Question

Question: 3-Bromo-1-phenyl-1-propene shows a complex NMR spectrum in which the vinylic proton at C2 is coupled with both the C1 vinylic proton (J = 16 Hz) and the C3 methylene protons (J = 8 Hz). Draw a tree diagram for the C2 proton signal, and account for the fact that a five-line multiplet is observed .

Short answer

In NMR spectroscopy splitting is caused by the hydrogen atoms which lie on the same or on different carbon atoms.

The signals aresplitby the non-equivalent protons only.

Step-by-step solution

Step 1: The splitting  of signals in NMR

In NMR spectroscopy splitting is caused by the hydrogen atoms which lie on the same or on different carbon atoms.

The signals aresplitby the non-equivalent protons only.

Step 2: The occurrence of splitting  in 3-Bromo-1-phenyl-1-propene

When C2 is coupled with C1 then the signal is split into two lines having a J value of 16 Hz. When C2 couples with the C3 proton we get a triplet so we can say that the two lines are further split into three lines.

Hence, we get total of six lines

plitting of signals