Using the ppm chemical shifts at the top of the spectrum, please label the peaks
ID: 587546 • Letter: U
Question
Using the ppm chemical shifts at the top of the spectrum, please label the peaks on this NMR spectrum from lowest to highest ppm
And which is the peak that corresponds to the solvent, CDCl3
STANDARD 1H OBSERVE Automation directory: /vnmr /asm/autodir File: 1305 Pulse Sequence: s2pul user: zzzusr Sample: 13 Nov. 8, 2017 Date: Solvent: CDC13 File: Starting Time: 01:46:32 Completion Time: 02:02:43 Total acq. time 1 minute 1304 UNITYplus-300 vi300 Ambient temperature PULSE SEQUENCE Relax. delay 1.500 sec Pulse 45.0 degrees Acq. time 2.000 sec Vidth 6003.3 Hz 16 repetitions DATA PROCESSIN300.1583398 MHZ Line broadening 0.1 Hz FT size 65536 Ch3 10 8 3 ppa 5.28 4.36 16-77 15.91 10.57 4.90 0.78 0-43 1.81Explanation / Answer
The peak for CDCl3 will arrive as a singlet around 7.26ppm for all samples in proton NMR and a triplet around 77.2ppm in Carbon-13 NMR. In the spectra given, apart from the sample peaks, there are certain minor peaks that may have risen due to the presence of impurities. Moreover, the seemingly major peak at 1.554ppm is that of water, absorbed by the solvent used for NMR sampling from the moisture in air.
For the given compound, the most shielded protons at 2.411ppm will arrive for the 3 methyl protons in the methoxy group due to the ring-current working with the ether linkage's oxygen, thus leaving the group in the vicinity of a large electron-density. The next most shielded peak will be the methyl attached to the beta-phenyl ring and that will arrive only at 4.02ppm. Then, due to the electronegativity of hydroxyl oxygen, its proton gives the signal at 6.4ppm as a singlet. The slight shielding here arrives due to the effect of the ring-current.
The peak at 7.533ppm arrives for the considerable deshielded proton lying in the ortho-position to the highly electron-withdrawing carbonyl group. Moreover, though another proton is also ortho to this group, being in the vicinty of electron-donating methoxy group also, that proton arrives as the singlet at 7.406ppm.
.Next, the doublet at 7.266ppm and 7.232ppm is due to the two similar protons in the beta phenyl ring, ortho to the methyl group, which is also the reason for their shielding. The next doublet at 7.506ppm and 7.512ppm arrives due to the protons in meta position to the methyl group, deshielded due to their vicinity to the alpha-phenyl ring.
Finally, due to the high deshielding effect of the carbonyl group, the proton in the aldehyde arrives as the most deshielded, around 10ppm.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.