Study of IR Spectra

Overview

• Topic: Understanding and interpreting IR spectra.
• Key focus on memorizing values associated with different functional groups.

Key Wave Numbers to Remember

• OH Bond: 3200 - 3650 cm⁻¹
• sp³ CH Stretch: ~3000 cm⁻¹

Example 1: Decane

• IR Spectrum Features:
  • Peak at ~3000 cm⁻¹ indicates presence of sp³ CH.
  • Two peaks: one for CH₂ and one for CH₃.
• Conclusion: Compound is Decane (C₁₀H₂₂) with a straight chain structure.

Example 2: Cyclohexane

• IR Spectrum Features:
  • Peak at 3000 cm⁻¹ for sp³ CH stretch.
  • Only one peak for CH₂ and no CH₃ present.
• Conclusion: Compound is Cyclohexane (C₆H₁₂).

Example 3: Cis-2-Pentene

• IR Spectrum Features:
  • Peaks at ~3000 cm⁻¹ (sp³ CH) and higher peak for sp² CH stretch.
  • Presence of double bond indicated by sp² CH stretch.
• Conclusion: Compound is cis-2-pentene with a cis isomer structure.

Example 4: Trans-2-Pentene

• IR Spectrum Features:
  • Similar to cis-2-pentene but shows a disturbance indicating trans configuration.
• Conclusion: Compound is trans-2-pentene.

Example 5: Alkyne (C≡C)

• IR Spectrum Features:
  • Stretch at ~2200 cm⁻¹ for C≡C.
  • Peaks for sp³ CH and sp CH.
• Conclusion: Identified as 1-octyne.

Example 6: Toluene

• IR Spectrum Features:
  • Peaks for sp² CH stretch ~3100-3200 cm⁻¹ and sp³ CH ~3000 cm⁻¹.
  • C=C stretch indicates aromatic character.
  • Mono-substituted peak indicates toluene structure.
• Conclusion: Compound is Toluene (C₇H₈).

Example 7: Meta-Substituted Benzene

• IR Spectrum Features:
  • Similar peaks as toluene but indicates meta-substitution.
• Conclusion: Meta-substituted aromatic compound.

Closing Thoughts

• Importance of recognizing and interpreting peaks in IR spectra.
• Viewers encouraged to engage with questions in the comments.
• Reminder to like and subscribe for more content.