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Downloading a Copy of IR Tutor. See the course home page for instructions on how to download zip file that will allow you to obtain a copy of the program "IR Tutor". Both a Mac and PC version are available

Playing with IR Tutor. IR Tutor (IR = infrared)is an interactive software program developed at Columbia University in the early 1990s by Professor Turro and Professor Fine and produced byCharles Abrams, who was a student here at the time. IR Tutor will be the basis for learning how to interpret infrared spectra. Of the various forms of spectroscopy, IR spectroscopy allow us to "see" the functional groups in a molecule against the background of a hydrocarbon backbone. Absorption of IR light causes the excitation of vibrations of a molecule, not the excitation of the electrons of amolecule, which is the case when UV or visible light is absorbed. Vibrations consist of the motion of two or more atoms relative to one another. The frequencies and energies of these vibrations depend on the kinds of bonds that connect the atoms together and the masses of the atoms. The following rules will serve as an important guideline: The frequency of a vibration will increase as the strengthof the bond between the atoms increases and will decrease as the masses of the atoms involved in the vibration increase. Thus, the frequency increases with increasing bond strength and decreases with increasing mass. These rules come from the use of a simple harmonic oscillator for vibrating atoms, as is explained by IR Tutor and the reading which was sent to you earlier in the week. Recall thatfunctional groups provide atoms with characteristic spectroscopic properties. Each functional group will possess an absorption at a characteristic frequency. Thus, when inspecting an IR spectrum of an unknown, we look at certain frequencies to see if there is a signal for an absorption of light there. If there is one, we deduce the functional group is present in the molecule and if there is none, wededuce the functional group is absent. The Strategy of Using IR Tutor The basic idea is to first inspect the IR spectra of saturated hydrocarbons and to assign the signals to the vibrations of CH and CC atoms. These signal will be expected to occur in all compounds containing a functional group in addition to the saturated hydrocarbon "backbone". Any new signals that don't correspond to astandard must be assigned to the vibrations of a functional group. By going through the exercises below you will be able to figure out how to assign signals to the important functional groups such as C=C bonds, C=O bonds, etc. The Structure of IR Tutor IR tutor consists of three main modules: (1) (2) (3) Introduction. Theory of IR spectroscopy. Interpretation of IR spectra.

The third module,Interpretation of IR spectra, is the heart of the program. One can start there and play with the spectra after reading the following general information about the program.

(1)

The module Introduction provides a brief review of the following submodules: (a) Definition of spectroscopy. (b) Nature of light. (c) Measurement of IR spectra.

(2) The Theory of IR spectroscopy module provides a briefreview of the following submodules: (a) (b) (c) Classical model of a vibrating molecule Quantum mechanical model of a vibrating molecule Normal modes and group frequencies

(3) The Interpretation of Spectra module provides a brief review of the following submodules: (a) a set of spectra of the following molecules: n-hexane, 2,3-dimethylbutane, 1hexene, 1-heptyne, 1-heptylcyanide, methyl benzene(toluene), 1-hexanol, 1-hexylamine, 1heptaldehyde, 3-heptanone, ethyl acetate, butyric anhydride. (b) for each spectrum the vibration associated with each signal in the spectrum can be animated by simply clicking on the body of the peak. (c) under the control menu a summary of all of the key vibrations can be see in one screen. (d) Under the overlay menu the spectra of several molecules can be...