Other Functional Groups Infrared absorption data for some functional groups not listed in the preceding table are given below. Table 1: Principal IR Absorptions for Certain Functional Groups Functional Group Names & Example compounds Absorption Ranges(cm-1) [Look for a single absorption in these regions, unless stated otherwise.] An infrared spectroscopy correlation table (or table of infrared absorption frequencies) is a list of absorption peaks and frequencies, typically reported in wavenumber, for common types of molecular bonds and functional groups. Functional Group Frequency (cm-1) intensity; water OH Stretch: 3700-3100: strong: alcohol OH stretch: 3600-3200: strong: carboxylic acid OH stretch: 3600-2500: strong If you shine infrared light on a molecule, it is possible that the molecule absorbs energy from light. Answer to 1. As such, it will be a valuable tool throughout this year. Try to associate each spectrum (A - E) with one of the isomers in the row above it. Infrared spectroscopy is a technique used to identify various functional groups in unknown substances through the identification of different covalent bonds that are present in the compound. IR spectra of organic compounds have two general areas: 4000-1500 cm-1: 1500-400 cm-1: The Functional Group Region . IR Spectroscopy by Functional Group Alkanes Indentification of absorbance Wavenumbers, cm-1 sp3 C-H stretch 2960-2850 (<3000) Alkenes sp2 C-H stretch 3100-3020 cm-1 (>3000) C=C stretch 1680-1620 cm-1 (often weak) Alkynes sp C-H stretch 3333-3267 cm-1 C-C triple bond stretch 2260-2100 cm-1 (often weak) Nitriles Functional Groups We have seen that IR is really a "Functional Group Detector." You should become accustomed to examining an IR spectrum and looking for characteristic bands that indicate the presence of a Functional Group. IR peaks and functional groups of each spectrum (cyclohexene, trans-bromocyclohexanol, and epoxycyclohexane) 2. 4. Beauchamp Spectroscopy Tables 4 Z:\classes\spectroscopy\all spectra tables for web.DOC IR Flowchart to determine functional groups in a compound (all values in cm-1). By identifying the different covalent bonds that are present in a compound, you can establish the types of functional groups present. Type of Vibration causing IR absorption 3000-2800 (Note: The absorptions can be seen as several distinct peaks in this region.) This lab manual contains copies of spectra of various compounds. 26 CHARACTERISTIC INFRARED ABSORPTION BANDS OF FUNCTIONAL GROUPS Class of Compounds -Absorption, cm 1 Intensity -Assignment Class of Compounds Absorption, cm 1 Intensity Assignment Alkanes and 2850-3000 s C-H stretch Carboxylic Acids 2500-3500 s, broad O-H stretch Alkyls 1450-1470 s C-H bend R-C(O)-OH 1710-1715 s, broad C=O stretch When you have made assignments check your answers by clicking on the structure or name of each isomer. 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