59th Annual Report on Research 2014

Technical Progress: Pyrolysis of Aldehydes

The pyrolysis of branched-alkyl chain aldehydes has been studied in a pulsed hyperthermal nozzle.  The goal of these experiments is to identify, via matrix-isolation FTIR, the products of gas-phase pyrolysis of pivaldehyde and isovaleraldehyde. (Figure 1)  This information will ultimately lead to a better understanding of the pyrolysis mechanism.  The results will be compared to the pyrolysis products of small, unbranched aldehydes that are described in the literature: acetaldehyde, propionaldehyde, and butyraldehyde. 

    pivaldehyde                     isovaleraldehyde

Figure 1.  Aldehydes studied in the 2013-2014 grant year

In the first year of PRF support, pyrolysis experiments were completed on both isovaleraldehyde and pivaldehyde.  Pyrolysis temperatures of 600-1200 ºC were employed on mixtures of 0.01-0.4% of the sample in argon, for each aldehyde.  While the assignment of the matrix-isolation FTIR spectra collected following pyrolysis will carry into the second year of PRF support, preliminary analysis has identified various products.  Several alkenes have been identified in the pyrolysis of both aldehydes.  For example, Figure 2 shows spectral signatures of ethylene and propene following the heating of pivaldehyde to 1000 ºC.

Figure 2.  Matrix-isolation FTIR spectra collected (A) following pyrolysis of pivaldehyde at 1000 °C and (B) of an unheated sample

Technical Progress: Isolation of the Acetonyl Radical

The goal of this project is to produce the acetonyl in the gas phase and isolate it in an argon matrix for characterization via FTIR.  To accomplish this, 4-nitrosooxy-2-butanone is investigated as a possible pyrolytic precursor molecule.  In the first year of PRF support, this precursor was synthesized as shown in Figure 3.  The short shelf life of this commercially unavailable molecule necessitates frequent synthesis during the course of the study.  Several trials of the synthetic reaction were conducted in order to optimize the yield and purity of the product.  Preliminary pyrolysis experiments of 4-nitrosooxy-2-butanone were conducted at 725 ºC.  Formaldehyde has been identified as one of the products of pyrolysis.  Future work will focus on determining if the acetonyl radical has been produced as well, via the pyrolysis step shown in Figure 3.  Various experimental conditions will be tested to optimize the production and trapping of the radical.          

    Figure 3.  Synthesis of 4-nitrosooxy-2-butanone and the suspected reaction for subsequent pyrolysis

Impact on Undergraduate Students

Two students were directly supported by PRF funds in the summer of 2014.  Brian Warner is a senior at Marshall University majoring in chemistry and biology.  Eric Sias is a sophomore chemistry major. Emily Wright, a senior chemistry major, also contributed to PRF-funded projects in Summer 2014, but her stipend was provided the Marshall Department of Chemistry’s Roger Combs Summer Research Fellowship.  All three of these students assisted in the collection of matrix-isolation FTIR spectra for the projects described here.  Brian has taken responsibility for assigning infrared spectra to identify products from pyrolysis of both isovaleraldehyde and pivaldehyde.  Eric conducted the synthesis of 4-nitrosooxy-2-butanone.  These students are continuing their research in the 2014-2015 academic year. 

The benefit to the involved students far exceeds their summer employment.  The students participated in the Department of Chemistry’s summer research program, which included approximately 20 undergraduate students, M.S. students, and local high school students and teachers working in Marshall chemistry faculty labs.  Participants gave short proposal talks at a kickoff luncheon, toured a local chemical plant, and engaged in social activities with professors.  The summer experience culminated in a formal research symposium featuring 10-15 minute oral presentations. 

Impact on Career of the PI

Securing research support from PRF was a highlight in the PI’s recent successful application for tenure and promotion to Associate Professor at Marshall University.  The PI plans to use grant funds to attend several meetings so she may keep current in her field and pursue collaborations with experts in complementary areas of research.  The undergraduate stipends provided by PRF also ensure a stable pool of student researchers in the lab for three years.  This will maintain a desired level of productivity and allow for continuity of expertise as upperclassmen train new students.