Nomenclature of Different Classes of Organic Compounds

Compounds of carbon and hydrogen are called hydrocarbons.

These are further divided into two classes: saturated and unsaturated hydrocarbon.

1) Saturated hydrocarbons- alkanes

Hydrocarbons in which all the carbon atoms are linked to one another by only single bonds are called saturated hydrocarbons.

These ma be either acyclic or cyclic hydrocarbons.

Saturated acyclic hydrocarbons are called alkanes. They are also called paraffins since they are relatively inert towards most of the chemical reagents.

General Formula: C_nH_2n+2

Primary suffix: ane

The IUPAC names of alkanes are obtained by adding suffix ane to he word root indicating the number of carbon atoms.

Types of alkanes

Depending upon the structure of the carbon chain, alkanes are of following two types :

 

Straight chain alkanes : These alkanes contains straight chains of carbon atoms in their molecules. Alkanes in which no carbon atom is linked to more than two other carbon atoms are called Staight chain alkanes.

CH₃-CH₂-CH₂-CH₃ Butane

CH₃-CH₂-CH₂-CH₂-CH₂-CH₃ Hexane

Branched chain alkanes

Alkanes in which at least one carbon atom is linked to three or four other carbon atoms are called branched chain alkanes.

The prefix iso is used when the second carbon of the branched chain alkanes carries 1 methyl group while the prefix neo is used when second carbon of the branched chain alkanes carries 2 methyl group.

Types of carbon and hydrogen atoms in alkanes

The carbon atom in an alkane molecules may be classified into four types as primary(1°) ,secondary (2°) , tertiary (3°) and quaternary (4°).

A carbon atom attached  to one other carbon atom is called a primary carbon atom and is designated as 1°.

A carbon atom attached to two other carbon atom is called a secondary carbon atom and is designated as 2°

A carbon atom attached to three other carbon atoms is called a tertiary carbon atom and is designated as 3°.

A carbon atom attached to 4 other carbon atoms is called a quarternary carbon atom and is designated as 4°.

The hydrogen atoms attached to 1° ,2° ,3° carbon atoms are called Primary ,secondary and tertiary hydrogen atoms.

 

Alkyl groups

The removal of one hydrogen atom from the molecule of an alkane gives an alkyl group.

General formula: C_nH_2n+1

Their names are derived by replacing the terminal ane of corresponding alkane by the suffix yl.

Alkane -ane +yl =Alkyl

2)Unsaturated hydrocarbons

Open chain hydrocarbons which contain carbon-carbon double or triple bonds in their molecules are called unsaturated hydrocarbons.

These are of two types :alkenes and alkynes.

Alkenes : Unsaturated aliphatic hydrocarbons containing a carbon carbon double bond are called alkene.

They are also called all olefins since the lower members of this class react with chlorine to form oily products.

General Formula: C_nH_2n

Primary suffix : ene

Common name : Alkane -ane + ylene

IUPAC name: Alkane -ane +ene = Alkene

Alkynes

Unsaturated aliphatic hydrocarbons containing a carbon carbon triple bonds are called alkynes.

They are called acetylenes after the name of the first member of this family.

General formula:  C_nH_2n-2

 Primary suffix: yne

 

3)Haloalkanes

Halogen derivatives of alkanes are called haloalkanes.

They are further classified as mono, di, tri and tetra haloalkanes accordingly as they contain 1, 2, 3,4 halogen atoms respectively in their molecules.

 

1) Monohaloalkanes  : The monohalogen derivatives of alkanes are called alkyl halides.

General formula : C_nH_2n+1 X where X=F,Cl, Br,I

Functional group : X (halogen)

Secondary prefix : Halo

Common names : Add the word halide (fluoride, chloride ,bromide, iodide) to the name of the alkyl group i.e. Alkyl + halide = Alkyl halide

IUPAC names :Add the secondary prefix halo to the name of corresponding alkane i.e. Halo + alkane=Haloalkanes

The position of both the halogen atoms are indicated.

2) Dihaloalkanes

Alkanes containing 2 halogen atoms per molecule are called dihaloalkanes.

General Formula: C_nH_2nX₂ where n=1,2,3 etc

Common name:  Dihalogen derivatives of alkanes have been divided into three categories:

1) Alkylidene dihalogen : Dihalogen derivatives of alkanes in which the two halogen atoms are attached to same carbon atom are called alkylidene dihalides or alkylidene halides.

Since the position on the same carbon atom are called geminal position, therefore, alkylidene dihalides are also called geminal dihalides or simply gem-dihalides.

2) Alkylene dihalides : Dihalogen derivatives of alkanes in which the 2 halogen atoms are attached to adjacent carbon atoms of the chain are called alkylene dihalides or alkylene halides.

Since position on the adjacent carbon atom are called vicinal position, therefore, alkylene dihalides are also called vicinal dihalides or simply vi-dihalides.

3) Polymethylene dihalides : Dihalogen derivatives of alkanes in which the 2 halogen derivatives are present on the terminal carbon atoms i.e. α , ω-position of the carbon chain are called polymethylene dihalides.

All types of dihalides are called dihaloalkanes, the position of the halogen atoms being indicated by lowest possible arabic numerals.

Formula	Common name	IUPAC
CH2Cl2	Methylene chloide	Dichloromethane
CH3-CHBr2	Ethylidene dibromide	1,1-Dibromoethane
BrCH2-CH2Br	Ethylene dibromide	1,2-Dibromoethane
CH3-CHCl-CH2Cl	Proplidene dichloride	1,1-Dichloropropane
CH3-CCl2-CH3	Isoproplidene dichloride	2,2-Dichloropropane
ClCH2-CH2-CH2-Cl	Trimethylene dichloride	1,3-Dichloropropane

3) Tri and tetrahaloalkanes

The general formula of trihaloalkanes is C_nH_2n-1X₃ while that of tetrahaloalkanes is C_nH_2n-2X₄ where n=1,2,3,4….

The position of the halogen atoms on the carbon chain be indicated by Arabic numerals.

4) Alcohols or alkanols

Alcohols are classified as monohydric ,dihydric, trihydric and polyhydric according as their molecule contains 1,2,3 and many hydroxyl groups.

 

Presence of two or more hydroxyl groups on the same carbon atom makes the molecule unstable, therefore, in di, tri and polyhydric alcohol , each hydroxyl group is present on a different carbon atom.

1) Monohydric alcohols 

General formula: C_nH_2n+1 OH (where n=1,2,3…) or R-OH

Functional group : OH (hydroxyl)

Secondary suffix : ol

Common names: Add the word alcohol to the name of alkyl group i.e.

Alkyl + alcohol = Alkyl alcohol

IUPAC names: Replace the terminal e from the name of corresponding alkane by the suffix ol.

Alkane -e +ol = Alkanol

Formula	Common Name	IUPAC name
CH3OH	Methyl alcohol	Methanol
CH3CH2OH	Ethyl alcohol	Ethanol
CH3CH2CH2OH	n-Propyl alcohol	Propan-1-ol
CH3CHOHCH3	Isopropyl alcohol	Propan-2-ol

2) Dihydric alcohols

General formula: C_nH_2n+1(OH)₂

Because of their sweet taste ,dihydric alcohols are called glycols.

Depending upon the relative position of the two hydroxyl groups, they are further classified as α, β, γ …ω glycols.

α-glycols are named by adding the word glycol to the common name of the alkene from which they have been prepared by direct hydroxylation.

β, γ ,ω glycols are named as the corresponding polymethylene glycols.

IUPAC name: Add the suffix diol to the name of the alkane containing the same number of carbon atoms as the diol.

Alkane + diol =Alkanediol

Formula	Common name	IUPAC name
OHCH2-CH2OH	Ethylene glycol	Ethane-1,2-diol
CH3-CHOH-CH2OH	Propylene glycol	Propane-1,2-diol
OHCH2-CH2-CH2OH	Trimethylene glycol	Propane-1,3-diol

3) Trihydric alcohol

General Formula: CnH_2n-1 (OH)₃

IUPAC name: Add the suffix triol to the name of the alkane containing the same number of carbon atoms as the triol.

Alkane + triol =Alkanetriol

The position of the hydroxyl group is indicated by arabic numerals.

5) Ethers

General Formula: R-O-R’ where R and R’ are same or different alkyl group.

If R=R’ ,ethers are called simple ethers and if R≠R’ then ethers are called mixed ethers.

Common names: In mixed ethers, add the word ether to the name of the alkyl groups arranged in alphabetical order.

In simple ethers , the numerical prefix di is added to the name of the alkyl group followed by the word ether.

IUPAC name: In the IUPAC system, ethers are called alkoxyalkanes.

The smaller alkyl group forms a part of the alkoxy group while the bigger alkyl group forms a part of the alkane.

 

The name of the ethers are then derived by adding the suffix alkoxy to the name of the alkane i.e. Alkoxy + alkane = Alkoxyalkane

Formula	Common name	IUPAC name
CH3-O-CH3	Dimethyl ether	Methoxymetahne
CH3-O-CH2CH3	Ethyl methyl ether	Methoxyethane
CH3CH2-O-CH2CH3	Diethyl ether	Ethoxyethane

6) Alkanoic acids

General Formula: C_nH_2n+1 COOH or R-COOH

Functional group: -COOH

Secondary suffix : oic acid

IUPAC names: Replace terminal e from the name of the corresponding alkane by the suffix oic acid

i.e. Alkane – e + oic acid = Alkanoic acid

Formula	Common name	IUPAC name
H-COOH	Formic acid	Methanoic acid
CH3-COOH	Acetic acid	Ethanoic acid
CH3CH2-COOH	Propionic acid	Propanoic acid
CH3CH2CH2CH2 -COOH	Butyric acid	Butanoic acid

7) Aldehydes or Alkanals

General formula : C_nH_2n+1 CHO or R-CHO

Functional group: -CHO

Secondary suffix: al

Common name: Replace ic acid from the common name of the corresponding acid which they give upon oxidation by the word aldehyde.

IUPAC : Replace the terminal e from the name of the corresponding alkane by the suffix ,al.

Alkane -e+al = Alkanal

Formula	Common name	IUPAC name
H-CHO	Formaldehyde	Methanal
CH3-CHO	Acetaldehyde	Ethanal
CH3CH2-CHO	Propionaldehyde	Propanal
CH3CH2CH2CH2-CHO	Butryaldehyde	Butanal

8) Ketone or Alkanones

General Formula: C_nH_2n+1 CO C_nH_2n+1 where n=1,2,3…. or R-CO-R’ where R and R’ may be same or different alkyl group.

If R = R’ , ketones are called simple ketones.

If R≠ R’ , ketones are called mixed ketones.

Functional group : -CO

Secondary suffix: one

Common name: In case of mixed ketones , name the alkyl group in alphabetical order and then add the word ketone.

In simple ketones, the numerical prefix di is used before the name of the alkyl group.

IUPAC : Replace the terminal e from the name of the corresponding alkane by the suffix , one.

Alkane -e +one = Alkanone

Formula	Common name	IUPAC name
CH3-CO-CH3	Dimethyl ketone or acetone	Propanone
CH3-CO-CH2CH3	Ethyl methyl ketone	Butan-2-one
CH3-CO-CH2CH2CH3	Methyl propyl ketone	Pentan-2-one
CH3CH2-CO-CH2CH3	Diethyl ketone	Pentan-3-one

9) Acid chlorides or acyl chlorides or Alkanoyl chlorides

General formula: RCOCl where R=H or any alkyl group

Functional group:  -COCl

Secondary suffix: oyl chloride

Common name: Replace ic acid from the common name of the corresponding acid by yl chloride

IUPAC name: Alkane -e + oyl chloride = Alkanoyl chloride

Formula	Common name	IUPAC name
H-COCl	Formyl chloride	Methanoyl chloride
CH3-COCl	Acetyl chloride	Ethanoyl chloride
CH3CH2-COCl	Propionyl chloride	Propanoyl chloride
CH3CH2CH2-COCl	Butyryl chloride	Butanoyl chloride

 

10) Acid anhydride

General formula: R-CO-O-CO-R’ or (RCO)₂O where R and R’ may be same or different alkyl group.

Functional group: -CO-O-CO-

Secondary suffix: anhydride

Common name: Replace the word acid from the common or IUPAC name of the corresponding acid by word anhydride.

Symmetrical anhydride of substituted carboxylic acids are named by adding the prefix bis to the name to indicate that two identical acyl group are present.

Unsymmetrical anhydride are named by writing the names of the two acids alphabetically before the word anhydride.

Formula	Common name	IUPAC name
(CH3CO)2O	Acetic anhydride	Ethanoic anhydride
(CH3CH2CO)2O	Propionic anhydride	Propanoic anhydride
(ClCH2CO)2O	Bis(Chloroacetic anhydride)	Bis(Chloroethanoic anhydride)
HCO-O-COCH3	Acetic formic anhydride	Ethanoic methanoic anhydride

11)  Esters 

General formula: R-COOR’

Functional group: -COOR“

Secondary suffix: oate

Common name or IUPAC name: Write the name of the alkyl group before the common or IUPAC name of the parent acid with its terminal ic acid replaced by oate.

Formula	Common name	IUPAC name
H-COOCH3	Methyl formate	methyl methanoate
H-COOC2H5	Ethyl formate	Ethyl methanoate
CH3-COOCH3	Methyl acetate	Methyl ethanoate
CH3-COOC2H5	Ethyl acetate	Ethyl ethanoate

12) Acid amide or Alkanamides

General formula: R-CONH₂

Functional group: -CONH₂

Secondary suffix: amide

Common name : Replace ic acid from the common name of the corresponding acid by the secondary suffix amide.

IUPAC name: Replace the terminal e from the name of the corresponding alkane by the suffix amide i.e. Alkane -e + amide = Alkanamide

Formula	Common name	IUPAC name
H-CONH2	Formamide	Methanamide
CH3-CONH2	Acetamide	Ethanamide
CH3-CH2-CONH2	Propanamide	Propanamide

13) Primary amines

General formula: R-NH₂

Functional group: -NH₂

Secondary suffix: amine

Common name : 1) Add the word amine to the name of the alkyl group , i.e.

Amino + amine = Alkylamine

2) Attach the prefix amino to the name of the corresponding alkane , i.e.

Amino + alkane = Aminoalkane

IUPAC name : Replace the terminal e from the name of the corresponding alkane by the secondary suffix amine i.e. Alkane -e + amine = Al

Formula	Common name	IUPAC name
H-CONH2	Formamide	Methanamide
CH3-CONH2	Acetamide	Ethanamide
CH3-CH2-CONH2	Propanamide	Propanamide

 

14) Secondary amines

General formula: R-NH-R’ where R and R’ may be same or different alkyl group.

Functional group: -NH (imino)

Secondary prefix: N-alkyl

Secondary suffix: amine

Common name : 1) Name the alkyl group in alphabetical order and then add the word amine.In case the two alkyl groups are same, the numerical prefix di is used before the name of the alkyl group.

2) Add the prefix N-alkyl before the name of the aminoalkane ; the smaller alkyl group forma a part of the N-alkyl group while the larger alkyl group forms a part of the alkane.

IUPAC name: Add the prefix N-alkyl to the name of the alkanamine  corresponding to the larger alkyl group , i.e. N-alkyl + alkanamine = N-Alkylalkanamine

Formula	Common name	IUPAC
CH3NHCH3	Dimethyl or N-Methylaminomethane	N-Methylmethanamine
CH3CH2CH2NHCH3	Ethylmethylamine or N-Methylaminoethane	N-Methylethanamine
(CH3CH2)3N	Diethylamine or N-Ethylaminoetahne	N-Ethylethanamine

15)  Tertiary amines

General formula: R-N(R’R“)  where R , R’ , R“ may be same or different alkyl group or two of them may be same while the third may be different.

Functional group: -N- 

Secondary prefix: N-alkyl , N-alkyl

Secondary suffix: amine

Common name : 1) Name the alkyl group in alphabetical order and then add the suffix amine.In case the two or all the three alkyl groups are same, the numerical prefix di and tri are used before the name of the alkyl group.

2) Add the prefix N-alkyl and N-alkyl to the name of the aminoalkane corresponding to the largest alkyl group.

Formula	Common name	IUPAC name
(CH3)3N	Trimethylamine or N,N-Dimethylaminomethane	N,N-Dimethylmethanamine
CH3CH2N(CH3)2	Ethyldimethylamine or N,N-Dimethylaminoethane	N,N -Dimethylethanamine
(CH3CH2)2NCH3
(CH3CH2)3N	Triethylamine or N,N-Diethylaminoethane	N,N-Diethylethanamine

16) Nitroalkane

General formula: R-NO₂

Functional group : 

Secondary prefix: nitro

Common name: There are no common names for nitroalkanes

IUPAC name: Add the secondary prefix nitro to the name of the alkane

Nitro+ alkane = Nitroalkane

Formula	Common name
CH3-O-N=O	Methyl nitrite
CH3CH2-O-N=O	Ethyl nitrite
CH3CH2CH2NO2	n-Propyl nitrite
CH3CH(NO2)CH3	Isopropyl nitrite

17) Alkyl nitrites

General formula: R-O-N=O

Functional group : -O-N=O

Secondary suffix: nitrite

Common names: Add the secondary suffix nitrite  to the name of the alkyl group i.e.

Alkyl + nitrite = Alkyl nitrite

IUPAC name: There are no IUPAC names for alkyl nitrites.

Formula	Common name
CH3-O-N=O	Methyl nitrite
CH3CH2-O-N=O	Ethyl nitrite
CH3CH2CH2NO2	n-Propyl nitrite
CH3CH(NO2)CH3	Isopropyl nitrite

18) Alkyl cyanide

General formula: R-C≡N

Functional group: -C≡N

Secondary suffix: nitrile

Common name: 1) Add the suffix cyanide to the name of the alkyl group ,i.e.

Alkyl + cyanide = Alkyl cyanide

2) Replace ic acid from the common name of the corresponding acid by the suffix onitrile.

Acetic acid -ic acid + onitrile = Acetonitrile

IUPAC name: Add the suffix nitrile to the name of the alkane containing the same number of carbon atoms as the alkyl cyanide i.e. Alkane + nitrile = Alkanenitrile

Formula	Common name	IUPAC  Name
CH3-CN	Methyl cyanide or Acetonitrile	Ethanenitrile
CH3CH2-CN	Ethyl cyanide or Propionitrile	Propanenitrile
CH3CH2CH2-CN	Propyl cyanide or Butyronitrile	Butanenitrile

19) Isocyanide

General formula: RNC

Functional group: 

Secondary suffix: Isocyanide or isonitrile

Common name: Add the suffix isocynanide or carbylamine to the name of the alkyl group.

IUPAC name: There are no IUPAC for isocynaide or isonitrile.

Formula	Common name
CH3NC	Methyl isocyanide or Methyl carbylamine or Methyl isonitrile
CH3CH2NC	Ethyl isocynaide or Ethyl carbylamine or Ethyl isonitrile