Question

Draw all constitutional isomers of molecular formula \({{\bf{C}}_{\bf{3}}}{{\bf{H}}_{\bf{6}}}{\bf{C}}{{\bf{l}}_{\bf{2}}}\).

a. How many signals does each isomer exhibit in its \({}^{\bf{1}}{\bf{H}}\) NMR spectrum?

b. How many lines does each isomer exhibit in its \({}^{{\bf{13}}}{\bf{C}}\) NMR spectrum?

c. When only the number of signals in both \({}^{\bf{1}}{\bf{H}}\) and \({}^{{\bf{13}}}{\bf{C}}\) NMR spectroscopy is considered, is it possible to distinguish all of these constitutional isomers?

Short answer

a.

b.

c.

d.\({}^{13}C\)NMR cannot be used to distinguish the isomers, but \({}^1H\) NMR can be used.

Step-by-step solution

Signals in \({}^{\bf{1}}{\bf{H}}\) NMR spectrum

The signals in\({}^{\bf{1}}{\bf{H}}\)NMR depend on the number of non-equivalent protons (the hydrogen atoms that have non-identical/different chemical environments).

The equivalent protons resonate at the same frequency and show only a single signal in the \({}^1H\) NMR spectrum.

Signals in \({}^{{\bf{13}}}{\bf{C}}\) NMR spectrum

The signals in \({}^{13}C\) NMR depend on the number of non-equivalent carbons (the carbon atoms that have non-identical/different chemical environments).

Constitutional isomers of \({{\bf{C}}_{\bf{3}}}{{\bf{H}}_{\bf{6}}}{\bf{C}}{{\bf{l}}_{\bf{2}}}\)

The constitutional isomers of \({C_3}{H_6}C{l_2}\) are:

Lines exhibited in the \({}^{{\bf{13}}}{\bf{C}}\) NMR spectrum by the isomers

The number of lines in \({}^{13}C\) NMR shown by each isomer is as follows:

Lines exhibited in the  \({}^{\bf{1}}{\bf{H}}\) NMR spectrum by the isomers

The number of lines in \({}^1H\) NMR shown by each isomer is as follows:

The number of signals in \({}^{13}C\)NMR cannot be used to distinguish the isomers as some of the \({}^{13}C\)spectra have the same number of signals.

However, in the case of \({}^1H\) NMR spectrum, each isomer gives a different spectrum with a different splitting pattern. Hence, it can be used to distinguish the isomers.