3.3.15.3 Proton NMR Spectroscopy

• What is Nuclear Magnetic Resonance (NMR) spectroscopy used for?

  Analyzing molecular structure
• What is the resonance frequency in NMR dependent on?

  B₀ and nucleus type
• The chemical shift in Proton NMR is measured in parts per million (ppm).


  True
• Signals in Proton NMR can be split due to coupling between neighboring protons
• Proton NMR is a crucial technique for identifying and characterizing organic compounds.

  True
• When placed in an external magnetic field, atomic nuclei align in two energy states: parallel and against
• NMR is used as a spectroscopy technique to identify nuclei and their environments
• Match the chemical environment with its approximate chemical shift range in Proton NMR:

  Alkanes ↔️ 0-4 ppm

  Alkenes ↔️ 4-6 ppm

  Aromatic ↔️ 6-8 ppm

  Aldehydes ↔️ 9-10 ppm
• When placed in an external magnetic field, nuclei align in two energy states: parallel and against.

  True
• Atomic nuclei in an external magnetic field align in two energy states: parallel and against.

  True
• Steps involved in the alignment of atomic nuclei in an external magnetic field

  1️⃣ Nuclei with odd protons or neutrons possess nuclear spin

  2️⃣ Magnetic moment is created

  3️⃣ External magnetic field (B₀) is applied

  4️⃣ Nuclei align in parallel or against energy states
• Match the environment with its approximate chemical shift in Proton NMR:

  Alkanes ↔️ 0-4 ppm

  Alkenes ↔️ 4-6 ppm

  Aromatic ↔️ 6-8 ppm

  Aldehydes ↔️ 9-10 ppm
• Atomic nuclei with an even number of protons or neutrons have nuclear spin and a magnetic moment.

  False
• The resonance frequency in NMR depends on the strength of the magnetic field and the type of nucleus.


  True
• The chemical shift in Proton NMR is measured in parts per million
• What property of atomic nuclei is essential for Proton NMR spectroscopy?

  Nuclear spin
• What information does Proton NMR spectroscopy provide about organic compounds?

  Hydrogen environments
• What structural information can chemical shifts in Proton NMR provide?

  Hydrogen environments
• Proton NMR provides information about the chemical environment of each proton in a molecule.

  True
• Proton NMR provides information about the chemical environment of each proton
• In an external magnetic field, protons align in two energy states
• The chemical shift is measured in parts per million (ppm).


  True
• Signals in proton NMR can be split due to coupling with neighboring protons
• What do relative integrated intensities in NMR spectra indicate?

  Relative number of protons
• What is the purpose of comparing relative integrated intensities in NMR spectroscopy?

  Determine proton ratios
• What does NMR spectroscopy measure to identify the types of nuclei and their environments in a molecule?

  Energy absorption
• Splitting patterns in proton NMR follow the n+1 rule, where 'n' represents the number of neighboring protons
• The chemical shift of a proton in NMR spectroscopy is measured in parts per million (ppm).

  True
• Combining chemical shift and splitting patterns in NMR helps identify different hydrogen environments in a molecule.


  True
• The area under a signal in NMR spectroscopy is directly proportional to the number of protons responsible for that signal.

  True
• In methane (CH₄), all protons are equivalent and form a single peak in the NMR spectrum.


  True
• A 3:1 ratio of integrated intensities suggests that there are three equivalent protons in one environment and one proton in a different environment.

  True
• What information do splitting patterns provide about a molecule?

  Number and arrangement of protons
• A proton with no neighboring protons will show a singlet
• What property of atomic nuclei is utilized in NMR spectroscopy?

  Nuclear spin
• Match the energy level with its properties:

  Lower energy level ↔️ Parallel alignment

  Higher energy level ↔️ Anti-parallel alignment
• Proton NMR provides information about the chemical environment of each proton
• In proton NMR, protons align in two states when placed in an external magnetic field
• The chemical shift in proton NMR is measured in parts per million
• What two key pieces of information are used to analyze NMR spectra?

  Chemical shift and splitting patterns