7.2.2 Interpretation of IR Spectra

• What is Infrared (IR) Spectroscopy used for?

  Identifying functional groups
• IR Spectroscopy measures the absorption of infrared radiation at specific frequencies.
• The infrared region of the electromagnetic spectrum is divided into near-IR, mid-IR, and far-IR bands.
• Match the region of the electromagnetic spectrum with its corresponding application:

  Gamma Rays ↔️ Cancer treatment

  Ultraviolet (UV) ↔️ Sterilization

  Infrared (IR) ↔️ Spectroscopy

  Microwaves ↔️ Microwave ovens
• What is stretching in molecular vibrations?

  Change in bond length
• Bending in molecular vibrations refers to changes in bond angle.
• Molecular vibrations in IR spectroscopy include both stretching and bending of chemical bonds.
• What are functional group peaks in IR spectra used for?

  Identifying functional groups
• Match the functional group with its approximate absorption range in IR spectra:

  O-H ↔️ 3200-3600 cm⁻¹

  C=O ↔️ 1650-1750 cm⁻¹

  C≡N ↔️ 2200-2300 cm⁻¹

  C-H ↔️ 2850-3100 cm⁻¹
• What does an IR spectrum provide for a molecule?

  Unique fingerprint
• The IR region of the electromagnetic spectrum is used in IR spectroscopy to identify functional groups in molecules.
• What is the crucial region for molecular identification in spectroscopy?

  Infrared region
• Molecules absorb specific frequencies in the infrared region corresponding to their functional groups
• Order the steps involved in molecular vibrations upon IR absorption:

  1️⃣ Molecules absorb IR radiation

  2️⃣ Bonds vibrate

  3️⃣ Molecular vibrations occur
• What type of vibration involves a change in bond length?

  Stretching
• Bending vibrations involve a change in bond angle.
• Which molecule is mentioned as an example for molecular vibrations?

  CO2
• Functional groups in molecules absorb infrared radiation at specific wavelengths
• What is the absorption range for O-H bonds in alcohols?

  3200-3600 cm⁻¹
• The absorption ranges for functional groups are crucial for their identification in IR spectra.
• What is the absorption range for C=O bonds in ketones?

  1680-1750 cm⁻¹
• Different functional groups absorb IR radiation at specific frequencies, creating a unique IR spectrum.
• In which functional group is the O-H bond found, and what is its absorption range?

  Alcohols, 3200-3600 cm⁻¹
• Comparing an IR spectrum to known absorption ranges allows for molecular structure determination.