Calculations of Prebiotic Molecules Formed from O(1D) Insertion Reactions Pubblico
Anderson, Thomas Andrew (2010)
Abstract
Abstract
Calculations of Prebiotic Molecules Formed from O(1D)
Insertion Reactions
By Thomas Anderson
This work explores the stationary points on the potential energy
surface for the
reactive organic molecules methanediol, methoxymethanol, and
aminomethanol. These
molecules are predicted by astrochemical models to be the small
molecular precursors to
larger, biologically-relevant molecules such as sugars and amino
acids in interstellar
environments. These three molecules are highly unstable and
therefore very short-lived
under regular laboratory conditions. Yet many such molecules are
present in interstellar
clouds, often at high abundance because their lifetimes are
significantly increased at the
low pressures and temperatures of interstellar environments. To
identify a molecule in
space, a rotational spectrum must be taken in the laboratory and
compared to
observational spectra. Due to the reactivity and instability of
these prebiotic precursors,
however, the gas phase spectra are not easily obtained, and
efficient laboratory
production mechanisms must be explored. O(1D) insertion reactions
into C-H bonds of
stable organic molecular precursors are one possible production
route for these molecules
because these reactions are highly exothermic, and therefore highly
efficient. To
examine the feasibility of such reactions for laboratory production
of these molecules, the
energies and structures of the singlet and triplet state minima and
transition states for
these three molecules were calculated at the MP2/Aug-cc-pVTZ level
of theory. These
results will serve as a starting-point for higher-level
calculations of the full potential
energy surface. In addition to the target molecules, the starting
material for each insertion
reaction as well as other potential molecular products were
investigated.
Table of Contents
Table of Contents
Chapter 1 Background
1
1.1
Introduction
..................................................................................................1
1.2
Atomic Oxygen
............................................................................................2
1.3
Methanediol and Methoxymethanol
............................................................4
1.4
Aminomethanol and N-Methylhydroxylamine
............................................5
1.5
Calculations..................................................................................................6
Chapter 2 Starting Materials
7
2.1
Introduction
..................................................................................................7
2.2
Atomic Oxygen
............................................................................................8
2.3
Methanol
......................................................................................................8
2.4
Dimethyl Ether
...........................................................................................10
2.5
Methylamine
..............................................................................................11
Chapter 3 Singlet Optimizations
13
3.1
Introductions
..............................................................................................13
3.2
Methanediol
...............................................................................................14
3.3
Methoxymethanol
......................................................................................16
3.4
Aminomethanol..........................................................................................21
3.5
N-Methylhydroxylamine............................................................................24
Chapter 4 Triplet Optimizations
28
4.1
Introductions
..............................................................................................28
4.2
Methanediol
...............................................................................................29
4.3
Methoxymethanol
......................................................................................32
4.4
Aminomethanol..........................................................................................34
4.5
N-Methylhydroxylamine............................................................................37
Chapter 4 Disscussion and Conclusions
41
5.1
Introductions
..............................................................................................41
5.2
Methanediol
...............................................................................................42
5.3
Methoxymethanol
......................................................................................43
5.4
Aminomethanol and N-Methylhydroxylamine
..........................................43
5.5
Summary
....................................................................................................44
Appendix A Starting Materials
46
Appendix B Singlet Molecules
47
B.1
Singlet Methanediol
...................................................................................47
B.2
Singlet Methoxymethanol
..........................................................................48
B.3
Singlet Aminomethanol
.............................................................................52
B.4
Singlet N-Methylhydroxylamine
...............................................................55
Appendix C Triplet Structures
57
C.1
Triplet Methanediol
...................................................................................57
C.2
Triplet Aminomethanol
..............................................................................57
Bibliography
59
List of Figures
2.01
MP2/Aug-cc-pVTZ optimized structure of
methanol..................................9
2.02
MP2/Aug-cc-pVTZ optimized structure of dimethyl ether.
......................10
2.03
MP2/Aug-cc-pVTZ optimized structure of
methylamine..........................12
3.01
Structures of the two methanediol singlet
conformations..........................13
3.02
Transition states of methanediol at the following relative
energies. .........15
3.03
Relative energies of the methanediol conformers and internal
motion
transition
states.......................................................................................................16
3.04
Structures of the three methoxymethanol singlet conformations at
the
following relative energies.
....................................................................................18
3.05
Structures of the five methoxymethanol singlet transition
states
determined by QST2 optimization.
........................................................................19
3.06
energies of the stationary points for singlet methoxymethanol.
................20
3.07
Structures of the four aminomethanol singlet conformations.
...................22
3.08
Structures of the four aminomethanol singlet transition
states
determined by QST3 optimization.
........................................................................23
3.09
Relative energies of the stationary points for singlet
aminomethanol .......24
3.10
The two stable structures of N-methylhydroxylamine singlet
conformations.
.......................................................................................................25
3.11
Transition states of N-methylhydroxylamine at the following
relative
energies
..................................................................................................................26
3.12
Relative energies of the stationary points for singlet
N-methylhydroxylamine.
.......................................................................................26
4.01
Triplet structures of methanediol.
..............................................................30
4.02
Relative energy level diagram of the singlet and triplet states
of
methanediol.
...........................................................................................................31
4.03
Example triplet dissociation structure of methoxymethanol.
....................32
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