Abstract: The multiplicity and the full spin of the ground state of large alternate molecules with conjugated bonds are considered. It is strictly shown that if the numbers of starred and unstarred atoms (say, carbon) differ from each other the full spin of the molecule is more than zero. Some possible planar and linear molecules having the full spin to be proportional to their sizes are presented. Particularly, they would be ferromagnets at infinite sizes.

Abstract: Unlike many other books on chemical bonding, this introduction to the subject does not adopt the traditional historical treatment in which the two basic theories of valence, molecular orbital and valence bond, are introduced and applied to increasingly complex molecules. Instead it develops the subject area from fundamental concepts which are important in chemistry as a whole. The validity of these concepts is examined within both the older empirical models and within the more recent ab-initio calculations. In this second edition, the contents have been extended to cover the mathematical basis of ab-initio calculations and the structure of computer programs used to carry these out. The new edition has also allowed the authors to extend the coverage of group theory techniques and update aspects of transition metal chemistry.

Abstract: Molecular receptors use intermolecular interactions for the selective binding of substrates. Macropolycyclic molecules containing appropriate binding sites and cavities of suitable size and shape, may be designed so as to display molecular recognition in the formation of selective inclusion complexes, cryptates, with metal cations, anions and molecules. Macrocyclic receptors which form stable and selective complexes with primary ammonium and guanidinium groups are discussed; they display central and lateral discrimination. Enhanced rates of intramolecular thiolysis and hydrogen transfer have been observed when suitable reactive groups are attached to the receptor. Macrobicyclic ligands form very stable and selective cryptates with alkali and alkaline-earth cations; they may be modified so as to selectively complex toxic heavy metal cations. Binuclear cryptates of two types have been synthesized: macrobicyclic complexes of an ellipsoidal Bis-Tren ligand and cylindrical macrotricyclic complexes. They display interesting properties (like cation-cation interactions, copper protein type spectral parameters etc.) and are suitable for formation of “cascade complexes” by interaction of substrates with the bound cations. Spherical macrotricyclic receptors form cryptates with cations, anions and small inorganic species. They display tetrahedral recognition and may be considered as topologically optimal receptors for the ammonium ion, the water molecule, the halide ions, with which they form cryptates where the substrate is held in the intramolecular cavity by a tetrahedral array of hydrogen bonds. Finally, the macrobicyclic Bis-Tren system in its protonated form, complexes triatomic species like the azide anion. It represents a further step in the design of abiotic molecular receptors for polyatomic molecules or ions. The main lines of further developments in the chemistry of macropolycycles comprise the design of receptors for other important groups (carboxylate, phosphate), of polynuclear complexes and cascade complexes of potential use in polynuclear catalysis, of molecular catalysts as enzyme models and new chemical reagents.

Abstract: A study has been made of the rate coefficients and product ion distributions for the reactions at 300 K of the ions N+, N2+, N3+, N4+, O+, O2+, and NO+ with CH3NH2, NH3, H2S, CH3OH, H2CO, COS, O2, H2O, CH4, CO2, CO, H2, and N2 molecules listed in increasing order of their ionization energies. These measurements are intended as a contribution to stratospheric chemistry. In the binary reactions of the ions of large recombination energy with molecules of low ionization energy, multiple ion products generally result and the rate coefficients are close to gas kinetic. Conversely, the low recombination energy ions NO+ and O2+ generally undergo ternary association reactions with the large ionization energy molecules. The reactions of N2+ and N4+ are very similar, the most common mechanism apparently being direct charge transfer usually followed by fragmentation, the nitrogen–nitrogen bonds in the reacting ions remaining intact. The N+ and N3+ reactions differ from the N2+ and N4+ reactions in that they show a gr...

Abstract: PART 1. EQUILIBRIUM 1. The properties of gases 2. The first law 3. The second law 4. Physical transformations of pure substances 5. Simple mixtures 6. Phase diagrams 7. Chemical equilibrium PART 2. STRUCTURE 8. Quantum theory: introduction and principles 9. Quantum theory: techniques and applications 10. Atomic structure and atomic spectra 11. Molecular orbitals for polyatomic systems 12. Molecular symmetry 13. Spectroscopy 1: rotational and vibrational spectra 14. Spectroscopy 2: electronic transitions 15. Spectroscopy 3: magnetic resonance 16. Statistical thermodynamics: the concepts 17. Statistical thermodynamics: the machinery 18. Molecular interactions 19. Materials 1: Macromolecules and aggregates 20. Materials 2: The solid state PART 3. CHANGE 21. Molecules in motion 22. The rates of chemical reactions 23. The kinetics of complex reactions 24. Molecular reaction dynamics 25. Processes at solid surfaces DATA SECTION ANSWERS TO EXERCISES ANSWERS TO PROBLEMS INDEX

Abstract: Perturbed-hard-chain theory for pure fluids, proposed previously by Beret, is modified slightly to yield better pure-component results. More important, it is extended to multicomponent mixtures. The perturbed-hard-chain theory is a synthesis of the polymer solution theories of Flory and Prigogine and the perturbed-hard-sphere theories of Alder and Barker and Henderson. The resulting equation of state is applicable to simple as well as complex molecules (for example, heptane, naphthalene, polystyrene). It can be used to calculate both gas and liquid phase properties. Extension of perturbed-hard-chain theory to mixtures is based on a one-fluid model without, however, making the usual assumption of random mixing. The perturbed-hard-chain theory has been applied to most fluids commonly encountered in natural-gas and petroleum refining operations. The theory gives good agreement with experiment for pure-component and fluid-mixture properties including vapor pressures, liquid densities, enthalpies, and K factors. Molecular parameters have been obtained for forty-five pure components and for more than sixty binary mixtures. Ternary and higher mixtures require no additional parameters.

Abstract: A dynamic technique, using radioactivity as a means of detection, makes it possible to measure the partial pressures of highly polar compounds in dilute aqueous solution. The results can be expressed in terms of the dimensionless distribution coefficient for transfer of a compound from dilute aqueous solution to the vapor phase. For acetic acid this coefficient is 1.1 X 10(-5), for acetamide 7.6 X 10(-8), for N-methylacetamide 4.1 X 10(-8), and for N,N-dimethylacetamide 5.4 X 10(-7). Thus acetamide is much more strongly solvated than the uncharged acetic acid molecule. The results suggest: (1) that the peptide bond represents an extreme among uncharged functional groups in the degree to which it is stabilized by solvent water; (2) that the very great hydrophilic character of the peptide bond may be associated mainly with hydrogen bonding of the solvent to the carbonyl oxygen atom (rather than the N-H group); and (3) that the observed equilibria of biosynthesis and hydrolysis of peptide bonds in aqueous solution are largely determined by differences between reactants and products in their free energies of solvation. It is anticipated that where "bound" water is found in proteins, it will often be found to be associated with peptide bonds, and will tend to be associated with the C-O group rather than with the N-H group.

Abstract: We have used Auger spectroscopy as a probe of local chemical environment both in the gas and condensed phases using a systematically chosen series of molecules [H2O, CH3OH, (CH3)2O, CH4, C2H4, and C2H2]. For the series of gas phase molecules, H2O, CH3OH, (CH3)2O, and CH4, where oxygen and carbon are, respectively, in similar bonding arrangements, characteristic fingerprint spectra (methanelike for C and waterlike for O) are shown to result. Additional fine structure, which is dependent on the specific molecular environment, appears on the spectra. In contrast, dramatic differences are observed for the series CH4, C2H2, and C2H4 in which major differences in hybridization exist at the carbon site. H2O, CH3OH, and (CH3)2O were studied both in the gas phase (electron excited) and in the condensed phase (x‐ray excited). The O(KVV) (K level–valence–valence transition) and C(KVV) spectra are shown to be similar when comparing the gas–solid results only if the multilayer spectra are properly corrected for electr...

Abstract: Low-temperature NMR studies of solid hydrogen at reduced ortho concentrations $Xl55%$ are interpreted in terms of possible quadrupolar glass phases in which the ortho molecules are frozen into random configurations. The quadrupolar glass is an extension of the concept of the dipolar glass of spins introduced by Edwards and Anderson.

Abstract: Single-crystal neutron-diffraction data with full-matrix least-squares refinements have yielded precise locations for all atoms (for the H atoms in particular), in both compounds. Hydrogen bonding with H atom sites disordered with equal occupancy, as previously postulated to be the source of zero-point entropy in the sulfate, is quantitatively verified. A thermally excited librational mode of the sulfate ion involving a rearrangement of hydrogen bonding has been found. The two structures, which have closely similar chains of Na ions with coordinated water molecules, are compared in detail. Measures of disagreement are: for the sulfate, R(F 2) = 0.082 for 1750 F 2 > a(F2); for the borate, R(F 2) = 0.060 for 1837 F 2 > o(F2).

Abstract: We calculate the loss of surface area accessible to solvent associated with coenzyme binding in Clostridium flavodoxin, in dogfish lactate dehydrogenase, and in lobster glyceraldehyde-3-phosphate dehydrogenase. The coenzymes are nearly buried in the complexes and lose on the order of 600 A*, while the proteins lose a similar amount of accessible surface area. Some of the loss can be attributed to conforma- tion changes in the protein, at least in the case of lactate de- hydrogenase, where we show that the apoenzyme has a larger Hydrophobic, electrostatic, and van der Waals forces are involved in all the various types of interactions made by the polypeptide chain of a protein: interactions with itself to fold into a globular structure; association with other chains to form multisubunit complexes; and the binding of small ligands. Thus when structural data are available from x-ray crystallography, the geometrical arrangement of polar atoms shows the presence of intra- and intermolecular hydrogen bonds and charge in- teractions and the volume of the Voronoi polyhedron around each atom describes the atomic packing (Richards, 1974; Chothia & Janin, 1975). The role of hydrophobicity can be assessed using the concept of accessible surface area (Lee & Richards, 1971). For a given protein atom this is the area of the surface over which the center of a water molecule can be placed while it is in van der Waals contact with the atom and not penetrating any other protein atom. Each square angstrom of protein accessible surface that is removed from contact with the solvent gives a hydrophobic free energy of 25 cal (Chothia, 1974). How do these different forces create the specific strong bonds that are essential for biological systems? From an analysis of the structure of the interfaces that occur between protein monomers, we concluded that hydrophobicity is the major force stabilizing protein-protein association; van der Waals forces and hydrogen bonds (i.e., complementarity) play

Abstract: The rotational structure of the fluorescence excitation spectrum of the B (v′=10) ←X (v″=0) transition of the van der Waals molecule HeI2 has been measured and analyzed. The analysis indicates that the molecule has a nonlinear equilibrium structure with R′=4.79±0.22 A and R″=4.47±0.13 A, where R is the perpendicular distance from the helium atom to a line drawn through the iodine atoms.

Abstract: The absolute Raman intensities of methanol, ethanol and water in the gas and liquid phases have been measured using 514.5 and 337.1 nm excitation. Large intensity changes were observed for the Raman lines of the OH stretching vibrations in changing from gas to liquid. The observed intensity changes are interpreted as due to the additional contribution of the charge transfer electronic excited state arising from hydrogen bond formation. The Raman intensities of methanol, ethanol and water in alkali halide solutions were also studied. The observed effects of halide ions on the intensities and their excitation wavelength dependences were found to be well correlated with the known charge transfer states resulting from electron transfer from the halide ion to the surrounding solvent molecules.

Abstract: The complexes formed from bacteriopsin and various retinyl compounds were analyzed by fluorescence and absorption spectroscopy. The binding of retinol occurs in two steps. In the first reaction the molecule is fixed in the retinal binding site of the protein. In this state, energy transfer from aromatic amino acid residues to the retinyl moiety is observed. all-trans-Retinal and the 13-, 11-, and 9-cis-retinols are bound in the chromophoric site. In the second reaction the cyclohexene ring and the side chain of the retinyl moiety are forced into a planar conformation. This reaction is mediated by a base (B1) with a pK of 3.8 and requires the oxygen atom but not the free hydroxyl group of retinol, indicating interaction with a group AH (pK greater than or equal to 10.5). The ring-chain planarization reaction is blocked for the 9-cis isomer of retinol. Binding studies with bacterioopsin and retinal isomers reveal that, as in the case of the corresponding retinols, B1 mediates ring-chain planarization in the case of the all-trans, 13-cis, and 11-cis isomers but not with the 9-cis isomer. Reconstitution of the purple complex from the intermediate 430-460-nm chromophore requires the presence of a second base (B2) with a pK of 4.6. This reaction is exclusive for all-trans- and 13-cis-retinal

Abstract: The strength of the bond between 125I-labelled C1q and immune complexes, Fc piece, dextran sulphate, polyglutamic acid and polylysine has been investigated. The binding of C1q to Fc piece, small molecular weight (less than 10,000) dextran sulphate, polyglutamic acid and polylysine have value; for the functional affinity constant (Ko) in the range of 0.2-1.5 X 10(4) M-1. In contrast the binding of C1q to immune complexes and large molecular weight polyions (greater than 100,000 is much greater and lies in the range 3 X 10(7)--4 X 10(8) M-1. The differences in the binding constants between the two groups can be explained if the Fc piece and small molecular weight compounds bind to only 1 head of the C1q molecule but the immune complexes and large molecules bind to 2 heads. There are probably 6 binding sites on the C1q molecule for dextran sulphate. The enhancement of the binding affinity of C1q by reduction in ionic strength and the reaction with polyions, indicate that ionic groups are present near or within the binding sites.