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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: pecan66 on February 02, 2014, 01:31:03 PM

Title: Working out structures using spectroscopic data
Post by: pecan66 on February 02, 2014, 01:31:03 PM
Cyanogen reacts with morpholine to form a single product A.

N#CC#N + N1CCOCC1  :rarrow: A

The spectroscopic data for A are shown below:

Carbon-13 data/ppm : 45.6, 66.2, 110.6, 142.1

IR data over 1500cm-1/cm-1 : 3290, 2234, 1620

Now I'm asking for help on this as I sometimes have trouble working out structures from the data in general. My attempt for this one is that I think the IR at 3290 must be either a N-H bond and so it should remain in the product. 2234 falls within the triple bond region so my guess is C#N but then I get stuck for 1620, this could either be a C=N bond or a C=O bond, my guess is that it's a C=N bond as carbonyls are usually around 1715. The problem is that I have no idea about how the reaction proceeds, I have worked out the HOMO and LUMO for both reagents but I don't know which way around they react.

Help would be much appreciated!

Thanks
Title: Re: Working out structures using spectroscopic data
Post by: AlphaScent on February 04, 2014, 03:44:55 PM
Any other conditions?  An acid? Water?
Title: Re: Working out structures using spectroscopic data
Post by: zsinger on February 04, 2014, 04:23:36 PM
Well….lets go step by step.  How would you expect the nitrogen (extra electron pair) or the oxygen (2 extra electron pairs) to react with one of the carbons (arbitrary b/c this is a symmetrical molecule).  Would the ring break?  Hope this helps.
                 -Zack
Title: Re: Working out structures using spectroscopic data
Post by: PhDoc on February 08, 2014, 04:43:27 PM
HOMO/LUMO not needed for this. What's your nucleophile? What's your electrophile? What's the likelihood a C-C bond will break to spit out a leaving group? What's the most logical intermediate you can obtain? What happens with the proton in the end?

What's your product?

If you have 6 carbons in your compound and 4 signals in your 13C, what (very fundamental) can you conclude? What functional group absorbs IR at 2234? Do all C=N bonds absorb at 1715? What happens to an IR absorption of a C=X when it's in conjugation with another group?

Please think about all this. You'll need it for any spectroscopy exam.