Faculty of Biotechnology
Organic Chemistry
Chapter 2
Dr. M. Abd-Elhakeem
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The nomenclature of organic molecules
started with common or traditional name
depending mainly on the origin in the history
of the science or the natural sources of the
compound.
But the relationship of these names to each
other is arbitrary, and no rational or
systematic principles.
NH2
OH
Aniline
Phenol
O
COOH
Benzoic acid
CH3
CH3
CH3
Xylene
Acetophenone
Naphthalene
CH3
Toluene
OCH 3
Anisole
O
H3C
O
acetaldehyde
H3C
H
OH
O
H
O
formaldehyde
H
H3C
acetic acid
OH
H3C
CH3
methanol
HC
H3C
OH
Acetone
ethanol
CH
Acetylene
 The
IUPAC nomenclature of organic
chemistry is a systematic method of
naming organic chemical compounds as
recommended by the International Union
of Pure and Applied Chemistry (IUPAC).
 every
possible organic compound should
have a name according to a number of
rules
1- The name of organic molecule is divided
in to two parts
Number of
carbon atom
Function group
FUNCTIONAL GROUP – atom or group of atoms which
gives an organic compound its characteristic chemical
properties.
First part
Second part
No of carbon
atoms
Function group
1. meth
2. eth
3.prop
4. but
5. pent
6.hex
7.hept
8. oct
9. non
10. dec
In case of
cyclic
form add
firstly
cyclo-
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Alkane
Alkene
Alkyne
Alcohol
Aldehyde
Ketone
Acid
Substitution
ane
ene
yne
anol
anal
anone
anoic
yl
H3C
H2C
CH3
OH
Propene
Propanol
H3C
COOH
propanoic acid
2- Put the lowest number that indicate the
position of function group.
H3C
H3C
H3C
O
CH3
3-pentanone
CH3
2-pentyne
HO
CH3
2-butanol
3- In case of branched chain (this means
there is one principle chain or parent chain
and substitutions)
A-The tallest chain is the parent
B- Substitution must take the lowest
number
CH3
CH3
H3C
H3C
CH3
2-methylpentane
CH3
CH3
2,4-dimethylpentane
 The
main chain (or parent chain)
must include the functional group
and so may not necessarily be the
longest chain.
C- In case of more than one substitution the
substituents with alphabetical priority has
the lowest numbering
D- Write name in alphabetical order
4- In case of presence of halogens
(Cl, F, Br, I) write the name of the
halogen (Chloro, Floro, Iodo,
Bromo)
CH3
CH3
1-ethyl-3-methylcyclohexane
CH3
H3C
Cl
CH3
CH3
2-chloro-4-methylpentane
CH3
1,3-dimethylcyclohexane
5- In Case of presence of two function groups.
A- In case of alkane chain and alkene chain the
alkene is the parent
B- Alkane – cyclo alkane the larger is the parent
C- Alkane, Alkene, alkyne – benzene the
Benzene is the parent
D- Benzene – any other group than the alkane,
alkene, and alkyne
Benzene is the substitution and called phenyl.
OH
CH3
4-phenylbutan-2-ol
order of group priority is alkane –
alkene- alkyne – amine – alcohol –
ketone – aldehyde - acid
H3C
HO
H2N
CH3
2-aminobutan-1-ol
COOH
OH
3-hydroxy-pentanoic
acid
Mono-substituents:
CH3
methylbenzene
Di-substituents
Br
COOH
Br
Br
NO 2
Br
1,2-dibromobenzene
o-dibromobenzene
Br
1,3-dibromobenzene
m-dibromobenzene
Br
1,4-dibromobenzene
2-nitrobenzoic acid
p-dibromobenzene
o-nitrobenzoic acid
O
Cl
Cl
OH
Cl
NH2
1,3,5-trichlorobenzene
3-aminobenzoic acid
CH3
F
1-fluoro-3-methylbenzene
CH3
OH
CH3
4,4-dimethylcyclohexanol
CH2CH2C(OH)(CH3)2
2-methyl-4-phenyl-2-butanol
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A primary carbon has one other C directly bonded to it.
A secondary carbon is directly bonded to two other C’s.
A tertiary carbon is directly bonded to three other C’s.
Multivalent atoms are 1º, 2º, or 3º by bonding to C’s.
Univalent atom or group not really 1º, 2º, or 3º on its
own - ID depends on type of carbon it is bonded to.