IR Adsorption Bands: Problem 32 a,e Ashley Johnson November 26, 2001

Adsorption Bands A compound exposed to radiation of a frequency that matched the frequency of one of its vibrations absorbs the energy , causing the bond to intensify a stretch or bend. By determining the wavenumbers of light absorbed by a compound, the kind of bonds it has can be found. (pg 497) Wavenumber-(another way to describe frequency) the number of waves in one centimeter

IR Spectrum Functional group region is where functional group of a compound shows adsorption (4000-1400 cm-1.) (Stretch vibrations are found in functional group region.) The fingerprint region is at 1400-600 cm-1 and is specific for each compound. (pg 498)

Problem 32 a. Give one adsorption band that could be used to distinguish between the compounds.

Problem 32 a. An aldehyde group adsorbs radiation at 2740 cm-1, so this absorption band is present for the first compound and absent for the second compound. (pg 513)

32 e. Give one adsorption band that could be used to distinguish between the compounds.

32 e. The hydrogen bonded to sp2 carbons of a benzene ring have adsorption bands at 1600 cm-1 and between 1500-1430 cm-1 Adsorption bands of 2960-2850 cm-1 would be present for the cyclohexane but absent for the benzene ring. (pg 506)