Post-Lab Questions Include copies of your IR spectrum, GC/MS chromatogram and ma
ID: 1087782 • Letter: P
Question
Post-Lab Questions Include copies of your IR spectrum, GC/MS chromatogram and mass spectrum, and 'H NMR spectra with your lab report. Make sure that you identify the label of your unknown in your report. (1) Propose a structure for your unknown that is consistent with the IR, GCMS, and 'H and 1sC NMR spectra. (Note: also the density, if requested by your instructor) (2) What are the major peaks in your IR spectrum. Assign these peaks to specific bond motions for functional groups that are present in your unknown. Note: only assign the major peaks in the 1500-4000 cm region. Absorptions in the 600 to 1200 cmm -1 region can be extremely helpful in determining how substituants are distributed on the arene ring. If you are interested in interpreting this region of your IR spectrum, consult your laboratory instructor. (3) What is the m/z value for the molecular ion for your unknown? What is the m/z value for the base peak in your unknown? Provide possible structures for ions that could be responsible for the major fragments (> 25% intensity) in your mass spectrum (4) Assign the peaks in your 'H NMR spectrum to the protons in your proposed structure. Explain how the chemical shifts, integrals and coupling in your spectrum are consistent with the proposed structure. (5) Assign the peaks in your 3C NMR spectrum to the carbons in your proposed structure. Explain how the chemical shifts in the spectrum are consistent with the proposed structure.Explanation / Answer
The proposed structure is based on mostly IR as the other images are not very clear.
2.
803 cm-1 could be assigned to aromatic or benzene type ring compounds. For 1017 and 1089 cm-1, it is because of carbon-oxygen bonding (C-O). At 1490 cm-1, it could be because of bonding between carbon and carbon double bond (C=C). For 2800-3000 cm-1, these peaks can be attributed to C-H bonding like alkane. Peaks appearing above 3500 cm-1 are because of O-H group. But these are not so prominent, maybe, because of water solvent, if used.