Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-10, Section: B, page: 6192. Adviser: Jonathan S. Weissman.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-10, Section: B, page: 6189. Adviser: David O. Morgan.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-10, Section: B, page: 6184. Adviser: David O. Morgan.

Thesis (Ph. D.)--Indiana University, Dept. of Biology, 2006. / "Title from dissertation home page (viewed June 28, 2007)." Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 2963. Adviser: Donald H. Burke.

(a) A study of the kinetics of nitration of a fully deuterated nitrobenzene and a comparison with the nitration of protium nitrobenzene in order to determine the molecularity of the reaction. (b) An investigation of the causes of the maximum in sulphuric acid media with particular respect to the acid side of the maximum. The substances used for nitrating were:- nitrobenzene p-chloronitrobenzene trimethylphenylammonium ion. The investigation involved the addition to 100[percent] sulphuric acid of bases other than water, and salts and unionised compounds to ascertain whether these substances gave rise to a maximum rate at certain concentrations. Activation energies and A factors were measured in various media.

The reversible denitration of several nitroguanidines in sulphuric acid media above 67%, in perchloric acid of 59-72% strength and in sulphuric acid-acetic acid media of 49-85% strength, has been investigated. The state of the nitroguanidine molecule in strong acid and the condition of the acid molecules themselves have been discussed. The equilibrium position between the nitroguanidine and corresponding guanidine has been established in all the media used and a correlation of equilibrium position with activity of water in the medium, deduced by Simkins and Williams, has been applied in suitable cases. The rate of denitration over the measurable range has been obtained for several compounds in sulphuric acid-water mixtures, for one in sulphuric acid-acetic acid mixtures and for two in perchloric acid-water mixtures. The rate of guanidine nitration was also measured in sulphuric acid-acetic acid. Rates in perchloric acid are directly proportional to the Hammett acidity function ho. In sulphuric acid this relation does not hold but a relation with ho together with the activities of certain solvent species does apply. The ultra-violet absorption spectra of the nitroguanidines in dilute acid were measured for use in the analysis of reactions. These, together with further spectral data, were used to furnish pKa values for several of the compounds. Certain acidity functions were also investigated, including the H+ function in sulphuric acid-water and perchloric acid-water mixtures, and the Ho function in the higher ranges of perchloric acid.

A number of isothermals have been determined for the sorption of the vapours of amino compounds on silica and ferric oxide gels. The sorbates studied include the normal aliphatic amines, from ethylamine to n-heptylamine, t-butylamine, ethylene diamine, cyclohexylamine and pyridine. Data for ethyl alcohol and water is also included, for comparative purposes. A standard 'gravimetric' technique has been used in every case, except that of ethylamine, for which a new technique has been developed. The ferric oxide isothermals all contain a large. hysteresis loop, the size of which does not vary with increasing molecular diameter. Silica gel B2 isothermals show a large loop with water, and small loops with ethyl alcohol, n-propylamine and ethylene diamine. Larger molecules give completely reversible isothermals. This data confirms the most important prediction of the 'open-pore' theory of capillary condensation. Reference is made to data in the literature which provides further confirmation of this prediction. Silica gel C and silica gel D systems both contain large hysteresis loops. Only a few results are quoted for the former system, as the isothermals obtained were not reproducible. Where possible, the Kelvin equation has been used to estimate the most frequent occurring pore space available for capillary condensation. In some cases an estimate of the true pore radius has been made, by correcting for the thickness of the adsorbed layer. Evidence is presented for orientation of sorbate molecules in the first layer on ferric oxide gel, and, to some extent, on silica gel D. The volumes adsorbed at saturation obey Gurwitsch Rule in every case. Ethylene diamine has been shown to have a lower freezing point in the adsorbed state than in the bulk state. The vapour pressures and surface tensions of some of the sorbates have been determined, using methods suitable for hygroscopic liquids.

The theory of the growth of a perfect crystal is outlined and a brief description is given of the development of this theory, taking into account the presence of imperfections, especially dislocations, in the crystal. The molecular 'growth spirals' and other features predicted by this theory put forward by Burton, Cabrera and Prank require improved experimental techniques for their study, which are described. The experimental study of the growth features divides itself into two parts: (1) Microscopic studies. (2) Interferometric studies. The different growth features observed on the faces of silicon-carbide (Si-C) crystals are illustrated and explained. The observed 'growth spirals' can be divided into three types: (1) Elementary spirals with step heights equal to the size of the X-ray unit cell. (2) Spirals originating from dislocations of multiple strength, the step heights being a multiple of the X-ray unit cell. (3) Interlaced spirals in which the step heights are a fraction of the unit cell. The microscopic studies illustrate the information about the shape of the spirals, the behaviour and interaction of growth fronts with one another, originating from different sources, the growth pattern for a number of screw dislocations emerging on the crystal face fault surfaces, and their statiscal properties such as density of dis-locations etc. From these studies the type of information obtainable about the conditions of growth is the size of the critical nucleus and the supersaturation. The interferometric techniques utilized for the measurement of step heights are discussed. A study of the measured step heights leads to an understanding of the interesting property of 'polytypism' as observed in silicon-carbide crystals which occur in different types as shown by X-ray diffraction data. The 'growth spirals' demonstrate the X-ray predictions and confirm them.

A number of inner-complex compounds of beryllium, aluminium, iron, copper and nickel have been prepared, and measurements of the molecular polarisation have been made on those which were sufficiently soluble in either benzene or dioxan. A heterodyne beat apparatus was used for dielectric constant measurements. The appropriate molecular refractions have been either measured or calculated, and, on the assumption that the molecules are symmetrical, the atomic polarisations have been estimated. These values of the atomic polarisations are discussed in relation to the force constants for the bending vibrations of the chelate rings and the effective dipole moments of the rings. It was found that the large atomic polarisations observed by previous workers for the acetylacetonates are apparently general for all inner-complex compounds in which the chelate ring contains six atoms. Exceptions may occur when the ring is held rigidly by some means, as in the salicylaldoxime complexes, where hydrogen bonding between the two oxime residues has been postulated to explain their unusually low atomic polarisations. For the other six-membered ring complexes, atomic polarisation values of between 29 and 67 c.c. were found for complexes containing two chelate rings in the molecule, and between 45 and 94 c.c. when three chelate rings are present, the variations being due to changes in the ring moment and the force constant. It was found that the force constants were considerably affected by changes in the strain of the chelate ring, since an increase in the strain of the ring increased its rigidity. Complexes of copper and nickel which contained five-membered rings have quite small atomic polarisations, this being attributed to the large force constants for the vibration of the rings which in these compounds are greatly strained.

The thesis is concerned with the assessment of optical stability in compounds whose activity is dependent upon restriction of rotation within the molecule. The introduction contains a review of past work in this field and particular reference is made to compounds whose activation energies of racemisation have been determined. In the experimental section, details are given of the determination of rate constants of racemisation of six substituted N-benzoyldiphenylamine 2-carboxylic acids in chloroform containing 2.5% by volume of ethanol. The results were used to estimate the constants E and A of the Arrhenius relationshipand the entropy of activation for each racemisation. As a help to the discussion of these results, determinations were later made of the racemisation of two of these acids in a variety of solvents. Details are also given of the racemisation of 6-nitro-, 4,6'-dinitro- and 4,6,4'-trinitro-diphenic acid together with the estimated E, A and values for the rate constants of racemisation in 2N-sodium carbonate solution. Rate constants for racemisation are discussed in terms of the activation energies and of the energy independentfactors. The discussion of the latter is based upon both the Absolute Reaction Rate theory of Glasstone,Laidler and Eyring, and the dynamical treatment of Slater. The influences on E and A of electrical effects, size effects and hydrogen bonding are considered. The optical stabilities of the three nitrodiphenic acids in alkaline solution are discussed and further compared with the stability of the dimethyl-esters and of the acids in organic solvents. Details of the synthetic work are given in the last section of the thesis.