Question

Can you please explain, in detail, how to draw a 1H NMR and 13C NMR spectrum from a bond-line structure. Molecular formula is C7H10BrClS, please convert to bond-line structure for corresponding spectrums.

Answer 1

Begin with a general examination of the spectrum:

a) determine how many signals (clusters) there are in the 1H spectrum and note their chemical shifts, and count the signals in the 13C spectrum.

b) determine how many 1H nuclei are present in each cluster (look at the integration)

c) determine the multiplicity of each signal cluster (count the peaks or read the label attached to the peak)

d) determine what additional information is available (often the molecular formula is given; that gives you a chance to subtract groups you’ve identified and to check what is left to identify)

e) compare the number of 1H signals with those in the 13C spectrum; this may tell you whether all carbon atoms bear 1H nuclei or whether there are carbons without 1H nuclei attached. II Now proceed to the interpretation of the spectrum

f) for each peak match the number of 1H nuclei and its multiplicity with a corresponding peak and combine them to groups (coupling is mutual)

g) record each group you recognize

h) when you have assigned all 1H groups that you recognize, add their formulas up and compare with the molecular formula; the difference will be a group or groups that you haven’t identified as yet or cannot see in the 1H spectrum; step

e) above will give you similar information. i) enter the “difference” and combine all fragments. III Check your work: make sure that you have accounted for all signals and for every atom of the molecular structure and that your combined structure satisfies all chemical shifts.

There can be many structure containg the formula so one need to understant the exact compound.

Without the data given one cann't predict it correctly.