4. How could you use proton NMR to distinguish between cach of the following pai

Question

4. How could you use proton NMR to distinguish between cach of the following pairs of constitutional isomers specific about the peaks, peak splitting, and/or peak location differences in the HNMR spectra. A. Ethyl acetate and butanoic acid B. Dimethyl ether and ethanol C. 1,4-diethylbenzene and 1.2-diethylbenzene 5. The three "CNMR spectra below all belong to molecules with formula C&H12.; In each spectrum, the signal at about 77 ppm is from the solvent used to prep the sample and should be ignored. Propose a structure for the hexane isomer responsible for each spectrum.

Explanation / Answer

4. 1H NMr as a tool for identification of constitutional isomers

A. Ethylacetate and butanoic acid

Ethylacetate would have a singlet at around 2.2 ppm for the CH3 next to C=O and a quartet at 3.7 ppm for the CH2 between CH3 and oxygen. A total of 3 peaks only.

Butanoic acid would have a typical peak at around 11 ppm for the -COOH proton, characteristic of carboxylic acids. A sextet for CH2 between CH3 and CH2 at around 1.4 ppm. A total of 4 peaks.

B. Dimethylether and ethanol

Dimethylether would show only 1 peak in the spectrum.

Ethanol would show three peaks in ratio 3: 2 : 1, of which 1 proton signal is exchnageble with D2O.

C. 1,4-diethylbenzene and 1,2-diethylbenzene

1,4-diethylbenzene is a symmetrical structure that would show a total of 3 peaks in the spectrum. Two doublets in aromatic region of equal intensity.

1,2-diethylbenzene on the other hand would show total of 4 peaks in the spectrum. A doublet and a triplet in aromatic region.

Related Questions

Navigate

• Browse (All)
• Browse 4
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.