Interpretation of a 13C magnetic resonance spectrum - Journal of

interpretative q

edited by Frank DeHaan Occidental Collage LOS Angeles. California 90041

experiments

Interpretation of a 13C Magnetic Resonance Spectrum H a r r y C. D o r n David G. I. K i n g s t o n a n d B r u c e R. S i m p e r s Virginia Polytechnic Institute and S t a t e University Blacksburg, Virginia 24061 T h e determination of t h e structures of organic compounds has been greatly assisted during t h e last few y e a t s b y t h e introduction of '3C magnetic resonance (crnr) spectroscopy a s a routine tool.1.2 Because of t h e increasing importance of this technique, i t would be helpful if some discussion of i t could he included in advanced undergraduate courses. T h e analysis and interpretation of t h e cmr spectrum of his(2-ethylhexyl) phthalate (I) provides a n instructive and yet simple example of t h e utility of this technique. L"

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~iaurs 1. 100 mHz proton magnetic resonance spectrum of bis(24hylhexyl) " phthalate

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The Experiment

I. Reading Assignment

47.616~(19751

11. The Spectra The spectra provided are 1) A 100 mHz proton magnetic resonance spectrum of unknown I (Fig. 1).

2) A proton decoupled cmr spectrum of unknown I (Fig. 2). 3) A coherent off-resonance proton decoupled cmr spectrum of unknown I (Fig. 3). Nure that the triple! at 77 ppm i n Figure%2 and :I is due to CDCll solvent. The peak at 67 ppm in F~gure:I is also n triplet. although rhis is only seen clearly under shghtly different experimental wnditions.

111. The Assignment Use the spectra provided to deduce a structure for unknown I and to assign the carhon resonances as far as possible to their correct cnrhons. The correlation charts in the assiened readine.. will ~rovide . ~ni!~nl asitrtance in rhis; f u r t h ~refinem~nc r