Ok so after analyzing the 13C spectra the instructor said he found 3 c=c bonds a

Question

Ok so after analyzing the 13C spectra the instructor said he found 3 c=c bonds and 2 c=o bonds. The formula had a total of 6 degrees of unsaturation and 6-5=1 indicating one aromatic ring.

the second 13C showed 4 c=c bonds and 2 c=o bonds for a total of 6. The formula had 8 deg. of unsat. so 8-6=2 indicating 2 aromatic rings... My question is how does he determine how many c=c and c=o bonds there are by looking at the 13C spectra? Is there a certain range that indicates the prescence of a c=c? c=o? If so, what are those ranges? Please help!

7.36 6.79 369 6.88 Jw12. 3 94 7.63 2.18 2Hif 8.0 4,62 1H, dd H,brd s Je12,7 i i i u u PPM und DEPT NMR: As much as possible match the peaks to carbons in your structure. p spectrum DEPT-135 c NMR -CH, and CH appear (up) and CH2 appears (do 200 190 170 160 150 140 130 120 110 100 90 80 70 60 50 ddle spectrum-DEPT-90 15c NMR only C-H appears (up) 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 tom spectrum proton decoupled 15c NMR spec shows all types of carbon trum solvent 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 users PhilDocumentsPhis documents Mclassesto book problems spectroscopy Chap 8

Explanation / Answer

Saturated alkane carbons have among the lowest chemical shifts (0–50 ppm); carbons of alcohols, alkyl halides, and amines have chemical shifts that are somewhat farther downfield (10–90 ppm), followed by the carbon atoms of alkenes and aromatics (100–170 ppm) and carbonyl carbons (150–220 ppm). Therefore, by checking range we can indicates the presence of a c=c and c=o groups.

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