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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
791

Adhesive microlamination protocol for low-temperature microchannel arrays

Paulraj, Prawin 26 March 2013 (has links)
A new adhesive bonding method is introduced for microlamination architectures, for producing low-temperature microchannel arrays in a wide variety of metals. Sheet metal embossing and chemical etching processes have been used to produce sealing bosses and flow features, resulting in approximately 50% fewer laminae over traditional methods. These lamina designs are enabled by reduced bonding pressures required for the new method. An assembly process using adhesive dispense and cure is outlined to produce leak-free devices. Feasible fill ratios were determined to be 1.1 in general and 1.25 around fluid headers, largely due to gaps between faying surfaces caused by surface roughness. Bond strength investigation reveals robustness to surface conditions and a bond strength of 5.5-8.5 MPa using a 3X safety factor. Dimensional characterization reveals a two sigma (95%) post-bonded channel height tolerance under 10% (9.6%) after bonding. Patterning tolerance and surface roughness of the faying laminae were found to have a significant influence on the final postbonded channel height. Leakage and burst pressure testing on several samples has established confidence that adhesive bonding can produce leak-free joints. Operating pressures up to 413 kPa have been satisfied, equating to tensile pressure on bond joints of 1.9 MPa. Higher operating pressures can be accommodated by increasing the bond area of devices. A two-fluid counterflow microchannel heat exchanger has been redesigned, fabricated and tested to demonstrate feasibility of the new method. Results show greater effectiveness and higher heat transfer rates, suggesting a smaller device than the original heat exchanger. A maximum effectiveness of 82.5% was achieved with good agreement between theoretical and experimental values. Although thermal performance was improved, higher pressure drops were noted. Pressure drops were predicted with a maximum error of 16% between theoretical and experimental values. Much of the pressure drop was found to be in the device manifolds, which can be improved in subsequent designs. Fluid flow simulation results show a 45-65X reduction in fluid leakage velocity past sealing bosses, thereby mitigating adhesive erosion concerns. Theoretical models indicate that the worst-case adhesive erosion rate is 1/12th the rate of aluminum and 1/7th the rate of stainless steel, implying satisfactory reliability in high fluid velocity applications. Economic comparison indicates an 83% reduction in material cost and 71% reduction in assembly cost with the new adhesive bonding process, when compared to diffusion bonding for the recuperator investigated in this study. Adhesive compatibility with common refrigerants is reviewed through literature references, with no adverse compatibility issues noted. The findings of this research suggest a fairly quick path to commercialization for the new bonding method. Future studies required to pursue commercialization are liquid and gas permeability evaluations, and long term strength and performance testing of adhesives in targeted applications. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Mar. 26, 2012 - Mar. 26, 2013
792

Syntheses And Characterization Of Benzimidazole Containing Polymers: A Comparitative Study On Donor Unit Effect And Influence Of H-bonding

Nurioglu, Ayda Goycek 01 January 2013 (has links) (PDF)
The first part of this work reports a comparative study on electrochromic properties of two Donor-Acceptor-Donor (DAD) type polymers, namely poly(2-heptyl-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole) (BImTh) and poly(4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-heptyl-1H-benzo[d]imidazole) (BImEd). DAD type polymers are designed to bear the same acceptor unit, benzimidazole and two different donor units, thiophene and 3,4-ethylenedioxy thiophene (EDOT) to make a comparison based on the donor unit effect. The resulting polymers are both multichromic and have low band gap values (1.93 eV for PBImTh and 1.74 eV for PBImEd). In the second part, 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-phenyl-1H-benzo[d]imidazole (BImBEd) is synthesized. In order to figure out the presence of an intramolecular hydrogen bonding between the amine bond of the imidazole ring and the oxygen of the EDOT molecule, different amounts of trifluoroacetic acid (TFA) and concentrated sodium hydroxide (NaOH) solutions were added during electrochemical polymerization. These treatments caused protonation of the imine and deprotonation of the amine bonds respectively. In order to prove the changes in the optical properties of the polymers due to different number of protonated and deprotonated imine and amine bonds, 1,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzene (BEDOT-B) was also synthesized and treated with the same procedures. Results showed that it is possible to control the main chain conformation of even an insoluble polymer via acid and base treatments during in situ polymerization.
793

Thermodynamic Studies of Halogen Bonding in Solution and Application to Anion Recognition

Sarwar, Md. Golam 19 December 2012 (has links)
Halogen bonding (XB), the interaction between electron deficient halogen compounds and electron donors, is an established non-covalent interaction in the solid and gaseous phases. Understanding of XB in the solution phase is limited. This thesis describes experimental studies of XB interactions in solution, and the application of XB interactions in anion recognition. Chapter 1 is a brief review of current understanding of XB interaction: theoretical models, studies of XB in solid and gaseous phases and examples in biological systems are discussed. At the end of this chapter, halogen bonding in the solution phase is discussed, along with applications of halogen bonding in organic syntheses. In chapter 2, linear free energy relationships involving the thermodynamics of halogen bonding of substituted iodoaromatics are studied. The utility of substituent constants and calculated molecular electrostatic potential values as metrics of halogen bond donor ability are discussed. Density Functional Theory (DFT) calculations are shown to have useful predictive values for trends in halogen bond strength for a range of donor-acceptor pairs. Chapter 3 describes the development of new multidentate anion receptors based on halogen bonding. Bidentate and tridentate receptors were found to exhibit significantly higher binding constants than simple monodentate donors. These receptors show selectivity for halide anions over oxyanions. Using 19F NMR spectra at different temperature, the enthalpies and entropies of anion bindings for monodentate and tridentate receptors were determined. The results indicate a positive entropy contribution to anion binding for both mono and tridentate receptors in acetone solvent. Finally in chapter 4, some mesitylene based receptors with 3-halopyridinium and 2-iodobenzimidazolium donors are introduced. The receptors perform halide anion recognition in aqueous solvent system through charge-assisted XB interactions. These findings can allude to utility in organic synthesis, supramolecular chemistry and drug design.
794

Analysis of chemical bonding and aromaticity from electronic delocalization descriptors

Feixas Geronès, Ferran 04 February 2011 (has links)
Interactions between electrons determine the structure and properties of matter from molecules to solids. Therefore, the understanding of the electronic structure of molecules will enable us to extract relevant chemical information. In the first part of this thesis, we focus our attention on the analysis of chemical bonding by means of the Electron Localization Function (ELF) and the Domain-Averaged Fermi Hole analysis (DAFH). In the second part, we assess the performance of some indicators of aromaticity by analyzing their advantages and drawbacks. We propose a series of tests based on well-known aromaticity trends that can be applied to evaluate the aromaticity of current and future indicators of aromaticity in both organic and inorganic species. Moreover, we investigate the nature of electron delocalization in both aromatic and antiaromatic systems in the light of Hückel’s (4n + 2) rule. Finally, we analyze the phenomenon of multiple aromaticity in all-metal clusters. / Les interaccions entre electrons determinen l’estructura i propietats de la matèria. Per tant, la comprensió de l’estructura electrònica de les molècules ens permetrà extreure informació química rellevant. En la primera part d’aquesta tesi, centrem la nostra atenció en l’anàlisi de l’enllaç químic per mitjà de la funció de localització electrònica (ELF) i l’anàlisi dels anomenats domain averaged Fermi holes (DAFH). En la segona part, s’avalua el comportament d’alguns indicadors d’aromaticitat analitzant els seus avantatges i inconvenients. Al llarg d’aquesta part, es proposen una sèrie de tests basats en tendències d’aromaticitat conegudes que es poden aplicar per avaluar el comportament dels indicadors actuals en espècies tan orgàniques com inorgàniques. A més a més, s’investiga la naturalesa de la deslocalització d’electrons en sistemes aromàtics i antiaromàtics que segueixen la regla 4n+2 que proposà Hückel. Finalment, analitzem el fenomen de l’aromaticitat múltiple en sistemes metàl•lics
795

Peeling failure in beams strengthened by plate bonding. A design proposal

Oller Ibars, Eva 10 September 2005 (has links)
La necesidad de refuerzo estructural en una infraestructura existente puede venir motivada por la aparición de nuevos condicionantes de uso o por la degradación de los materiales. Desde finales de los años sesenta, la técnica del refuerzo mediante la adhesión de platabandas metálicas se ha llevado a la práctica como alternativa a otros métodos de refuerzo tradicionales. Sin embargo, las platabandas metálicas presentan algunas desventajas, como son su peso y su posible corrosión por agentes atmosféricos, que pueden solventarse sustituyéndolas por laminados de polímeros reforzados con fibras (FRP). Estos materiales poseen relaciones resistencia/peso y rigidez/peso mayores que el acero, facilitando su colocación, reduciendo costes y plazos de ejecución.En numerosos estudios empíricos se observa como la aplicación de laminados encolados puede resultar en una rotura frágil que conduce al desprendimiento prematuro del refuerzo antes de alcanzar la carga última.El principal objetivo de este trabajo es el desarrollo de un método simple y efectivo para dimensionar y comprobar el refuerzo de estructuras existentes con laminados adheridos de tal forma que se eviten los modos prematuros de rotura que conducen al desprendimiento del laminado. Se ha dedicado especial atención a la transferencia de tensiones de laminado a hormigón que resulta el punto clave del correcto comportamiento de este tipo de refuerzo.En el Capítulo 2, tras una revisión histórica de las líneas de investigación existentes, experimentales y teóricas, se ha evaluado mediante una base de datos experimental la fiabilidad de los modelos teóricos existentes para pronosticar y prevenir los modos de rotura prematuros antes mencionados. Esta base de datos experimental incluye resultados de la literatura existente y de una campaña experimental llevada a cabo por el autor en el Laboratorio de Tecnología de Estructuras de la Universidad Politécnica de Cataluña.Para resolver las deficiencias de los modelos teóricos existentes, en el Capítulo 3, se ha aplicado la teoría de la Mecánica de Fractura No Lineal a un caso de corte puro para modelizar el comportamiento de la interfase y sus roturas prematuras. Se han obtenido las distribuciones de tensiones en la interfase y en el laminado junto a la fuerza máxima transferida en función de tres parámetros (energía de fractura, máxima tensión tangencial y deslizamiento asociado a dicha tensión).La formulación de un caso de corte puro se ha extendido a un caso general de una viga bajo cargas transversales en el Capítulo 4. Se ha estudiado la evolución del desprendimiento del laminado en dos casos específicos: un elemento entre dos fisuras contiguas, y un elemento entre el extremo del laminado y la siguiente fisura. Se han obtenido las distribuciones de tensiones para las distintas fases del proceso. Cabe mencionar que la fuerza transferida entre dos fisuras alcanza su máximo valor cuando la tensión tangencial máxima llega a la fisura menos cargada. En este instante, ya se puede haber iniciado o no la formación de una macrofisura. El elemento entre el extremo del laminado y la siguiente fisura es similar al caso de corte puro.Las distribuciones de tensiones presentadas en el Capítulo 4 nos ayudan a comprender el comportamiento de un elemento reforzado con laminados adheridos en su cara traccionada, sin embargo, resultan complejas en la práctica. En el Capítulo 5 se describe un nuevo método de dimensionamiento y verificación basado en la obtención de una relación entre el máximo cortante antes de que se produzca el desprendimiento prematuro del refuerzo y el momento aplicado. Esta relación está asociada a la fuerza máxima transferida entre fisuras. A partir de la predicción del valor máximo de cortante, se verifica el desprendimiento del extremo del laminado evaluando la fuerza transferida entre dicho punto y la siguiente fisura. Se ha verificado la fiabilidad de esta propuesta mediante la base de datos de ensayos a flexión.Finalmente, en el Capítulo 6 se resumen las principales conclusiones del trabajo presentado en esta tesis y se sugieren futuras líneas de investigación. / The strengthening of aging infrastructures is in most cases required because of the necessity for increased levels of service loads or because of the degradation of structural materials. The technique of strengthening by externally bonding steel plates has been in practice since the late 1960's. However, steel plates present some disadvantages in terms of weight and corrosion that can be solved by replacing them with fiber reinforced polymer (FRP) laminates. FRP laminates provide benefits such as high strength-to-weight and stiffness-to-weight ratios, corrosion resistance as well as reduced installation costs due to their easy-handling.Existing experimental work has shown that the application of externally bonded laminates can result in a catastrophic brittle failure in the form of a premature debonding of the laminate before reaching the design load.The main aim of this research has been the development of a simple effective method to design and verify the strengthening of an existing structure with an externally bonded plate while preventing the premature peeling failure that causes the laminate to debond. Special attention has been drawn on to transfer of stresses from laminate to concrete through the interface, which is the main key in the correct performance of externally reinforced concrete structures.After a historical overview of the existing experimental and theoretical lines of research, the suitability of using existing theoretical models to forecast and prevent peeling failures is evaluated in Chapter 2 by means of an experimental bending test database. This database includes results from the existing literature and results from an experimental program conducted by the author at the Structural Technology Laboratory of the Technical University of Catalonia.To solve the weaknesses of the existing theoretical models, in Chapter 3, Non-Linear Fracture Mechanics theory is applied in a pure shear case to model the interface behavior and its premature failures. The stress distributions, together with the maximum transferred force are obtained as a function of three model parameters (the fracture energy, the maximum shear stress and the sliding associated to this stress).The formulae of a pure shear specimen are then extended to a general case of a beam under transverse loads in Chapter 4. For this purpose, the evolution of the debonding process is studied for two specific cases: a beam element between two cracks, and a beam element between the laminate end and the nearest crack. The stress distributions are obtained for the different stages observed in the debonding process. A specific highlight observed was that the transferred force between cracks is at maximum when the maximum shear stress reaches the less-loaded crack. In this instance, a macrocrack may or may not have already initiated. Another point observed is related to the beam element between the laminate end and the nearest crack, which is similar to the pure shear specimen.The stress distributions derived in Chapter 4 allow us to understand the behavior of an externally reinforced element, but are awkward for design purposes. Chapter 5 describes both a new design and verification method based on a maximum shear force-bending moment relationship associated to the theoretical maximum transferred force between two consecutive cracks before peeling occurs. After calculating the predicted value for the maximum shear force from the peeling relationship, the developed method verifies the debonding at the laminate end by checking the transferred force between the laminate end and the first crack in the laminate. The reliability of this proposal is verified by means of the assembled bending test database.Finally, the main conclusions drawn from the work presented in this dissertation are summarized in Chapter 6. Future work and research lines are suggested as well.
796

Effects of Ultrasound in Microelectronic Ultrasonic Wire Bonding

Lum, Ivan 28 November 2007 (has links)
Ultrasonic wire bonding is the most utilized technique in forming electrical interconnections in microelectronics. However, there is a lacking in the fundamental understanding of the process. In order for there to be improvements in the process a better understanding of the process is required. The mechanism of the bond formation in ultrasonic wire bonding is not known. Although there have been theories proposed, inconsistencies have been shown to exist in them. One of the main inconsistencies is the contribution of ultrasound to the bonding process. A series of experiments to investigate the mechanism of bond formation are performed on a semi automatic wire bonder at room temperature. 25 µm diameter Au wire is ball bonded and also 25 µm diameter Al wire is wedge-wedge bonded onto polished Cu sheets of thickness 2 mm. It is found that a modified microslip theory can describe the evolution of bonding. With increasing ultrasonic power the bond contact transitions from microslip into gross sliding. The reciprocating tangential relative motion at the bond interface results in wear of surface contaminants which leads to clean metal/metal contact and bonding. The effect of superimposed ultrasound during deformation on the residual hardness of a bonded ball is systematically studied for the first time. An innovative bonding procedure with in-situ ball deformation and hardness measurement is developed using an ESEC WB3100 automatic ball bonder. 50 µm diameter Au wire is bonded at various ultrasound levels onto Au metallized PCB substrate at room temperature. It is found that sufficient ultrasound which is applied during the deformation leads to a bonded ball which is softer than a ball with a similar amount of deformation without ultrasound. No hardening of the 100 µm diameter Au ball is observed even with the maximum ultrasonic power capable of the equipment of 900 mW. In summary, the fundamental effect of ultrasound in the wire bonding process is the reciprocating tangential displacement at the bond interface resulting in contaminant dispersal and bonding. A second effect of ultrasound is the softening of the bonded material when compared to a similarly non-ultrasound deformed ball.
797

Strong Hydrogen Bonds in Anion-Solvent Clusters: Structural and Thermochemical Properties

Nieckarz, Robert John January 2008 (has links)
Insight into the effect of secondary interactions, fluorination, as well as substituent effects on strong ionic hydrogen bonds has been acquired through studies of FHF-, NFnH3-n•••F- (n = 0..2) and [M-H]- (M = Glycine, Alanine, Valine, Serine) clustered with ROH (R = H, CH3, C2H5). Excellent agreement was observed between thermochemical values obtained from high pressure mass spectrometry measurements and those predicted from MP2(full)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations. In the examination of the clustering of FHF-, a strong correlation between the hydrogen bond strength and the gas phase acidity of the solvent was observed. In addition, several interesting observations on various structural and thermochemical properties were made for each of the three solvents. Upon formation of clusters with water, it was found that the large entropic advantage of one particular structure, which was not the most enthalpically favored, was significant enough to make it the predominant species within the ion source. In the case of methanol solvation, no evidence of secondary interaction of the methyl group and any other moiety could be found. The structural details revealed from calculations of the ethanol-solvated clusters indicate that secondary interactions between the terminal methyl group and FHF- had an impact on the length of both the FHF and OHF bonds present. In an attempt to gain insight into the effects of fluorination on hydrogen bonding, clusters of NFnH3-n (n = 0..2) and F- have been computationally investigated. The hydrogen bond energy in NH3∙∙∙F-, NFH2∙∙∙F- and NF2H∙∙∙F- were calculated to be -67.9 kJ∙mol-1, -120.2 kJ∙mol-1 and -181.2 kJ∙mol-1, respectively, and clearly show the effect of fluorination on hydrogen bond strength in amine-fluoride systems. The change in enthalpy and entropy for the clustering of methanol to NF2H∙∙∙F- to form the fluoride bound dimer of methanol and difluoramine has been measured via high pressure mass spectrometry to be -68.3 kJ∙mol-1 and -90.5 J∙K-1∙mol-1. These values are in excellent agreement with the calculated analogues, -70.9 kJ∙mol-1 and -88.5 J∙K-1∙mol-1. Finally, an examination of the thermochemical properties associated with the formation of a hydrogen bond linkage between protic solvents and deprotonated amino acids has been performed. In addition to observations of the effect of side chain substitution, a comparison between measured and calculated properties has provided insight into the thermochemical effects arising from the isomeric nature of this clustering system. A new theoretical model describing the impact of a distribution of isomers on thermochemical measurements made via high pressure mass spectrometry is given. When this new model was applied, and the distribution of isomers correctly accounted for, the measured values of 〖∆H〗^°, 〖∆S〗^° and 〖∆G〗_298^° consistently agreed, to a very high degree of accuracy, with those predicted by MP2(full)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations. As well, IR spectra for the clustering of deprotonated glycine with ROH have been calculated and analyzed to demonstrate the ability of techniques such as IRMPD to identify the presence of a distribution of isomers.
798

Physicochemical and Structural Aspects of Nucleic Acids

Chatterjee, Subhrangsu January 2007 (has links)
This thesis consists of seven research publications concerning (i) pKa studies of nucleobases in model nucleotides to understand why RNA duplexes are more stable than DNA duplexes (Paper I), (ii) the role of Me(T)-π interactions in the relative stability of DNA-RNA heteroduplexes (Paper II), (iii) pKa measurements in nucleotides with different 2′-substituents (paper III), (iv) a conformation study of constrained sugars and a pKa study of 1-thyminyl to reveal effect of sugar constraints on the pKa of the nucleobase (paper IV), (v) NMR and MD studies of 1′, 2′-oxetane constrained thymidine incorporated Dickerson Drew dodecamer (paper V), (vi) the sequence dependent pKa perturbation of 9-guaninyl moeity in single stranded (ss) DNA and RNA (paper VI), (vii) the non identical chemical nature of internucleotidic phosphates in (ss) RNA using 31P NMR (paper VI), and an alkaline hydrolysis study of phosphodiesters in ssRNAs (paper VII). The architecture of DNA and RNA molecules is determined by (a) hydrogen bonding (b) base stacking (c) a variety of additional non-covalent interactions. In paper (I) we showed that A-U and G-C base pairings in RNA are more stable than A-T and G-C base pairings in DNA by 4.3 and 1 kJ mol-1 respectively. Me(T)-π interaction plays a dominant role in the relative stability of DNA-RNA duplexes (paper II). In paper III and IV, we have shown that 1′ , 2′- oxetane and azetidine rings have strong inductive effect on pyrimidine bases, and that the H2′-sugar proton can be the marker to understand the pseudoaromaticity of pyrimidine bases, as well as increasing constraints in sugar reducing the basicity of nucleobases. A 1′, 2′-oxetane locked thymidine (T) moiety deforms the local structure of Dickerson-Drew dodecamer, d(CGCGAATTCGCG)2- investigated by High resolution NMR and MD study, as is discussed in the paper V. In papers VI and VII, we showed sequence context dependent pKa (N1) of 9-guaninyl perturbation in (ss) DNAs and RNAs and the non identical chemical nature of inter-nucleotidic phosphate groups in single stranded RNAs.
799

Effects of Ultrasound in Microelectronic Ultrasonic Wire Bonding

Lum, Ivan 28 November 2007 (has links)
Ultrasonic wire bonding is the most utilized technique in forming electrical interconnections in microelectronics. However, there is a lacking in the fundamental understanding of the process. In order for there to be improvements in the process a better understanding of the process is required. The mechanism of the bond formation in ultrasonic wire bonding is not known. Although there have been theories proposed, inconsistencies have been shown to exist in them. One of the main inconsistencies is the contribution of ultrasound to the bonding process. A series of experiments to investigate the mechanism of bond formation are performed on a semi automatic wire bonder at room temperature. 25 µm diameter Au wire is ball bonded and also 25 µm diameter Al wire is wedge-wedge bonded onto polished Cu sheets of thickness 2 mm. It is found that a modified microslip theory can describe the evolution of bonding. With increasing ultrasonic power the bond contact transitions from microslip into gross sliding. The reciprocating tangential relative motion at the bond interface results in wear of surface contaminants which leads to clean metal/metal contact and bonding. The effect of superimposed ultrasound during deformation on the residual hardness of a bonded ball is systematically studied for the first time. An innovative bonding procedure with in-situ ball deformation and hardness measurement is developed using an ESEC WB3100 automatic ball bonder. 50 µm diameter Au wire is bonded at various ultrasound levels onto Au metallized PCB substrate at room temperature. It is found that sufficient ultrasound which is applied during the deformation leads to a bonded ball which is softer than a ball with a similar amount of deformation without ultrasound. No hardening of the 100 µm diameter Au ball is observed even with the maximum ultrasonic power capable of the equipment of 900 mW. In summary, the fundamental effect of ultrasound in the wire bonding process is the reciprocating tangential displacement at the bond interface resulting in contaminant dispersal and bonding. A second effect of ultrasound is the softening of the bonded material when compared to a similarly non-ultrasound deformed ball.
800

Strong Hydrogen Bonds in Anion-Solvent Clusters: Structural and Thermochemical Properties

Nieckarz, Robert John January 2008 (has links)
Insight into the effect of secondary interactions, fluorination, as well as substituent effects on strong ionic hydrogen bonds has been acquired through studies of FHF-, NFnH3-n•••F- (n = 0..2) and [M-H]- (M = Glycine, Alanine, Valine, Serine) clustered with ROH (R = H, CH3, C2H5). Excellent agreement was observed between thermochemical values obtained from high pressure mass spectrometry measurements and those predicted from MP2(full)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations. In the examination of the clustering of FHF-, a strong correlation between the hydrogen bond strength and the gas phase acidity of the solvent was observed. In addition, several interesting observations on various structural and thermochemical properties were made for each of the three solvents. Upon formation of clusters with water, it was found that the large entropic advantage of one particular structure, which was not the most enthalpically favored, was significant enough to make it the predominant species within the ion source. In the case of methanol solvation, no evidence of secondary interaction of the methyl group and any other moiety could be found. The structural details revealed from calculations of the ethanol-solvated clusters indicate that secondary interactions between the terminal methyl group and FHF- had an impact on the length of both the FHF and OHF bonds present. In an attempt to gain insight into the effects of fluorination on hydrogen bonding, clusters of NFnH3-n (n = 0..2) and F- have been computationally investigated. The hydrogen bond energy in NH3∙∙∙F-, NFH2∙∙∙F- and NF2H∙∙∙F- were calculated to be -67.9 kJ∙mol-1, -120.2 kJ∙mol-1 and -181.2 kJ∙mol-1, respectively, and clearly show the effect of fluorination on hydrogen bond strength in amine-fluoride systems. The change in enthalpy and entropy for the clustering of methanol to NF2H∙∙∙F- to form the fluoride bound dimer of methanol and difluoramine has been measured via high pressure mass spectrometry to be -68.3 kJ∙mol-1 and -90.5 J∙K-1∙mol-1. These values are in excellent agreement with the calculated analogues, -70.9 kJ∙mol-1 and -88.5 J∙K-1∙mol-1. Finally, an examination of the thermochemical properties associated with the formation of a hydrogen bond linkage between protic solvents and deprotonated amino acids has been performed. In addition to observations of the effect of side chain substitution, a comparison between measured and calculated properties has provided insight into the thermochemical effects arising from the isomeric nature of this clustering system. A new theoretical model describing the impact of a distribution of isomers on thermochemical measurements made via high pressure mass spectrometry is given. When this new model was applied, and the distribution of isomers correctly accounted for, the measured values of 〖∆H〗^°, 〖∆S〗^° and 〖∆G〗_298^° consistently agreed, to a very high degree of accuracy, with those predicted by MP2(full)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations. As well, IR spectra for the clustering of deprotonated glycine with ROH have been calculated and analyzed to demonstrate the ability of techniques such as IRMPD to identify the presence of a distribution of isomers.

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