21.1 Spectroscopic Identification of Organic Compounds

Which spectroscopic technique is primarily used to determine the presence of functional groups in an organic compound based on absorption peaks?

A. Mass Spectrometry

B. Infrared Spectroscopy

C. Nuclear Magnetic Resonance Spectroscopy

D. Ultraviolet-Visible Spectroscopy

In mass spectrometry, what does the molecular ion peak represent?

A. The ion with the highest mass-to-charge ratio

B. The ion with the lowest mass-to-charge ratio

C. The ion formed by the loss of an electron from the parent molecule

D. The ion formed by the gain of an electron by the parent molecule

Which of the following is NOT a factor that influences chemical shifts in NMR spectroscopy?

A. Electron shielding

B. Magnetic field strength

C. Presence of functional groups

D. Temperature

In NMR spectroscopy, what does spin-spin splitting indicate?

A. Number of protons in the molecule

B. Presence of magnetically equivalent protons

C. Presence of magnetically non-equivalent protons

D. Strength of the magnetic field

Which spectroscopic technique provides information about the molecular weight of an organic compound?

A. Infrared Spectroscopy

B. Ultraviolet-Visible Spectroscopy

C. Nuclear Magnetic Resonance Spectroscopy

D. Mass Spectrometry

a) Explain the basic principle behind mass spectrometry in identifying organic compounds. [3]

b) How is the molecular ion peak in a mass spectrum significant in determining the molecular weight of an organic compound? [2]

a) Describe the principle of infrared (IR) spectroscopy in the identification of functional groups in organic compounds. [3]

b) How can absorption peaks in an IR spectrum be used to identify specific functional groups? [2]

a) Explain the fundamental concept behind nuclear magnetic resonance (NMR) spectroscopy in determining the molecular structure of organic compounds. [3]

b) What information can chemical shifts in an NMR spectrum provide about the environment of specific hydrogen atoms in a molecule? [2]

a) Describe the process of fragmentation in mass spectrometry and its significance in identifying organic compounds. [3]

b) Why might some organic compounds produce more than one significant peak in a mass spectrum? [2]

c) How can mass spectrometry be used in conjunction with other spectroscopic methods to determine the structure of an organic compound? [3]

a) Explain the difference between transmittance and absorbance in the context of infrared (IR) spectroscopy. [3]

b) How can the presence of a carbonyl group be identified using IR spectroscopy? [2]

c) Why is it essential to use a reference compound when analysing an IR spectrum? [2]