The literature on the mechanism of electrophilic aromatic hydrogen-exchange reactions is reviewed. A number of mono-tritiated polynuclear aromatic hydrocarbons and substituted benzenes have been prepared and their rates of detritiation in anhydrous trifluoroacetic acid have been measured. The deactivating effect of the halogens on the meta position has been determined in the [2-3H]-4-halogenoanisoles and (2-3H]-4-halogeno-toluenes; some interaction between the methoxy group and the medium being noted for the former series. Concurrent de-iodination accompanying the detritiation of [2-3H]-4-iodoanisole has been observed. Partial rate factors in detritiation have been determined for the 2-, and 3- positions in toluene and in diphenylmethane; the 1-, 3-, and 4- positions in fluorene; the 1-, 2-, 3-, and 4- positions in phenanthrene; the 2-position in 9,10-dihydrophenanthrene; and the 9-position in anthracene. These results are compared with other aromatic substitutions, such as halogenation and nitration; and with calculated reactivity data: some inconsistencies have been noted. A preliminary study has been made of the rate of detritiation of o- and p- tritiatedw-phenyl-n-alkyltrimethylsilanes, Ph(CH2)nSiMe3 (where n = 1 to 4). Because of various side reactions it proved possible to measure the rate of detritiation of only the two n = 4 compounds by the normal technique. A modified technique made possible measurements on the tritiated benzyltrimethylsilane. The rates of detritiation and de-t-butylation of [3-3H]-t-butylbenzene in trifluoroacetic acid - aqueous perchloric acid at 25° have been measured. The effect of the de-alkylation reaction on the rate of detritiation has been considered.

Current theoretical interpretations of the electronic spectra of solvated halide ions are described and critically discussed. Various consequences of the models are then examined, and compared with experimental results. The effect of ion association on the electronic spectra of several systems is then reviewed, and examples of the analytical methods used to obtain dissociation constants from spectrophotometric data discussed. Brief reviews are given of previous investigations into the effect of anions on the OH stretching frequency of alcohols, and into the ability of carbon tetrachloride to act as an electron acceptor. The spectra of various iodides in several solvents of low polarity have been found to depend upon the identity of the counter-ion, and it is shown that the energies of such spectra have anomalous temperature coefficients. The spectrum of iodide has also been recorded in binary solvent mixtures and the results are discussed in terms of equilibria between free ions, solvent shared ion pairs, and contact ion pairs. The dissociation constant of tetra-n-hexylammonium iodide in dich1oromethane has been evaluated, together with equilibrium constants for the systems n-Hex4NI + cyclo-hex2H2N+ = n-Hex4N+ + cyclo-hex2H2NI in dichloromethane, and n-hex4NI + MeOH = n-hex4NI.MeOH in carbon tetrachloride. This last system has been studied quantitatively by both ultra-violet and infra-red measurements. Finally, the results of the present work are compared with the conclusions drawn from previous conductimetric, N.M.R., E.S.R., and spectrophotometric measurements.

A review is presented of the acid-catalysed electrophilic aromatic displacement reactions. Acidity dependence, solvent isotope effects, and substituent effects are assessed as criteria for the assignation of the detailed mechanisms to these reactions. The mechanisms of reactions, including hydrogen exchenge, between tertiary-alkyl derivatives and nucleophiles are discussed in terms of carbonium-ion mechanisms. The ortho-, meta-, and para-isomers of t-outyl-toluene, labelled with tritium in the t-butyl group, have been prepared by a route involving the reduction of the 2-methyl-2-tolylpropionic acids by tritium-labelled diborane. Relative specific activities showed that sodium diborohydride completely exchanged borane with diborane in diglyme. Attempts to prepare an optically active (asymmetric at the quaternary caroon atom) tertiary-alkylaromatic, labelled with tritium at a position beta to the ring, were unsuccessful. A preliminary investigation, using vapour phase chromatography for analysis, has been made of the trans-t-butylation of t-butylaromatics in trifluoro-acetic acid, and in trifluoroacetic acid/perchloric acid. The mixed acid medium removed polyalkylaromatics, presumaoly by oxidation, at a rate comparable to the trans-t-butylation reaction. In trifluoroacetic acid an equilibrium is set up between t-butyl trifluoro-acetate and the possible t-butylaromatics.

A review of the development of the study of metal solutions is presented, with particular emphasis on the various models proposed to describe their physical properties. Electron spin resonance and optical absorption measurements are reviewed in detail. The electron spin resonance absorption of solutions of alkali metals in liquid ammonia has been studied as a function of the concentration of metal and of added alkali metal halides. When the concentration of metal is less than 0.01 molal there are small negative deviations in the g-factor for added chlorides and bromides, but very large deviations for added iodides, the shifts for a given salt molality being then a function of the cation. These shifts are enhanced at higher metal concentrations and higher temperatures, and are accompanied by a marked increase in the line width. The visible and near infra-red absorption spectra of some of these solutions have been measured and the appearance of a shoulder in the 12,500 cm-1 region has been confirmed. These results are discussed in terms of a specific interaction between unpaired electrons and iodide ions. A confined model for the solvated electron is developed by analogy with related systems, and is used to describe the spectral properties of electrons trapped in various media.

The effects of variations in extra-molecular, and molecular factors on chromatographic behaviour is reviewed. The relation between molecular structure and the chromatographic behaviour of substituted phenols is considered for the following systems. (a) Adsorption chromatography on alumina surfaces. (b) Reversed-phase thin-layer chromatography on cellulose impregnated with ethyl oleate. In adsorption chromatography, the mechanism responsible for the chromatographic process is thought to be hydrogen bonding between the phenolic group and the hydroxylated alumina surface. In the systems studied, the gross effect of this inter- molecular hydrogen bonding is so strong that, in the simple alkyl phenols, with no ortho-groups, the effects of substituents on chromatographic behaviour is negligible, and hence the Martin relation is not valid for these compounds. Where alkyl substituents are present in one or both ortho-positions, the values increase with an increase in the chain length of the substituent. This is attributed to a steric effect rather than to electronic ones. The bulkier is the ortho-substituent the greater is the steric effect. For the halogenated phenols, intermolecular hydrogen bonding between halogen atoms and the hydroxylated surfaces is important. In mixed halogeno-; alkyl-substituted phenols, the effect of the addition of a group to the molecule is dependent upon the natures of the groups already in the molecule. This is also so for the substituted nitrophenols. This represents a real deviation from the Martin relation. Internal hydrogen bonding, and external hydrogen bonding are both important in governing the chromatographic behaviour of the nitrophenols. The effects of other substituents in the nitrophenol molecules in modifying the strengths of these hydrogen bonds are also of importance. In the reversed-phase thin-layer chromatography, the behaviour of the phenols is dependent upon the removal of the phenol from the stationary phase into the mobile phase by the solvation of the phenolic group by the mobile phase. The Ivlartin relation is shown to be approximately valid in these systems, but is modified by the presence of other structural features in the molecule. Steric effects are considered to be more important than electronic effects in modifying chromatographic behaviour. The effect of internal hydrogen bonding is significant in the chromatography of the nitrophenols. Solvation of the nitro-group by the eluent is also important. For the polyamide/cellulose system, the chromatographic behaviour of the phenols is dependent upon the nature of the eluents. Por non-aqueous systems some real failures of the llartin relation are seen. In other cases, e.g. where ortho-groups are present in the molecule, the chromatographic behaviour is dependent upon the steric hindrance of the approach of the phenolic group to the polyamide surface. Here the Martin relation is approximately valid. In aqueous eluents, solvation of the pheiiolic group by the eluent is thought to govern the chromatographic process. The Ivlartin relation is approximately valid, but is modified by other constitutive effects, e.g. internal hydrogen bonding, the presence of double bonds and steric effects. In all systems it appears that, though steric effects cannot be entirely separated from electronic effects, the former are more important than the latter.

Mutants of Escherichia coli were isolated and identified as lacking key enzymes of specific anaplerotic equences. With these muntants it was shown that growth on pyruvate or precursors thereof necessitates the functioning of an acetyl-COA dependant PEP carboxylase, and that growth on acetate requires the operation of isocitrate lyase. The growth of all the PSP carboxylase-less mutants on acetate was inhibited by addition of pyaruvate or precursors thereof. Analysis of this effect of pyruvate and substances derived from it on the behaviour of whole cells and cell-free extracts suggested that the phenomenan is due to the inhibition by PEP of isocitrate lyase. Further studies with mutants which lacked the ability to convert pyruvate to PEP or which were derepressed for isocitrate lyase suggested that the inhibition of isocitrate lyase by PEP was of physiological significance and provides a means whereby the rate of operation of the glyoxylate cycle is controlled. Isocitrato lyase has been partially purified and its properties investigated. An anaplerotic enzyme of glyoxylate metabolism, tartronic semi-aldehyde/(TSA) reductase was shown to be formed during growth of E. coli on DL-glycerate. Studies on the behaviour of mutants devoid of glycollic oxidase or PEP carboxylase or citrate synthase activities indicate, however, that the formation of TSA reductase is not an indication of a pathway of glycerate metabolism distinct from the glycolytic sequences: rather it is concluded that it functions as one component of the enzymic system catalysing the interconversion of the D and L isomers of glycerate.

No description available.

The structures of HgFe(CO)4, CdFe(CO)4 and Fe (CO)4 (HgX)2 , which were originally reported in 1928-1929, have been determined by a study of their infra-red spectra and are shown to contain metal-metal bonds. The reaction of mercuric chloride with iron pentacarbonyl at low temperatures gave the reported Fe(CO)5HgCl2 and also a 1:2 adduct, Fe(CO)5 2HgCl2 . Treatment of substituted iron carbonyls with mercuric salts gave analogous complexes. with mono phosphine (arsine or stibine) iron tetracarbonyls, the products could not be identified but with the disubstituted derivatives Fe(CO)3 (Eph3 )2 , E = P, As, Sb., 1:1 adducts of the type Fe (CO)3 (Eph3 )2 HgX2 were isolated. The phosphite derivative gave a 1:2 adduct. The diolefin iron tricarbonyls, eg. norbornadiene iron tricarbon yl showed no reaction with mercuric chloride. Physical studies, in particular the infra-red spectra (2200-200 cm-1), showed that the 1:1 adducts are probably dimeric in the solid and dissociate in solution to the "parent" carbonyl, mercuric halide and an ionic species, Fe(CO)3 [P(OPh)3]2 2HgCl2 was a 1:1 electrolyte in solution. The infra-red spectra of the ''parent" substituted carbonyls were studied in detail. In view of the similarity of iron pentacarbonyl to cyclopentadienyl cobalt dicarbonyl the reactions of the latter with mercuric salts were investigated. Both 1:1 and 1:2 adducts, (C5H5)Co(CO)2 1 or 2 HgX2 were isolated. Physical studies support a dimeric structure in the solid containing mercury-cobalt bonds and bridging halogens. Dissociation occurs in solution. The donor property of Fe(CO)3 (PPh3 )a has been briefly investigated with other metal and non-metal salts. In the introduction to this thesis metal-metal bonded complexes are reviewed. Also included are compounds relevant to their preparation.

No description available.

The Introduction consists of a discussion of the way in which transition metals are bonded to olefins. The synthesis of chloro-olefin complexes of the type (PPh3)2Pt (olefin) are reported. These were prepared either by using the established methods of preparation starting from (PPh3)4Pt or hydrazine reduced cis-(PPh3)2PtC12, or by reaction of the olefins with (PPh3)2Pt (trans-stilbene) in ether solution, which proved to be a superior method of synthesising the olefin complexes. The conditions under which these chloro-olefin complexes isomerise to the vinyl ones, (PPh3)2Pt (chlorovinyl) C1, or in some cases break down to afford cis-(PPh3)2PtC12 are also reported. It is indicated from kinetic studies of the isomerisations of (PPh3)2Pt (C2C14) and (PPh3)2Pt (C2C13H) to the corresponding cis-vinyl complexes in various solvent systems, that the former probably proceeds via a process similar to SN1 (lim) solvolysis of t-butyl chloride, whilst the latter occurs more rapidly via a system of which the mechanism is probably intermediate between an SN1 and intramolecular type of process. The reactions of (PPh3)4Pt and (PPh3)2Pt (trans-stilbene) with chloromethyl cyanides, CF3CN and chloroacetone compounds are also reported. The complex (PPh3)2Pt (CF3CN) has been prepared as well as complexes containing NH and polymerised CF3CN fragments. The crystal structure of the complex (PPh3)2Pt (CF3CN)2NH is reported. Reactions with the chloro-ligands resulted in the formation of either cis-(PPh3)2PtC12 or complexes analogous to chlorovinyl ones. Infrared data of all novel complexes, n.m.r. data of many and some mass spectrum data are reported and discussed.