Summary of ir stretching frequencies pdf

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Note that Aromatic compounds because of the large number of C Department of Chemistry and Biochemistry The Michael Faraday Laboratories, NIU DeKalb, IL () Typical IR Absorption Frequencies For Common IR Spectrum Table by Frequency Range Absorption (cm-1) Appearance Group Compound Class Medium N-H stretching secondary amine Medium C-H Infrared (IR) spectroscopy is one of the most common spectroscopic techniques used by organic and inorganic chemists. Therefore, the functional groups present in a molecule can be deduced from When analyzing an IR spectrum: never consider absorptions in the fingerprint region. The most useful bands in an infrared spectrum correspond to stretching frequencies, and those will be the ones we’ll focus on. Graphics source: Wade, Jr., L.G. Organic Chemistry, 5th ed. Only look in the FG region. Infrared Spectroscopy. Simply, it is the absorption measurement of different IR • Covalent bonds can vibrate in several modes, including stretching, rocking, and scissoring. Pearson Education Inc., Table of Characteristic IR Absorptions. frequency, cm –– (s, sh) – (s,b) – (m) – (m) – (n, s) – (s) – (m) – (m) – (m) – (v) – (w) – (s) – (s) – (s) – (s) – (s) (s) – IR Stretching Frequencies: What Do they Depend On? Directly on the strength of the bonding between the two atoms (~ k) Inversely on the reduced mass of the two atoms (v ~ 1/m) Expect: will increase with increasing bond strength (bond order) and reasing mass Examples of stretching frequencies and correlations with bond strengths (bond order) Typical IR Absorption Frequencies For Common Functional Groups Bond Functional Group Frequency in cm(Intensity*) C-H Alkane (s)-CH(m)-CH (m) Alkene (m), (s) Aromatic (s), (s) Alkyne (terminal) (s) Aldehyde(w) C=C Alkene (w-m) Aromatic (w-m) Provides information about the vibraions of functional groups in a molecule.