(a) Match the following compounds to the correct ^1 H NMR...

(a) Match the following compounds to the correct $^{1}$ H NMR spectroscopic data given in the table. (b) What coupling patterns do you expect to see in the spectrum of compound $\mathbf{B} ?$ (c) Explain why the signal at $\delta 1.15 \mathrm{ppm}$ in the spectrum of $\mathbf{C}$ is a singlet. (FIGURE CANNOT COPY) $$\begin{array}{ll} \text { Compound } & \text { 1 H NMR } \delta / \text { ppm (relative integral) } \\ \text { A } & 2.69(4 \mathrm{H}), 2.43(6 \mathrm{H}), 1.24(2 \mathrm{H}) \\ \text { B } & 2.30(2 \mathrm{H}), 2.22(6 \mathrm{H}), 1.06(3 \mathrm{H}) \\ \text { C } & 1.41(2 \mathrm{H}), 1.15(9 \mathrm{H}) \\ \hline \end{array}$$

(a) Match the following compounds to the correct $^{1}$ H NMR spectroscopic data given in the table. (b) What coupling patterns do you expect to see in the spectrum of compound $\mathbf{B} ?$ (c) Explain why the signal at $\delta 1.15 \mathrm{ppm}$ in the spectrum of $\mathbf{C}$ is a singlet.
(FIGURE CANNOT COPY)
$$\begin{array}{ll}
\text { Compound } & \text { 1 H NMR } \delta / \text { ppm (relative integral) } \\
\text { A } & 2.69(4 \mathrm{H}), 2.43(6 \mathrm{H}), 1.24(2 \mathrm{H}) \\
\text { B } & 2.30(2 \mathrm{H}), 2.22(6 \mathrm{H}), 1.06(3 \mathrm{H}) \\
\text { C } & 1.41(2 \mathrm{H}), 1.15(9 \mathrm{H}) \\
\hline
\end{array}$$

Key Concepts

Proton NMR Spectroscopy

Proton NMR spectroscopy is a crucial analytical technique used to observe the magnetic environment of hydrogen nuclei within a molecule. It provides information about the chemical structure of compounds by measuring the resonance frequency of protons, which is influenced by their electronic surroundings and hence can be correlated with the molecular framework.

Chemical Shift

Chemical shift refers to the position on the NMR spectrum where a proton's signal appears, typically reported in parts per million (ppm). It reflects the electronic environment around the hydrogen atom; protons in different chemical environments will resonate at different frequencies due to varying degrees of electron shielding or deshielding.

Spin-Spin Coupling and Multiplicity

Spin-spin coupling is the interaction between non-equivalent neighboring protons, resulting in splitting of NMR signals into multiplets. The observed pattern, often described by the n+1 rule, gives insight into the number of adjacent hydrogens, thereby providing important structural information regarding the proximity of different groups within a molecule.

Integration (Peak Area)

Integration in an NMR spectrum measures the relative number of protons contributing to each signal. By comparing the areas under different peaks, one can deduce the relative proton counts in various chemical environments, aiding in the determination of molecular structure and the assignment of specific signals to particular groups.

Singlet Formation in NMR

A singlet in an NMR spectrum occurs when a set of equivalent protons do not experience any spin-spin coupling with adjacent protons. This lack of splitting means that there are no neighboring protons with which to interact, which is often indicative of an isolated chemical environment or substitution pattern that prevents coupling.

Transcript

Please give Ace some feedback