC naming system is that it assigns each
compound a name that not only identifies it but also enables one to
draw its structural formula.
• Continuous-Chain Alkane is an alkane in which all carbon atoms are
connected in a continuous nonbranching chain.
• Branched-Chain Alkane is an alkane in which one or more branches
(of carbon atoms) are attached to a continuous chain of carbon
atoms.
IUPAC Names
for
ContinuousChain Alkanes
• All Alkane names end in -ane
• Beginning with the five-carbon alkane,
Greek numerical prefixes are used to
denote the actual number of carbon atoms
in the Continuous chain.
Alkanes
IUPAC Names for Branched-Chain Alkanes
• To name branched-chain alkanes, we must be able to name the
branch or branches that are attached to the main carbon chain.
These branches are formally called substituents.
• Substituent is an atom or group of atoms attached to a chain (or ring)
of carbon atoms. (in general term)
• Alkyl groups – substituents of Alkanes
- is the group of atoms that would be obtained by
removing a hydrogen atom from an alkane.
Alkyl Groups
• The two most commonly encountered alkyl groups are the two
simplest: the one-carbon and two-carbon alkyl groups. Their formulas
and names are:
• The extra long bond in these formulas (on the left) denotes the point
of attachment to the carbon chain.
• Alkyl groups are always found attached to another entity (usually a
carbon chain).
Alkyl Groups
• Alkyl groups are named by taking the stem of the name of the alkane
that contains the same number of carbon atoms and adding the
ending -yl.
IUPAC RULES for naming Branched-Chain
Alkanes
Rule 1:
Identify the longest continuous carbon chain (the parent chain), which
may or may not be shown in a straight line, and name the chain.
Rule 2:
Number the carbon atoms in the parent chain from the end of the chain
nearest a substituent (alkyl group).
• Additional guideline for numbering carbon atom chains:
If both ends of the chain have a substituent the same distance in,
number from the end closest to the second-encountered substituent.
Rule 3:
If only one alkyl group is present, name and locate it (by number), and prefix the
number and name to that of the parent carbon chain.
Rule 4:
If two or more of the same kind of alkyl group are present in a molecule,
indicate the number with a Greek numerical prefix (di-, tri-, tetra-, penta-, and so
forth). In addition, a number specifying the location of each identical group must
be included. These position numbers, separated by commas, precede the
numerical prefix. Numbers are separated from words by hyphens.
Rule 5:
When two kinds of alkyl groups are present on the same carbon chain,
number each group separately, and list the names of the alkyl groups in
alphabetical order.
• Additional guidelines for numbering carbon atom chains:
If there are substituents equidistant from each end of the chain and there is no
third substituent to use as the “tie-breaker,” begin numbering at the end nearest
the substituent that has alphabetical priority—that is, the substituent whose
name occurs first in the alphabet.
3-ethyl-5-methylheptane
Rule 6:
Follow IUPAC punctuation rules, which include the following:
(1) Separate numbers from each other by commas.
(2) Separate numbers from letters by hyphens.
(3) Do not add a hyphen or a space between the last-named substituent and
the name of the parent alkane that follows.
Practice #1: Give the IUPAC name for each
of the following branched-chain alkanes
2,3-dimethylpentane
4-ethyl-2,7-dimethyloctane
Practice #2: Give the IUPAC name for each
of the following branched-chain alkanes
3,6-Dimethyloctane
3,4,4,5-Tetramethyloctane
Practice #4: Draw the Skeletal Structural
Formula of the following
• Pentane
• 2-methylbutane
• 2,2-dimethylpropane
• 3-ethyl-5-methylheptane
Line-angle Structural Formulas for Alkanes
• A structural formula in which a line represents a carbon–carbon bond and a
carbon atom is understood to be present at every point where lines meet and
at the ends of lines.
• The zigzag (sawtooth) pattern used in line-angle structural formulas has a
relationship to the three-dimensional shape of the molecules that are
represented.
• The structures of branched-chain alkanes can also be designated using LineAngle Structural Formulas.
PRACTICE:
Hexane
2-Methylpentane
3-Methylpentane
• 2,2-Dimethylbutane
• 2,3-Dimethylbutane
Practice:
2-methylpropane
3-ethyl-5-methylheptane
Cycloalkanes
• Saturated hydrocarbon in which carbon atoms connected to one
another in a cyclic (ring) arrangement are present.
• The general formula for cycloalkanes is 𝑪𝒏 𝑯𝟐𝒏
Ex. Butane (C₄H₁₀) -> Cyclobutane (C₄H₈)
• Line-angle structural formulas are generally used to represent
cycloalkane structures.
IUPAC NOMENCLATURE FOR CYCLOALKANES
• IUPAC naming procedures for cycloalkanes are similar to those for
alkanes.
• The ring portion of a cycloalkane molecule serves as the name base,
and the prefix cyclo- is used to indicate the presence of the ring.
• Alkyl substituents are named in the same manner as in alkanes.
IUPAC NOMENCLATURE FOR CYCLOALKANES
• Numbering conventions used in locating substituents on the ring include the
following:
1. If there is just one ring substituent, it is not necessary to locate it by number.
2. When two ring substituents are present, the carbon atoms in the ring are
numbered beginning with the substituent of higher alphabetical priority and
proceeding in the direction (clockwise or counterclockwise) that gives the
other substituent the lower number.
3. When three or more ring substituents are present, ring numbering begins at
the substituent that leads to the lowest set of location numbers. When two or
more equivalent numbering sets exist, alphabetical priority among substituents
determines the set used.
Practice: Give the IUPAC names to each of the
following Cycloalkanes.
Methylcyclopropane 1-Ethyl-4-methylcyclohexane 4-Ethyl-1,2-dimethylcyclopentane
Chemical Properties of Alkanes and
Cycloalkanes
• Combustion reaction – is a chemical reaction between a substance
and oxygen (usually from air) that proceeds with the evolution of
heat and light (usually as a flame);
• All alkanes and cycloalkanes are flammable
• Complete combustion products: carbon dioxide (CO₂) and water (H₂O)
• Incomplete combustion products: Carbon monoxide (CO) and Carbon dioxide
(CO₂)
• Halogenation - is a chemical reaction between a substance and a
halogen in which one or more halogen atoms are incorporated into
molecules of the substance.
• Halogens are the elements in Group VIIA of the periodic table: Fluorine (F₂),
Chlorine (Cl₂), Bromine (Br₂), and Iodine (I₂)
• Hydrogen atoms are replaced with halogen atoms (a substitution
reaction)
• Requires the presence of heat or light
• In halogenation of an alkane, the alkane is said to
undergo fluorination, chlorination, bromination, or
iodination, depending on the identity of the halogen
reactant.
• Halogenated alkane – is an alkane derivative in which
one or more halogen atoms are present.
• Halogenated cycloalkane – is a cycloalkane derivative
in which one or more halogen atoms are present.
Nomenclature and Properties of Halogenated
Alkanes
• The IUPAC rules for naming halogenated alkanes are similar to those for
naming branched alkanes, with the following modifications:
1. Halogen atoms, treated as substituents on a carbon chain, are called
fluoro-, chloro-, bromo-, and iodo-.
2. When a carbon chain bears both a halogen and an alkyl substituent, the
two substituents are considered of equal rank in determining the
numbering system for the chain. The chain is numbered from the end
closer to a substituent, whether it be a halo- or an alkyl group.
3. Alphabetical priority determines the order in which all substituents
present are listed.
Practice: Give the IUPAC name of the following
Halogenated Alkanes
3-Bromo-1-chlorobutane
1-Ethyl-2-fluorocyclohexane
2-Chloro-3-methylbutane