Chapter 15, Problem 78IP

Interpretation Introduction

Interpretation: The structure of a given molecular formula ${\text{C}}_{\text{12}}{\text{H}}_{\text{8}}{\text{Br}}_{\text{2}}$ to be predicted using spectrum details.

Concept Introduction:

${}^{\text{1}}\text{H}\text{NMR}$: The ${}^{\text{1}}\text{H}\text{NMR}$ spectrum gives information on the different electronic environment of protons. The number of signal (proton types) generated in ${}^{\text{1}}\text{H}\text{NMR}$ are predicted by performing symmetry operations (rotation or reflection symmetry).

The ${}^{\text{13}}\text{C}\text{NMR}$ spectrum gives information on the different electronic environments of carbon. As like ${}^{\text{1}}\text{H}\text{NMR}$, the number of signals generated in ${}^{\text{13}}\text{C}\text{NMR}$ are predicted by performing symmetry operations (rotation or reflection symmetry). Only chemical shift values are reported in the spectrum but not the multiplicity and integration values because the coupling between two neighboring ${}^{\text{13}}\text{C}{-}^{\text{13}}\text{C}$ nuclei are weakly involved due to the low abundance of ${}^{\text{13}}\text{C}$ isotopes of carbon atom.

HDI Calculation:

$\begin{array}{l}\text{HDI=}\frac{\text{2(C)+2+N-H-X}}{\text{2}}\\ \text{where}\\ \text{C}\text{represent}\text{the}\text{number}\text{of}\text{carbon}\\ \text{N}\text{represent}\text{the}\text{number}\text{of}\text{nitrogen}\\ \text{H}\text{represent}\text{the}\text{number}\text{of}\text{hydrogen}\\ \text{X}\text{represent}\text{the}\text{number}\text{of}\text{halogen}\text{.}\end{array}$