PORTAGE CHEMISTRY 219 STUDY GUIDE –
COMPLETE REVIEW & PRACTICE PREPARATION
Part 1: Spectroscopy and Structure Identification (Questions 1-20)
1. In an IR spectrum, a strong, broad peak around 3300 cm⁻¹ is indicative of which functional
group?
a) Carbonyl (C=O)
b) Nitrile (C≡N)
c) Hydroxyl (O-H)
d) Alkene (C=C)
Answer: c) Hydroxyl (O-H)
2. A compound with the molecular formula C₄H₈O shows a strong IR absorption at 1715 cm⁻¹.
Its ¹H NMR spectrum has a singlet at δ 2.1 ppm. The most likely structure is:
a) 2-butanone
b) Butanal
c) Ethyl vinyl ether
d) 2-methylpropanal
Answer: a) 2-butanone
3. In ¹³C NMR spectroscopy, the number of unique carbon signals directly tells you:
a) The number of carbon atoms in the molecule.
b) The number of different electronic environments for carbon atoms.
c) The molecular weight of the compound.
d) The presence of symmetry in the molecule's IR spectrum.
Answer: b) The number of different electronic environments for carbon atoms.
4. The coupling constant (J value) in ¹H NMR is a measure of:
a) The strength of the external magnetic field.
b) The distance between two coupled protons.
c) The energy difference between spin states.
d) The interaction between nuclei through chemical bonds.
Answer: d) The interaction between nuclei through chemical bonds.
5. A compound with the formula C₃H₆O₂ has a ¹H NMR spectrum with a singlet at δ 11.5 ppm.
This signal is most consistent with:
a) An aldehyde proton
b) A carboxylic acid proton
,c) An alcohol proton
d) An alkene proton
Answer: b) A carboxylic acid proton
6. In Mass Spectrometry, the molecular ion peak (M⁺) represents:
a) The most stable fragment of the molecule.
b) The radical cation of the intact molecule.
c) The molecule after it has lost an electron.
d) Both b and c.
Answer: d) Both b and c.
7. A compound shows a parent ion peak at m/z = 114 and a strong peak at m/z = 71. This is a
classic pattern for:
a) A ketone undergoing alpha-cleavage.
b) A McLafferty rearrangement.
c) The loss of a methyl group.
d) A chlorinated compound.
Answer: a) A ketone undergoing alpha-cleavage.
8. Which of the following compounds would show a λmax in its UV-Vis spectrum at the
longest wavelength?
a) 1,3-butadiene
b) 1,3,5-hexatriene
c) Ethene
d) 2-butene
Answer: b) 1,3,5-hexatriene
9. In a ¹H NMR spectrum, a quartet and a triplet are often indicative of:
a) An isopropyl group
b) An ethyl group
c) A tert-butyl group
d) A vinyl group
Answer: b) An ethyl group
10. A carbonyl carbon in a ¹³C NMR spectrum typically appears in the range of:
a) 0-50 ppm
b) 50-100 ppm
c) 100-150 ppm
d) 180-220 ppm
Answer: d) 180-220 ppm
,11. What is the index of hydrogen deficiency (IHD) for a molecule with the formula C₆H₁₂O?
a) 0
b) 1
c) 2
d) 3
Answer: b) 1
12. A compound C₅H₁₀O has a strong IR peak at ~1700 cm⁻¹ and two singlets in its ¹H NMR at δ
1.0 ppm (9H) and δ 2.1 ppm (3H). The structure is:
a) Pentanal
b) 2-pentanone
c) 3-pentanone
d) 2,2-dimethylpropanal
Answer: d) 2,2-dimethylpropanal
13. The base peak in a mass spectrum is:
a) The molecular ion peak.
b) The peak corresponding to the most stable carbocation.
c) The tallest peak, assigned a relative intensity of 100%.
d) The peak from the isotope with the highest atomic mass.
Answer: c) The tallest peak, assigned a relative intensity of 100%.
14. A proton that is deshielded will appear in a ¹H NMR spectrum:
a) At a higher δ (ppm) value.
b) At a lower δ (ppm) value.
c) As a singlet.
d) With a larger coupling constant.
Answer: a) At a higher δ (ppm) value.
15. Which technique is best for distinguishing between cis and alkenes?
a) IR Spectroscopy
b) Mass Spectrometry
c) ¹H NMR (using coupling constants)
d) UV-Vis Spectroscopy
Answer: c) ¹H NMR (using coupling constants)
16. A compound with IHD=4 could contain:
a) A benzene ring.
b) Two double bonds and a ring.
c) A triple bond and a double bond.
, d) All of the above.
Answer: d) All of the above.
17. The IR absorption for a nitrile group (C≡N) is typically found near:
a) 2250 cm⁻¹
b) 1710 cm⁻¹
c) 1650 cm⁻¹
d) 3500 cm⁻¹
Answer: a) 2250 cm⁻¹
18. In ¹H NMR, a deuterated solvent like CDCl₃ is used because:
a) It is cheap.
b) Deuterium atoms do not produce significant signals in the ¹H NMR region.
c) It dissolves all organic compounds.
d) It shifts the TMS signal.
Answer: b) Deuterium atoms do not produce significant signals in the ¹H NMR region.
19. The "DEPT-135" NMR experiment is particularly useful for identifying:
a) CH and CH₃ groups (positive) vs. CH₂ groups (negative).
b) The exact coupling constants between protons.
c) The number of nitrogen atoms.
d) The molecular ion.
Answer: a) CH and CH₃ groups (positive) vs. CH₂ groups (negative).
20. A broad NMR signal for an O-H or N-H proton is primarily due to:
a) Coupling to many other protons.
b) Slow chemical exchange.
c) The presence of deuterium.
d) The high electronegativity of oxygen.
Answer: b) Slow chemical exchange.
Part 2: Aromaticity and Reactions of Aromatic Compounds (Questions 21-35)
21. Which of the following is aromatic?
a) Cyclobutadiene
b) Cycloheptatriene
c) Pyridine
d) Cyclooctatetraene (tub-shaped)
Answer: c) Pyridine
COMPLETE REVIEW & PRACTICE PREPARATION
Part 1: Spectroscopy and Structure Identification (Questions 1-20)
1. In an IR spectrum, a strong, broad peak around 3300 cm⁻¹ is indicative of which functional
group?
a) Carbonyl (C=O)
b) Nitrile (C≡N)
c) Hydroxyl (O-H)
d) Alkene (C=C)
Answer: c) Hydroxyl (O-H)
2. A compound with the molecular formula C₄H₈O shows a strong IR absorption at 1715 cm⁻¹.
Its ¹H NMR spectrum has a singlet at δ 2.1 ppm. The most likely structure is:
a) 2-butanone
b) Butanal
c) Ethyl vinyl ether
d) 2-methylpropanal
Answer: a) 2-butanone
3. In ¹³C NMR spectroscopy, the number of unique carbon signals directly tells you:
a) The number of carbon atoms in the molecule.
b) The number of different electronic environments for carbon atoms.
c) The molecular weight of the compound.
d) The presence of symmetry in the molecule's IR spectrum.
Answer: b) The number of different electronic environments for carbon atoms.
4. The coupling constant (J value) in ¹H NMR is a measure of:
a) The strength of the external magnetic field.
b) The distance between two coupled protons.
c) The energy difference between spin states.
d) The interaction between nuclei through chemical bonds.
Answer: d) The interaction between nuclei through chemical bonds.
5. A compound with the formula C₃H₆O₂ has a ¹H NMR spectrum with a singlet at δ 11.5 ppm.
This signal is most consistent with:
a) An aldehyde proton
b) A carboxylic acid proton
,c) An alcohol proton
d) An alkene proton
Answer: b) A carboxylic acid proton
6. In Mass Spectrometry, the molecular ion peak (M⁺) represents:
a) The most stable fragment of the molecule.
b) The radical cation of the intact molecule.
c) The molecule after it has lost an electron.
d) Both b and c.
Answer: d) Both b and c.
7. A compound shows a parent ion peak at m/z = 114 and a strong peak at m/z = 71. This is a
classic pattern for:
a) A ketone undergoing alpha-cleavage.
b) A McLafferty rearrangement.
c) The loss of a methyl group.
d) A chlorinated compound.
Answer: a) A ketone undergoing alpha-cleavage.
8. Which of the following compounds would show a λmax in its UV-Vis spectrum at the
longest wavelength?
a) 1,3-butadiene
b) 1,3,5-hexatriene
c) Ethene
d) 2-butene
Answer: b) 1,3,5-hexatriene
9. In a ¹H NMR spectrum, a quartet and a triplet are often indicative of:
a) An isopropyl group
b) An ethyl group
c) A tert-butyl group
d) A vinyl group
Answer: b) An ethyl group
10. A carbonyl carbon in a ¹³C NMR spectrum typically appears in the range of:
a) 0-50 ppm
b) 50-100 ppm
c) 100-150 ppm
d) 180-220 ppm
Answer: d) 180-220 ppm
,11. What is the index of hydrogen deficiency (IHD) for a molecule with the formula C₆H₁₂O?
a) 0
b) 1
c) 2
d) 3
Answer: b) 1
12. A compound C₅H₁₀O has a strong IR peak at ~1700 cm⁻¹ and two singlets in its ¹H NMR at δ
1.0 ppm (9H) and δ 2.1 ppm (3H). The structure is:
a) Pentanal
b) 2-pentanone
c) 3-pentanone
d) 2,2-dimethylpropanal
Answer: d) 2,2-dimethylpropanal
13. The base peak in a mass spectrum is:
a) The molecular ion peak.
b) The peak corresponding to the most stable carbocation.
c) The tallest peak, assigned a relative intensity of 100%.
d) The peak from the isotope with the highest atomic mass.
Answer: c) The tallest peak, assigned a relative intensity of 100%.
14. A proton that is deshielded will appear in a ¹H NMR spectrum:
a) At a higher δ (ppm) value.
b) At a lower δ (ppm) value.
c) As a singlet.
d) With a larger coupling constant.
Answer: a) At a higher δ (ppm) value.
15. Which technique is best for distinguishing between cis and alkenes?
a) IR Spectroscopy
b) Mass Spectrometry
c) ¹H NMR (using coupling constants)
d) UV-Vis Spectroscopy
Answer: c) ¹H NMR (using coupling constants)
16. A compound with IHD=4 could contain:
a) A benzene ring.
b) Two double bonds and a ring.
c) A triple bond and a double bond.
, d) All of the above.
Answer: d) All of the above.
17. The IR absorption for a nitrile group (C≡N) is typically found near:
a) 2250 cm⁻¹
b) 1710 cm⁻¹
c) 1650 cm⁻¹
d) 3500 cm⁻¹
Answer: a) 2250 cm⁻¹
18. In ¹H NMR, a deuterated solvent like CDCl₃ is used because:
a) It is cheap.
b) Deuterium atoms do not produce significant signals in the ¹H NMR region.
c) It dissolves all organic compounds.
d) It shifts the TMS signal.
Answer: b) Deuterium atoms do not produce significant signals in the ¹H NMR region.
19. The "DEPT-135" NMR experiment is particularly useful for identifying:
a) CH and CH₃ groups (positive) vs. CH₂ groups (negative).
b) The exact coupling constants between protons.
c) The number of nitrogen atoms.
d) The molecular ion.
Answer: a) CH and CH₃ groups (positive) vs. CH₂ groups (negative).
20. A broad NMR signal for an O-H or N-H proton is primarily due to:
a) Coupling to many other protons.
b) Slow chemical exchange.
c) The presence of deuterium.
d) The high electronegativity of oxygen.
Answer: b) Slow chemical exchange.
Part 2: Aromaticity and Reactions of Aromatic Compounds (Questions 21-35)
21. Which of the following is aromatic?
a) Cyclobutadiene
b) Cycloheptatriene
c) Pyridine
d) Cyclooctatetraene (tub-shaped)
Answer: c) Pyridine
