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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5574_Библиотеки_им_академика_М_И_Перельмана.pdf
c h A P T e r 2 u nomenclature of Organic compounds
2,5-Dimethyl-4-(1-methyl propyl)-heptane
That longest chain having maximum substituent is considered as the principle chain whose side chains
have the lowest numbered locants. For example,
in cases where the names of the complex radicals are composed of the identical words, priority for
citation is given to the radical which contains the lowest locant at the rst cited point of difference in the
radical. For example,
101
2.4.2 Nomenclature of Unsaturated Hydrocarbons
1. The following additional rules are
observed while naming such hydrocarbons
a. The double bond or the triple bonds should be given the lowest number in the principle chain. For
example,
H3CHC
Pent-2-ene Pent-1-yne
CHCH2CH3 HC C CH2CH2CH
3
b. When both double and the triple bonds are present, the numbering of the principal chain should
be done from that end which is near to the rst multiple bond (double or triple).
The terminal ‘e’ in the name of principle chain is dropped when followed by a sufx beginning with ‘a’,
‘e’, ‘i’, ‘o’, ‘u’ or ‘y’. The terminal ‘e’ of ‘-ene’ or ‘-diene’ or ‘-yne’or ‘diyne’ is omitted as it comes before
‘y’ of ‘-yne’ but ‘e’ is not dropped in case of ‘-ene diyne’ as in this case terminal ‘e’ of ‘ene’ comes before
‘d’ of ‘-diyne’. For example,
102
3
3
5
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(Triple bond nearer to the end of the chain) (Double bond is near to the end of the chain)
c. if, however, when both double bond and triple bond are equidistant from either of the two ends,
double bond should be given lower locant.
Note: Terminal ‘e’ of ‘-ene’ is retained as the next sufx begins with ‘d’.
2. The following additional rules are observed
while naming such hydrocarbons:
a. maximum number of double and triple bonds should be there in the principal chain.
b. maximum length of the principal chain.
c. lowest positional numbers (locants) for the multiple bonds.
d. maximum number of substituents should be present in the principal chain.
e. lowest locants for all the substituents.
For example,
c h A P T e r 2 u nomenclature of Organic compounds
2,3-Diethyl-buta-1,3-diene
3-Ethynyl-hexa-1, 5-diene
103
Note: if a double bond and a triple bond have same positions, double bond should be included.
For example,
2.4.3 Nomenclature of Cyclic (Alicyclic) Hydrocarbons
1. nomenclature of simple cyclic hydrocarbons and their derivatives: The following rules are observed
in naming these hydrocarbons:
a. cyclo (a primary prex) is used immediately before the word root in case of alicyclic hydrocarbons.
For example,
104
Cyclohexane Cyclohexene Cyclohexyne
hexane
2-Cyclohexylpentane
3-Cyclopropyl-prop-1-ene
4-Cyclohexylbuta-1,3-diene
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b. if two or more alkyl groups or other substituent groups are present in the ring, their positions are
indicated by arabic numerals, i.e. 1, 2, 3, 4, …, etc. While numbering the carbon atoms of the ring,
the substituent which comes rst in the alphabetical order is given the lowest number provided it
does not violate the lowest sum rule. For example,
c. if the ring contains fewer carbon atoms than the alkyl group attached to it, the compound is named
as a derivative of alkane and the ring is treated as cycloalkyl substituent. Otherwise it is named as a
derivative of cycloalkane. For example,
if however, the side chain contains a multiple bond or a functional group, the alicyclic ring is treated
as the substituent irrespective of the size of ring. For example,
d. if a multiple (double or triple) bond and some other substituents are present in the ring, numbering
is done in such a way that the multiple bond gets the lowest number. For example,
c h A P T e r 2 u nomenclature of Organic compounds
3-Methyl-cyclohex-1-ene
Bicyclo-(2,2,1)-heptane
(norborane)
e. if a compound contains an alicyclic ring and benzene ring, it is named as a derivative of benzene.
For example,
2.4.4 Nomenclature of Polycyclic Hydrocarbons
in addition to such monocyclic compounds, a large number of polycyclic compounds are also known. They
contain two or more rings having two or more carbon atoms in common. systematic naming of compounds
having more than one ring is done by putting the prexes bicyclo, tricyclo, etc. before the name of alkane
denoting the total number of carbon atoms in the ring.
The ring carbon atoms are now numbered commencing with any one of the carbon atoms at the junction
and is continued to the next junction rst along the longest path (maximum number of carbon atoms), then
along the shorter paths, successively, and nally along the shortest path. The number of carbon atoms in-
volved in each of these paths is written in a square bracket in descending order, which is inserted in between
the words ‘bicyclo’ and ‘alkane’. The following example will explain these rules:
105
2.5 IUPAC NOMENCLATURE OF COMPOUNDS CONTAINING ONE FUNCTIONAL GROUP,
MULTIPLE BONDS AND SUBSTITUENT
The basic rules of iuPAc system illustrated with the help of suitable examples are discussed below:
1. The longest possible continuous chain of carbon atoms containing the functional group and the
maximum number of double or triple bonds (if any) are identied and word root corresponding to it is
noted: All the atoms or groups or side chains present on it are regarded as substituents. While deciding
106
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the principal chain, the functional group should always be included irrespective of whether the principal
chain also denotes the longest chain or not. The following example will make this point clear .
In this alcohol, the longest carbon chain contains ve carbon atoms but does not include the func-
tional group, i.e. –OH. However if the functional group is to be included, the longest possible carbon
chain contains only four carbon atoms. hence in accordance with the above rule, shorter carbon chain
containing the functional group is selected as the principle chain while giving it an iuPAc name.
2. Principal chain in a compound must be numbered in such a way
that functional group gets the lowest possible number followed by double bond, triple bond and the
substituents, i.e. functional group > double bond > triple bond > substituents. For example,
3.
a. select the appropriate word root denoting the total number of carbon atoms in the principal
chain.
b. Attach the primary sufx, i.e. ‘-ane’, ‘-ene’, or ‘-yne’ after the root word depending upon whether
the principal chain is alkane, alkene or alkyne, respectively. Positional number of the primary
sufx is indicated before the primary sufx.
c. Attach the secondary sufx (for the functional group) after the primary sufx. Positional number
of the secondary sufx is indicated before the secondary sufx.
d. Numbering the chain terminating functional groups: When a chain terminating functional group
such as –CHO, –C≡N, –COOR, –CONH
, –COCl, etc., is present, it is always given positional
2
number 1 and number ‘1’ is usually omitted from the nal name of the compound.
e. Alphabetical order of the prexes: The prexes and other substituents should be placed in alpha-
betical order before the word root. For example,
c h A P T e r 2 u nomenclature of Organic compounds
C
Pent-3-ene-1-al
5
2-Chloro-5-cyclohexyl-methyl-hex-3-enoic acid
N-Ethyl-4-methylpentan-2-amine
N-Ethyl-N-methyl-benzenamine
N-Ethyl-N-methyl-butan-2-amine
107
108
—SO3H > — COOH> R(CO)2O > — COOR > — C — X > — C — NH2 >
—C � N > — C � O > — C � O > — OH > — NH
2
>
—O — > — C � C — > — C � C —
O O
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2.6 NOMENCLATURE OF POLYFUNCTIONAL COMPOUNDS
Organic compounds which contain two or more functional groups are called polyfunctional compounds.
Their systematic names are obtained as follows.
1. When an organic compound contain two or more
different functional groups, the highest priority group (the priority order given below) is selected as
the characteristic group or principal functional group or main functional group while all the remaining
groups are called secondary functional groups and are treated as substituents.
The order of priority while selecting the principal functional group is as follows:
it may be noted that while writing the names of the polyfunctional compounds the principal functional
group is indicated by adding the secondary sufx after the primary sufx while the secondary functional
groups are indicated by adding suitable prexes before the word root. The secondary sufxes of some of
the principle functional groups along with their corresponding prexes when they are treated as secondary
functional groups listed below.
COOH
(C)OOH
COOR
(C)OOR
O
C X
(C) OX – oyl halide
O
C NH
2
Carboxy Carboxylic acid
– oic acid
Carbalkoxy or alkoxy carbonyl Alkyl…..carboxylate
Halocarbonyl Carbonyl halide
Carbamoyl Carboxamide
Alkyl…..oate
Contd
.…
c h A P T e r 2 u nomenclature of Organic compounds
(C)ONH
O
C H
(C)HO – al
C N
(C) N
2
– amide
Formyl or aldo -Carbaldehyde
Cyano Carbonitrile
– Nitrile
109
C O
OH Hydroxy ol
NH
2
O
N OH Hydoxyimino Oxime
N NH
Note: The chain terminating functional groups with their carbon atoms shown in the brackets (given in the above table) are the part of their
respective acyclic principal chains while the carbon atoms of these groups which are shown without brackets are not part of their principal
chains.
2
Oxo or keto one
Amino Amine
Oxa Alkoxy
Hydrazono hydrazone
2. While selecting the principal chain present in a polyfunctional com-
pound, care should be taken that it must contain the principal functional group and the maximum
number of secondary functional groups and multiple bonds, if any.
3. The principal chain present in a polyfunctional compound must
be numbered in such a way that the principal group gets lowest possible number followed by double
bond, triple bond and the substituents.
4. The prexes for the secondary functional groups and other substituents should
be written in alphabetical order before the word root as explained earlier.
The rest of the rules for numerical prexes are the same as explained earlier.
some examples of the polyfunctional compounds:
110
CH3——CH2——C——CH2——CH
3
N——OH
Pentan-3-one-oxime
HN—N
2
COOH
1
23
4
4-Hydrazonocyclohexane-1-carboxylic acid
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O
CH
3
C C
CH
3
4
2
3 1
CH
2
COOC
CH
2H5
3
Ethyl-2-ethyl-2-methyl-3-oxobutanoate 3-Carboxamidopent-3-enoic acid
O
2 1 2 3 4 5
CH
Cl
2
CH C
CH
2
CONH
1
CH
1
2
CH
2
2-(2-Chloromethyl)-3-oxopent-4-enamide 3-Carbethyloxy-but-2-enoic acid
4 3 2 1
NC
CH
CH
2
OCH
Ethyl-4-cyano-3-methoxybutanoate
5 4 3 2 1
CH
3
CH
C
CONH
2
4 3 2 1
C
CH
3
CHCOOH
COOC2H
CH
3
COOC
2
2H5
CH
5
2
COOH
1. The prex ‘hydroxyimino’ is attached to the name of parent hydride when it is present as a
secondary functional group. For example,
When oxime is the principal functional group, the name ‘oxime’ is placed as a separate word after the
name of the aldehyde or ketone. For example,
2. The prex ‘hydrazono’ is attached to the name of the parent hydride when it is present
as a secondary functional group. For example,