May 31, 2013
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Pre-Dental
So I have been trying to figure out this degree of unsaturation problem, and I keep ending up with 12 degrees of unsaturation. Can someone explain to me why it is 11? I included a picture but the question is:
How many degrees of unsaturation are present in the anxiolytic drug Valium (diazepam), molecular formula C16H13ClN2O?
 

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DatRav27

2+ Year Member
Jul 19, 2014
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Pre-Dental
This is how I approach this problem. The problem is asking you on the bond connectivity and if there are double or triple bond (unsaturation) present.

First use the saturated formula CnH(2n+2) which will get you to C16H34

Now lets deal with the Cl. How does it play a role in this molecule? It connects with a carbon and TAKES the place of a H. So the saturated molecule should have 1 less Hydrogen from what we predicted.

Now we have C16H33

Now the two nitrogens. Lets assume they are amines for the saturated solution. They connect with the carbon and TAKE the place of a hydrogen BUT add on TWO hydrogens (NH2). Net gain of 1 hydrogen per N. So the saturated molecules would have 2 more H of the current formula we predicted.

Now we have C16H35.

All you have to do now is subtract the H difference divided by two.

35-13=22/2= 11 degrees of unsaturation!!
 
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discensdentibus

5+ Year Member
Mar 8, 2013
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A faster alternative: C-1/2(X-N) + 1
C=carbons
X= H and Halos
N= nitrogens
O have no effect

16-1/2(14-2) +1
16-6+1 =11
 
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