Alkane Structural Isomers Formula

Hello friends,

So you all are here by reading the title of this blog.You all wanna know that formula for finding structural isomers of Alkanes.But before, I would like to tell you some important things related to this formula.So let's start by basic introduction.

You all here for formula of structural isomers of Alkanes then you should aware with Alkanes, structural isomers and with many more other terms which are related with the topic.So for your sake of convenience (and to increase the length of blog 😂), I just wanna to give you quick recall of all these terms.I won't make it complicated.If you want, then you can directly see the formula but remember before the formula must see the important points related with the formula.

Quick recall

1. Alkanes :) These are Organic compounds which only have single bond between their carbon atoms.Alkanes are also called saturated compounds.Examples are methane, ethane etc.
2. Isomers :) Firstly, isomers are of two types.

(i) Structural Isomers

(ii) Stereo Isomers

In this blog, we'll only talk 'bout structural Isomers.

>> Structural Isomers :) We can simply say that isomers are different forms of same compound. By proper definition, Compounds having same molecular formula but different structures are called structural isomers.Here, different structure means that atoms are arranged in different form.For example, butane has 2 structural Isomers.(Image of the Isomers are possible below.)

 Structural Isomer

Structural Isomer

>>Note : Isomers of compounds are only possible with compunds which have atleast 4 carbon atoms.             

Important points

So, before you know formula, I wanna put conditions in your mind that are related with this formula.These formulas are 

• only valid for Alkanes
• only upto Octane (alkane with 8 carbon atoms).
• After Octane, this formula doesn't work.

>> So while using the formula always keep things in the mind.

Formula

Friends, try to understand the given formula clearly.If you are facing the problem in understanding in what is written in the formula then you can see it from the image provided above each formula.

Now we talk 'bout the formula:)

Formula upto heptane

• Formula (upto heptane) :) [{2^(n-4)}+1]
• n= number of carbon atoms

The above written formula is valid only upto heptane (compund with 7 carbon atoms which contain only single bond between them).This means you can get the structural isomers of alkane only upto heptane by using this formula.

Formula for octane

• Formula (for Octane) :) [{2^(n-4)}+1]+1
• n= number of carbon atoms

The above written formula is valid only for Octane (compund with 8 carbon atoms which contain only single bond between them).This means you can only get the structural isomers of octane by using the formula.

Formula for nonane

• Formula (for Nonane) :) [{2^(n-4)}+1]+2
• n= number of carbon atoms

The above written formula is valid only for Nonane (compund with 9 carbon atoms which contain only single bond between them).This means you can only get the structural isomers of Nonane by using the formula.

• You've to remember that Decane (compund with 10 carbon atoms which contain only single bond between them) has total 75 structural isomers.

Now after getting the formula upto Heptane, for Octane and for Nonane.You have to remember the formula of Decane.

Note >> There are total 3 separate formulas are given above :--

1. First for finding the total possible structural isomers for alkanes upto Heptane.This formula works upto Heptane.
2. Second for finding total possible structural isomers for Octane.This formula works only for Octane.
3. Thrid for finding total possible structural isomers for Nonane.This formula works only for Nonane.
4. At last, after getting total possible structural isomers upto Decane.You must remember that total structural isomers possible for Decane is 75.

>>Now, I will show you how you can find the structural isomers of Alkanes (upto Decanes by using this formula).

Examples

1. Find the possible structural isomers for butane.

SOLUTION:) Total number of carbon in butane= 4

Since,

Number of isomers = [{2^(n-4)}]+1

                                       [{2^(4-4)}]+1     __(n=4)

                                       [{2^0}]+1.       __(2^0=1)

                                       1+1

                                       2

Thus, total possible structural isomers for butane are 2.

2. Find the possible structural isomers for nonane.

SOLUTION:) Total number of carbon in butane= 9

Formula for nonane = [{2^(n-4)}+1]+2

Since, 

Number of isomers =[{2^(n-4)}+1]+2

                                       [{2^(9-4)}+1]+2   _(n=9)

                                       [{2^5}+1]+2     _(2^0=1)

                                       [32+1]+2

                                       35

Thus, total possible structural isomers for butane are 35.

>>You can clearly see from above examples that the given formula is working accurately.You can check yourselves by solving problems using the formula.

>>That is all for this blog.If you find something interesting nd useful.Then keep coming back for such contents.

Thank you 😊🙏.