<p>For decades there has been
interest in understanding early prebiotic Earth, including its atmospheric
chemistry. Saturn’s moon Titan is the only other body in our Solar System with
an atmosphere thought to resemble that of early Earth’s, and for this reason it
has garnered a lot of attention over the years. Much is now known about the
smaller molecules present in that atmosphere, starting with the most abundant,
N<sub>2</sub> and CH<sub>4</sub>, and going up to slightly larger molecules
such as cyanoacetylene and benzene. As the molecules get larger, however, so does
the gap in knowledge, especially as it pertains to nitriles. This dissertation
aims to add to the story of Titan’s nitriles by first characterizing a molecule
thought to be the photochemical product of the reaction between cyanoacetylene
and benzene, 3-phenyl-2-propyne-nitrile (PPN). The UV spectra of PPN proved
immensely interesting due to the strong presence of in-plane and out-of-plane
vibrations of b<sub>2</sub> and b<sub>1</sub> symmetry, respectively. This is
possibly a result of strong vibronic coupling between several excited
electronic states or Coriolis coupling between complementary b<sub>1</sub> and
b<sub>2</sub> vibrational levels.
The multi-layer extension of the multi-configuration time dependent Hartree
(ML-MCTDH) algorithm was used to understand how the excited states and the vibrational
levels might interact, and emission and absorption spectra were modeled and
compared to the experimental spectra. The second group of molecules studied included
the <i>ortho</i>-, <i>meta</i>-, and <i>para</i>-methyl
PPN. Strong methyl rotor activity is seen in the <i>m</i>-methyl PPN, with some activity in the <i>p</i>-methyl PPN. The methyl rotor activity in the <i>m</i>-methyl PPN is similar to other <i>meta</i>-substituted toluenes, and allows us to describe the methyl
rotor barrier height in both ground and excited electronic state. Additionally,
in all three methylated PPNs we see evidence for strong vibronic coupling in
the abundance of out-of-plane vibrations, as had been seen in PPN.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/8041067 |
| Date | 11 June 2019 |
| Creators | Khadija M Jawad (6634604) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/The_UV_spectroscopy_of_3-phenyl-2-propynenitrile_and_it_s_methylated_derivatives/8041067 |
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