Chapter 18, Problem 18.103P

Interpretation Introduction

Interpretation:

The product with a detailed mechanism for the given reaction is to be drawn by referring to the ${}^{\text{1}}\text{H}\text{NMR}$ and ${}^{\text{13}}\text{C}\text{NMR}$ signals.

Concept introduction:

In an ${}^{\text{1}}\text{H}$ NMR, the number of signals is equal to the number of types of protons in the molecule. The chemically equivalent protons absorbed at the same magnetic field and produce one signal, whereas the chemically non-equivalent or distinct protons absorbed at different magnetic fields produce different signals. The separation of NMR peaks into a number of smaller peaks is called the splitting of NMR peaks. The non-equivalent protons can couple each other’s signals whereas equivalent protons do not. The multiplicity of the peak depends on the number of neighboring protons, which can be determined by $\text{(}N\text{+1)}$ rule, where $N$ is the number of neighboring protons. If the signal for particular proton appears as singlet indicates that the proton has no neighboring protons.

${}^{\text{13}}\text{C}\text{NMR}$ provides valuable information about the carbon skeleton. Each signal in the ${}^{\text{13}}\text{C}\text{NMR}$ equals to the number of distinct carbon atoms in the given unknown. In most of the ${}^{\text{13}}\text{C}\text{NMR}$ spectra, almost every time all the signals would appear as singlets. The saturated carbon atoms appear in the range $\text{δ}\text{0-35 ppm}$ if it is a simple alkane fragment. If it is attached to any electronegative element such as halogens, or nitrogen then the range is $\text{δ}\text{25-70 ppm}$. Triple bonded carbon atoms range from $\text{δ}\text{65-85 ppm}$. Alkene carbons range from $\text{δ}\text{105-150 ppm}$. Carbonyl carbon atoms in acids, esters, amides, and anhydrides range from $\text{δ}\text{120-185 ppm}$. Carbonyl carbons in aldehydes and ketones range from $\text{δ}\text{190-220 ppm}$.