Nomenclature of hydrocarbons- Class X

Nomenclature of hydrocarbons:

Alkane :

Alkane is a saturated hydrocarbon whose general formula is C_nH_2n+2.
Molecule of alkane consist only single covalent bonds.
First member of alkane family is methane ( CH₄ ).
IUPAC and common name of fist member of alkane is methane .
Other name of methane is Marsh gas.

Nomenclature of Alkane family:

IUPAC name of alkane may consist three part.
Branch name , root name and family name ( Suffix ane )

Branch name:

It is prefix of alkane name .
Branch is alkyl group.
Branch name is taken according to its position on root.
If there are more than two branch in alkane , then proper rule is followed in naming.

Root name :

It comes after branch name.
It depend on number of carbon atoms present in root of molecules.

Family name:

Family name of alkane is ane which comes after root name.
Thus family name is suffix of alkane .

How to name Alkane compound:

Step -1 : Determine root of alkane.

Step -2: Count number of carbons present in root of molecules and then decide its root name.

Step -3 :
If there is one branch in root, then give number the carbons atoms of root from that end so that branch gets lowest possible number.
if there are two or more branches in root, then give number the carbons atoms of root from that end so that sum of number associated with branch is minimum.
If there are two or more unlike branch then name that branch first which comes first according alphabetically.
If two branches are equidistant from both ends, then give number in root from the end which is nearest the simple branch.

Example :

Naming of CH₄

Root name : meth

Family name : ane

So IUPAC name : methane

Common name: methane

Naming of C₂H_6:

CH₃ ----- CH₃

Root name : eth

Family name : ane

So IUPAC name : ethane

Common name : ethane

Naming of C₃H_8:

CH₃ --- CH₂ --- CH₃

Root name : prop

Family name : ane

So IUPAC name : propane

Common name : propane

Naming of C₄H_10:

CH₃ --- CH₂ ---CH₂-- CH₃

Root name : but

Family name : ane

So IUPAC name : butane

Common name : n-butane

Naming of

(Counting from either sides , mehyl branch get number 2 from either side)

Branch name: 2-methyl

Root name : prop

Family name : ane

So IUPAC name : 2-methyl propane

Common name : iso-butane

Naming of

(Counting from either sides , both mehyl branches get number 2 from either side)

Branch name: 2,2- dimethyl

Root name : prop

Family name : ane

So IUPAC name : 2,2- dimethyl propane

Common name : neo-pentane

other examples:

Branch name: 2,2,5,5 -tetra methyl

Root name : hept

Family name : ane

So IUPAC name : 2,2,5,5 -tetra methyl heptane

Question: Naming the following compound

Ans:

Branch name: 4 -ethyl,2-methyl

Root name : hex

Family name : ane

So IUPAC name : 4 -ethyl,2-methyl hexane

Question:

Ans:

Branch name: 3 -ethyl,2,4- dimethyl

Root name : hex

Family name : ane

So IUPAC name : 3 -ethyl,2,4- dimethyl hexane

Question:

Ans:

Branch name: 3 -methyl, 6 ( 1'-methyl ethyl )

Root name : oct

Family name : ane

So IUPAC name : 3 -methyl, 6 ( 1'-methyl ethyl ) octane

Question:

Ans:

Branch name: 5-ethyl,3-methyl

Root name : hept

Family name : ane

So IUPAC name : 5-ethyl,3-methyl heptane

Alkene :

Alkene is a unsaturated hydrocarbon whose general formula is C_nH_2n.

Molecule of alkene consist at least one double covalent bond.

First member of alkene family is ethene ( C₂H₄).

IUPAC name of fist member of alkene is ethene . its common name is ethylene.

Nomenclature of Alkene family:

IUPAC name of alkene may consist three part.

Branch name , root name and family name ( Suffix ene )

Branch name:

It is prefix of alkene name .

Branch is alkyl group or any substitution

Branch name is taken according to its position on root.

If there are more than two branch in alkene , then proper rule is followed in naming.

Root name :

It comes after branch name.

It depend on number of carbon atoms present in root of molecules.

Family name:

Family name of alkene is ene which comes after root name.

How to name Alkene compound:

Step -1 : Determine root of alkene.

Step -2: Count number of carbons present in root of molecules and then decide its root name.

Step -3 :

Give number the carbon atoms of root from that end so that double bond gets lowest possible number.

Name the compound in proper order: branch name, root name, family name

Example :

Naming of C₂H₄

Root name : eth

Family name : ene

So IUPAC name : ethene

Common name: ethylene

Naming of C₃H_6:

CH₃ ----- CH==CH₂

Root name : prop

Family name : ene

So IUPAC name : propene

Common name : propylene

Alkyne :

Alkyne is a unsaturated hydrocarbon whose general formula is C_nH_2n-2.

_.Molecule of alkyne consist at least one triple covalent bond.

First member of alkyne family is ethyne ( C₂H₂).

IUPAC name of fist member of alkyne is ethyne . its common name is Acetylene.

Nomenclature of Alkyne family:

IUPAC name of alkyne may consist three part.

Branch name , root name and family name ( Suffix ene )

Branch name:

It is prefix of alkyne name .

Branch is alkyl group or f group.

Branch name is taken according to its position on root.

If there are more than two branch in alkyne , then proper rule is followed in naming.

Root name :

It comes after branch name.

It depend on number of carbon atoms present in root of molecules.

Family name:

Family name of alkene is yne which comes after root name.

How to name Alkene compound:

Step -1 : Determine root of alkyne.

Step -2: Count number of carbons present in root of molecules and then decide its root name.

Step -3 :

Give number the carbon atoms of root from that end so that triple bond gets lowest possible number.

Name the compound in proper order: branch name, root name, family name

Example :

Naming of C₂H₂

Root name : eth

Family name : yne

So IUPAC name : ethyne

Common name: Acetylene

Naming of C₃H_6:

Root name : prop

Family name : yne

So IUPAC name : propyne

Common name : methyl acetelene

Wednesday, June 9, 2021