[earthnation112]

Just had a question regarding degree of unsaturation, after having watched tutorials online regarding on how to figure out a compound using Infrared spectra, NMR 1H and 13C, they generally always tell you to calculate the degree of unsaturation to find out how many pi electrons there are present in the compound.

First question is does the method actually always generally work? I have tried it on quite a few compounds and it doesn’t even come close, what am I doing wrong?

The formula I use is:

DoU= (2C+2+N −X−H) / 2

Where:
C is the number of carbons
N is the number of nitrogen's
X is the number of halogens (F, Cl, Br, I)
H is the number of hydrogens 

A example is the compound I have attached below.

Using the formula above the degree of unsaturation would equal:

DoU= (2C+2+N −X−H) / 2
DoU= (2x4+2+1 −0−11) / 2
DoU= 0

But clearly this is wrong as I have an benzene which equals one ring. So the answer should be 1 and not 0 right? Where am I going wrong? Any input would be greatly appreciated . Thank You

       

[Burner]

First of all, this compound is definitely not C₄H₁₁NO₂. There are 6 carbon atoms in a benzene ring. You need to count the atoms again to come up with the correct molecular formula.

Secondly,

But clearly this is wrong as I have an benzene which equals one ring. So the answer should be 1 and not 0 right?

A benzene ring has a ring and 3 double bonds, so the answer should be least 4, not 1 or 0.

[earthnation112]

Thank you for the reply, I was reading all this from my professors note so I'm guessing he made a mistake I should have drawn the molecule myself including the bonds. Thanks for the input.

So does the degree of unsaturation work generally always with any compound?

Thanks for that I was confused thinking a benzene is only 1 as it contains a ring and missed out the 3 double bonds, making the number 4.