EVERYTHING YOU NEED TO KNOW ABOUT ALKANE FOR GRADE 11 Part:1

ALKANES

Alkanes are the aliphatic/ open carbon chain organic compounds which has a single covalent  bond between two carbon. The general formula for alkanes is CnH2n+2,where n is a natural number.

Alkanes are commonly known as paraffins due to its little affinity for chemical reactions.

 

IUPAC Nomenclature

No. of carbon atoms    present in parent chain	Word root	No. of carbon atoms    present in parent chain	Word root
1	Meth-	7	Hept-
2	Eth-	8	Oct-
3	Prop-	9	Non-
4	But-	10	Dec-
5	Pent-	11	Undec-
6	Hex-	12	Dodec-

                                                                                                                                                               

 NAMING OF ALKANES FOR THIS SHEET:

• IDENTIFICATION OF No. of carbon in long/ parent chain.            
• IDENTIFICATION OF PREFIX
• COUNTING THE BRANCHING/ NUMBERING

Now we name some primary alkanes.

IDENTIFICATION OF PARENT CHAIN

The chain of carbon with maximum number of carbon is considered the parent chain.

Count the total number of carbon in long chain. According to the table above, we write the word root.

For eg: If the total carbon in long chain is 5, we write Pent-. Since the carbon is bonded by a single chain, we write suffix -ane.

  Similarly, you can try naming the following primary alkanes.

ANSWER:

 Naming of secondary and tertiary alkanes:            

Like in primary alkanes, we count no. of carbon in long chain. In secondary and tertiary alkanes, we find branches of carbon chain. We count the no. of carbon chains in every possibilities and choose the carbon chain with maximum no. of carbon chain.

For eg: 

Also, no. of branching also effects the choosing of parent carbon chain. If two possibilities of same no. of carbon arises, we choose the parent chain having maximum no. of branching.

For eg:

IDENTIFICATION OF PREFIX

 Now, let's name some compounds.

THE PARENT CHAIN CONSISTS OF THE LONGEST CARBON CHAIN IN GIVEN STRUCTURAL  FORMULA. THE LONGEST CHAIN HERE IS THREE.   

      

In naming of alkanes with more than one branching, we write the prefix in alphabetical order.

Foe eg: The above given organic compound has two branching. One on 2nd carbon of methyl and the other on 3rd carbon of ethyl. E of ethyl comes first than M of methyl in alphabetical order.

So, we write it as 3-ethyl 2-methyl Hexane instead of 2-methyl 3-ethyl Hexane.

NUMBERING:

Numbering orders:

In the picture above, the counting of carbon such that the branching comes early/ has high position is preferred. 

Some examples of naming of alkane are given: