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. By identifying the different covalent bonds that are present in a compound, you can establish the types of functional groups present. IR spectra of organic compounds have two general areas: 4000-1500 cm-1: 1500-400 cm-1: The Functional Group Region . When you have made assignments check your answers by clicking on the structure or name of each isomer. Answer to 1. 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. Other Functional Groups Infrared absorption data for some functional groups not listed in the preceding table are given below. Functional Groups We have seen that IR is really a "Functional Group Detector." 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 4. Peaks in this region are characteristic of specific kinds of bonds, and therefore can be used to identify whether a specific functional group is present. You should become accustomed to examining an IR spectrum and looking for characteristic bands that indicate the presence of a Functional Group. 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 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.] In physical and analytical chemistry, infrared spectroscopy (IR spectroscopy) is a technique used to identify chemical compounds based on the way infrared … 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 Absorbed energy can cause a bond to stretch or bend.We call that a stretching or bending vibration. As such, it will be a valuable tool throughout this year. 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