- Unknown H Mass Spectrum 100t 90 91 80 70 60 Abundance 50 40 30 20 140 31 65 77 E 20 40 60 80 100 120 140 Ir Spectru 1 (20.19 KiB) Viewed 80 times
- Unknown H Mass Spectrum 100t 90 91 80 70 60 Abundance 50 40 30 20 140 31 65 77 E 20 40 60 80 100 120 140 Ir Spectru 2 (24.24 KiB) Viewed 80 times
- Unknown H Mass Spectrum 100t 90 91 80 70 60 Abundance 50 40 30 20 140 31 65 77 E 20 40 60 80 100 120 140 Ir Spectru 3 (24.24 KiB) Viewed 80 times
- Unknown H Mass Spectrum 100t 90 91 80 70 60 Abundance 50 40 30 20 140 31 65 77 E 20 40 60 80 100 120 140 Ir Spectru 4 (48.61 KiB) Viewed 80 times
- Unknown H Mass Spectrum 100t 90 91 80 70 60 Abundance 50 40 30 20 140 31 65 77 E 20 40 60 80 100 120 140 Ir Spectru 5 (34.35 KiB) Viewed 80 times
Unknown H Mass Spectrum 1007 904 91 80 70- 60- ABUNDANCE 50 40- 30 140 20- 51 10 65 77 40 20 60 80 100 120 140 1802 IR spectrum 1000 30 200
1. Examine the IR spectrum. Initially look for evidence of the easily detected functional groups such as OH, NH, C-H, =C-H, (C=0)H, C=0, and C-O stretching frequencies. 2. Examine the mass spectrum. Examine the mass spectrum for the [M]' peak, the [M+1]' peak and the [M+2]* peak as appropriate. Also, find the base peak. Is the molecular ion odd or even? Odd molecular weights imply odd numbers of nitrogen atoms. Even molecular weights imply the absence of nitrogen atoms or an even number of nitrogen atoms. Does the IR substantiate the presence or absence of nitrogen? Does the IR indicate the presence of one or more oxygen atoms? Check for evidence of isotopic cluster patterns (C1/Cl or 79Br/51Br). 3. Examine the 'Hand C NMR spectra a. Examine the integration for each distinct group of signals to determine the ratio of various types of protons in the molecule from the proton NMR. b. Examine the chemical shifts to each distinct group of resonances. Look for evidence of aromatic and alkene protons. If there is evidence for aromatic or alkene protons, does the IR data substantiate the find and does the IR and 1H NMR integration data indicate the type of alkene or aromatic substitution pattern? Looking at the mass spectrum for an m/z of 77 or 91 can also substantiate the presence of aromatic groups. Do the shifts substantiate the presence of electron withdrawing groups suspected by IR (e.g. CO2H, C-O-C, (C=OJH, etc.)? If not, do halogens seem likely to
be involved? Check the MS for evidence of isotopic cluster patterns (SC1/C or 198r/Br) or the loss of and presence of mass 19 (F) or 127 (1)ions. c. Examine the splitting pattern observed for each distinct group of H NMR resonances. Use coupling constants to ascertain which resonances are related. Use the relationships derived from the coupling constant data, along with the n + 1 rule, to assign alkyl groups and their connectivity. Again the caveat is that the structures must be consistent will ALL that data. 4. Continue your analysis along the lines suggested above using ALL the spectral data available to confirm the absence or presence of functional groups and substructures. Draw out partial structures based on your findings and then fit the pieces together like a jigsaw puzzle. Once likely structures have been proposed, select the one(s) which best fits all of the data. Careful review of all the data should allow all but the best candidates to be rejected on the basis of inconsistencies with the available data.