4. IR analysis of unknowns. Identify major peaks from both spectra including any
ID: 513987 • Letter: 4
Question
4. IR analysis of unknowns. Identify major peaks from both spectra including any peaks that may support the functional group identity. (10 pts. each) 5. NMR spectra with complete interpretation of peaks for both unknowns. Discuss integration of peaks, chemical shifts and splitting. (15 pts. each (there are 4 spectra total: two 1H NMR and two 15C NMR.)) 6. Mass spec interpretation including molecular weight and important fragments. Detail how these fragments confirm your structure. DRAw out the fragments that correspond to the peaks. (15 pts. each) 7. A drawn structure for each unknown. You have been given the molar mass of your unknowns and the info that all alkyl halides are the bromine version. All unknowns contain only one functional group (so none contain both an and an alcohol). Draw a structure for your unknown that conforms to all available data. (10 pts. each)Explanation / Answer
4. alcohol
IR
3350 cm-1 for O-H stretch
2850-2950 cm-1 for sp3 -C-H stretch
1470 cm-1 for C-O stretch
5. NMR
1H NMR
0.9 ppm (triplet, 3H) for CH3 next to CH2
1.5 ppm (multiplet, 4H) for CH2's in between
3.5 ppm (triplet, 2H) for CH2 next to -OH
3.7 ppm (singlet, 1H) for -OH proton
13C
14 ppm for CH3 carbon
18 ppm for CH2 carbon next to CH3
34 ppm for CH2 carbon between two CH2's
34 ppm for CH2 next to -OH
6. Mass
M+ 74
loss of OH give m/z 57
loss of CH2 gives m/z 43
7. structure
CH3-CH2-CH2-CH2-OH
4. Alkane
IR
2850-2950 cm-1 for C-H stretch
5. NMR
1H NMR
0.8 ppm for CH3's next to CH2
1.3 ppm (10H) for CH2's
13C NMR
14 ppm for CH3 carbon
22.7 ppm for CH2's next to CH3
29 ppm for CH2's between two CH2
31.8 for CH2 in the center
6. Mass
M+ 100
loss of CH3CH2 gives m/z 71
loss of CH2 gives m/z 57
7. Structure
CH3-CH2-CH2-CH2-CH2-CH2-CH3
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