How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]
(b)

Verified step by step guidance

1. Identify the molecular structure of the given compound. Understanding the structure is crucial as it helps in determining the number of unique hydrogen environments.
2. Examine the symmetry of the molecule. Symmetrical molecules often have fewer distinct NMR signals because equivalent hydrogens produce the same signal.
3. Determine the number of unique hydrogen environments. Look for hydrogens in different chemical environments, such as those attached to different functional groups or in different positions relative to other atoms or groups.
4. Consider the effect of electronegative atoms or groups nearby. Hydrogens near electronegative atoms may experience different chemical shifts, leading to distinct signals.
5. Count the number of distinct hydrogen environments identified. Each unique environment corresponds to a separate signal in the ¹H NMR spectrum.

Key Concepts

¹H NMR Spectroscopy

¹H NMR (Proton Nuclear Magnetic Resonance) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms. Each distinct hydrogen environment in a molecule produces a unique signal in the NMR spectrum, allowing chemists to deduce the number and types of hydrogen atoms present.

Chemical Equivalence

Chemical equivalence in NMR refers to hydrogen atoms that are in identical environments within a molecule, resulting in them producing the same signal in the NMR spectrum. Identifying chemically equivalent hydrogens is crucial for predicting the number of distinct signals, as equivalent hydrogens do not contribute additional signals.

Symmetry in Molecules

Symmetry in molecules can significantly affect the number of distinct NMR signals. Symmetrical molecules often have fewer distinct hydrogen environments because symmetry can make different hydrogens chemically equivalent. Recognizing symmetry elements, such as planes or axes, helps in determining which hydrogens are equivalent and thus how many unique signals will appear in the spectrum.