4. \'H NMR spectrum of the ketone (2-methyl-4-heptanone) is provided in your man

Question

4. 'H NMR spectrum of the ketone (2-methyl-4-heptanone) is provided in your manual (figure 12). There is a duplicate HNMR available on Blackboard. 12 pts a. Complete the Table below 5pts b. Use the space provided to explain briefly how or why you assigned a proton to a specific group of peaks using concepts like molecular structure (near C-O), peak integration, and splitting. How do you account for the peaks at 0.870 ppm? Do not use the space to state that your assignments agree with the spectrum, instead provide reasoning. 5pts Proton Chemical Shift Integration Splitting* Record to 0.01ppm) (s, d, t, q, m) H1 H2 H3 H4 H5 H6 report splitting over 4 peaks as “m" or multiplet c. Show the calculation of the J value of proton 4 (assume 300Hz/ppm conversion) 2 pts.

Explanation / Answer

H1: 0.870 ppm, 6 protons, doublet.

H2: 2.095 ppm, 1 proton, multiplet.

H3: 2.222-2.245 ppm, 2 protons, doublet.

H4: 2.296-2.345 ppm, 2 protons, triplet.

H5: 1.517—1.590 ppm, 2 protons, multiplet.

H6: 0.870 ppm, 3 protons, triplet.

C) H4 appear as a triplet. So take any two neighboring peaks into consideration. Substracts the lower valuevfrom upper value. Let's take peaks from right, so the difference is 2.321-2.296 = 0.025. Now since the nmr is 300 mHz, multiply this value with 300 . So 0.025 x 300 = 7.5 Hz.

So the coupling constant is 7.5 Hz.

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