4. Mr.burhan Abdi
4
Classification of organic compounds
Aliphatic compounds
These are open chain compounds
These can be subdivided
Saturated - alkanes
Unsaturated – alkenes and alkynes
Cyclic or closed chain compounds
Cyclic compounds whose rings are made up of only one kind of
atoms, i.e. carbon atoms are called homocyclic or cabocyclic
compounds.
Aliphatic cyclic compounds are called alicyclic compounds eg
cyclopropane, cyclobutane etc
5. Mr.burhan Abdi
5
Organic compounds containing one or more fused or
isolated benzene rings and their functinalized
derivatives are called benzenoids or aromatic
compounds,
eg benzene, toluene, naphthalene, anthracene etc.
Cyclic compounds containing one or more heteroatoms
(usually O,N, S etc) are called hetrocyclic compounds eg
ethylene oxide, tetrahydrofuran (THF), furan, pyrole etc
6. Functional Groups
Mr.burhan Abdi
6
Most organic molecules have C– C and C – H σ
bonds.
These bonds are strong, nonpolar, and not readily broken.
Organic molecules may have the following structural
features as well:
Heteroatoms—
Atoms other than carbon or hydrogen.
Common heteroatoms are nitrogen, oxygen, sulfur, phosphorus,
and the halogens.
p Bonds.
The most common π bonds occur in C – C and C – O double
bonds.
7. Mr.burhan Abdi
7
Functional Groups
These structural features distinguish one organic molecule from
another.
They determine a molecule’s geometry, physical properties,
and reactivity
Functional group is an atom or a group of atoms with
characteristic chemical and physical properties.
It is the reactive part of the molecule.
A functional group determines all the following properties
of a molecule:
Type and strength of intermolecular forces
Physical properties
Nomenclature
Chemical reactivity
8. An Overview of Functional Groups
Mr.burhan Abdi
8
We can subdivide the most common functional
groups into three types.
Hydrocarbons
Compounds containing a C – Z σ bond where Z = an
electronegative element
Compounds containing a C=O group
A functional group is the structural unit responsible for a given
molecule’s reactivity under a particular set of conditions.
9. Hydrocarbons
Mr.burhan Abdi
9
Hydrocarbons are compounds made up of only the
elements carbon and hydrogen.
They may be aliphatic or aromatic.
[1] Aliphatic hydrocarbons.
Aliphatic hydrocarbons can be divided into three subgroups.
Alkanes have only C – C σ bonds and no functional group.
Ethane, CH3CH3, is a simple alkane.
Alkenes have a C – C double bond as a functional group.
Ethylene, CH2––CH2, is a simple alkene.
Alkynes have a C – C triple bond as a functional group.
Acetylene, HC– CH, is a simple alkyne.
[2] Aromatic hydrocarbons.
This class of hydrocarbons was so named because many of the
earliest known aromatic compounds had strong, characteristic
odors.
11. Compounds containing C–Z σ Bonds
Mr.burhan Abdi
11
Several types of functional groups that contain C – Z
bonds.
The electronegative heteroatom Z creates a polar bond,
making carbon electron deficient.
The lone pairs on Z are available for reaction with protons and
Other electrophiles, especially when Z = N or O.
13. Compounds Containing a C=O Group
Mr.burhan Abdi
13
Many different types of functional groups possess a
C – O double bond (a carbonyl group)
The polar C – O bond makes the carbonyl carbon an
electrophile .
While the lone pairs on O allow it to react as a nucleophile
The carbonyl group also contains a π bond that is more
easily broken than a C – O σ bond.
15. Atenolol and Donepezil are examples of useful drugs that contain a variety of
functional groups.
Atenolol is a a blocker, a group of drugs used to treat hypertension.
Donepezil is used to treat mild to moderate dementia associated with
Alzheimer's disease.
Mr.burhan Abdi
15
16. Assignment
Mr.burhan Abdi
16
Oseltamivir (trade name Tamiflu), the most effective
antiviral drug against avian influenza currently
available, can be prepared in 10 steps from shikimic
acid. Identify the functional groups in Tamiflu and
shikimic acid.
17. Structural Formula
Mr.burhan Abdi
17
Structural formula is a formula that shows how the
atoms of a molecule are bonded to one another.
Representation of structural formula
Expanded Formula
Condensed Formula
Skeletal Formula
3-dimensional Formula
Fisher Projection Formula
18. a) Expanded Structure
Mr.burhan Abdi
18
Expanded structure indicate the way which the
atoms are attached to each other and are not
representation of the actual shapes of the molecules.
Example :
C4H10
Expanded structure
19. b) Condensed Formulae
Mr.burhan Abdi
19
Condensed structures are most often used for
compounds having a chain of atoms bonded
together, rather than a ring
The following conventions are used
All of the atoms are drawn in, but the two-electron bond
lines are generally omitted.
Atoms are usually drawn next to the atoms to which they
are bonded.
Parentheses are used around similar groups bonded to
the same atom.
Lone pairs are omitted.
20. Mr.burhan Abdi
20
Remember
It is usually best to start at the left side of the molecule
The carbon atoms must be tetravalent.
21. c) Skeletal Structure
Mr.burhan Abdi
21
Skeletal structures are used for organic compounds
containing both rings and chains of atoms.
Three important rules are used to draw them
Assume there is a carbon atom at the junction of any two
lines or at the end of any line.
Assume there are enough hydrogens around each carbon
to make it tetravalent.
Draw in all heteroatoms and the hydrogens directly
bonded to them.
Other atoms such as O, Cl, N and etc are shown
CH3CH(Cl)CH2CH3 =
Cl
23. Exercise
Mr.burhan Abdi
23
Rewrite each of the following structures using skeletal
formula
O
CH3
CH2
CH2
C CH3
(CH3)2CHCH2CH2CH(CH3)CH2CH3
CH2= CHCH2CH2CH = CHCH3
O
CH3
CH2
CH ( CH3
) CH2
C OH
1.
2.
3.
4.
24. d) 3-Dimensional Formula
Mr.burhan Abdi
24
Describes how the atoms of a molecule are arranged
in space
Example :
C
Br
H
H
H
(Bromoethane)
C
Br
H
H
H C
H
Br
H
H
C
H
H
Br
H
Indication :-
bonds that lie in the
plane of the page
bonds that lie behind
the plane
bonds that project out
of the plane of the
paper
OR OR
25. e) Fischer Projection
Mr.burhan Abdi
25
Vertical lines represent bonds that project behind the
plane of the paper.
Horizontal lines represent bonds that project out of
the plane of paper
The interaction of vertical and horizontal lines
represent a carbon atom, that is stereocentre.
26. Example : 2 – butanol , CH3CH(OH)CH2CH3
Mr.burhan Abdi
26
CH3
HO
CH2
CH3
H
CH3
H
CH2
CH3
OH
OR
28. Introduction to Nomenclature
Mr.burhan Abdi
28
How organic compounds named?
Based on plant or animal source from which it was
obtained
With the isolation and preparation of thousands of
new organic compounds it became clear that each
organic compound must have an unambiguous
name, derived from a set of easily remembered
rules.
29. Mr.burhan Abdi
29
A systematic method of naming compounds was
developed by the International Union of Pure and
Applied Chemistry (IUPAC)
It is referred to as the IUPAC system of nomenclature
The IUPAC system of nomenclature has been regularly
revised since it was first adopted in 1892.
Revisions in 1979 and 1993 and recent extensive
recommendations in 2004 have given chemists a variety
of acceptable names for compounds.
30. Mr.burhan Abdi
30
Naming organic compounds has become big
business for drug companies.
The IUPAC name of an organic compound can be
long and complex, and may be comprehensible only
to a chemist.
As a result, most drugs have three names:
1. Systematic
name
2. Generic name
3. Trade name
31. Mr.burhan Abdi
31
Systematic:
The systematic name follows the accepted rules of
nomenclature and indicates the compound’s chemical
structure; this is the IUPAC name.
Generic:
The generic name is the official, internationally approved name
for the drug.
Trade:
The trade name for a drug is assigned by the company that
manufactures it.
Trade names are often “catchy” and easy to remember.
Companies hope that the public will continue to purchase a
drug with an easily recalled trade name long after a cheaper
generic version becomes available.
33. Introduction
Mr.burhan Abdi
33
Alkanes are aliphatic hydrocarbons having only C–C
and C – H σ bonds.
They are also called saturated hydrocarbons
because they have the maximum number of
hydrogen atoms per carbon.
Because their carbon atoms can be joined together
in chains or rings, they can be categorized as acyclic
or cyclic.
Acyclic alkanes
Cyclic alkanes
34. Mr.burhan Abdi
34
Acyclic alkanes
Acyclic alkanes have the molecular formula CnH2n + 2
where n = an integer
Contain only linear and branched chains of carbon atoms.
Alkanes with C’s connected to no more than 2 other C’s are straight-
chain or normal alkanes
Alkanes with one or more C’s connected to 3 or 4 C’s are branched-
chain alkanes
36. Mr.burhan Abdi
36
Cycloalkanes
Contain carbons joined in one or more rings.
Because their general formula is CnH2n
They have two fewer H atoms than an acyclic alkane with
the same number of carbons.
Simple cycloalkanes are named by adding the prefix
cyclo- to the name of the acyclic alkane having the
same number of carbons.
37. Types of Carbon and Hydrogen Atoms in Alkane
Mr.burhan Abdi
37
Carbon atoms in alkanes and other organic
compounds are classified by the number of other
carbons directly bonded to them.
A primary carbon (1° carbon ) is bonded to one other
C atom.
A secondary carbon (2° carbon) is bonded to two
other C atoms
A tertiary carbon (3° carbon) is bonded to three other
C atoms.
A quaternary carbon (4° carbon) is bonded to four
other C atoms.
39. Mr.burhan Abdi
39
Hydrogen atoms are classified as primary (1°),
secondary (2°), or tertiary (3°) depending on the type
of carbon atom to which they are bonded.
A primary hydrogen (1° H) is on a C bonded to one other
C atom.
A secondary hydrogen (2° H) is on a C bonded to two
other C atoms.
A tertiary hydrogen (3° H) is on a C bonded to three other
C atoms.
41. Exercise
Mr.burhan Abdi
41
Classify the designated carbon atoms as 1°, 2°, 3°,
or 4°. (b) Classify the designated hydrogen atoms as
1°, 2°, or 3°.
42. Assignment
Mr.burhan Abdi
42
Classify the carbon atoms in each compound as 1°,
2°, 3°, or 4°.
Classify the hydrogen atoms in each compound as
1°, 2°, or 3°.
43. Naming Alkanes
Mr.burhan Abdi
43
The name of every organic molecules have these
parts
Prefix - reveals the identity, location, and number of
substituents attached to the carbon chain.
Locant - gives the location of the primary functional group
Parent name - indicates the number of carbons in the
longest continuous carbon chain in the molecule.
Suffix - indicates what functional group is present.
44. Mr.burhan Abdi
44
Follows specific rules
1. Find parent hydrocarbon chain
2. Carbons in that main chain are numbered in
sequence
3. Substituents are identified numbered
4. Write compound name is single word
5. Name a complex substituents as though it were a
compound itself
45. Mr.burhan Abdi
45
Step 1 Find the parent hydrocarbon
Find the longest continuous chain of carbon atoms in
the molecule, and use the name of that chain as the
parent name.
The longest chain may not always be apparent from the manner
of writing; you may have to “turn corners.”
46. Mr.burhan Abdi
46
If two different chains of equal length are present,
choose the one with the larger number of branch
points as the parent
47. Mr.burhan Abdi
47
Step 2 Number the atoms in the main chain
Beginning at the end nearer the first branch point, number
each carbon atom in the parent chain.
48. Mr.burhan Abdi
48
If there is branching an equal distance away from
both ends of the parent chain, begin numbering at
the end nearer the second branch point.
49. Mr.burhan Abdi
49
Step 3 Identify the number of substituents
Assign a number, called a locant, to each substituent to
locate its point of attachment to the parent chain.
50. Mr.burhan Abdi
50
If there are two substituents on the same carbon,
give both the same number.
There must be as many numbers in the name as there
are substituents.
51. Mr.burhan Abdi
51
Step 4 Write the name as a single word
Use hyphens to separate the different prefixes, and use
commas to separate numbers.
If two or more different substituents are present, cite them
in alphabetical order.
If two or more identical substituents are present, use one
of the multiplier prefixes di-, tri-, tetra-, and so forth, but
don’t use these prefixes for alphabetizing.
Full names for some of the examples we have been using
follow.
55. Mr.burhan Abdi
55
Step 5 Name a complex substituent as though it
were itself compound.
In some particularly complex cases, a fifth step is
necessary. It occasionally happens that a substituent on
the main chain has sub-branching.
In the following case, for instance, the substituent at C6 is
a three-carbon chain with a methyl sub-branch. To name
the compound fully, the complex substituent must first be
named.
56. Mr.burhan Abdi
56
Converting IUPAC name into corresponding
Structure
3-ethyl-4-methylhexane
Steps
Identify parent name and function group
At end of the name – suffix
Number the carbon skeleton in either direction
Add the substituents at appropriate carbons
57. Mr.burhan Abdi
57
Give the structure corresponding to each IUPAC
name.
3-methylhexane
3,5,5-trimethyloctane
3,3-dimethylpentane
58. Naming of Cycloalkane
Mr.burhan Abdi
58
Are cyclic alkanes.
Have 2H fewer than the open chain. (CnH2n)
Are named by using the prefix cyclo- before the
name of the alkane chain with the same number of
carbon atoms.
59. Mr.burhan Abdi
59
Cycloalkanes are named by using similar rules, but
the prefix cyclo- immediately precedes the name of
the parent.
60. Mr.burhan Abdi
60
Step1
Count the number of carbon atoms in the ring and use the
parent name for that number of carbons. Add the prefix
cyclo- and the suffix -ane to the parent name.
Step2
Name and number the substituents.
No number is needed to indicate the location of a single
substituent.
61. Mr.burhan Abdi
61
For rings with more than one substituent, begin
numbering at one substituent and proceed around
the ring clockwise or counterclockwise to give the
second substituent the lower number.
62. Mr.burhan Abdi
62
With two different substituents, number the ring to
assign the lower number to the substituents
alphabetically.
66. Alkenes
Mr.burhan Abdi
66
Alkenes are also called olefins.
Alkenes are compounds that contain a carbon–carbon
double bond.
Terminal alkenes have the double bond at the end of the
carbon chain
Internal alkenes have at least one carbon atom bonded
to each end of the double bond
Cycloalkenes contain a double bond in a ring
67. Mr.burhan Abdi
67
The double bond of an alkene consists of one σ
bond and one π bond.
The π bond is much weaker than the σ bond of a C –
C double bond, making it much more easily broken.
As a result, alkenes undergo many reactions that alkanes
do not.
68. Nomenclature
Mr.burhan Abdi
68
Alkenes are named using a series of rules similar to
those for alkanes with the suffix -ene used instead of
-ane to identify the family.
Compounds with two double bonds are named as dienes
by changing the -ane ending of the parent alkane to the
suffix -adiene.
Compounds with three double bonds are named as
trienes, and so forth.
Always choose the longest chain that contains both atoms
of the double bond.
73. Mr.burhan Abdi
73
Alkynes, compounds that contain a carbon–carbon
triple bond.
Like alkenes, alkynes are nucleophiles with easily
broken π bonds, and as such, they undergo addition
reactions with electrophilic reagents.
74. Mr.burhan Abdi
74
Alkynes contain a carbon–carbon triple bond.
A terminal alkyne has the triple bond at the end of
the carbon chain, so that a hydrogen atom is directly
bonded to a carbon atom of the triple bond.
An internal alkyne has a carbon atom bonded to each
carbon atom of the triple bond.
75. Mr.burhan Abdi
75
An alkyne has the general molecular formula CnH2n
– 2, giving it four fewer hydrogens than the
maximum number possible.
Because every degree of unsaturation removes two
hydrogens, a triple bond introduces two degrees of
unsaturation.
The triple bond of an alkyne consists of one σ bond
and two π bonds.
76. Mr.burhan Abdi
76
Both o bonds of a C – C triple bond are weaker than
a C – C r bond, making them much more easily
broken.
As a result, alkynes undergo many addition reactions.
Alkynes are more polarizable than alkenes because
the electrons in their o bonds are more loosely held.
77. Nomenclature
Mr.burhan Abdi
77
Alkynes are named in the same way that alkenes
were named.
In the IUPAC system, change the -ane ending of the
parent alkane to the suffi x –yne.
Choose the longest carbon chain that contains both
atoms of the triple bond and number the chain to give the
triple bond the lower number.
Compounds with two triple bonds are named as diynes,
those with three are named as triynes, and so forth.
Compounds with both a double and a triple bond are
named as enynes.
The chain is numbered to give the first site of unsaturation
(either C – – C or C – – – C) the lower number.
81. Structure
Mr.burhan Abdi
81
Alkyl halides are organic molecules
containing a halogen atom X bonded to
carbon atom.
The functional group is -X, where -X may be F,
Cl, Br or I.
Two simple members of this class are methyl
chloride (CH3Cl) and ethyl chloride
82. Mr.burhan Abdi
82
Alkyl halides are classified as primary (1°),
secondary (2°), or tertiary (3°) depending on
the number of carbons bonded to the carbon
with the halogen.
83. Nomenclature
Mr.burhan Abdi
83
An alkyl halide is named as an alkane with a
halogen substituent—that is, as a halo
alkane.
To name a halogen substituent, change the -
ine ending of the name of the halogen to the
suffix –o (chlorine → chloro).
87. Structure
Mr.burhan Abdi
87
The functional group of an alcohol is the hydroxyl (-
OH) group.
Therefore, an alcohol has the general formula ROH.
The simplest and most common alcohols are methyl
alcohol (CH3OH) and ethyl alcohol (CH3CH2OH).
When a hydroxyl group is linked directly to an
aromatic ring, the compound is called a phenol
88. Mr.burhan Abdi
88
Alcohols are classified as primary (1°),
secondary (2°), or tertiary (3°) based on the
number of carbon atoms bonded to the carbon
with the OH group.
92. Structure
Mr.burhan Abdi
92
Carboxylic acids are organic compounds
containing a carboxy group (COOH).
The word carboxy (for a COOH group) is derived from
carbonyl
(C=O) + hydroxy (OH).
Although the structure of a carboxylic acid is
often abbreviated as RCOOH or RCO2H, keep in
mind that the central carbon atom of the
functional group is doubly bonded to one oxygen
atom and singly bonded to another.
93. Nomenclature of Carboxylic Acid
Mr.burhan Abdi
93
To name a carboxylic acid using the IUPAC
system:
[1] If the COOH is bonded to a chain of carbons, find
the longest chain containing the COOH group, and
Change the -e ending of the parent alkane to the suffix
-oic acid.
If the COOH group is bonded to a ring, name the ring and
add the words carboxylic acid.
[2] Number the carbon chain or ring to put the COOH
group at C1
Apply all of the other usual rules of
nomenclature.
97. Structure
Mr.burhan Abdi
97
Aldehydes and ketones contain a carbonyl
group.
An aldehyde contains at least one H atom bonded to the
carbonyl carbon.
An aldehyde is often written as RCHO.
Remember that the H atom is bonded to the carbon atom, not
the oxygen.
A ketone has two alkyl or aryl groups bonded to it.
a ketone is written as RCOR, or if both alkyl groups are the
same, R2CO.
98. Nomenclature of Aldehyde
Mr.burhan Abdi
98
To name an aldehyde using the IUPAC system:
[1] If the CHO is bonded to a chain of carbons, find
the longest chain containing the CHO group, and
change the -e ending of the parent alkane to the
suffix -al.
If the CHO group is bonded to a ring, name the ring
and add the suffix –carbaldehyde.
[2] Number the chain or ring to put the CHO group at
C1, but omit this number from the name.
Apply all of the other usual rules of
nomenclature.
101. Nomenclature of Ketone
Mr.burhan Abdi
101
In the IUPAC system all ketones are identified by the
suffix -one.
To name an acyclic ketone using IUPAC rules:
[1] Find the longest chain containing the carbonyl
group, and change the -e ending of the parent
alkane to the suffix –one.
[2] Number the carbon chain to give the carbonyl
carbon the lower number.
Apply all of the other usual rules of
nomenclature.
105. Introduction
Mr.burhan Abdi
105
In the early days of organic chemistry, the word
aromatic was used to describe such fragrant
substances as benzaldehyde (from cherries,
peaches, and almonds), toluene (from Tolu balsam),
and benzene (from coal distillate).
It was soon realized, however, that substances
grouped as aromatic differed from most other
organic compounds in their chemical behavior.
106. Mr.burhan Abdi
106
Today, we use the word aromatic to refer to the class
of compounds that contain six-membered benzene-
like rings with three double bonds.
Many valuable compounds are aromatic in part,
including steroids such as estrone and well-known
pharmaceuticals such as the cholesterol-lowering
drug atorvastatin, marketed as Lipitor.
107. Mr.burhan Abdi
107
Because these compounds possessed strong and
characteristic odors, they were called aromatic
compounds.
It is their chemical properties, though, not their odor
that make these compounds special.
Aromatic compounds resemble benzene—they are
unsaturated compounds that do not undergo the
addition reactions characteristic of alkenes.
108. Nomenclature
Mr.burhan Abdi
108
Monosubstituted Benzenes
To name a benzene ring with one substituent, name
the substituent and add the word benzene.
Carbon substituents are named as alkyl groups.
109. Mr.burhan Abdi
109
Many monosubstituted benzenes, such as those
with methyl (CH3 – ), hydroxy ( – OH), and amino
( – NH2) groups, have common names that you
must learn, too.
110. Mr.burhan Abdi
110
Disubstituted Benzenes
There are three different ways that two groups can
be attached to a benzene ring, so a prefix— ortho,
meta, or para—can be used to designate the
relative position of the two substituents.
Ortho, meta, and para are also abbreviated as o, m,
and p, respectively.
– ortho- (o) on adjacent carbons (1,2)
– meta- (m) separated by one carbon (1,3)
– para- (p) separated by two carbons (1,4)
112. Mr.burhan Abdi
112
If the two groups on the benzene ring are
different, alphabetize the names of the
substituents preceding the word benzene.
If one of the substituents is part of a common
root, name the molecule as a derivative of that
monosubstituted benzene.
113. Mr.burhan Abdi
113
Polysubstituted Benzenes
For three or more substituents on a benzene
ring:
[1] Number to give the lowest possible numbers
around the ring.
[2] Alphabetize the substituent names.
[3] When substituents are part of common roots,
name the molecule as a derivative of that
monosubstituted benzene.
The substituent that comprises the common root is
located
at C1.
115. Mr.burhan Abdi
115
Naming Aromatic Rings as Substituents
A benzene substituent (C6H5 – ) is called a phenyl
group, and it can be abbreviated in a structure as Ph
–
A phenyl group (C6H5 – ) is formed by removing one
hydrogen from benzene (C6H6).
116. Mr.burhan Abdi
116
Benzene, therefore, can be represented as PhH,
and phenol would be PhOH
The benzyl group, another common substituent
that contains a benzene ring, differs from a
phenyl group.
117. Mr.burhan Abdi
117
Finally, substituents derived from other substituted
aromatic rings are collectively called aryl groups.
118. Mr.burhan Abdi
118
Alkyl-substituted benzenes are sometimes referred
to as arenes and are named in different ways
depending on the size of the alkyl group.
If the alkyl substituent is smaller than the ring (six or fewer
carbons), the arene is named as an alkyl-substituted
benzene.
If the alkyl substituent is larger than the ring (seven or
more carbons), the compound is named as a phenyl-
substituted alkane.
A functional group is the structural unit responsible for a given molecule’s reactivity under a particular set of conditions.
A functional group is the structural unit responsible for a given molecule’s reactivity under a particular set of conditions.
Formic acid formic acid, a caustic compound isolated from certain ants, comes from the Latin word formica, meaning ant; and allicin, the pungent principle of garlic, is derived from the botanical name for garlic, Allium sativum.
Other compounds were named by their discoverer for more personal reasons. Adolf von Baeyer supposedly named barbituric acid after a woman named Barbara, although speculation continues on Barbara’s identity—a lover, a Munich waitress, or even St. Barbara.
In IUPAC nomenclature, carboxylic acids are identified by a suffix added to the parent name of the longest chain,
and two different endings are used depending on whether the carboxy group is bonded to a chain or ring.
