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Infrared Spectroscopy Table definitions

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  • Wave Number
    Numerical value representing the frequency of IR absorption, crucial for identifying specific bond types in molecules.
  • Carbonyl Region
    Section of the IR spectrum around 1700 cm⁻¹, where various carbonyl-containing compounds show characteristic absorptions.
  • Fingerprint Region
    Area below 1500 cm⁻¹ in the IR spectrum, often ignored due to its complexity and lack of specificity for functional group identification.
  • Conjugation
    Structural feature allowing resonance with adjacent double bonds, typically lowering IR absorption values by about 20 cm⁻¹.
  • Banana Bonds
    Highly strained bonds in small rings, causing IR absorptions to shift about 100 cm⁻¹ higher than expected.
  • Complex Carbonyl
    Functional group with a carbonyl that produces multiple IR absorption peaks due to additional bonds, such as O–H or C–H.
  • Acid Chloride
    Carbonyl compound with a chlorine atom, showing the highest absorption in the carbonyl region, typically around 1790 cm⁻¹.
  • Aldehyde
    Carbonyl compound with a hydrogen attached, displaying two IR absorptions: one in the carbonyl region and another near 2700 cm⁻¹.
  • Cumulene
    Molecule with consecutive double bonds, absorbing in the 1900–2000 cm⁻¹ range of the IR spectrum.
  • Nitrile
    Functional group with a carbon–nitrogen triple bond, absorbing slightly higher than alkynes, typically between 2210–2300 cm⁻¹.
  • Terminal Alkyne
    Alkyne located at the end of a carbon chain, showing both a triple bond and a C–H absorption in the IR spectrum.
  • Alcohol
    Functional group with an O–H bond, producing a broad, strong IR absorption typically spanning the 3200–3600 cm⁻¹ region.
  • Amines
    Nitrogen-containing functional groups, showing smaller, less broad IR absorptions in the same region as alcohols.
  • Percent Transmittance
    Y-axis measurement in IR spectra, indicating how much light passes through a sample at each wave number.
  • Mnemonic CORN
    Memory aid for recalling the order of carbonyl absorptions: Chloride, Oxygen (acid/ester), R/H (aldehyde/ketone), Nitrogen (amide).