Chapter 14 Purification, classification and nomenclature of organic compound 2 by TEACHING CARE Online coaching and tuition classes

 

 

The substituent dimethyl is cited first because it is alphabetized under d. Similarly,

C2H5 CH3                                CH3

 

1              2             3|

4|      5

6             |7           8

9             10

 

CH3 – CH2 – CH – C – CH2 – CH2 – C H – CH2 – CH2 – CH3

|1

|2

H3 C – C – CH 3                            Complex substituent

 

CH3

( 1, 1-dimethylpropyl)

 

4-(1, 1-Dimethylpropyl) –3-ethyl-4, 7-dimethyldecane

 

When the names of two or more complex substituents are composed of identical words, priority for citation is given to the substituent which has lowest locant at the first cited point of difference within the complex substituent. For example,

 

             1-methylbutyl

 

 

12            11             10             9              8

7            6             |5           4

3              2              1

 

C H3 – C H 2 – C H 2 – C H 2 – C H 2 – C H – C H 2 – C H – C H 2 – C H 2 – C H 2 – C H 3

 

2-methylbutyl

 

– 5(1-methyl butyl)-7-(2-methyl butyl) dodecane

The substituent (1-methylbutyl) is written first because it has lower locant than the substituent (2-methylbutyl).

When the same complex substituent (substituted in the same way) occurs more than once, it is indicated by the multiplying prefix bis (for two), tris (for three), tetra kis (for four) etc.

 

1,1 dimethylpropyl

 

10             9              8                                                                                     2           1

C H3 – C H 2 – C H 2 – C H 2 – C H 2 – C– C H 2 – C H 2 – C H – C H3

|

CH3

1,1 dimethylpropyl

 

5, 5-Bis (1, 1-dimethylpropyl)-2-methyldecane

 

(viii) Cyclic hydrocarbons : These compounds contain carbon chain skeletons which are closed to form rings. The saturated hydrocarbons with ring of carbon atoms in the molecule are called cycloalkanes. These have the general formula Cn H2n .

The cyclic compound is named by prefixing cyclo to the name of the corresponding straight chain alkane.

For example,

C3H6, Cyclopropane                 C₄H₈, Cyclobutane                     C₅H₁₀, Cyclopentane                       C6H12, Cyclohexane

 

If side chains are present, then the rules given in the previous section are applied. For example,

 

 

 

 

CH₃

Methylcyclohexane

C₂H₅

Ethylcyclopentane

 

When more than one side chains are present, the numbering is done beginning with one side chain so that the next side chain gets the lower possible number. For example,

 

CH₃

 

 

CH₃

CH₃

 

6

5

 

 

CH₂CH₂CH₃

CH₃    CH₃

1

2

3

 

 

CH₂CH₃

 

1.3-Dimethylcyclobutane

1-Methyl-3-propylcyclohexane

(Not 5-Methyl-1-propyl cycloalkane)

3-Ethyl-1, 1-dimethylcyclohexane

(Not 1-Ethyl-3,3-dimethylcyclohexane)

 

 

When a single ring system is attached to a single chain with a greater number of carbon atoms or when more than one ring system is attached to a single chain, then it a named as cycloalkylalkanes. For example,

 

1              2              3              4

–

• CH2 – CH2 – CH 2 – CH 2 – CH 3

 

 

 

CH₃

C H 2 – C H 2 – C H 2 – C H 3

1-Cyclopropyl butane

 

 

• CH 2 – CH 2 – CH 2 –

1-Cyclobutylpentane

 

1, 3-Bis (2-methylcyclopropyl) propane

CH₃

lowest possible nu

Cyclohexyl cyclohexane

 

In case of substituted cycloalkenes, the double bond is given the                     mber and numbering is done in such a way that the substituents get the lowest number.

 

CH₃

2

1

CH₃

3

2

1

CH₃

 

3-Methylcyclohex-1-ene                                                               2, 3-Dimethylcyclopent-1ene

 

Note :®According to the IUPAC system of Nomenclature, certain trivial or semi- systematic names may be used for unsubstituted radicals. For example, the following names may be used,

(CH3)2CH –	Isopropyl	(CH3)2 CH – CH2 –	Isobutyl
CH3 – CH 2 –CH – | CH3 (CH3 )2 CH – CH2 – CH2 –   CH3 | CH3 – CH2 – C – | CH3	Sec- Butyl     Isopentyl tert-Pentyl	(CH3)3 C –   (CH3)3 C – CH2 – (CH3)2 CH – CH2 – CH2 – CH –	tert-Butyl     Neopentyl Isohexyl

 

 

 

However, when these are substituted, these names cannot be used as such. For example,

CH(CH3)2

 

1              2              3

|4           5            6              7              8

9             10

 

C H3 – C H 2 – C H 2 – C H – C H – C H 2 – C H 2 – C H 2 – C H 2 – C H3

|

CH3 –CH–CH2 –CH3

5-sec -Butyl-4 -isopropyldecane

 

 

CH3

|

CH2

CH3

|

CH – CH3

 

8             7             6

5           4           |3      2

1            1             2

| 3           4

5           6             7             8

 

C H₃ – C H₂ – C H₂ – C H– C H – C– C H₂ – C H₃ ; C H3 – C H2 – C H – C H2 – C H – C H2 – C H2 – C H3

 

|

CH3 –CH

|

CH3

|

CH3

|

CH2 –CH3

1|

Cl – C – CH₃

2|

CH3

 

3,3-Diethyl -5-isopropyl -4 -methyloctane                                                                5-(1-chloro-1- methylethyl)- 3-isopropyloctane

 

It may be noted that while writing the substituent’s name in alphabetical order, the prefixes iso-and neo-are considered to be part of the fundamental name. However, the prefixes sec-and tert-are not considered to be the part of the fundamental name.

(2)  Rules for IUPAC names of polyfunctional organic compounds

Organic compounds which contain two or more functional groups are called polyfunctional compounds. Their IUPAC names are obtained as follows,

• Principal functional group : If the organic compound contains two or more functional groups, one of the functional groups is selected as the principal functional group while all the remaining functional groups (also called the secondary functional groups) are treated as substituents. The following order of preference is used while selecting the principal functional

Sulphonic acids > carboxylic acids > anhydrides > esters > acid chlorides > acid amides > nitriles > aldehydes > ketones > thiols > alcohols >alkenes > alkynes.

All the remaining functional groups such as halo (fluoro, chloro, bromo, iodo), nitroso (–NO), –nitro (–NO₂), amino (–NH₂) and alkoxy (–OR) are treated as substituents.

The decreasing order of seniority among the principal groups

 

Order of preference	Preflx	Suffix (ending)	Order of preference	Preflx	Suffix (ending)
–  SO3H –  COOH –  COOR   –  COX –  CONH2 –  C º N –  CHO > C = O	Sulpho Carboxy Alkoxy carbonyl Haloformyl Carbamoyl Cyano Formyl Keto	Sulphonic acid –  oic acid Alkyl alkanoate   Oyl halide –  amide –  nitrile –  al –  one	–  OH –  NH2 C = C   –  C º C – –  O – –  X –  NO2	Hydroxy Amine –   – Epoxy Halo Nitro	–  ol –  amine –  ene   –  yne – – –

• Selecting the principal chain : Select the longest continuous chain of carbon atoms containing the principal functional group and maximum number of secondary functional groups and multiple bonds, if any.
• Numbering the principal chain : Number the principal chain in such a way that the principal functional group gets the lowest possible number followed by double bond and triple bond and the substituents, e.

Principal functional group > double bond > triple bond > substituents

 

 

 

• Alphabetical order : Identify the prefixes and the positional numbers (also called locants) for the secondary functional groups and other substituents and place them in alphabetical order before the word

 

 

Substituent

 

 

 

4-Hydroxy pentanoic acid

 

Principal functional group

 

 

5              4|             3              2

C H₃ – C H – C H ₂ – C H ₂ –

 

Some other examples are :

O                                                                                                                                          O

 

5              4||    3          2          1

5              4            3             2           1

₄        3||   _{2        1}

 

C H3 –

C – C H ₂ C H ₂ COOH  ;

C H₃ – C H – C H₂ – C H – C H₃ ; C H3 – C – C H2 – C HO

 

(-COOH is principal group) 4-oxopentanoic acid)

|               |

NH2                   OH

(-CHO is principal group) 3-Oxobutanal

 

 

O

1             2||    3              4

(-OH is principal group) 4- Aminopentan- 2-ol

 

 

3              2             1

 

C H  – C – C H  – C H

• OH ;

NC – C H   – C H   – COOH ;       ^{3        2       1}

 

3                         2              2

2             2                            C H ₃ – C H – COOH

 

(-CO is principal group) 4 – Hydroxybutane- 2- one

(-COOH is principal group) 3-cyanopropanoic acid

|

NH2

 

CH3

(-COOH is principal group) 2- Aminopropanoic acid

 

4             3|      2      1         ; 4

3           2      1

–        – –

4              3             2           1

;        –          –        –

4              3       2            1

;          –     =        –

 

C H3 – C –

|

C– C H3

||

C H3

C H     C

|      ||

COOH

C H2

|

C H2      C H

|

COOH

C H3     C

|

C H      COOH

 

OH O

CH3   O

OH                        F

COOC2H5

 

(-CO is principal group)

3-Hydroxy- 3- methylbutan- 2-one

CH3

(-COOH is principal group) 3-Methyl – 2-oxo butanoic acid

(-COOH   is principal group)

• Fluoro-4-hydroxybutanioc acid

O

• Carbethoxybut-2-en-1-oic acid or 3-Carbethoxy-2-butenoic acid

 

6       5     4|       3

2          1              5

_{4       3}        2||   ₁

5      4              3            2            1

 

H C º C– C H – C HOH – C H 2 COCl ; C H₂ = C H – C H₂ – C – C H₃ ; OH C– C H ₂ – C H = C H – C HO

 

3-Hydroxy-4-methylhex-5-yn-1-oyl chloride or 3-Hydroxy-4-methylhex-5-ynoyl chloride

CH3

Pent- 4-en- 2-one

Pent-2-ene-1, 5-dial

 

6             5              4

₃      2|     ₁

4      3            2           1

 

C H3 – C H2 – C H = C H – C H C HO ;

2-Methylhex – 3-en-1-al

HOOC– C H = C H – COOH

But-2-ene-1, 4-dioic acid (or But-2-enedioic acid)

 

• Polyfunctional compounds containing more than two like functional groups : According to latest convention (1993 recommendations for IUPAC nomenclature), if an unbranched carbon chain is directly linked to more than two like functional groups, the organic compound is named as a derivative of the parent alkane which does not include carbon atoms of the functional For example,

CN                                                                                                 COOH

 

₃        2|       ₁

5          4             3|      2          1

 

NC – C H ₂ – C H – C H ₂ – CN

Propane-1, 2, 3-tricarbonitrile

(formerly 3-cyanopentane-1, 5-dinitrile)

HOOC – C H 2 C H 2 – C H – C H 2 C H 2 – COOH

Pentane-1, 3, 5-tricarboxylic acid

(formerly 4-carboxyheptane-1, 7-dioic acid)

 

Following the above rule, citric acid may be named as,

 

 

 

COOH

 

1             2|    3

HOOC – C H ₂ – C – C H ₂ – COOH

|

OH

• Hydroxypropane-1, 2, 3-tricarboxylic acid (formerly 3-carboxy-3-hydroxypentane-1, 5-dioic acid )

 

Note :®If none of the choices in a multiple choice question follows 1993 recommendations, the choice corresponding to earlier system of nomenclature as given in parentheses should be taken as correct. If, however, all the three like groups are not directly linked to the unbranched carbon chain, the carbon atoms of the two like groups are included in the parent chain while the third which forms the side chain is considered as a substituent group. For example,

 

CH2CN         (substituent group)

CH₂COOH

(substituent group)

 

6 5          4

3|       2          1

6 5          4

3|       2          1

 

N CC H ₂ C H ₂ – C H – C H ₂ C N

3-(Cyanomethyl) hexane-1, 6-dinitrile

HOOCC H 2 C H 2 – C H – C H 2 COOH

3-(Carboxymethyl) hexane-1, 6-dioic acid

 

 

 

Sometimes, the bonds between carbon atoms are represented by lines. For example, n-hexane has a continuous chain of six carbon atoms which may be represented as,

`

CH3 – CH2  – CH2  – CH2  – CH2  – CH3

n – Hexane

In this notation, the carbon atoms are represented by line ends and intersections. It is assumed that the required number of hydrogen atoms are present wherever they are necessary to satisfy the tetravalency of carbon. A single line represents a single bond (C – C), two parallel lines represent a double bond (C = C) and three parallel lines represent a triple bond (C º C). For example,

 

1

2                                                                                                                                                                 2

3                                                                                                                                                                 1

 

1-Methyl-3-propylcyclohexane                               3-Ethyl-1, 1-dimethylcyclohexane

(Not 1-ethyl-3, 3-dimethylcyclohexane)

• Methyl cyeclohex-1-ene

 

1                 3

 

4                 2                                                                       2                  4

 

1

 

 

Pent-1-ene

Buta-1, 3-diene

1,3-Dicyclohexyl propane

 

 

4

2                   4

2

1                3                  5

3                                                                       3

2                 4                                     1                                   5                                  1

 

 

• Cyclobutyl pentane

Penta-1, 4-diene

• Methylbuta-1, 3-diene (a line at position 2 corresponds to CH₃ group )

 

 

 

 

1                                      5

 

 

 

• Cyclohexyl butan-2-ol

1, 3-Dimethyl cyclohex-1-ene

• Hydroxy-4-methyl pentan-2-one

 

 

 

3                                                                         O

OH

4              2                                                        2

 

 

 

 

 

3-Ethyl penta-1, 3-diene

O

5

6

 

3, 3, 5-trimethylhex-1-en-2-ol

3

 

 

5, 6-Dimethylcyclohex-2-en-1-one

 

2                   4               6

1                   3                 5

 

 

1-Bromo-3-methyl pentan-2-one

Hexa-1, 3, 5-triene

 

 

Many hydrocarbons and their derivatives contain two fused or bridged rings. The carbon atoms common to both rings are called bridge head atoms and each bond or chain of carbon atoms connecting both the bridge head atoms is called as bridge. The bridge may contain 0, 1, 2 etc. carbon atoms. For example,

Bridge head atom

 

Bridge head atom

 

CH

Zero carbon bridge

CH                     One carbon bridge

 

 

 

One carbon bridge

CH₂

CH₂

One carbon bridge

Two carbon

ìïCH ₂

CH       CH ₂ üï

Two carbon

 

í

bridge        |

CH

2      |    ý

bridge

 

 

Bridge head atom

ïîCH 2

CH 2 ïþ

CH

Bridge head atom

 

 

These bicyclic compounds are named by attaching the prefix ‘bicyclo‘ to the name of the hydrocarbon having the same total number of carbon atoms as in the two rings. The number of carbon atoms in each of the three bridges connecting the two bridge head carbon atoms is indicated by arabic numerals, i.e., 0, 1, 2 etc. These

arabic numerals are arranged in descending order; separated from one another by full stops and then enclosed in square brackets. The complete IUPAC name of the hydrocarbon is then obtained by placing these square brackets containing the arabic numerals between the prefix bicyclo and the name of alkane. For example,

 

 

 

Bicyclo [2, 2, 1] heptane (also called norbornane)

Bicyclo [3, 1, 1] heptane          Bicyclo [2, 2, 2] octane          Bicyclo [4, 4, 0] decane

(also called decalin)

Bicyclo [1, 1, 0] butane

 

If a substituent is present, the bicyclic ring system is numbered. The numbering begins with one of the bridge head atoms, proceeds first along the longest bridge to the second bridge head atom, continues along the next longest bridge to the first bridge head atom and is finally completed along the shortest path. For example,

 

1         Cl

2 7         8

3     2     1

9

8   CH3                                                                               1             3

 

3       6  5

4

6      7                                                                  7             4

4

5

5

 

8-Chlorobicyclo [3, 2, 1] octane

• Methylbicyclo [4, 3, 0] nonane

2, 6, 6-Trimethylbicyclo [3, 1, 1] hept-2-ene

 

 

 

 

Compounds in which one carbon atom is common to two different rings are called spiro compounds. The IUPAC name for a spiro compound begins with the word spiro followed by square brackets containing the number of carbon atoms, in ascending order, in each ring connected to the common carbon atom and then by the name of the parent hydrocarbon corresponding to the total number of the carbon atoms in the two rings. The position of substituents are indicated by numbers ; the numbering beginning with the carbon atom adjacent to the common carbon and proceeding first around the smaller ring and then around the larger ring and finally ending on the common carbon atom. For example,

 

5       6                 1

7

4                          2

8      9      1     2   Cl

7

10           3

 

3                                                                                                           6      5      4

Spiro [2.4] heptane                                                                                         2-Chlorospiro [3.5] decane

 

 

Unbranched assemblies consisting of two or more identical hydrocarbon units joined by a single bond are named by placing a suitable numerical prefix such as bi for two, ter for three, quater for four, quinque for five etc. before the name of the repititive hydrocarbon unit. Starting from either end, the carbon atoms of each repititive hydrocarbon unit are numbered with unprimed and primed arabic numerals such as 1, 2, 3…., 1′, 2′, 3′ , 1”, 2”,

3”….. etc. The points of attachment of the repititive hydrocarbon units are indicated by placing the appropriate locants before the name. For example,

 

2                                         2′

1           1‘

3                                         3′

1, 1′ -Bicyclopropane

3         4

 

 

 

 

4′        3′

4”

3”

 

1, 1′, 2′, 1” -Tercyclobutane

As an exception, unbranched assemblies consisting of benzene rings are named by using appropriate prefix with the name phenyl instead of benzene. For example,

 

3        2

4                1        1′

2′      3′

4′

 

1”

2”      3”

 

4”

 

5        6                6′       5′

6”

5”

 

1, 1′, 4’, 1” -Terphenyl

Note :®If two atoms/groups of same preference occupy identical positions from either end of the parent chain, the lower number must be given to the atom/group whose prefix comes first in the alphabetical order. For example,

4          3          2          1                                                          5              4              3     2           1

 

Cl C H2 C H2 C H2 C H2 Br

CH₃ – CH  – C– CH – CH₃

 

1-Bromo-4-chlorobutane

|              ||

OCH3   O

|

OCH2CH3

 

2-Ethoxy-4-methoxypentan-3-one

• When two or more prefixes consist of identical words, the priority for citation is given to that group which contains the lowest locant at the first point of For example,

 

 

3

 

 

 

Cl

2       3

– 1              2          1               4

1  C H ₂ – C H ₂ –                    Cl

 

1-(2-chlorolphenyl)-2-(4-chlorophenyl) ethane

• If a compound contains a benzene ring coupled to an alicyclic ring, it is named as a derivative of benzene, e. compound having lowest state of hydrogenation. For example,

 

 

 

 

5        6

4                1         1

⁴   NO₂

 

 

3     2

CH₃

1-(2-Methylcyclohexyl)-4-nitro benzene

 

• In the common system of nomenclature, prefixes iso and neo are used only for compounds containing

 

an isopropyl group, (CH3 )2 CH

chain.

and a tert-butyl group, (CH3 )3 C

respectively at the end of the carbon

 

 

Aromatic compounds are those which contain one or more benzene rings in them. An aromatic compound has two main parts : (1) Nucleus,     (2) Side chain

• Nucleus :The benzene ring represented by regular hexagon of six carbon atoms with three double bonds in the alternate positions is referred to as The ring may be represented by any of the following ways,

 

• (ii) (iii)                       (iv)

• Side chain : The alkyl or any other aliphatic group containing at least one carbon atom attached to the nucleus is called side These are formed by replacing one or more hydrogen atoms in the ring by alkyl

 

radicals i.e., R (R may be – CH3 , – C2 H5 , – C3 H7

etc.)

Ring or nucleus

 

Side chain

 

 

If one atom of hydrogen of benzene molecule is replaced by another atom or group of atoms, the derivative formed is called monovalent substituted derivative. It can exist only in one form because all the six hydrogens of benzene represent equivalent positions. For example, C₆ H₅ X , where X is a monovalent group.

When two hydrogen atoms of benzene are replaced by two monovalent atoms or group of atoms, the resulting product can have three different forms. These forms are distinguished by giving the numbers. The position occupied by one of the substituent is given as 1 and the other position is numbered in a clockwise direction.

• Ortho (or 1, 2-) : The compound is said to be ortho (or 1, 2-) if the two substituents are on the adjacent carbon
• Meta (or 1, 3-) : The compound is said to be meta or (1, 3-) if the two substituents are on alternate carbon

 

 

 

• Para (or 1, 4-) : The compound is said to be para or (1, 4-) if the two substituents are on diagonally situated carbon

Ortho, meta and para are generally represented as o-, m- and p- respectively as shown below,

 

X

X

(1, 2-) Ortho

X

 

(1, 3-) Meta

X

X

 

2

(1, 4-) para

3

 

X

 

Aryl group : The radicals obtained by removal of one or more hydrogen atoms of the aromatic hydrocarbon molecules are known as aryl radicals or aryl groups. For example,

 

CH₂–

CH–

–C–

 

 

 

 

 

Phenyl (From nucleus)

From side chains

 

 

Nomenclature of different aromatic compounds : The names of few simple aromatic compounds are given below :

 

 

Hydrocarbons

CH₃

Benzene      Toluene

CH₂CH₃

Ethylbenzene

 

CH₃

CH₃

 

 

1, 2-Dimethyl benzene (o-xylene)

CH₃

 

 

CH₃

1, 3-Dimethylbenzene (m-Xylene)

CH₃

CH₃

1, 4-Dimethylbenzene (p-Xylene)

CH₃

 

 

H₃C                      CH₃

1, 3, 5-Trimethyl benzene (Mesitylene)

 

The aromatic hydrocarbons may also contain two or more benzene rings condensed together.

 

 

 

 

Naphthalene                                       Anthracene

Halogen derivatives

 

Nuclear substituted                                                               Side chain substituted

Phenanthrene

 

Cl                          CH3                             Cl

Cl                                  Cl

CH₂Cl

CHCl₂

CCl₃

 

 

 

 

Chlorobenzene

2-Chlorotoluene (o-Chlorotoluene)

,1,2-Dichlorobenzene (o-Dichlorobenzene)

Phenyl chloromethane (Benzyl chloride)

Phenyl dichloromethane (Benzal chloride)

Phenyl trichloromethane (Benzo chloride)

 

 

Hydroxy derivatives                                                                                                       OH

 

 

OH                 CH3

OH

CH₂OH                       OH                                      OH OH

 

 

 

 

 

 

Phenol

 

Ethers

 

2-Methyl phenol

o-Cresol

 

OCH₃

 

Benzyl alcohol

 

1, 2-Dihydroxybenzene (Catechol)

 

OCH₂CH₃

OH

1, 3-Dihydroxybenzene (Resorcinol)

 

 

O

OH

1, 4-dihydroxybenzene

 

 

 

 

 

Methoxybenzene (Anisole)

Ethoxybenzene

Phenoxybenzene (Phenetole)

 

Aldehydes and ketones (Nuclear substituted)

CHO

COCH₃

CO

 

 

 

 

 

Benzaldehyde

 

Carboxylic acids (Nuclear substituted)

Methyl phenyl ketone (Acetophenone)

Diphenyl ketone (Benzophenone)

 

 

COOH

 

COOH

CH₃

COOH

COOH

COOH

 

COOH

OH                                      COOH

 

COOH

 

 

COOH

 

Benzoic acid

o-Toluic acid

2-Hydroxy benzoic acid (o-salicylic acid)

Phthalic acid

Isophthalic acid

Terephthalic acid

 

Acid derivatives

O

C      Cl

O

C      NH₂

 

O

COOCH₃     OC             CO

 

 

COOC₂H₅

 

 

COOC₆H₅

COOC₂H₅

 

 

 

 

 

 

Benzoyl chloride

 

Benzamide

 

Methyl benzoate

 

Benzoic anhydride     Ethyl benzoate

 

Phenyl benzoate

Br

Ethyl 4-bromobenzoate

 

 

 

Amino derivatives (Nuclear substituted)                      Sulphonic acids       Nitro derivatives

 

NH₂

CH₃

NH₂

CH₂NH₂

SO₃H

NO₂

NO₂

 

 

 

 

 

Aniline (Aminobenzene)

 

• Amino toluene or

o-Toluidine

 

Benzyl amine

 

Benzene sulphonic acid

 

 

Nitrobenzene

NO₂

1, 3-Dinitrobenzene (m-Dinitrobenzene)

 

Some tips for nomenclature of aromatic compounds : For IUPAC nomenclature of substituted benzene compounds, the substituent is placed as prefix to the word benzene. It may be noted that common names of many substituted benzene compounds are still universally used. Some important tips for nomenclature of organic compounds are given below,

• When the benzene ring is named as substituent on the other molecule, it is named as phenyl group. It is treated in the nomenclature just like the name of an alkyl It is abbreviated as Ph. For example,

CH₂CH₂CHO                                                                                                                                                                  ^{4   5}

Ph                                                              C2 H5

|  3        2       1                                           3|           2            1

 

or  Ph CH ₂CH ₂CHO

• Phenylpropanal

C H = C H COOH

3-Phenylprop-2-enoic acid

C6 H5 – C  –

|

C H – C H3

|

 

 

 

1              2       3      4

C6 H5   OH

 

CH ₂ – C º C – CH₃ or Ph

C H ₂ – C º C– C H₃

Phenylbut-2-yne

 

 

• Disubstituted, trisubstituted or tetrasubstituted benzenes are named by using the numbers for the positions

 

of the substituents.

CH₃

1

2

NO₂

1

 

 

3

CH₃

5

NO_{2      4}

2

3

NO₂

 

1, 3-Dimethyl benzene

1, 2-Dichlorobenzene

1, 3, 5-Trinitrobenzene

 

• If different groups are attached to the benzene ring, then the following rules are kept in mind,
• The principal group is fixed as number
• The numbering of the chain is done in any direction (clockwise or anticlockwise) which gives lower number to the
• The substituents are written in alphabetical For example,

 

NH₂                                                                 COOH

 

 

 

 

 

 

2-Chlorophenol

3             5

2              6

 

COOH

 

CH₃

2, 3-Dimethyl aniline

1 2

6

5              3

HO          4

Br

 

NO₂

 

 

4-Aminobenzoic acid (–COOH is principal group)

2-Bromo-5-hydroxy- 3-nitrobenzoic acid

 

 

 

 

CHO

2

3

 

1  Cl

NH₂

 

6

 

5

CH₃

NO₂

 

 

OCH

4

O₂N     3

2

NO₂

Cl

C H                                       CH

 

3                                                                                                       2    5                                            3

 

4-Methoxy benzaldehyde

 

 

OCH₃

Cl

 

 

CH₃

1-Chloro, 2, 4, dinitrobenzene

 

 

OH

 

 

 

CH₃

 

 

 

 

CH₃

4-Ethyl-2-methylaniline

3-Chloro-4-methyl nitrobenzene

COH

 

 

OMe

OH

 

2-Chloro-4-methyl anisole

 

3, 4-Dimethylphenol

 

4-Hydroxy-3-methoxy benzaldehyde