The ¹H NMR spectra of three isomers with molecular formula C₄H₉Br are shown here. Which isomer produces which spectrum?
b. <IMAGE>

Verified step by step guidance

1. Analyze the molecular formula C4H9Br, which indicates the presence of four carbons, nine hydrogens, and one bromine atom. This suggests the possibility of structural isomers such as 1-bromobutane, 2-bromobutane, and 2-methyl-2-bromopropane.
2. Examine the 1H NMR spectrum provided. Note the chemical shift values (in ppm), the splitting patterns (multiplets, doublets, singlets, etc.), and the relative integration of the peaks, which correspond to the number of protons in each environment.
3. Identify the peak near 3-4 ppm, which is characteristic of protons attached to a carbon bonded to a bromine atom. This region helps distinguish the position of the bromine in the molecule.
4. Look at the splitting patterns and chemical shifts of the peaks in the 0-2 ppm region. These peaks correspond to alkyl protons and provide information about the branching and connectivity of the carbon chain.
5. Match the observed spectrum to the expected NMR patterns for each isomer. For example, 1-bromobutane will show a triplet for the CH3 group, a multiplet for the CH2 groups, and a distinct peak for the CH2-Br group. Similarly, 2-bromobutane and 2-methyl-2-bromopropane will have unique splitting patterns and chemical shifts based on their structures.

Key Concepts

1H NMR Spectroscopy

Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number of hydrogen atoms in different environments within a molecule, indicated by peaks in the spectrum. The position of these peaks, measured in parts per million (PPM), reflects the electronic environment surrounding the hydrogen atoms, allowing chemists to infer structural details.

Chemical Shifts

Chemical shifts in 1H NMR spectra refer to the specific PPM values at which the peaks appear, influenced by the electronic environment of the hydrogen atoms. Different functional groups and molecular structures cause variations in these shifts, helping to identify the presence of specific groups such as alkyl, aromatic, or halogenated carbons. Understanding chemical shifts is crucial for interpreting the spectrum and correlating it with the corresponding isomer.

Integration of Peaks

The integration of peaks in a 1H NMR spectrum indicates the relative number of hydrogen atoms contributing to each signal. The area under each peak is proportional to the number of protons in that environment, allowing for the determination of the ratio of different types of hydrogen in the molecule. This information is essential for distinguishing between isomers, as it helps to confirm the molecular structure based on the integration values.