How can one differentiate between singlet, doublet, and triplet peaks in NMR?

In NMR, singlet peaks represent one resonance, doublet peaks two closely spaced resonances, and triplet peaks three closely spaced resonances.

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool used by chemists to determine the structure of molecules. It works by applying a magnetic field to a sample and then measuring the energy absorbed by the nuclei when they are exposed to radiofrequency radiation. The resulting spectrum shows peaks that correspond to different resonances, or energy levels, of the nuclei. For a more detailed explanation of NMR spectroscopy, see Nuclear Magnetic Resonance (NMR) Spectroscopy.

Singlet peaks are the simplest type of peak in an NMR spectrum. They represent a single resonance, meaning that the nucleus is in one specific energy state. This usually indicates that the atom in question is not adjacent to any other atoms of the same type, or that it is adjacent to atoms of the same type but they are all in the same chemical environment.

Doublet peaks are slightly more complex. They represent two closely spaced resonances, which usually indicates that the atom in question is adjacent to one other atom of the same type in a different chemical environment. The two peaks are of equal intensity and are separated by a specific distance, known as the coupling constant. More on how coupling constants influence NMR can be found in the section on Coupling Constants in NMR.

Triplet peaks are even more complex. They represent three closely spaced resonances, which usually indicates that the atom in question is adjacent to two other atoms of the same type in different chemical environments. The three peaks are not of equal intensity; instead, the middle peak is twice as intense as the outer peaks. This pattern is known as a 1:2:1 triplet. Understanding how these peaks are influenced by the chemical environment can be explored further in Chemical Shifts in NMR.

IB Chemistry Tutor Summary: In NMR spectroscopy, singlet, doublet, and triplet peaks tell us about the molecule's structure. Singlet peaks show a single resonance, indicating no nearby identical atoms or identical atoms in the same environment. Doublet peaks show two resonances, suggesting one nearby identical atom in a different environment. Triplet peaks show three resonances, indicating two nearby identical atoms in different environments.