IUPAC Nomenclature of Organic Compounds

 Nomenclature of Alkanes:

-         Alkanes are open chain (acyclic) hydrocarbons with general formula C_nH_2n+2 where n is integer number.

-         Alkanes contain only single bonds.

-         Methane CH₄ is the simplest member of alkanes it contain one carbon atom bonded by four sp3 orbitals to four hydrogens.

-          The following table show the first  ten Alkanes

Name	Molecular Formula	Structural Formula
Methane	CH4	CH4
Ethane	C2H6	CH3CH3
Propane	C3H8	CH3CH2CH3
Butane	C4H10	CH3CH2CH2CH3
Pentane	C5H12	CH3CH2CH2CH2CH3
Hexane	C6H14	CH3CH2CH2CH2CH2CH3
Heptane	C7H16	CH3CH2CH2CH2CH2CH2CH3
Octane	C8H18	CH3(CH2)6CH3
Nonane	C9H20	CH3(CH2)7CH3
Decane	C10H22	CH3(CH2)8CH3

 

Alkyl group (R):

-         The alkyl group is obtained by elimination of one hydrogen atom from the corresponding alkane.

-         Have the general formula C_nH_2n+1 

-         The alkyl group is named by changing the suffix (ane) by (yl) 

-         Examples:

Methane       CH4	Methyl     CH3
Ethane           C2H6	Ethyl        C2H5
Propane        C3H8	Propyl      C3H7
Butane          C4H10	Butyl        C4H9
Pentane         C5H12	Pentyl      C5H11

  

The IUPAC Nomenclature of alkanes:

-         In the IUPAC nomenclature the first part of the name determined according to the number of carbon atoms in the compound and the second part according to the functional group as follow:

-         The first part of the name (prefix) (according to the no. of (C) atoms):

No. of carbon atoms	The first part of name
1	Meth--
2	Eth--
3	Prop--
4	But--
5	Pent--
6	Hex--
7	Hept--
8	Oct--
9	Non--
10	Dec--

 

-         The second part of the name (suffix) (according to functional group)

Organic family	Functional group	Suffix
Alkanes	No function group but all bonds are single	alkane
Alkenes	Double bond(=)	alkene
Alkynes	Triple bond(Ξ)	alkyne
Alcohols	Hydroxyl group (–OH)	alkanol
Aldehydes	Aldehyde group (–CHO)	alkanal
Ketones	Carbonyl group (-CO-)	alkanone
Carboxylic acids	Carboxykic group (–COOH)	alkanoic acid

 

Steps of Nomenclature of alkanes:

1. Choose the longest continuous parent carbon chain (note that the longest chain not necessarily straight)
2. If there are two equal chains choose the chain with higher number of substituents (branches)
3. Number the carbon atoms (the first part of the name, or prefix) and the second part (suffix) will be (ane).
4. If there are branches in the parent chain use the following rules

A- Number the carbon atoms giving the branches the lowest numbers.

B- If the branches are of the same type add before the branch name the following starts:

  2=di 

  3=tri

  4=tetra

  5 = penta

C- If the branches are different they should be ordered alphabetically.

D- All branches should end by ----yl

E- If the branch itself is also branched determine the longest chain and follow steps a, b, c, and d and all the name of the branch is written inside a brackets as [   ].

IUPAC nomenclature of Organic compounds contain functional group:

1. Choose the longest continuous parent chain contain the functional group and number the carbon atoms giving the functional group the lowest number.
2. Determine the no. of carbon atoms (the first part of the name, or prefix) and the second part (suffix) will be according to the functional group.
3. Step (3), The same as for alkanes nomenclature.

Examples: What is the name of the following compounds