الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
In the current work, we have performed computational studies on
thermodynamics and kinetics unimolecular and bimolecular decomposition
reactions of 1,2-ethanediol monoacetate. In the latter case, methyl radical
(•CH3) was used. All calculation were carried out using high level ab initio
(CBS-QB3, G3MP2) and density functional theory (DFT) (BMK/6-
31+G(d, p) methods. The results were compared with n-butanol and ethyl
acetate data to examine the consequence of presence of the ester group.
The thesis consists of three chapters as follows:
Chapter 1 presents introduction of different categories of energy
resources, non- renewable and renewable energy resources. Using of nonrenewable
sources as fuels became limited in many countries because of
gases emission. Various forms of renewable energy sources were
discussed. Biofuels represent one of the promising renewable energy
resources. Among different biofuel compounds, bioalcohols, bioesters and
biodiesel were reviewed.
Small bioalcohols like biomethanol and bioethanol have many defects
as biofuels such as low internal energy, high vapor pressure, low boiling
point, , high vapor pressure and some of them has a toxic properties. Those
lead to emission large quantities into environment.
Recently, researchers have developed many chemical techniques to
produce ethylene glycol from biomass. Ethylene glycol is viscous liquid
used as a coolant for automotive engines and characterized by high
viscosity, low melting point -13 °C, high hydrophobicity, and toxicity.
Production of 1,2-ethanediol monoacetate could be prepared from
ethylene glycol in acetic acid solution containing LiNO3 and Pd(OAc).
1,2-ethanediol monoacetate has many advantages over lower
alcohols, and ordinary esters such as high internal energy, low water
absorption, low toxicity, high boiling point, besides providing easiest and
fastest H-abstraction. So, it can easily decomposed at both atmospheric and
combustion regime.
Therefore, our attention in this work was paid to 1,2-ethanediol
monoacetate decomposition as model biofuel because of expected good
ignition behavior due to its high oxygen content, low vapor pressure, high
internal energy compared to its constituents.
Chapter 2 gives a short background on quantum chemical calculations
and a detail description of the procedures used throughout this work.
Geometry optimizations have been performed at the BMK/631+G (d, p)
levels of theory. For all stationary points we have carried out frequency
calculations at the same level to characterize their nature as minima or
transition states and to correct energies for zero-point energy and thermal
contributions. IRC calculations carried out at BMK/6-31+g (d, p). Ab
initio multilevel (CBS-QB3, G3MP2) procedures also have been used to
obtain more accurate results.
Chapter 3 presents results and discussion which can be summarized
as follows:
1,2-ethanediol monoacetate has four conformers with high stability of
M3 conformer due to intra-molecular hydrogen bond (IHB) relative to the
rest of configurations.
Bond dissociation energies (BDEs) of 1,2-ethanediol monoacetate at CBSQB3
show the following:
1. The Cα-Cβ and Cβ-O bonds are the weakest bonds and have
comparable strength.
2. O-H alcoholic bond is strongest bond 107.23 kcal/mol.
3. The C-H bonds strengths of 1,2-ethanediol monoacetate follow the
order Cα- H < Cδ-H < Cβ-H.
4. Enthalpies of formation from isodesmic equations at BMK/6-
31+G(d, p) and atomization energies at CBS-QB3 level give the
most accurate results when compared with the available
experimental data and gives confidence on the unknown value.
Pyrolysis of 1,2-ethanediol monoacetate can proceed through either
complex or simple decompositions. The first type represents reactions,
which precedes through cyclic transition states, while the second type
includes simple fission of bonds to produce radicals.
This work investigated sixteen channels for 1,2-ethanediol
monoacetate decomposition including seven H-transfer reactions and nine
simple bond fission reactions. Potential energy diagram indicates that the
formation of acetic acid and vinyl alcohol represents the most
thermodynamically and kinetically preferable reaction until 400 K. After
that, production of vinyl acetate becomes the main channel. The calculated
enthalpies of formation for 1,2-ethanediol monoacetate and its radicals
show a good agreement with the available experimental data. All of the
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investigated channels are endothermic and the degree of endothermicity
depends of the type of reaction.
Rate constants calculations for all channels at different temperatures
were computed using the transition state theory (TST) in conjunction with
Wigner correction.
Bimolecular oxidation of 1,2-ethanediol monoacetate using methyl
radical (•CH3) has been done. Thermochemistry and kinetics of 1,2-
ethanediol monoacetate oxidation has been studied using density
functional theory BMK/6-31+G(d,p) and ab initio CBS-QB3 calculations.
Oxidation by methyl radical (•CH3)of 1,2-ethanediol monoacetate occurs
through H-abstraction reactions. 1,2-ethanediol monoacetate has four
positions for H-abstraction (alpha, beta, delta, and alcoholic position).
Comparison has been done between1,2-ethanediol monoacetate results and
with n-butanol and ethyl acetate results.
The comparison between between1,2-ethanediol monoacetate
oxidation and with n-butanol and ethyl acetate oxidation by methyl radical
(•CH3) shows the effect of structures from one to other.
1,2-ethanediol monoacetate could function as a biofuel because of
its physical properties and decomposition pattern that is comparable to
alcohols and esters.