7.1.2 Interpretation of Mass Spectra

• What is the mass-to-charge ratio referred to in mass spectrometry?

  $m / z$
• In mass spectrometry, molecules are converted into ions during the ionization stage.
• Ions are accelerated by an electric field in mass spectrometry to provide them with kinetic energy.
• Which ions are deflected more in a magnetic field during mass spectrometry?

  Smaller $m / z$ ratios
• The output of mass spectrometry is a mass spectrum showing peaks corresponding to different m / z ratios.
• What is the primary purpose of mass spectrometry?

  Determine $m / z$ ratio
• Stages of mass spectrometry in the correct order:

  1️⃣ Ionization

  2️⃣ Acceleration

  3️⃣ Deflection

  4️⃣ Detection
• Match the ionization method with its description:

  Electron Impact ↔️ Bombardment with high-energy electrons

  Electrospray Ionization ↔️ Spraying solution into a fine mist
• Ions are accelerated by a magnetic field during the acceleration stage of mass spectrometry.

  False
• Ions are deflected by a magnetic field based on their m / z ratio.
• What generates the signal in the detection stage of mass spectrometry?

  Ions hitting the detector
• What does mass spectrometry determine?

  $m / z$
• Electron impact ionization occurs in the gas phase.
• Electrospray ionization is used for molecules in the liquid phase.
• What type of field deflects ions in mass spectrometry?

  Magnetic
• The detector in mass spectrometry generates a signal proportional to ion abundance.
• The output of mass spectrometry is a mass spectrum showing peaks corresponding to different m / z</latex> ratios.
• Match the ionization method with its description:

  Electron Impact ↔️ Bombardment with high-energy electrons causes fragmentation

  Electrospray Ionization ↔️ Sprays a fine mist into ions with applied voltage
• The molecular ion peak (M+) in a mass spectrum provides the molecular weight of the compound.
• The first step to identify the molecular ion peak is to locate the highest $m / z$ peak.
• Stages of mass spectrometry in order

  1️⃣ Ionization

  2️⃣ Acceleration

  3️⃣ Deflection

  4️⃣ Detection
• In electron impact ionization, molecules are bombarded with high-energy electrons.
• What phase is electron impact ionization used in?

  Gas
• Isotopic peaks in mass spectra arise due to differences in the number of neutrons in isotopes.
• Carbon-13 has a natural abundance of 1.1%.
• Match the element with its isotopes:

  Carbon ↔️ $^{12}C$, $^{13}C$

  Chlorine ↔️ $^{35}Cl$, $^{37}Cl$

  Bromine ↔️ $^{79}Br$, $^{81}Br$
• What is the ratio of intensities observed for peaks at $m / z$ values of $50$ and $52$ in the mass spectrum of $CH_{3}Cl$?


  $3:1$
• Isotopic peaks arise in mass spectra due to the presence of different isotopes of elements
• What are the two isotopes of carbon and their natural abundances?

  $^{12}C$ (98.9%), ^{13}C</latex> (1.1%)
• The isotope $^{37}Cl$ is more abundant than $^{35}Cl$


  False
• A compound containing chlorine would exhibit peaks at $M^ +$ and $M +$$2$ due to the isotopes ^{35}Cl and $^{37}Cl$.
• Why are peaks observed at m / z</latex> values of $50$ and $52$ in the mass spectrum of $CH_{3}Cl$?


  $^{35}Cl$ and $^{37}Cl$
• Match the fragment ion type with its formation:

  Alkyl Cations ↔️ Loss of neutral alkyl groups

  Acyl Cations ↔️ Loss of neutral acyl groups

  Aryl Cations ↔️ Loss of neutral aryl groups

  Hydroxyl Cations ↔️ Loss of neutral hydroxyl groups
• Common fragmentation pathways include the loss of water molecules or carbon monoxide.
• What fragment ion is formed when propanol loses $OH$?


  $CH_{3}CH_{2}CH_{2}^ +$
• Mass spectrometry determines the mass-to-charge ratio ($m / z$) of ions.
• Arrange the stages of mass spectrometry in the correct order:

  1️⃣ Ionization

  2️⃣ Acceleration

  3️⃣ Deflection

  4️⃣ Detection
• What are the two primary ionization methods in mass spectrometry?

  EI and ESI
• Electron impact (EI) is suitable for large, polar molecules.

  False
• Electrospray ionization (ESI) is ideal for larger, polar molecules like proteins.