Além do interesse intrínseco pelos seus aspectos mecanísticos, as reações de hidrólise de compostos carbonílicos apresentam também a interessante particularidade da reação pelo próprio solvente, a água. Dentre estas reações, conhecidas como \"reações de água\" (Robertson, 1967; Johnson, 1967), estudou-se neste trabalho a hidrólise de carbonatos, através do cálculo das energias de transferência da fase gasosa para o solvente, de reagentes (R), estado de transição (ET) e produtos (P). O estudo da solvatação de modelos moleculares para R e ET indica uma correlação entre reatividade e estrutura molecular. Os resultados usando o enfoque de \"super-molécula\" mostram maior concordância com os dados experimentais do que o cálculo de solvatação da molécula simples e indicam que a solvatação dos modelos de ET é mais eficiente que para R e, portanto, há um aumento da reatividade. O estudo mais detalhado das estruturas de R, ET e P, em misturas água/acetonitrila para carbonatos de difenila e bis(2,4-dinitrofenila), sugere a existência de duas ligações de hidrogênio: entre o oxigênio da água do \"cluster\" e um dos hidrogênios dos anéis aromáticos (CF e CDNF), e entre o hidrogênio da água e o oxigênio do grupo nitro do outro anel aromático (CDNF). A consequente diminuição da liberdade conformacional em relação à fase gasosa, provocada por estas ligações de hidrogênio (CF e CDNF), expõe um dos hemisférios da carbonila ao ataque da água, provocando então uma aceleração entrópica do processo. Os efeitos eletrônicos, devidos às ligações de hidrogênio, estão de acordo com a maior acidez esperada dos hidrogênios dos anéis do CDNF em relação ao CF. Também mostram uma compensação no CDNF, pouco contribuindo para alterar a densidade eletrônica no seu carbono carbonílico, enquanto que indica uma soma de efeitos no CF, contribuindo então para um aumento desta densidade eletrônica no CF, de acordo com sua conhecida baixa reatividade. O trabalho permite ainda concluir sobre o relativo sucesso do uso de método semi-empírico PM3 e modelo relativamente simples de solvatação (Cramer & Truhlar, 1991), para o cálculo de energia de transferência em misturas de água/acetonitrila, na faixa de fração molar da água (0,40 a 1,00) onde o método apresenta resultados concordantes com os valores experimentais. / In addition to their intrinsic mechanistic interest, hydrolysis reactions of carbonyl compounds in aqueous media exhibit the interesting peculiarity of direct reaction with the solvent itself, i.e., water. In the present work, we have investigated a representative example of one of these \"water reactions\" (Robertson, 1967; Johnson, 1967), the hydrolysis of carbonates, via quantum chemical ca1culation of the free energies of transfer of the reagents (R), the transition state (TS) and the products (P) from the gas phase to water. A model study of the solvation of R and TS points to a correlation between reactivity and molecular structure. Results using the \"super-molecule\" approach show greater agreement with experiment than solvation ca1culations on the isolated molecule and imply that the solvation of the TS is more effective than that of R in increasing reactivity. A more detailed study of the structures of R, TS and P for diphenyl- (DPC) and bis(2,4-dinitrophenyl)carbonates (DNPC) in acetonitrile/water mixtures suggests the existence of two possible types of hydrogen bonds, i.e., between oxygen of the water c1uster and an aromatic ring hydrogen (DPC and DNPC) or, in the case of DNPC, between the protons of water and the oxygens of the nitro group of the second aromatic ring. The decrease in conformational degrees of freedom reI ative to the gas phase provoked by these hydrogen bonds exposes one of the hemispheres of the carbonyl group to attack by water, resulting in an entropic acceleration of the reaction. The electronic effects on the hydrogen bonds are in line with the greater acidity of the aromatic ring hydrogens of DNPC relative to those of DNP. In DNPC, there is a compensation effect, with very little alteration of the electron density on the carbonyl carbon, while in DPC a sum of effects increases the electron density on the carbonyl carbon, in line with the known lower reactivity of the latter. This work points to the relative success of the semi-empirical PM3 method combined with relatively simple solvation models (Cramer & Truhlar, 1991) for ca1culating free energies of transfer involving acetonitrile/water mixtures in the water mole fraction range from 0.40-1.00.

No description available.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Two major hurdles face the production of recombinant spider silk protein (rSSp) based materials. First, the production of sufficient quantities of rSSp has proven difficult due to their highly repetitive nature and protein size (>250kDa). Secondly, rSSp and native silks are practically insoluble in water based solutions, necessitating the use of harsh organic solvents that can remain in the material after production. While others are working on solving production problems, this dissertation demonstrates a novel aqueous solubilization method that is rapid (<1 minute) and results in near 100% solubilization of the rSSp. From this new solubilization method films, foams, gels (hydrogels and lyogels), adhesives, coatings and fibers have been produced as well as the previously unreported sponge. All of these novel materials were derived from entirely aqueous solutions with and without minor additives to influence the final physical state of the rSSp.

No description available.

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23918号 / 工博第5005号 / 新制||工||1781(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 佐藤 啓文, 教授 作花 哲夫, 教授 佐藤 徹 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

It was found that there exist three major water environments when water is dissolved in nitrobenzene. 2H NMR has proved that these solvatomers exist irrespective of whether lithium salt is added to the system. 7Li NMR experiments suggested that the first solvatomer is majority nitrobenzene, the second a mixed solvation shell consisting of nitrobenzene and water and the third solvatomer is a large water aggregated at the glass surface. The mixed solvation state is short lived and is promoted by addition of water of by supersaturating the system upon cooling. This is a high energy state and decays either into the homogenous bulk NB state or to the surface of the glass wall, depending on if glass surface is present. In the 7Li NMR experiments, the hydrophobicity of the salt, determined by the anion, affects the relative intensity of the three 7Li resonances. Addition of lithium serves to promote hydrogen bonding in the majority nitrobenzene solvatomer, as confirmed by FTIR and neutron diffraction studies. There is no evidence that it has an effect on the size of the mixed solvatomer or the water aggregate immobilized on the glass surface. A reasonable hypothesis is that lithium exchanges between the water species which are formed independent of lithium involvement. The system is summarized as follows: Below critical water concentration (~200mM) nitrobenzene/water is a homogeneous distribution of water molecules in nitrobenzene. Addition of lithium salt to such a system has two main affects. First, the lithium promotes hydrogen bonding between the dissolved water molecules, as confirmed by FTIR and neutron scattering. Second, the hydrogen bonded water may precipitate causing microheterogeneity of the system, leading to a second resonance observed in both the 2H and 7Li NMR spectra (LiNB/W). In the presence of glass, a third solvation state can nucleate at the glass surface; this solvation state has character even closer to that of bulk water (LiW). These two supplementary solvation states can be artificially induced by either adding aliquots of water or cooling.

Experimental mole fraction solubilities of several carboxylic acids (2-methoxybenzoic acid, 4-methoxybenzoic acid, 4-nitrobenzoic acid, 4-chloro-3-nitrobenzoic acid, 2-chloro-5-nitrobenzoic acid,2-methylbenzoic acid and ibuprofen) and 9-fluorenone, thianthrene and xanthene were measured in a wide range of solvents of varying polarity and hydrogen-bonding characteristics. Results of these measurements were used to calculate gas-to-organic solvent and water-to-organic solvent solubility ratios, which were then substituted into known Abraham process partitioning correlations. The molecular solute descriptors that were obtained as the result of these computations described the measured solubility data to within an average absolute deviation of 0.2 log units. The calculated solute descriptors also enable one to estimate many chemically, biologically and pharmaceutically important properties for the ten solutes studied using published mathematical correlations.

The Abraham solvation model (ABSM) is an experimentally derived predictive model used to help predict various solute properties. This work covers various uses for the ABSM including predicting molar enthalpies of vaporization, predicting solvent coefficients for two new solvents (2,2,5,5-tetramethyloxolane and diethyl carbonate), predicting values for multiple new ionic liquids (ILs). This work also introduces a novel method for updating IL ABSM parameters by updating cation- and anion-specific values using linear algebra and binary matrices.