Degree of Unsaturation: C9H6N4 | Structural Isomerism

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In summary, the degree of unsaturation in a compound with the molecular formula C9H6N4 is 9. This is because rings are also counted as a degree of unsaturation in addition to pi electrons. The formula for calculating degree of unsaturation is based on the molecular formula alone and does not require structural information.
  • #1
phoenixXL
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Question
Find out the degree of unsaturation in a compound having the molecular formulae C9H6N4.

Attempt
The point lies in making the possible structure(s).
The structure that I felt possible is as follows
Struct.png

In the compound above there are 8-π electrons,
Hence the degree of unsaturation is 8(Ans)

Problem

The problem comes from the topic of structural isomerism and the book says the answer to be 9

Please help me out. Thanks for your time.
 
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  • #2
Hint: you are aware of the fact degree of unsaturation for cyclohexane - despite the compound being saturated - is 1?

In other words, degree of unsaturation is not only about pi electrons. There are formulas to calculate degree of unsaturation based on the molecular formula alone (without any structural information).
 
  • #3
Okay, I didn't knew about that.
I looked Wikipedia and found that rings are counted as a degree of unsaturation, therefore I get the missing "1" from my answer. Also I was unaware of the formula(curious to see its derivation).
Thank You.
 
  • #4
phoenixXL said:
Also I was unaware of the formula(curious to see its derivation).

There is no derivation - it is more like a definition.
 
  • #5
phoenixXL said:
Okay, I didn't knew about that.
I looked Wikipedia and found that rings are counted as a degree of unsaturation, therefore I get the missing "1" from my answer. Also I was unaware of the formula(curious to see its derivation).
Thank You.

##DU = 1 + \frac{1}{2}∑[n_i (v_i - 2)]## where ni is the number of atoms of an element and vi is the valency of that element. Note that this gives you the total number of rings and π bonds.
 

What is the degree of unsaturation for C9H6N4?

The degree of unsaturation for C9H6N4 is 4. This means that there are 4 pi bonds or rings present in the molecule.

How do you determine the degree of unsaturation for a molecule?

The degree of unsaturation can be calculated using the formula (2n+2)-x, where n is the number of carbon atoms and x is the number of hydrogen atoms. This formula assumes that the molecule is fully saturated with hydrogen atoms.

What is structural isomerism?

Structural isomerism is a type of isomerism where two or more compounds have the same chemical formula but different structural arrangements. This means that they have the same number and types of atoms, but the atoms are connected in different ways.

How many structural isomers are possible for C9H6N4?

There are a total of 5 structural isomers possible for C9H6N4. These include 3 positional isomers and 2 chain isomers.

What are the differences between positional and chain isomers?

Positional isomers have the same carbon skeleton, but differ in the position of functional groups or double bonds. Chain isomers, on the other hand, have different carbon skeletons. They have the same number of atoms, but the atoms are arranged in different chains.

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