Mass spectrometry Knowledge-Based Practice

Questions

1. 1.

   According to the nitrogen rule in mass spectrometry, an uncharged organic molecule composed solely of carbon, hydrogen, oxygen, and nitrogen produces an odd nominal molecular ion mass. What structural characteristic of the molecule does this observation directly indicate?

   • A) It contains an odd number of oxygen atoms.
   • B) It contains an odd number of nitrogen atoms.
   • C) It contains an even number of nitrogen atoms.
   • D) It contains an odd number of carbon atoms.
2. 2.

   In the mass spectrum of an organic compound containing a single halogen atom, the molecular ion peak ($M$) and the $M+2$ peak appear with approximately equal relative intensities. Which halogen is present in the compound?

   • A) Bromine
   • B) Chlorine
   • C) Fluorine
   • D) Iodine
3. 3.

   In a mass spectrometer where ions are accelerated through the same electric potential difference, which type of ion experiences the greatest degree of deflection when passing through a uniform magnetic field?

   • A) An ion with a high mass and a low positive charge
   • B) An ion with a high mass and a high positive charge
   • C) An ion with a low mass and a low positive charge
   • D) An ion with a low mass and a high positive charge
4. 4.

   In electron ionization mass spectrometry, which statement correctly describes the molecular ion peak, denoted as $M^{+\bullet}$?

   • A) It corresponds to the signal representing the most abundant ionic species detected in the mass spectrum.
   • B) It is produced when an incoming high-energy electron is captured by a neutral molecule to yield a radical anion.
   • C) It represents the intact radical cation formed when a neutral molecule loses a single electron, providing the nominal molecular mass.
   • D) It represents the most stable fragment ion resulting from primary bond cleavage of the parent structure.
5. 5.

   In the mass spectrum of an organic compound, which statement correctly defines the base peak?

   • A) The peak corresponding to the ion with the highest relative abundance, assigned an arbitrary intensity of 100%
   • B) The peak produced by the intact, unfragmented radical cation that indicates the molecular mass
   • C) The peak detected at the lowest mass-to-charge ratio that represents the primary fragment
   • D) The peak generated exclusively by the presence of heavier stable isotopes such as carbon-13

Answers and step-by-step solutions appear after you finish the test.