Question

Нь He Ha -CEC Hd a) Given that the 'H NMR spectrum was acquired at 300 MHz, convert the ppm values for the alkenyl region to Hz and provide the cis proton coupling constant to 1 decimal place. b) Please provide the chemical shift values for Он i) Both alkyne carbons ii) The aromatic carbon bearing the substituent ili)H vi) H v) He iv) H H NMR spectrum 7.50 745 740 7.35 6.0 58 S.6 n (ppm) S4 52 75 0.5 8.5 8.0 7.0 65 60 40 n pm) 35 30 25 20 15 1.0 0.0 1C NMR spectrum 100 80 90 (ppms 60 40 30 170 160 150 140 130 120 110 70 20 10 61- 019- t691

Answer 1

(a)

Here Hb, Hc and Hd are alkenyl H atoms. Here Hc and Hd are cis- H atoms therefore the chemical shift value for them will be:

Hc = 4.93 ppm

Hd = 5.81

Hb = 4.97 ppm

fxppm Hz 106 here f center frequency 300Hz

Plug the values to convert in Hz:

300x 10 Hz x 4.93 He in Hz 106 He in Hz 1479 Hz here f center frequency =300 MHz = 300 x 106 Hz

300 x 10 Hz x 5.81 Hs in Hz 106 Ha in Hz =1743 Hz

300 x 10 Hz x 4.97 Hb in Hz 106 Ho in Hz -1491 Hz

The range of cis-proton coupling constant is 6-14 Hz.

b)

(i) The chemical shift value for alkyne carbon in C-13 spectra is approx. 80 ppm

(ii) The aromatic C bearing the substituent will be in the range of close to 140-150 ppm.

(iii) Ha = 4.01 ppm, Hb = 4.97 ppm , Hc = 4.93 ppm, Hd = 5.81