Question

6. Two products, A and B, are formed from the following reaction. At high temperature, A is converted to B but no reverse reaction is observed. 130-160° ethene A + B Me3P H The spectral data for A and B are shown below. For product A, an IR peak at ~2000 cm?¹ is observed. Spectral Data for A Spectral Data for B ¹H NMR (?, ppm) ¹H NMR (?, ppm) -16.88 (d, J = 36 Hz, 1H) 1.86 (s, 15H) 1.86 (s, 15H) 1.01 (d, J = 9 Hz, 9H) 1.24 (d, J = 10 Hz, 9H) 1.13, 1.27 (m, 4H) 5.75, 6.95 (m, 2H) 8.12 (m, 1H) ¹³C NMR (?, ppm) ¹³C NMR (?, ppm) 10.27, 18.82, 92.50, 123.78, 129.18 10.29, 10.55, 16.93, 90.19 One IR peak at ~2000 cm?¹ No IR bands at ~1800 - 2000 cm?¹ (a) Based on the spectral data, predict the chemical structures of A and B, and assign the NMR and IR peaks. (10 marks) (b) Propose a plausible mechanism for the reaction. (4 marks) Page 4 of 12

          6. Two products, A and B, are formed from the following reaction. At high temperature,
A is converted to B but no reverse reaction is observed.
130-160°
ethene
A + B
Me3P
H
The spectral data for A and B are shown below. For product A, an IR peak at ~2000
cm?¹ is observed.
Spectral Data for A
Spectral Data for B
¹H NMR (?, ppm)
¹H NMR (?, ppm)
-16.88
(d, J = 36 Hz, 1H)
1.86
(s, 15H)
1.86
(s, 15H)
1.01
(d, J = 9 Hz, 9H)
1.24
(d, J = 10 Hz, 9H)
1.13, 1.27
(m, 4H)
5.75, 6.95
(m, 2H)
8.12
(m, 1H)
¹³C NMR (?, ppm)
¹³C NMR (?, ppm)
10.27, 18.82, 92.50, 123.78, 129.18
10.29, 10.55, 16.93, 90.19
One IR peak at ~2000 cm?¹
No IR bands at ~1800 - 2000 cm?¹
(a) Based on the spectral data, predict the chemical structures of A and B, and assign
the NMR and IR peaks.
(10 marks)
(b) Propose a plausible mechanism for the reaction.
(4 marks)
Page 4 of 12

6. Two products, A and B, are formed from the following reaction. At high temperature,
A is converted to B but no reverse reaction is observed.
130-160°
ethene
A + B
Me3P
H
The spectral data for A and B are shown below. For product A, an IR peak at 2000
cm?¹ is observed.
Spectral Data for A
Spectral Data for B
¹H NMR (?, ppm)
¹H NMR (?, ppm)
-16.88
(d, J = 36 Hz, 1H)
1.86
(s, 15H)
1.86
(s, 15H)
1.01
(d, J = 9 Hz, 9H)
1.24
(d, J = 10 Hz, 9H)
1.13, 1.27
(m, 4H)
5.75, 6.95
(m, 2H)
8.12
(m, 1H)
¹³C NMR (?, ppm)
¹³C NMR (?, ppm)
10.27, 18.82, 92.50, 123.78, 129.18
10.29, 10.55, 16.93, 90.19
One IR peak at 2000 cm?¹
No IR bands at 1800 - 2000 cm?¹
(a) Based on the spectral data, predict the chemical structures of A and B, and assign
the NMR and IR peaks.
(10 marks)
(b) Propose a plausible mechanism for the reaction.
(4 marks)
Page 4 of 12

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