2. Introduction to organic chemistry
Chemists in the early nineteenth century knew that living
things, produce an immense variety of carbon compounds
Organic compounds because they were produced by living organisms.
They were unable to synthesize organic compounds because of
vitalism.
According to vitalism, organisms possessed a mysterious “vital
force,”enabling them to assemble carbon compounds.
Friedrich Wöhler (1800-1882), a German chemist, was the
first scientist to realize that he had produced an organic
compound by synthesis in a laboratory.
3. Organic compounds vs Inorganic
compounds
Organic Compounds
• Low melting points
• Low boiling points
• Most are insoluble in water but
soluble in organic liquids
• Few Polar organic compounds with
low molar masses and are water
soluble
• Flammable or highly flammable.
• Composed of molecules with
covalent bonds.
• Formed mainly of C, H, O, N
• Do not ionize, so they don´t conduct
the electricity
Inorganic Compounds
• High melting points
• High boiling points.
• Soluble in water
• Insoluble in organic liquids
• Nonflammable
• Composed of molecules with ionic
bonds
• Formed by atoms of any element
• They ionize, so conduct the
electricity
4. Organic Chemistry
Studies the structure, properties,
composition, reactions, and
preparation of carbon-based
compounds, hydrocarbons, and their
derivatives.
Organic compound all carbon-containing
compounds with the exceptions of carbon
oxides, carbides, and carbonates, which are
considered inorganic.
5. Properties of Carbon atom
Element in group 14 of the periodic table.
With the electron configuration of 1s2 2s2
2p2
carbon nearly always shares its electrons
and forms four covalent bonds.
In organic compounds, carbon atoms are
bonded to hydrogen atoms or atoms of
other elements like nitrogen, oxygen,
sulfur, phosphorus, and the halogens.
carbon atoms bond to other carbon atoms
and form chains from two to thousands of
carbon atoms in length.
it forms complex, branched-chain
structures, ring structures, and even
cagelike structures.
6. Carbon atom
Carbon has the ability to form very long chains of
interconnecting C-C bonds. This property is called catenation.
Carbon-carbon bonds are strong, and stable. This property
allows carbon to form an almost infinite number of compounds.
Covalency: This property is that the 4 hybrid orbitals are equal in
energy intensity and therefore the 4 carbon bonds are equal and
the same class.
By sharing their electrons with other atoms can lead to carbon
single bonds, double or triple so that each pair represents a
covalent bond and share two and three pairs of electrons.
8. Hydrocarbons
The simplest organic compounds are hydrocarbons,
which contain only the carbon and hydrogen.
Types of hydrocarbons:
• Composed entirely of single bonds and are saturated with
hydrogen.
• The general formula for saturated hydrocarbons is CnH2n+2
Saturated hydrocarbons
(alkanes)
• Double bond alkenes and have the formula CnH2n
• Triple bonds alkynes, with general formula CnH2n-2.
Unsaturated hydrocarbons
have one or more double or
triple bonds between carbon
atoms.
• Are hydrocarbons containing one or more carbon rings to which
hydrogen atoms are attached.
• The general is CnH2n.
Cycloalkanes
• Are hydrocarbons that have Aromatic hydrocarbons at least one aromatic (benzene) ring.
9. Models and hydrocarbons
Molecular formulas give no information about the geometry of the
molecule.
A structural formula shows the general arrangement of atoms in
the molecule but not the exact, threedimensional geometry.
The ball-and-stick model demonstrates the geometry of the
molecule clearly,
Space-filling model gives a more realistic picture of what a
molecule would look
10. Multiple carbon-carbon
bonds
Carbon atoms can bond to
each other not only by
single covalent bonds but
also by double and triple
covalent bonds.
Saturated hydrocarbon
contains only single bonds
Unsaturated
hydrocarbon has at least
one double or triple bond
between carbon atoms
11. Alkanes
Saturated Hydrocarbons
General formula CnH2n+2 where n is equal to the
number of carbon atoms in the alkane
Called saturated because each carbon is bonded to
four other atoms
Only single bonds
Names are derived form the greek or latin name for the
number of carbon atoms and the suffix –ane
12. Molecular formula: gives the actual
number of atoms of each kind present
in a molecule of the substance.
Structural formula: show bond lines
for all covalent bonds present in a
molecule. Gives more information
than the molecular formula.
Condensed structural formula:
show the hydrogen atoms right next to
the carbon atoms to which they are
atached.
13.
14. Homologous series
A series of compounds that differ from one
another by a repeating unit is called a
homologous series.
The unbranched alkanes are a homologous
series because they differ by the number of CH2
units in each
Have properties that vary in a regular and
predictable manner
Melting point, boiling point, and density
increase as the number or C atoms increases.
# of C’s prefix
1 meth
2 eth
3 prop
4 but
5 pent
6 hex
7 hept
8 oct
9 non
10 dec
15. Isomers
Compounds that have the same molecular formula, but
different structural formulas
Different compounds having the same molecular formula
Example: Butane & Isobutane
Basic principle of organic chemistry: the order and
arrangement of atoms in an organic molecule
determine its identity.
Mp= -138º C
Bp= -0.5º C
Mp= -159º C
Bp= -12º C
16. Alkyl Group When naming branched-chain alkanes, the longest continuous
chain of carbon atoms is called the parent chain.
All side branches are called substituent groups because they
appear to substitute for a hydrogen atom in the straight chain.
A hydrocarbon group (symbolized –R) that results when one
hydrogen atom is removed from an alkane.
Change –ane ending to –yl
17. IUPAC RULES TO NAME ALKANES
Step 1.
• Count the number of carbon atoms in the longest continuous chain ( the parent chain of the structure)
Step 2.
• Number each carbon in the parent chain. Locate the end carbon closest to a substituent group give all the
substituent groups the lowest position numbers possible.
Step 3.
• Name each alkyl group substituent. Place the name of the group before the name of the parent chain.
Step 4.
• If the same alkyl group occurs more than once as a branch on the parent structure, use a prefix (di-, tri-,
tetra-, and so on) before its name to indicate how many times it appears. Then, use the number of the
carbon to which each is attached to indicate its position.
Step 5.
• When different alkyl groups are attached to the same parent structure, place their names in alphabetical
order. Do not consider the prefixes (di-, tri-, and so on) when determining alphabetical order.
Step 6.
• Write the entire name, using hyphens to separate numbers from words and commas to separate numbers.
20. Compound name:
3-ethyl-2-methylhexane
long chain
side group side group
position on
long chain
Additional rule: list side groups in alphabetical order
21. CH3
CH3 – CH – CH – CH – CH3
CH3 CH3
Example:
CH3
CH3 – CH – CH – CH – CH3
CH3 CH3
CH3
CH3 – CH – CH – CH – CH3
CH3 CH3
CH3
CH3 – CH – CH – CH – CH3
CH3 CH3
CH3
CH3 – CH – CH – CH – CH3
CH3 CH3
No matter how the long chain is
selected, the name is the same:
2, 3, 4 - trimethylpentane
Note the tri; use di, tri, tetra, etc, but don’t use
them for alphabetical order
22.
23. Cycloalkanes
Carbon atoms can form ring
structures.
Cyclic hydrocarbon An organic
compound that contains a hydrocarbon
ring.
To indicate that a hydrocarbon has a
ring structure, the prefix cyclo- is used
with the hydrocarbon name.
Thus, cyclic hydrocarbons that contain
only single bonds are called
cycloalkanes.
24. Naming substituted cycloalkanes
Substituted cycloalkanes are named by following the
same IUPAC rules used for straight-chain alkanes, but
with a few modifications.
The ring is always considered to be the parent chain.
Because a cyclic structure has no ends, numbering is started on the carbon that
is bonded to the substituent group.
When there are two or more substituents, the carbons are numbered around
the ring in a way that gives the lowest-possible set of numbers for the
substituents.
If only one group is attached to the ring, no number is necessary.
25. Answers:
10. a) methylcyclopentane
B) 2-ethyl-1,4-dimethylcyclohexane
C) 1,3-diethylcyclobutane
26. Alkenes
Unsaturated hydrocarbons that contain one or more
double covalent bonds between carbon atoms in a chain
The simplest alkene has two carbon atoms double bonded
to each other.
The general formula for the series is CnH2n.
27.
28. Naming alkenes
Their names are formed by changing the
-ane ending of the corresponding alkane
to -ene.
To name alkenes with four or more
carbons in the chain, it is necessary to
specify the location of the double bond.
This is done by numbering the carbons
in the parent chain, starting at the end of
the chain that will give the first carbon in
the double bond the lowest number.
Cyclic alkenes are named in much the
same way as cyclic alkanes; however,
carbon number 1 must be one of the
carbons connected by the double bond.
29. In alkenes, the parent chain is always the longest chain that contains the double
bond, whether or not it is the longest chain of carbon atoms.
The position of the double bond, not the branches, determines how the chain is
numbered.
Some unsaturated hydrocarbons contain more than one double (or triple) bond.
The number of double bonds in such molecules is shown by using a prefix (di-,
tri-, tetra-, and so on) before the suffix -ene.
The positions of the bonds are numbered in a way that gives the lowest set of
numbers.
30. Example:
CH3 – CH2 – CH2 – C = CH2
CH2
CH3
CH3 – CH2 – CH2 – C = CH2
CH2
CH3
2 – ethyl 1-pentene
length of
long chain
containing
double
bond
side-group
position
of side-group
position of
double bond
31. Answers:
A) 4-methyl-2-pentene
B) 2,2,6-trimethyl-3-octene
32. Properties and uses of alkenes
Like alkanes, alkenes are nonpolar and therefore have
low solubility in water as well as relatively low melting
and boiling points.
However, alkenes are more reactive than alkanes
because the second covalent bond increases the
electron density between two carbon atoms, providing
a good site for chemical reactivity.
33. Alkynes
Unsaturated hydrocarbons that contain one or more triple bonds
between carbon atoms in a chain .
Triple bonds involve the sharing of three pairs of electrons.
General formula CnH2n-2
The simplest and most commonly used alkyne is ethyne ( C2H2)
Nomenclature of alkynes is identical to that of alkenes, the only
exception is the ending:
yne.
34.
35. Properties and uses of alkynes
Alkynes have physical and chemical properties similar
to those of alkenes. Alkynes undergo many of the
reactions alkenes undergo.
However, alkynes are generally more reactive than
alkenes because the triple bonds of alkynes have even
greater electron density than the double bonds of
alkenes.
36. Aromatic Compounds
Benzene
Organic compounds that contain benzene rings as part of their
structures
The term aromatic was originally used because many of the
benzene-related compounds known in the nineteenth century
were found in pleasant-smelling oils that came from spices,
fruits, and other plant parts.
Now define as anything that has a benzene ring
Six sided structure with single and double mobile bonds
Resonance—a word used to describe the phenomenon in which
no single Lewis structure can be used
37. The German chemist Friedrich August Kekulé proposed a
different kind of structure for benzene a hexagon of carbon
atoms with alternating single and double bonds
Linus Pauling proposed the theory of hybrid orbitals, this
theory predicts that the pairs of electrons that form the
second bond of each of benzene’s double bonds are not
localized between only two specific carbon atoms as they
are in alkenes.
Instead, the electron pairs are delocalized, which means
they are shared among all six carbons in the ring.
This delocalization makes the benzene molecule
chemically stable
In this representation, the circle in the middle of the
hexagon symbolizes the cloud formed by the three pairs of
electrons.
39. Naming substituted aromatic
compounds
Substituted benzene compounds are named in the
same way as cyclic alkanes.
Substituted benzene rings are numbered in a way that
gives the lowest-possible numbers for the substituents.
40. Naming
2 substituents…2 different ways
One way…same as before
Other way…uses the terms ortho, meta, and para
Ortho (1,2 distribution)
Meta (1,3 distribution)
Para (1,4 distribution)
41.
42. Answers:
A) propylbenzene
B) 1-ethyl-2-methylbenzene or o-ethylmethylbenzene
C) 1-ethyl-2,3-dimethylbenzene
43. Carcinogens
Many aromatic compounds, particularly benzene,
toluene, and xylene, were once commonly used as
industrial and laboratory solvents.
However, tests have shown that the use of such compounds
should be limited because they can affect the health of
people who are exposed to them regularly.
Health risks linked to aromatic compounds include
respiratory ailments, liver problems, and damage to the
nervous system.
Beyond these hazards, some aromatic compounds are
carcinogens, which are substances that can cause cancer.
44. Hydrocarbon
Derivatives
Hydrocarbon
derivatives contain
other elements besides
C and H; most
commonly O, N, or
halogen atom
Functional group:
group of atoms that
gives the compound its
characteristic
properties
Hydrocarbons
derivatives
Alkyl halide
Alcohols
Ethers
Aldehydes
Ketones
Carboxylic Acids
Esters
45. Functional
group:
Specific
group of
atoms that
gives an
organic
compound
certain
characteristi
cs properties
