Page | 1 NMR Lab B Spectroscopy II 1H NMR, 13C NMR and IR Spectroscopy Guidelines and Tips 5. 1H NMR peaks should be labeled using letters (a, b, c, etc.), starting with the peak that is the most downfield (highest ppm). 13C NMR peaks should be labeled using numbers (1, 2, 3, etc.), starting with the peak that is most downfield (highest ppm). 6. When labeling peaks, don’t mistake residual solvent peaks or the TMS peak for a signal (peak) from the sample. 1H NMR: singlet at 7.26 ppm due to residual CHCl3 from CDCl3 (solvent); singlet at 0 ppm due to TMS. 13C NMR: three peaks of equal intensity at 77.16 ppm due to CDCl3 (solvent); singlet at 0 ppm due to TMS 3. Chemical shifts (δ) should be reported as the center of the peak set. For peaks with odd multiplicities (triplet, quintet, etc.), the chemical shift is that of the middle peak. For peaks with even multiplicities (doublet, quartet, etc.), the chemical shift is reported as the average of the two central most peaks. 4. The peak labels in the expanded regions are in hertz (Hz) for assigning coupling constants. a. The coupling constant (J) for a given multiplet is equal to the distance, in Hz, between adjacent peaks. 5. Integral values are proportional to the number of hydrogens represented by a given peak. 6. Use the following abbreviations for peak multiplicities. For our purposes, a multiplet (m) is a peak that cannot be assigned a simple, first-order splitting pattern (i.e., not a singlet, doublet, triplet, etc.) singlet (s) quartet (q) septet (sept) doublet (d) quintet (quint) octet (oct) triplet (t) sextet (sext) nonet (non) multiplet (m) 7. A broad singlet results from a hydrogen attached to an electronegative atom (-OH, -NH2, etc.). 8. Hydrogens on electronegative atoms (-OH, -NH2, etc.) often show no coupling to neighboring hydrogens. 9. IR frequencies should be reported in reciprocal centimeters (cm-1). 10. Work your way through the following problems and record your answers in the answer pack. When solving the unknowns, remember to be systematic and use the data to assemble molecular fragments.Page | 2Page | 3Page | 4Page | 5Page | 6Page | 7 5. 13C NMR IRPage | 8 1H NMRPage | 9 6. 13C NMR IRPage | 10 1H NMRPage | 11 7. 13C NMR IRPage | 12 1H NMRPage | 13 8. 13C NMR IRPage | 14 1H NMRPage | 15 9. 13C NMR IRPage | 16 1H NMRPage | 17 10. Complete the spectroscopy data tables in the answer pack using the 13C NMR, IR and 1H NMR spectra shown below. The molecular formula for this compound is C5H9N. 13C NMR IRPage | 18 1H NMRPage | 19 11. Complete the spectroscopy data tables in the answer pack using the 13C NMR, IR and 1H NMR spectra shown below. The molecular formula for this compound is C5H11NO. 13C NMR IRPage | 20 1H NMRPage | 21 12. Complete the spectroscopy data tables in the answer pack using the 13C NMR, IR and 1H NMR spectra shown below. The molecular formula for this compound is C6H11ClO. 13C NMR IRPage | 22 1H NMRPage | 23Page | 24Page |