Question

5. (10 points) Analysis of 'H NMR spectrum. Below is the 'H NMR spectrum of the product from this week's experiment. 3H, t, J = 7.1 Hz 1H, d, J= 15.8 Hz 2H, q, J = 7.1 Hz 5H, m 1H, d, J= 15.8 Hz. TT 2 1 10 9 8 7 6 5 4 3 1 ppm Summary of peaks (ppm): 1.32 (3H, t, J = 7.1 Hz), 4.24 (2H, q, J= 7.1 Hz), 6.43 (1H, d J = 15.8 Hz), 7.24-7.57 (5H, m), 7.67 (1H, d, J=15.8 Hz). 1) Draw the structure of the product on the spectrum and label the hydrogens Ha, Hb, etc. Assign the hydrogens to the signals. 2) Explain the difference in the chemical shifts of the vinyl hydrogens? 3) Is this product trans or cis? Why?

Please fully answer all parts of the question.

Answer 1

DECEMBER TUESDAY He Ha s 1.32ppm, & , 34,Jofil the H S 424 ppm, 9, 24.,J= He- He s 6.43 ppm, d, 1H,J=15.8t2 HJ S 7.67 ppom, d, 1H, 3=15.8 Hz He s 7:24-7057ppm, m, 54 by 4 comes in higher chemical shift though He is adjacent to carbonyl Carbon. This is because en or fod the positive charge generated on that carbon by resonance. So it is more deshielded and appears at higher chemical shift. O The procduct es trans, because the coupling constant is high (5=15.8 42). For eis isomer, it is around a Hz. The only difference between a caprice and a lifelong passion is that the caprice lasts a little longer -Oscar Wilde.