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NAME: Brian Warner

PROJECT TITLE: Thermal Decomposition of Propionaldehyde

The thermal decomposition of aldehydes branches into many common processes such as the production of biofuels and the combustion of cigarettes. That is why it is important to identify the decomposition pathways of various aldehydes. This decomposition can lead to many products including highly reactive radicals. These radicals are difficult to capture using conventional spectroscopic techniques because their characteristic unpaired electron makes them highly reactive. In order to trap and detect the radical intermediates, matrix-isolation Fourier transform infrared spectroscopy (MI-FTIR) can be utilized. MI-FTIR uses cold temperatures (4 K) and a dilute matrix (1 sample: 400-1000 Ar) to measure vibrational spectra with sharp, easily identifiable absorption peaks. This technique can be used to identify radicals and other pyrolysis products from the thermal decomposition of molecules such as propionaldehyde.

            For this experiment, the thermal decomposition of propionaldehyde will be induced by a pyrolysis valve, and MI-FTIR will be used to determine the identity of the products produced. The pyrolysis valve provides an oxygen free environment for the reactions to take place. A few reactions that may take place when propionaldehyde is exposed to high temperatures are:

CH3CH2CHO + ∆                                   CH3CH2 + CO + H          radical decomposition,
CH3CH2CHO + ∆                                   CH3CH=C=O + H2          elimination,
CH3CH2CHO + ∆                                   CH3C≡CH + H2O            isomerization/elimination.

Spectra obtained will enable the identification of these products as well as products from unpredicted reaction pathways. The results can also be used to help determine the reaction mechanisms for the thermal decomposition of propionaldehyde.

            Experiments on other aldehydes, such as butyraldehyde, have been conducted and the results are being analyzed. It is suspected that propionaldehyde will follow a similar reaction pathway as butyraldehyde due to the structural similarities between the two molecules. It will be an interesting point of analysis to determine the differences between the molecules that differ by only a methylene group.


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