Question

Hints for identifying compounds in multiple-choice problems (problems 1:5); 1. Closely compare the given compounds. Determine which piece of information (molecular weight from MS, number of peaks in the NMR, presence of a special functional group in the IR, etc) would be the easiest for distinguishing between the given compounds. You might not need to use all types of given spectra to find your correct compound! 2. Based on your answer from step 1, consult the appropriate spectrum first. For example, if you determined that each of the given compounds have different molecular weights, look at the MS spectrum first. Use the MS to figure out the molecular weight of the compound, then find which compound matches that molecular weight. 3. Once you think you have identified the correct compound, check the other types of spectra to make sure your proposed compound matches the other given spectra. For example, if you used the molecular weight from the MS to select the "correct" compound, make sure that you see it's expected number of peaks in the NMR and it's expected functional groups in the IR, etc. Hints for solving unknowns (problem 6-7): 1. Start by figuring out the molecular weight of your compound (on the mass spectrum). 2. Determine if there are any halogens (using the mass spectrum). 3. Estimate the number of heavy atoms (C, N, or O) using the equation: # C, N, O (MW-X)/14, where MW = molecular weight of your compound and X = weight of any halogens present. 4. Use the IR to determine any special functional groups (O-H, C=O, C-O, N-H, etc). 5. Propose a molecular formula based on the information from steps 1-4. 6. Calculate the number of unsaturations (hydrogen deficiency index). 7. Scan the H NMR to see if you can identify any special functional groups (aromatic or vinylic hydrogen peaks, methyl group singlets, ethyl group triplet-quartets, etc). 8. Draw a few structures that include the functional groups and/or halogens seen in your spectra. Make sure the molecular weight matches that seen in your mass spectrum! 9. Make predictions for the peaks on your proposed structures. 10. Compare your predicted peaks with those on the actual spectra. If one of your proposed structures closely matches the given spectra, you may have the right answer! 11. If your proposed compound peaks do not match the given spectra, repeat steps 8-10.

Answer 1

HNMR Two signal belong to ethyl group ОН Group IGNOR arbitrary intensity 2 aliphatic carbons are present 30220 2000 2001 2002 203 ppm ims O-H stretching VC-H stretching Which compound below gives the spectra above? (1 pt) In 1H NMR, one quartet and one triplet presents which confirms the ethyl group. Further one more OH is presents. In 13C NMR, two aliphatic carbon are present. From IR, Only O-H and C-H stretching appaers. Molecular weight is 46 m/z Using the above all information we can deduce the structure. Hen ce Ethanol is correct compound for this all spectrum.