Question

TLC and Spectroscopy5 CNMR spectra of analgesic components, 5pts Carbon 13 NMR (sCNMR) is a spectroscopic tool that can help identify a molecule's linuobuars CNMR spectra are simple and fairly casy to interpret. Each unique carbon ina molecuie as a peak in the CNMR spectrum. Equivalent carbons will have identical signals. 1 of a carbon peak in the spectrum is influenced by functional groups that carbon. Determine the number of unique carbons present in each 6 of the lab then match the two of the compounds to the CNMR spectra shown. contain or are near the analgesic compound in Figure CNanl Each analgesic standard used in this lab has a different number of unique carbons. On each analgesic compound below label t Then, based on the number of lines in the CNMR, assign the appropriate compound Appendix page A-15 for examples of identifying unique carbons. the unique carbons with letters. to the spectra below. Hint: See the HN NW Ibuprofen Salicylamide Caffeine Acetaminophen Aspirin Match the analgesic compound to the CNMR spectra below. oo 12 100 0 180160 140 120 100 ฮ0 00 4029 Compound Compound

Answer 1

First spectrum is for Acetaminophen and second spectrum is for caffeine.

the remaining spectra are given below.

ibuprofen 40 20 PPM

aspirin PPM

salicylamide PPM

Carbon NMR

The chemical shift value is determined by the chemical environment of the carbon. If it is completely shielded the chemical shift value will shift towards zero. Shielded means high electron density around the carbons. So carbons attached to more electronegative atoms will be deshielded and give signals at high ppm. Carbons attached to less electronegative atoms will be deshielded and give signals at low ppm.

Basic delta values for 13C NMR

-CH₃, -CH₂, -CH and tertiary carbon       0-50 ppm

-O-C-     60 ppm

-CN        115 ppm

Aromatic carbons     120-150 ppm

Esters, amides, anhydrides and acid halides       155-180 ppm

Aldehydes & ketones          200-220 ppm