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Dissertations / Theses on the topic 'Chemical reactions'

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Published: 4 June 2021
Last updated: 1 August 2024

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1

Wickham, Andrew. "Fast chemical reactions." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309276.

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2

Steele, Aaron J. "Collective behavior in chemical systems." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5386.

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Thesis (Ph. D.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains vii, 126 p. : ill. (some col.) + video files. Includes supplementary video files in a zip file. Includes abstract. Includes bibliographical references.
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3

Ginovska, Bojana. "Computational study of chemical reactions." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/B_Ginovska_112607.pdf.

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4

Parsons, R. W. "Mathematical models of chemical reactions." Thesis, Bucks New University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371228.

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5

Miners, Scott A. "Chemical reactions inside carbon nanotubes." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33062/.

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The work presented in this thesis describes the development and application of strategies to evaluate the influence of extreme confinement within narrow single-walled carbon nanotubes (SWNT) on the pathways of preparative chemical reactions. Methodologies to reduce carbon nanotube length were critically assessed in order to aid the access and egress of reactants and products to and from the SWNT internal channel during confined reactions. A reliable procedure for the encapsulation of organic molecules within carbon nanotubes was developed utilising a novel fractional distillation procedure which exploits the effect of nanoscale confinement on the phase behaviour of liquids. Confinement of the halogenation of N-phenylacetamide within SWNT demonstrated, for the first time, that narrow SWNT are effective hosts for chemical reactions on a preparative scale in the absence of metallic catalysts. The selective formation of the para-brominated regioisomer improved from 68 to 97% as a direct result of confinement. Furthermore, the confinement of a range of azide-alkyne 1,3-dipolar cycloaddition reactions within SWNT showed a consistent increase in selectivity for the 1,4-triazole (up to a 55% increase). The magnitude of this effect can be tuned by varying the SWNT diameter or the steric bulk of the reactant substituents. In addition to the dominant steric factors, the results herein suggest that the electronic properties of carbon nanotubes induce an additional, more subtle influence on selectivity. Investigating the autocatalytic Soai reaction in the presence of carbon nanotubes demonstrated, on a fundamental level, that the helicity of SWNT induces an effect on the formation of chiral molecules. Since carbon nanotubes exist as a racemic mixture of P and M enantiomers, their presence has a symmetrising effect whereby an enantioselective Soai reaction affording 90% ee becomes racemic upon the addition of (6,5)-SWNT. These results clearly demonstrate the ability of carbon nanotubes to influence the properties of preparative chemical reactions.
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6

Denuault, Guy. "Microelectrode studies of chemical reactions." Thesis, University of Southampton, 1989. https://eprints.soton.ac.uk/179323/.

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Neumann's integral theorem has been used to establish exact analytical solutions for chronoamperometric experiments and for the steady state limiting current for CE and catalytic EC mechanisms. To convert these solutions into a useful form, FORTRAN programs have been written for the necessary numerical calculations. The analytical response of microdiscs, for chronoamperometry as well as the steady state for CE and EC' reactions is presented. A different theoretical approach, as well as digital simulations, are used for the interpretation of steady state limiting currents for EC' reactions, in particular, silver(II)-substrate coupled reactions. The radius dependence of the ratio between the kinetically and the diffusion controlled currents has been calculated for various kinetic schemes. The anodic oxidations of Cr(III), water and of Mn(II) in the presence of catalytic quantities of Ag(I), were investigated using Pt microdiscs with radii between 0.3 and 62.5 m. Because of the enhanced rate of diffusion to microelectrodes, kinetic currents are observed for the Ag(I) mediated oxidation of Cr(III). It is shown that there is good agreement between the experimental i_k/i_d= f(a) plots and those computed assuming a mechanism where the rate determining step is electron transfer from Cr(III) to Ag(II). The rate constant was determined as 9x10^6 mol^-1 cm^3 s^-1. The Ag(II)-Mn(II) reaction must be substantially faster since in most conditions the measured current is determined by the diffusion of Mn(II) to the surface. As expected but in complete contrast, the Ag(II) water reaction is too slow to observe kinetic currents at microelectrodes.
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7

Larsson, Per-Erik. "Modelling Chemical Reactions : Theoretical Investigations of Organic Rearrangement Reactions." Doctoral thesis, Uppsala University, Department of Quantum Chemistry, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3475.

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Chemical reactions are ubiquitous and very important for life and many other processes taking place on earth. In both theoretical and experimental studies of reactivity a transition state is often used to rationalise the outcome of such studies. The present thesis deals with calculations of transition states in radical cation rearrangements, and a principle of least motion study of the rearrangements in the barbaralyl cation.

In particular, alternative quadricyclane radical cation (Q∙+) rearrangements are extensively studied. The rearrangement of Q∙+ to norbornadiene is extremely facile and is often used as a prototype for one-electron oxidations. However, electron spin resonance (ESR) experiments show that there are additional cations formed from Q∙+. Two plausible paths for the rearrangement of Q∙+ to the 1,3,5-cycloheptatriene radical cation are located. The most favourable one is a multistep rearrangement with two shallow intermediates, which has a rate-limiting step of 16.5 kcal/mol. In addition, a special structure, the bicyclo[2.2.1]hepta-2-ene-5-yl-7-ylium radical cation, is identified on these alternative paths; and its computed ESR parameters agree excellently with the experimental spectrum assigned to another intermediate on this path. Moreover, this cation show a homoconjugative stabilization, which is uncommon for radical cations.

The bicyclopropylidene (BCP) radical cation undergoes ring opening to the tetramethyleneethane radical cation upon γ-irradiation of the neutral BCP. This rearrangement proceeds through a stepwise mechanism for the first ring opening with a 7.3 kcal/mol activation energy, while the second ring opening has no activation energy. The dominating reaction coordinate during each ring opening is an olefinic carbon rehybridization.

The principle of least motion is based on the idea that, on passing from reactant to product, the reaction path with the least nuclear change is the most likely. By using hyperspherical coordinates to define a distance measure between conformations on a potential energy surface, a possibility to interpret reaction paths in terms of distance arises. In applying this measure to the complex rearrangements of the barbaralyl cation, a correct ordering of the conformations on this surface is found.

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8

Liu, Z. "Insight into chemical reactions : from heterogeneous to enzymatic reactions." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398116.

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9

Reding, Derek James. "Shock induced chemical reactions in energetic structural materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28174.

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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Hanagud, Sathya; Committee Member: Kardomateas, George; Committee Member: McDowell, David; Committee Member: Ruzzene, Massimo; Committee Member: Thadhani, Naresh.
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10

Beta, Carsten. "Controlling chemical turbulence in surface reactions." [S.l. : s.n.], 2005. http://www.diss.fu-berlin.de/2005/14/index.html.

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11

Santiso, Erik Emilio. "Effect of Confinement on Chemical Reactions." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-08102007-145433/.

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The goal of this project is to gain a fundamental understanding of the different factors that influence chemical reactions in confinement through the systematic study of simple model systems. For this purpose, we consider three different examples: (1) The rotational isomerization of small hydrocarbons in carbon nanopores, showing the impact of the steric hindrance imposed by the confining material on the reacting system; (2) The unimolecular decomposition of formaldehyde on carbon pores, as an example of the effect of physical interactions on a reaction?s mechanism and equilibrium; and (3) The thermal splitting of water over defective graphene and nanotube surfaces, showing how chemical interactions with a catalytic substrate can completely modify the chemical landscape and hence the equilibrium and dynamics of the system. Our main findings from these studies are: (1) In the molecular sieving limit, the steric hindrance imposed by the pore walls can cause dramatic changes in the potential energy surface of a reaction, with the rate varying as the double exponential of the pore dimensions; (2) Physical interactions with a catalytic support can alter both the thermodynamic properties of the confined molecules and the reaction dynamics, the latter being especially important in reactions with relatively low activation barriers; (3) Chemical modification of a carbon substrate can give rise to completely different reaction mechanisms, which could be exploited in the systematic molecular-level design of improved catalytic materials.
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12

Száraz, Ildikó. "Chemical reactions in aluminium electrolytic capacitors /." Luleå, 2003. http://epubl.luth.se/1402-1544/2003/05.

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13

Hought, Julian L. "Advanced control of batch chemical reactions." Thesis, University of Huddersfield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314422.

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14

Bondi, D. K. "The quantum theory of chemical reactions." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382755.

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15

Šepelák, Vladimír, Paul Heitjans, and Klaus-Dieter Becker. "Mössbauer spectroscopy for studying chemical reactions." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186672.

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16

Šepelák, Vladimír, Paul Heitjans, and Klaus-Dieter Becker. "Mössbauer spectroscopy for studying chemical reactions." Diffusion fundamentals 12 (2010) 23, 2010. https://ul.qucosa.de/id/qucosa%3A13874.

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17

Rowe, Stephen Michael. "The use of reaction inhibition techniques for control of runaway polymerisation reactions." Thesis, London South Bank University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336802.

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18

Adesina, Olumide, Cassandra T. Eagle, Ayobami Olukanni, and Reza Mohseni. "Purification of Cyclohexene for Cyclopropanation Reactions." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/143.

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Environmentally friendly reactions yielding cis-cyclopropanes are desired in the insecticide industry as these are most effective at reducing the population of insects while remaining benign to the environment. We are exploring the best parameters for the most effective cis-cyclopropanation reactions. An alkene and a diazo compound react together in the presence of a dirhodium catalyst to produce cyclopropanes. First however, the starting materials must be pure. Alfa Aesar supplies cyclohexene which is reported to be 99% pure, however, Gas column chromatography/Mass spectroscopy reveals that the sample is only 3% cyclohexene. Using an adopted published procedure, we discovered that distillation under nitrogen produces cyclohexene in greater than 95% pure. This is suitable for use in cyclopropanation reactions.
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19

Holder, Grant Newton. "Redox reactivity of mononuclear and binuclear rhenium complexes." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/30392.

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20

Mathews, Karen Lesley. "The Chemical and Cellular Basis of Allergic Reactions to Drugs and Chemicals." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507509.

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21

Liao, Rongzhen. "Quantum Chemical Cluster Modeling of Enzymatic Reactions." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-43026.

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The Quantum chemical cluster approach has been shown to be quite powerful and efficient in the modeling of enzyme active sites and reaction mechanisms. In this thesis, the reaction mechanisms of several enzymes have been investigated using the hybrid density functional B3LYP. The enzymes studied include four dinuclear zinc enzymes, namely dihydroorotase, N-acyl-homoserine lactone hydrolase, RNase Z, and human renal dipeptidase, two trinuclear zinc enzymes, namely phospholipase C and nuclease P1, two tungstoenzymes, namely formaldehyde ferredoxin oxidoreductase and acetylene hydratase, aspartate α-decarboxylase, and mycolic acid cyclopropane synthase. The potential energy profiles for various mechanistic scenarios have been calculated and analyzed. The role of the metal ions as well as important active site residues has been discussed.   In the cluster approach, the effects of the parts of the enzyme that are not explicitly included in the model are taken into account using implicit solvation methods.   For all six zinc-dependent enzymes studied, the di-zinc bridging hydroxide has been shown to be capable of performing nucleophilic attack on the substrate. In addition, one, two, or even all three zinc ions participate in the stabilization of the negative charge in the transition states and intermediates, thereby lowering the barriers.   For the two tungstoenzymes, several different mechanistic scenarios have been considered to identify the energetically most feasible one. For both enzymes, new mechanisms are proposed.   Finally, the mechanism of mycolic acid cyclopropane synthase has been shown to be a direct methyl transfer to the substrate double bond, followed by proton transfer to the bicarbonate.   From the studies of these enzymes, we demonstrate that density functional calculations are able to solve mechanistic problems related to enzymatic reactions, and a wealth of new insight can be obtained.
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22

Russell, Caroline. "Quantum mechanical wavepacket calculations on chemical reactions." Thesis, University of Oxford, 1998. https://ora.ox.ac.uk/objects/uuid:bc8fa8c2-7fbd-4fb4-bddf-8086442e36b7.

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The quantum mechanical time-dependent wavepacket method is introduced in the context of the field of chemical dynamics. The theory of the method is presented for two processes of interest in dynamics: molecular photodissociation, and reactive scattering. For the first of these processes, an expression is derived for the absorption spectrum of a molecule undergoing an electronic bound-continuum transition. For the second process, a time-dependent formulation is obtained for the S-matrix, and the "flux formulation" for the calculation of initial state-selected reaction probabilities (ISSRPs) is shown to be equivalent to summing over appropriate S-matrix elements. The time-dependent wavepacket theory for molecular photodissociation is used in the calculation of the photodetachment spectrum of the FH̅₂ anion. Spectra are calculated for two different energy resolutions, and previously unobserved structure is seen in the higher resolution spectrum. The structure is assigned by studying energy-dependent wavefunctions corresponding to each peak in the spectrum. Some peaks are assigned to direct scattering states, while others are assigned to quantum mechanical resonance states localised in the reactant and product valleys of the potential energy surface. The implication of this is that a high-resolution photodetachment experiment may provide the first experimental evidence for resonances in the F + H2 reaction. For reactive scattering, the time-dependent wavepacket method is used (in conjunction with the rotationally adiabatic approximation for J > 0 calculations) to calculate ISSRPs for various initial states of the nearly-thermoneutral ionmolecule reaction: N+(3P)+H2(1Σ+g)→NH+(X2II)+H(2S). Dense resonance structure in the reaction probabilities for J = 0 is attributed to the influence of the deep wells in. the potential energy surface for the reaction. The ISSRPs are used to calculate initial state-selected cross sections and rate constants which are compared with the results of some earlier trajectory calculations and with experimental data. The implications of the results for the astrophysical significance of the reaction are discussed.
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23

Hammar, Peter. "Quantum Chemical Studies of Enantioselective Organocatalytic Reactions." Licentiate thesis, Stockholm : Bioteknologi, Biotechnology, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4701.

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24

Moore, Emily L. "Laser studies of gas phase chemical reactions." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320640.

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25

Remmert, Sarah M. "Reduced dimensionality quantum dynamics of chemical reactions." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:7f96405f-105c-4ca3-9b8a-06f77d84606a.

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In this thesis a reduced dimensionality quantum scattering model is applied to the study of polyatomic reactions of type X + CH4 <--> XH + CH3. Two dimensional quantum scattering of the symmetric hydrogen exchange reaction CH3+CH4 <--> CH4+CH3 is performed on an 18-parameter double-Morse analytical function derived from ab initio calculations at the CCSD(T)/cc-pVTZ//MP2/cc-pVTZ level of theory. Spectator mode motion is approximately treated via inclusion of curvilinear or rectilinear projected zero-point energies in the potential surface. The close-coupled equations are solved using R-matrix propagation. The state-to-state probabilities and integral and differential cross sections show the reaction to be primarily vibrationally adiabatic and backwards scattered. Quantum properties such as heavy-light-heavy oscillating reactivity and resonance features significantly influence the reaction dynamics. Deuterium substitution at the primary site is the dominant kinetic isotope effect. Thermal rate constants are in excellent agreement with experiment. The method is also applied to the study of electronically nonadiabatic transitions in the CH3 + HCl <--> CH4 + Cl(2PJ) reaction. Electrovibrational basis sets are used to construct the close-coupled equations, which are solved via Rmatrix propagation using a system of three potential energy surfaces coupled by spin-orbit interaction. Ground and excited electronic surfaces are developed using a 29-parameter double-Morse function with ab initio data at the CCSD(T)/ccpV( Q+d)Z-dk//MP2/cc-pV(T+d)Z-dk level of theory, and with basis set extrapolated data, both corrected via curvilinear projected spectator zero-point energies. Coupling surfaces are developed by fitting MCSCF/cc-pV(T+d)Z-dk ab initio spin orbit constants to 8-parameter functions. Scattering calculations are performed for the ground adiabatic and coupled surface models, and reaction probabilities, thermal rate constants and integral and differential cross sections are presented. Thermal rate constants on the basis set extrapolated surface are in excellent agreement with experiment. Characterisation of electronically nonadiabatic nonreactive and reactive transitions indicate the close correlation between vibrational excitation and nonadiabatic transition. A model for comparing the nonadiabatic cross section branching ratio to experiment is discussed.
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26

Totenhofer, Ashley James. "Theory of molecular scattering and chemical reactions." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489000.

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A valuable source of information on the intermolecular potential and scattering dynamics of chemical reactions is the measurement of reactive angular distributions. Theoretical research is also necessary to understand structure in angular distributions measured by the most advanced experimental techniques. This thesis studies the angular scattering of four state-to-state chemical reactions.
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27

Farahani, Pooria. "Theoretical Studies of Seemingly Simple Chemical Reactions." Licentiate thesis, Uppsala universitet, Teoretisk kemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-228291.

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28

Lind, Maria E. S. "Quantum Chemical Modeling of Asymmetric Enzymatic Reactions." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116694.

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Computational methods are very useful tools in the study of enzymatic reactions, as they can provide a detailed understanding of reaction mechanisms and the sources of various selectivities. In this thesis, density functional theory has been employed to examine four different enzymes of potential importance for biocatalytic applications. The enzymes considered are limonene epoxide hydrolase, soluble epoxide hydrolase, arylmalonate decarboxylase and phenolic acid decarboxylase. Besides the reaction mechanisms, the enantioselectivities in three of these enzymes have also been investigated in detail. In all studies, quite large quantum chemical cluster models of the active sites have been used. In particular, the models have to account for the chiral environment of the active site in order to reproduce and rationalize the experimentally observed selectivities. For both epoxide hydrolases, the calculated enantioselectivities are in good agreement with experiments. In addition, explanations for the change in stereochemical outcome for the mutants of limonene epoxide hydrolase, and for the observed enantioconvergency in the soluble epoxide hydrolase are presented. The reaction mechanisms of the two decarboxylases are found to involve the formation of an enediolate- or a quinone methide intermediate, supporting thus the main features of the proposed mechanisms in both cases. For arylmalonate decarboxylase, an explanation for the observed enantioselectivity is also presented. In addition to the obtained chemical insights, the results presented in this thesis demonstrate that the quantum chemical cluster approach is indeed a valuable tool in the field of asymmetric biocatalysis.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

 

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29

Amar, Yehia. "Accelerating process development of complex chemical reactions." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288220.

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Process development of new complex reactions in the pharmaceutical and fine chemicals industries is challenging, and expensive. The field is beginning to see a bridging between fundamental first-principles investigations, and utilisation of data-driven statistical methods, such as machine learning. Nonetheless, process development and optimisation in these industries is mostly driven by trial-and-error, and experience. Approaches that move beyond these are limited to the well-developed optimisation of continuous variables, and often do not yield physical insights. This thesis describes several new methods developed to address research questions related to this challenge. First, we investigated whether utilising physical knowledge could aid statistics-guided self-optimisation of a C-H activation reaction, in which the optimisation variables were continuous. We then considered algorithmic treatment of the more challenging discrete variables, focussing on solvents. We parametrised a library of 459 solvents with physically meaningful molecular descriptors. Our case study was a homogeneous Rh-catalysed asymmetric hydrogenation to produce a chiral γ-lactam, with conversion and diastereoselectivity as objectives. We adapted a state-of-the-art multi-objective machine learning algorithm, based on Gaussian processes, to utilise the descriptors as inputs, and to create a surrogate model for each objective. The aim of the algorithm was to determine a set of Pareto solutions with a minimum experimental budget, whilst simultaneously addressing model uncertainty. We found that descriptors are a valuable tool for Design of Experiments, and can produce predictive and interpretable surrogate models. Subsequently, a physical investigation of this reaction led to the discovery of an efficient catalyst-ligand system, which we studied by operando NMR, and identified a parametrised kinetic model. Turning the focus then to ligands for asymmetric hydrogenation, we calculated versatile empirical descriptors based on the similarity of atomic environments, for 102 chiral ligands, to predict diastereoselectivity. Whilst the model fit was good, it failed to accurately predict the performance of an unseen ligand family, due to analogue bias. Physical knowledge has then guided the selection of symmetrised physico-chemical descriptors. This produced more accurate predictive models for diastereoselectivity, including for an unseen ligand family. The contribution of this thesis is a development of novel and effective workflows and methodologies for process development. These open the door for process chemists to save time and resources, freeing them up from routine work, to focus instead on creatively designing new chemistry for future real-world applications.
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Tyler, Lydia Justine. "Chemical reactions of an acyl carrier protein." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272174.

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31

Liljenberg, Magnus. "Quantum Chemical Studies of Aromatic Substitution Reactions." Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206964.

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In this thesis, density functional theory (DFT) is used to investigate the mechanisms and reactivities of electrophilic and nucleophilic aromatic substitution reactions (SEAr and SNAr respectively). For SEAr, the σ-complex intermediate is preceded by one (halogenation) or two (nitration) π-complex intermediates. Whereas the rate-determining transition state (TS) for nitration resembles the second π-complex, the corresponding chlorination TS is much closer to the σ-complex. The last step, the expulsion of the proton, is modeled with an explicit solvent molecule in combination with PCM and confirmed to be a nearly barrierless process for nitration/chlorination and involves a substantial energy barrier for iodination. It is also shown for nitration that the gas phase structures and energetics are very different from those in polar solvent. The potential energy surface for SNAr reactions differs greatly depending on leaving group; the σ-complex intermediate exist for F-/HF, but for Cl-/HCl or Br-/HBr the calculations indicate a concerted mechanism. These mechanistic results form a basis for the investigations of predictive reactivity models for aromatic substitution reactions. For SEAr reactions, the free energy of the rate-determining TS reproduces both local (regioselectivity) and global reactivity (substrate selectivity) with good to excellent accuracy. For SNAr reactions good accuracies are obtained for Cl-/HCl or Br-/HBr as leaving group, using TS structures representing a one-step concerted mechanism. The σ-complex intermediate can be used as a reactivity indicator for the TS energy, and for SEAr the accuracy of this method varies in a way that can be rationalized with the Hammond postulate. It is more accurate the later the rate-determining TS, that is the more deactivated the reaction. For SNAr reactions with F-/HF as leaving group, the same method gives excellent accuracy for both local and global reactivity irrespective of the degree of activation.

QC 20170510

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32

Elvira, Katherine S. "Digital microfluidic platforms for automated chemical reactions." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9561.

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Microfluidic technology allows the miniaturisation and automation of chemical and biological processes. Specific advantages include the ease of process automation and integration, high analytical throughput, reduced sample and power consumption, increased speed and efficiency of reactions and system portability. Droplet-based microfluidics can be broadly categorised into 'conventional' channel devices or digital microfluidic (DMF) devices. The latter are also known as electrowetting-on-dielectric (EWOD) devices. Both platforms have distinct characteristics, with specific advantages and disadvantages when applied to chemical or biological analysis. High-throughput droplet manipulation is easily achieved with channel microfluidic devices, but it is hard to access individual droplets in this format. On the other hand, DM devices are designed for the manipulation of individual droplets in low-throughput. The bulk of the work in this thesis focuses on developing a complete platform for droplet manipulation using digital microfluidics. Extensive experimentation was undertaken to determine all relevant components of the device, including the composition of the dielectric layer, electrodes and hydrophobic layer. Once the optimum device had been constructed and tested, full automation of device function and droplet manipulation was achieved. Characterisation of on-chip droplet operations was subsequently performed. Special attention was given to droplet 'dispensing' and 'splitting'. Once the fabricated DMF devices had been fully characterised, three proof of principle experiments were developed to investigate the capabilities of DMF devices. To this aim, first a fluorescent dilution series was performed and characterised on-chip, second a peptide bond formation experiment was performed, and finally, iron oxide nanoparticle synthesis was performed on-chip. The integration of DMF devices with a miniaturised spectrometer was used to provide an on-line detection system. Channel microfluidic devices were also investigated with respect to the high-through-put creation of droplet interface bilayers (DIBs). Aqueous droplets containing lipids were formed in an oil carrier medium. As droplets were brought together a lipid bilayer was formed at the interface, creating an artificial membrane. This approach can be used as a platform technology to study trans-membrane proteins and drug-membrane interactions. Although there has been a lot of interest in this area, previous work has focused on the low-throughput formation of DIBs. The method developed here enables the formation of DIBs at rates in excess of 1 DIB per second.
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33

Dantus, Marcos Zewail Ahmed H. Zewail Ahmed H. "Femtosecond transition-state spectroscopy of chemical reactions /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06202007-112232.

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34

Potter, Earl Douglas Zewail Ahmed H. Zewail Ahmed H. "Ultrafast control and dynamics of chemical reactions /." Diss., Pasadena, Calif. : California Institute of Technology, 1993. http://resolver.caltech.edu/CaltechETD:etd-04042008-113817.

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35

Omiya, Kazuhiro. "Theoretical Study on Chemical Reactions in Solution." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149571.

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36

Ghosh, Pranab. "Studies on chemical reactions of carbocyclic compounds." Thesis, University of North Bengal, 1991. http://hdl.handle.net/123456789/767.

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37

Saleh, Nail Asad. "Dynamical solvent effect in 1-(9-anthryl)-3-(4-dimethylaniline) propane charge transfer reactions /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060138.

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38

Bouma, Marinus Jan. "Multicomponent reactions as a tool for exploring new reactions and chemical diversity." Paris 11, 2010. http://www.theses.fr/2010PA112302.

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Les réactions multi-composants (MCRs, MultiComponent Reactions) sont des procédés permettant de combiner en une seule opération synthétique au moins trois réactifs pour conduire à un produit incorporant de manières substantielles les substrats de départ. Les réactions MCRs sont des réactions idéales pour explorer l'espace chimique, qui est défini comme l'espace de tous les caractéristiques qui englobent les petites molécules organiques pouvant être créées. En plus, lorsque les réactions multicomposantes sont réalisées, de nombreux réactifs sont réunis, qui peut augmenter la chance de découvrir de nouvelles réactions comparé aux réactions traditionnelles à deux composants. Dans cette thèse, deux nouvelles réactions ainsi que la recherche vers des nouvelles structures hétérocycliques sont décrits. L'utilisation des stratégies multicomposantes, dans cette thèse, une nouvelle méthode de synthèse one-pot directe d'α-cétoamides aromatiques par couplage oxydatif entre une isocyanure et un aldéhyde, promu par ZnCl2 est décrit. La réaction est réalisée dans des conditions douces en utilisant l'acide acétique et hydroxylamine de méthyle. Une autre partie de cette thèse, caractéristiques de l'investigation de la réactivité des isocyanures α-acides dans une MCR vers oxazoles. Cette réaction pourrait être étendue en utilisant une réaction de Diels Alder, pour former des hétérocycles complexes. Suivant ce principe, des synthèses générales d'un pot vers pyrrolopyridines, naphtyridines, furoquinolines et phénanthrolines fonctionnalisé sont présentés et la différence entre isocyanoacetates et isocyanoacetamides est discutée. Avec la combinaison de la chimie multicomposant et l'organocatalyse, une synthèse multicomposant énantiosélective d'oxazoles est aussi présentée. En présence d'un acide chiral phosphorique des excès énantiomériques jusqu'à 87% ont donné. Le champ d'application de cette réaction n'a pas encore été complètement examiné
Multicomponent reactions (MCRs) are reactions where three or more starting materials are combined in a single reaction step to form a product that incorporates essentially all of the atoms of all the components. MCRs are the ideal reactions to explore the chemical space and the use of multicomponent reactions can easily lead to the discovery of new reactions. Ln this thesis, both new reactions as well as investigations towards new heterocyclic structures are presented. Using multicomponent strategies, a new method towards important aromatic α-ketoamides is described. The method is a direct one-pot synthesis of α-ketoamides by a ZnCl2 promoted oxidative coupling between an isocyanide and an aldehyde. The reaction is realised under miId conditions using both acetic acid and methyl hydroxylamine as shuttle molecules. This method towards aromatic α-ketoamides is complementary to a method towards aliphatic α-ketoamides earlier developed by our group. Another part of this thesis features the investigation of the reactivity of α-acidic isocyanides in a multicomponent reaction towards oxazoles. This reaction could be extended using a Diels Alder reaction, to form complex heterocycles. Following this principle, general one-pot syntheses towards functionalised pyrrolopyridines, naphthyridines, furoquinolines and phenanthrolines are presented and the difference between isocyanoacetates and isocyanoacetamides is discussed. Combining multicomponent chemistry and organocatalysis, an enantioselective multicomponent synthesis of oxazoles is also described. High enantioselectivities were obtained using chiral phosphoric acids
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39

Grigsby, Charles Owen 1951. "Kinetics of rock-water reactions." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/37986.

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40

Tomlinson, Haydn. "Three topics in theoretical chemical dynamics." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288522.

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41

Amass, Dorothy Gwendoline. "Block co-polymerization by transformation reactions." Thesis, Aston University, 1996. http://publications.aston.ac.uk/9679/.

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The aim of this study was to use the transformation of anionic to metathesis polymerization to produce block co-polymers of styrene-b-pentenylene using WC16/PStLi and WC16/PStLi/AlEtC12 catalyst systems. Analysis of the products using SEC and 1H and 13C NMR spectroscopy enabled mechanisms for metathesis initiation reactions to be proposed. The initial work involved preparation of the constituent homo-polymers. Solutions of polystyryllithium in cyclohexane were prepared and diluted so that the [PStLi]o < 2x10-3M. The dilution produced initial rapid decay of the active species, followed by slower spontaneous decay within a period of days. This was investigated using UV/visible spectrophotometry and the wavelength of maximum absorbance of the PStLi was found to change with the decay from an initial value of 328mn. to λmax of approximately 340nm. after 4-7 days. SEC analysis of solutions of polystyrene, using RI and UV/visible (set at 254nm.) detectors; showed the UV:RI peak area was constant for a range of polystyrene samples of different moleculor weight. Samples of polypentenylene were prepared and analysed using SEC. Unexpectedly the solutions showed an absorbance at 254nm. which had to be considered when this technique was used subsequently to analyse polymer samples to determine their styrene/pentenylene co-polymer composition. Cyclohexane was found to be a poor solvent for these ring-opening metathesis polymerizations of cyclopentene. Attempts to produce styrene-b-pentenylene block co-polymers, using a range of co-catalyst systems, were generally unsuccessful as the products were shown to be mainly homopolymers. The character of the polymers did suggest that several catalytic species are present in these systems and mechanisms have been suggested for the formation of initiating carbenes. Evidence of some low molecular weight product with co-polymer character has been obtained. Further investigation indicated that this is most likely to be ABA block copolymer, which led to a mechanism being proposed for the termination of the polymerization.
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42

Fu, Yunyi Michael. "Development of a polymer-supported reagent for Trost-Lu isomerization reactions and reagents for Mitsunobu reactions." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39793989.

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43

Fu, Yunyi Michael, and 付運毅. "Development of a polymer-supported reagent for Trost-Lu isomerization reactions and reagents for Mitsunobu reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39793989.

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44

Brennan, C. M. "Ring closure reactions." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384611.

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45

Srinivasan, Ravi 1971. "Microfabricated reactors for partial oxidation reactions." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9865.

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46

Bertram, Matthias. "Controlling turbulence and pattern formation in chemical reactions." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964948931.

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47

Romero, Segura Rafael Martín. "Development of hypervalent iodine(iii)-mediated chemical reactions." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/402470.

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El iode hipervalent representa una poderosa eina per dur a terme diferent reaccions d’oxidació en condicions lliures de metalls. S’han realitzat estudis mecanístics que inclouen experiments de control físic-orgànics relatius a la diaminació intermolecular d’alquens mediats per iode(III) que han servit per a demostrar la veracitat dels càlculs computacionals realitzats prèviament. Aquesta informació va proporcionar una visió crucial per al desenvolupament d’una nova reacció enantioselectiva de diaminació d’estirens catalitzada per iode(III). El disseny d’un nou catalitzador quiral de iode basat en l’ús de l’àcid làctic com a font econòmica de quiralitat representa la clau d’aquest assoliment. L’optimització del catalitzador implica l’increment de la densitat d’electrònica en el nucli de iode i un motiu d’amida secundària en la cadena lateral de lactat quiral. Entre els diferents oxidants terminals, el mCPBA ha resultat ser el més eficient conduint a bons rendiments i excel·lent enantioselectivitats (>99% ee). L’abast de la reacció comprèn alquens terminals i alquens interns dins del motiu de l’estirè. En un estudi addicional, es va aconseguir la formació d’un nou enllaç carboni-bor. Així doncs, la borilació de sals de diariliodoni va ser possible després d’identificar el contra-anió del reactiu de diariliodoni més adequat. Mitjançant la generació in situ umpolung al centre de bor, la seva arilació per el reactiu hipervalent esdevé possible. Amb aquest fi, diferent acetats de diariliodoni van ser sintetitzats, demostrant la gran aplicabilitat d’aquest nou mètode respecte al grup aromàtic transferible. Aquest mètode s’afegeix a l’escàs nombre de reaccions de borilació en condicions lliures de metalls.
Los reactivos de iodo hipervalente representan una herramienta muy poderosa para la realización de diferentes oxidaciones libres de metal. Se llevaron a cabo estudios mecanísticos incluyendo experimentos físico-orgánicos de control respecto a la diaminación intermolecular de alquenos, demostrando la veracidad de los cálculos DFT previamente realizados. Esta información resultó crucial para el desarrollo de una pionera diaminación enantioselectiva de estirenos catalizada por iodo(III). Uno de los mayores logros es el diseño de un nuevo catalizador de iodo quiral basado en el ácido láctico como fuente económica de información estereoquímica. La optimización del catalizador incluye un aumento crucial de electrondensidad en el núcleo de iodo y la presencia del grupo amida en la cadena de lactato quiral. Entre los diferentes oxidantes terminales probados, mCPBA resultó ser el más eficiente, dando buenos rendimientos y una enantioselectividad sin precedentes, siendo ésta siempre superior al 90% ee. Esta reacción puede extenderse a alquenos terminales e internos que contengan la estructura de estireno. Este logro representa uno de los resultados más avanzados en la diaminación asimétrica de alquenos. En un estudio adicional, se consiguió una nueva formación de enlaces carbono-boro. Aquí, la borilación de sales de diariliodonio fue posible tras la identificación de un contraión apropiado en el reactivo de diariliodonio. Gracias a la generación in situ de un umpolung en el centro de boro, su arilación por el reactivo hipervalente es posible. Con esta finalidad, se sintetizaron diferentes acetatos de diariliodonio y se demostró la gran aplicabilidad de esta metodología en la transferencia de grupos aromáticos. Este protocolo representa uno de los pocos procesos económicos de borilación en ausencia de metal.
Hypervalent iodine(III) reagents represent a powerful tool for the realisation of different metal-free oxidation reactions. Mechanistic studies including physical-organic control experiments concerning the oxidative iodine(III)-mediated intermolecular diamination of alkens were carried out, demonstrating the veracity of previous DFT calculations. This information provided crucial insight for the development of a pioneering iodine(III)-catalysed enantioselective diamination of styrenes. The design of a novel chiral iodine catalyst based on lactic acid as economic chiral information source represents the key accomplishment. Catalyst optimisation involves a crucial electrondensity enhancement at the iodine core and a secondary amide motive in the chiral lactate side chain. Among different terminal oxidants, conventional mCPBA emerged as the most efficient one leading to good yields and unprecedented enantioselectivities of above 90% ee. The scope of the reaction comprises terminal and internal alkenes within the styrene motif. It represents the state of the art in asymmetric diamination of alkenes. In an additional study, a novel carbon-boron bond formation was accomplished. Here, borylation of diaryliodonium salts was encountered feasible upon identification of a suitable counterion in the diaryliodonium reagent. By generating an in situ umpolung at the boron centre, its arylation by the hypervalent reagent becomes viable. To this end, different diaryliodonium acetates were synthesised, thereby successfully demonstrating a broad applicability of this new methodology regarding the transferable aromatic group. This protocol adds to the still scarce number of economic borylation reactions under metal-free conditions.
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48

Fick, Jerker. "Chemical reactions in ventilation systems : Ozonolysis of monoterpenes." Doctoral thesis, Umeå University, Chemistry, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-97.

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Chemicals in indoor air, either emitted from a source or from a reaction, have been suggested to cause ill health in buildings. However, no clear correlations between exposure and health effects have been made.

In this thesis we studied the reaction between monoterpenes, a group of biogenic unsaturated C10 hydrocarbons, and ozone. Ozonolysis of monoterpenes was used as model reactions for unsaturated compounds in ambient air. Also the products formed from these reactions have been suggested as important participants in the occurrence of discomfort and ill health in buildings.

To enable a reliable and sensitive measurement of ppb-ppt levels of monoterpenes and the formed products in the presence of ozone an evaluation of available scrubber materials was made. Potassium iodide was shown to remove ambient levels of ozone and have a recovery of >95% for all monoterpenes and formed products included in the investigation.

Experimental conditions showed to have a large impact on the initial steps of the ozonolysis, and also on the composition of the formed products. We showed that water plays an important and complex role both in the initial stage of ozonolysis of ∆3-carene and in the formation and composition of products from the ozonolysis of ∆-pinene. The use of experimental design facilitated the evaluation of the investigated reactions. We showed that the formation of OH radicals could be studied using multiple linear regression models and that the presence or absence of OH radicals had a profound impact on the formation of many of the formed products. We also made an observation of the lack of formed OH radicals in the ozonolysis of limonene and discussed probable causes of this observation.

Despite the short reaction times and the ambient levels of ozone and monoterpenes used in our experiments we showed that a number of oxidation products were formed, and that the reaction rate is significantly increased in a ventilation system. This formation is underestimated by theoretical calculations and leads to high amounts of known irritants in the indoor air. We showed that theoretical calculations underestimate the formation of these oxidation products 3-13 times, depending on ventilation system and monoterpene.

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49

Goto, Masashi. "Kinetics of atmospheric chemical reactions of fluorinated hydrocarbons." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/145179.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(地球環境学)
甲第11759号
地環博第1号
新制||地環||1(附属図書館)
23402
UT51-2005-D508
京都大学大学院地球環境学舎地球環境学専攻
(主査)教授 川崎 昌博, 教授 田村 類, 助教授 川崎 三津夫
学位規則第4条第1項該当
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50

Bijlsma, Sabina. "Estimating rate constants of chemical reactions using spectroscopy." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/81947.

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