For the following alkene molecules, predict the number of peaks in the alkene region of the ¹H NMR, their splitting and the general range of coupling constants for each.

Question

| Organic Chemistry 2

Accepted Answer

The protons of phenyl groups are not in the alkene region but in the aromatic region.

2 different alkene H ⇒ 2 signals
H see only 1 proton (H): doublet
H see only 1 proton (H): doublet
H and H are trans: J (Hz) = 11-18 (Typical: 16Hz)

⇒ 2 doublets with a J ~ 16 Hz

2 alkene H but same environment ⇒ 1 signal
H and H are equivalent and do not see any other proton: singlet

⇒ 1 singlet

2 different alkene H ⇒ 2 signals
H see only 1 proton (H): doublet
H see 3 protons (H and 2 H): triplet of doublet
H and H are cis: J (Hz) = 6-14 (Typical: 10Hz)

⇒ 1 doublet with a J ~ 10 Hz (for H) + 1 triplet of doublet J ~ 10 Hz and 6 Hz (for H)

Exercise 4 | Alkenes

Organic Chemistry 2 - Exercise 4