Please explain why the answer is either cis or trans isomer, and how does one pr

Question

Please explain why the answer is either cis or trans isomer, and how does one proton signal shift to the left. I can't understand how it happens with a nearly symmetrical molecule. Thank you in advance.

Problem 6 (1 pt Use the iH NMR and 13CNMR spectra to determine the structure of a compound whose chemical formula is C2H2CB and assign the peaks in each spectrum. Note: In both iHNMR and 13CNMR spectra, ignore the TMS peak at 0 ppm. 1H NMR: doublet at 5.74 ppm (1) and a doublet at 4.44 ppm (1).The for relative integrations each peak are included in a parentheses. 40 120 1000

Explanation / Answer

1) you will not get two different peaks in the C13 NMR (as both the carbons are similar), we will get only one peak near 120.

2) in H-NMR we will obtain two peaks (one for cis alkene and other for trans alkene). If we are taking mixture of two stereo-alkenes.

Now the two peaks will be singlet (no splitting as both the hydrogens are chemically equivalent)

The two peaks will be distinguished by C13 satellites of each peak

A) in Cis alkene the JH-H coupling [ 6.4peak] will be 6Hz

B) in trans alkene the JH-H coupling [ 6,3peak] will be 12Hz

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