bluuebunny/crossref_metadata_2025 huggingface dataset:
Methods of calculation of band structures
Authors: Altmann Simon L
Published: November 2023

In parallel with the development of modern computers in the last twenty or thirty years, several methods for the calculation of the energy eigenvalues E(k) in crystals have been perfected, and computer programs now exist which make the calculation of band structures a fairly routine matter. Some results of such calculations have already been discussed in the last chapter. No attempt, however, will be made in this chapter to give an account of the accurate methods of numerical calculation now available. The discussion will concentrate instead on the methods that provide some simple, although approximate, insights into the main features of band structures.
Phase stability: Brillouin zone effects
Authors: Altmann Simon L
Published: November 2023

Copper is face-centred cubic but, when zinc is added to it, this phase eventually becomes unstable and it changes over to the body-centred cubic structure. It is possible to explain such changes of phase by considering the change in the Fermi energy which takes place when the Fermi surface expands (as it must, for increasing electron concentrations) until it touches a face of the Brillouin zone. We shall study in the first few sections of this chapter the rules which determine such phase transformations in alloys. We shall then consider another effect which is due to the properties of the Fermi energy at the Brillouin zone edges, and which requires that regular one-dimensional chains be unstable with respect to transformations into structures with alternating short and long bonds. This effect is called the Peierls instability.
Surface and impurity states
Authors: Altmann Simon L
Published: November 2023

We have so far seen that the electron states of a periodic structure are described by Bloch functions which form energy bands as a function of k, and that these bands are such that, in general, forbidden energy gaps exist between them. It is reasonable to expect, on the other hand, that electrons which arise from impurities or from surface states in the crystal will not give rise to periodic states and will not, therefore, be described by Bloch functions. We must expect, accordingly, that the corresponding energies may appear in the forbidden energy gaps, as will be confirmed in this chapter. The first thing which we shall do is to look for the possible existence of states in the gap, and this will lead in§ 1 to the Tamm states. We shall then consider a simple model of surface states (Shockley states) in§ 2. A more detailed method of calculation of surface and impurity states, proposed by Koster and Slater, will be discussed in § 3 and will serve as a simple introduction to the use of Green functions. A practical example of this treatment will be given in § 4.
Lariat ethers
Authors: Gokel George W
Published: November 2023

The award of the 1987 Nobel prize in chemistry to Charles J. Pedersen, Donald J. Cram, and Jean-Marie Lehn provided important recognition to the field called variously ‘macrocycle chemistry’, ‘host-guest chemistry’, ‘supramolecu lar chemistry’ or ‘molecular recognition’. In its essence, the field encompasses the study of non-covalent interactions that occur between hosts and guests or substrates and receptors of many different types. Although Liittringhaus had previously prepared examples of what are now known as crown ethers (e.g. (1)), Pedersen recognized their importance as cation binders when he uncovered these compounds in the 1960s. Lehn elaborated these macrocycles into macrobicyclic ‘cryptands’ (e.g. (2)) or three-stranded crown ethers that can completely envelop a cation, anion, or other molecular species.
Bridged pyridine hosts
Authors: Bell Thomas W , Sahni Suresh K
Published: November 2023

The popularity of pyridine as a structural unit m macrocycles is largely explained by its unique combination of coordination properties. Pyridine’s dipole moment (2.2D; ID= 3.34 × 10 Cm) coincides with the orientation of its nonbonded electron pair, leading to stable solvates and u-complexes with metal cations and other Lewis acids. Low-lying π* molecular orbitals further stabilize pyridine complexes of transition metals by d-electron back bonding. Pyridine is also an effective hydrogen-bond acceptor, while pyridinium ions and pyridones are good hydrogen-bond donors. Thus, bridged pyridine hosts can be used to form complexes with hard or soft metals or with charged or neutral molecular guests.
Clathrasils and zeosils: inclusion compounds with silica host frameworks
Authors: Gies Hermann
Published: November 2023

The structural analogy of crystalline phases of ice and crystalline phases of silica is well known and has been reviewed by several authors.1 In 1981, structure determinations of the mineral melanophlogite2 and synthetic ZSM-39 (dodecasil 3C),3 isostructural with the clathrate hydrates of Type I and II respectively, expanded that relationship to include clathrate-type compounds. In 1983, the name clathrasils was introduced for a family of silica host-frameworks. In a new general classification scheme for porous tectosilicates proposed by Barrer5 and expanded by Liebau et al., clathrasils and zeosils are branches of the porosils, a subclass of the porous tectosilicates, which comprises all silica end endmembers with the general formula [SiO2]
The structural chemistry and reactivity of organic guests in layered aluminosilicate hosts
Authors: Thomas John M , Theocharis Charis R
Published: November 2023

There has been an explosive growth in the studies carried out on sheet aluminosilicate intercalates since the subject was last reviewed by one of us1 in 1982. In this series of publications, reference to inclusion compounds based on layered silicate hosts has hitherto been brief (see Chapter 7, Volume 1). There are many reasons for the enhanced interest: first, more powerful techniques are now available to probe the nature of the wide variety of guest-host systems discovered within this family of solids; second, an ever-widening range of catalytic reactions has been discovered with aluminosilicates as the precursor catalyst; third, there is considerable scope for exquisite modification of both the parent layered solid and also the resulting solid intercalate.
Porphyrins for the future
Authors: Milgrom Lionel R
Published: November 2023

The porphyrins we have dealt with so far are naturally occurring, and are involved in the light-harvesting reactions of photosynthesis and the electron-or oxygen-transporting and storage functions of cellular metabolism. Synthetic porphyrins are also useful, and, as our knowledge progresses, the number of applications is expanding. Sophisticated porphyrin derivatives are already being tried out in laboratories around the world in a wide variety of applications, including medicine, electronics, and alternative energy generation. However, before we examine some of these new applications, we should start with a lucky fluke that led to one of the most successful families of synthetic pigments ever invented—the phthalocyanines.1 These blue to green pigments now have a wide variety of uses, including artists’ colours, printing inks (especially for bank notes), surface coatings, paper dyes, floor coverings, and even as high temperature lubricants for space vehicles. But the success of synthetic pigments like the phthalacyanines is relatively recent.
Crystallographic studies of inter- and intra-molecular interactions
Authors: Krygowski Tadeusz M
Published: November 2023

Inter- and intra-molecular interactions of chemical species are of primary importance in chemical research. They influence chemical reactivity and are associated with changes in the geometry of the chemical species involved. Hence, knowledge of the precise geometry of chemical systems is valuable as the starting point for understanding their chemical{ physical and biological properties (Hoffmann, 1983). The most effective way to study molecular geometry is by crystallography with X-ray and (to a lesser extent) neutron diffraction on crystals. The thousands of crystal and molecular structures solved and published annually mean that thousands of geometries of chemical species become available for interpretation.
Strain in cyclo-annulated aromatic systems
Authors: Boese R , Blaser D , Niederprum N , Miebach T
Published: November 2023

One of the essentials for organic crystal structure investigations is the availability of a single crystal. Because of the special problems of investigation and the difficulties in handling crystals of highly strained molecules, which are usually extremely sensitive to heat or are liquid under ambient conditions, the first part of this contribution will describe the techniques for crystallizing samples and for getting them onto the diffractometer without damage.
Influence of electric field on polymorphism in isotactic polypropylene
Authors: Paukszta D , Garbarczyk J , Sterzynski T
Published: November 2023

As happens with small molecules, polymorphism often also occurs in synthetic polymers. Thus, polyethylene crystallizes in orthorhombic and triclinic forms, polypropylene in monoclinic and orthorhombic forms (Wunderlich 1973; Samuels, Yee 1972; Neapolitano, Pirozzi 1986). These polymers provide examples of this phenomenon and of transformations between the different forms. One among several factors that can lead to the formation of one, rather than another, of the polymorphic modifications is the addition of specific low molecular weight compounds to the polymers.
Phasing at low resolution
Authors: Roth M
Published: November 2023

The specificity of low resolution diffraction is that it does not depend on local atomic order but is determined only by the local scattering length density in the unit cell and by the translational symmetry of this density in the crystal. An important domain of application of low resolution diffraction is, therefore, the structure determination of systems showing local atomic disorder. Examples of such cases are the studies of RNA in a virus (Bentley et al., 1987), detergent micelles in membrane protein crystals (Zulauf et al., 1986; Roth et al., 1989) , lipid domains in lipoproteins (Banaszak el al., 1989). Another application is the structural study of large complex systems which often do not diffract to atomic resolution. They may also be too large to be phased by heavy atom derivative techniques. This domain of application is probably going to become more important in the future, with the development for instance of structural studies of ribosomes (Yonath et al., 1989; Trakhanov et al., 1989).
Accurate solutions of the maximum entropy equations. Their impact on the foundations of direct methods
Authors: Navaza J
Published: November 2023

Information theory provides a conceptually clear framework where the importance of the many possible combinations of data and prior knowledge can be assessed. The theoretical interest of the formulation resides in the independence of the maximum entropy estimates, with respect to missing information. Its major contribution is perhaps the new insight it gave to the foundations of direct methods (Bricogne, 1984). Most procedures based on the maximum entropy principle produce estimates m(r) of the electron density function p(r), which agree with the experimental data. Then, according to the non- committance of the method, if some expected property of the electron density is not displayed by the estimated map, we can safely conclude that the data and prior information used to construct it, were not sufficient enough to bring out the sought property. Despite the attractive qualities of the formulation, some difficulties are encountered when trying to apply it to the phase problem:
X-ray structure refinement with X-PLOR
Authors: Bhat T N
Published: November 2023

Molecular dynamics coupled with structure factor least-squares (Brunger et. al., 1987; Van Gunsteren et. al., 1987; Fujinaga et. al., 1989; Weis et. al., 1990; and references therein ) is a very useful refinement procedure for macromolecules. It uses Metropolis method (Metropolis et.al., 1953) coupled to molecular dynamics to optimize molecular energy along with agreements between observed and calculated structure factors. Methods such as the ones using derivatives, quasi Newtons, or conjugate gradients may be compared to rapid cooling. These methods look for nearby minima, which may not be the lowest. By contrast, the Metropolis method (also known as simulated annealing) takes ‘down hill’ steps while sometimes allowing ‘uphill’ steps so as to skip a barrier giving rise to a local minimum. Ideally, the ‘uphill’ steps taken during the optimization need be ‘large’ enough to skip all local minima but at the same time ‘small’ enough to be contained by the global minimum. Since this is hard to be satisfied in crystallographic refinements of macro molecules which have many local minima, such a method may only aim for a minimum which is ‘more’ global than the initial one, rather than a global minimum.
Application of organotin groups as markers in analysis of coal liquefaction products and petroleum fractions
Authors: Rafii Esfandiar , Maire* Jean Claude , Ngassoum Martin , Faure, Robert , Lena Louis
Published: November 2023

Aside from their industrial applications, organotin compounds have also been widely used as intermediates or reagents in organic synthesis. More recently, organotin groups have been used as markers for the structural elucidation of complex molecules with the aid of spectroscopic techniques. The possibility of using tri-n-butyltin compounds as markers is illustrated, with reference to multinuclear NMR spectroscopy, for the quantitative analysis of phenols in liquid fractions derived from coal, and of sulphur compounds in petroleum fractions.
Recent chemistry of the silicon-silicon double bond
Authors: West* Robert , Shepherd Brian , Gillette Gregory , Millevolte Anthony , Driess, Matthias , Tan Robin
Published: November 2023

Disilenes, compounds containing silicon-silicon bonds, were first synthesized in 1981:

When the first organosilicon compounds were synthesized in the 1860’s, multiple bonds were already well known in carbon chemistry. The first attempts to make multiply-bonded silicon compounds were reported as early as 1869. But these efforts, and all others, were unsuccessful for more than a century, and the belief gradually arose that multiple bonds to silicon would be impossible to form.
Function and characterization of CVD zeolites with controlled pore-opening sizes
Authors: Niwa Miki , Murakami Yuichi
Published: November 2023

Chemical vapour deposition (CVD) zeolites with precisely-controlled pore-opening sizes have been synthesized which show enhanced shapeselectivity and hence, increased efficiency in applications which include catalytic reactions and separations. The method involves the deposition of a silicon alkoxide on the external surface of the zeolites; the resulting layer of silica thus formed exerts a fine control on the pore-opening sizes. As examples of application, the selective cracking of octane isomers on mordenite, and the separation of oxygen and nitrogen on zeolite A, are described. The structure of the silica layer deposited on the external surface has been characterized by XPS, and indirectly by EXAFS by using a germanium alkoxide as a convenient probe in place of the silicon alkoxide. The germanium oxide layer formed on the zeolite was found to be very thin, but upon aggregation, the pore-controlling property of the layer was eliminated completely. These observations suggest that the silica layer on the CVD zeolite obtained under the controlled experimental conditions must also be very thin.
Antitumour activity of organotin compounds and inhibition of membrane signal transduction
Authors: Arakawa Yasuaki
Published: November 2023

Dibutyltin dichloride exhibits in vivo antitumour activity towards Ehrlich ascites tumour, IMC-carcinoma, P-388 Iymphocytic leukaemia, and Sarcoma 180 system in descending order of activity in mice. In addition, in a two0stage mouse skin carcinogenesis system of initiation and promotion, the optimal dose of the dibutyltin compound inhibits the promotion stage more strongly, especially the first stage of the two-stage promotion system, than the initiation stage. On the other hand, in vitro studies reveal that the dibutyltin compound dramatically inhibits the proliferation of thymic lymphosarcoma cells and HeLa cells, and further inhibited the initiation stage of the two-stage transformation of BALB/c 3T3 cell. Furthermore, dibutyltin dichloride inhibits phosphatidylinositol (PI) turnover and arachidonate release without affecting directly the Ca+ entry into the cells. The compound also causes a significant increase in the membrane order of inositol phospholipids (PIP) that serve as the substrate of phospholipase C. Moreover, the compound inhibits the selectivity of phosphorylation of lipocortin, a phospholipase A inhibitory protein, whereas the compound has no direct inhibitory effect on phospholipase C, phospholipase A and protein kinase C.
Tolerance of Ceratocystis ulmi to organotin adducts
Authors: Eng George , Khoo Lian E , Stockton, Laura L , Coddington Stephen P
Published: November 2023

Several series of organotin adducts have been screened in vitro against the growth of Ceratocystis ulmi, the causative agent of Dutch elm disease, by using a shake culture method. Maximal activities were obtained with triphenyltin halide adducts of the general formula, Ph SnX·L where X = Cl or Br and L = Me SO, PhCONH, or Ph PO. The nature of the anionic group, X, or the ligand, L, did not have a significant impact on the inhibition studies, suggesting that the species involved in the inhibition is the cation Ph Sn+ or its hydrated form, [Ph Sn(H2O)2]+.
Organofunctional polysiloxanes as selective extractants and metal ion support materials
Authors: Brisdon B J , England R
Published: November 2023

The concept of attaching chemically useful species to polymer supports in order to improve their performance, facilitate their use, and enable product separations to be achieved with minimum energy expenditure has been well exploited in many areas of chemistry. Of the considerable number of polymeric materials that have been investigated as support matrices, nearly all are solids and many suffer from the severe disadvantage of being difficult to functionalize chemically in a reproducible and controlled manner.
Stereoregulating effects of alkoxysilanes in propylene polymerization
Authors: Gupta V K
Published: November 2023

There is great interest in the development of new generation Ziegler-Natta catalysts supported on magnesium compounds for the stereospecific polymerization of propylene. Such a catalytic system includes a solid precatalyst with mainly magnesium chloride as the support, an organic ‘internal’ Lewis base, titanium tetrachloride, and a co-catalyst solution consisting of a trialkylaluminium and an ‘external’ Lewis base. The activity and stereospecificity of the catalytic system are highly dependent on the details of preparation and the nature of the components used as pre-catalyst and co-catalyst.
Reaction pathways in the thermolysis of organotin and organosilicon compounds
Authors: Harrison P G , Ashworth A , Clark E N , Podesta D , Oquab, D , McManus J
Published: November 2023

The thermal decomposition of a number of tetraorganostannanes, R Sn (R = Me, Et, CH=CH, n-Pr, i-Pr, n-Bu, sec-Bu), tetraalkylsilanes, R Si (R = Me, Et), trimethylstannane, Me SnH, and trialkylsilanes, R SiH (R = Me, i-Pr), has been investigated. The decomposition of tetralkylstannanes follows several possible routes depending upon the nature of the organic group and the presence or otherwise of oxygen.
Organotin and inorganic tin complexes of some aromatic Schiff bases
Authors: Beng Teo Soon , Guan, Teoh Siang , Yeow Yeap Guan
Published: November 2023

Organotin(IV), inorganic tin(II), and tin(IV) derivatives of 2-hydroxy- 1-naphthaldehyde- or salicyldehyde-substituted aniline Schiff bases have been prepared. The 1/1 and 1/2 molecular adducts have been characterized by elemental analyses, and by IR and NMR spectroscopic techniques, which indicate that coordination to tin occurs through the hydroxyl oxygen or the azomethine nitrogen, or through both these atoms. The crystal structure of the 1:2 diphenyltin dichloride adduct with 1-(4-methoxyphenylimino) methyl-2-naphthol is reported.
Synthesis and characterization of a series of diorganotin derivatives of ex-amino acids
Authors: Ang Tian Tse , Khoo Lian Ee
Published: November 2023

Recently several diorganotin compounds of bicyclic structure have been found to be active in vivo against P388 lymphocytic leukaemia in mice. This has prompted us to prepare and characterize eight new diorganotin derivatives of comparable structural similarity to the above-mentioned compounds by condensing diorganotin oxides, R SnO, with the Schiff base of the following a-amino acids, (1)-(4).
Studies on some triphenyltin(IV) complexes containing potentially bidentate, biologically-active anionic groups
Authors: Chandra Shubhra , Gioskos S , Magee, R J , James B D
Published: November 2023

Triphenyltin(IV) derivatives have been synthesized which contain anions from various biologically-active acids which include: dithio- and monothiocarbamates (DTC and MTC), phthalic acid (PTA), salicylaldehyde (SAL), phenoxyacetic acid (PAA), imidazole (IMI), 2-mercaptoethanol (MET), 2-aminoethanethiol (AET), 2-mercaptopyridine-N-oxide (PNO) and acetylsalicylic acid (ASA). The coordination about the tin atom was investigated by IR, Sn NMR and Mossbauer spectroscopic methods. The triphenyltin cation with S-bonding groups generally acquires a fourcoordinated structure (MTC, OTC, MET, AET, PNO). On the other hand, combination with 0-bonding groups can produce several structural possibilities: four-coordinate (ASA), five-coordinate cis trigonal bipyramid (SAL) and six-coordinate, and polymeric (IMI, PTA, PAA). The tolerance of eight plant-pathogenic fungi to the compounds was investigated by growth-inhibition tests. Although some influence of the chelating anionic group has been reported previously, no systematic dependence of fungitoxicity on the coordination number of tin was observed with these complexes.
Partial miscibility of strictly binary polymer systems
Authors: Koningsveld R , Stockmayer W H , Nies E
Published: November 2023

In the experimental practice of polymer research virtually all studied samples contain many usually homologous components. Nowadays many polymerization mechanisms lead to samples having very narrow molar-mass distributions (MMD) but such products still differ somewhat in average molar-mass values, such as the number average, M, and the weight average, M. The ratio M/M provides a measure of the width of the number distribution, and ‘living’ polymerizations produce samples with M/M typically around 1.05. Even then, the sample contains some thousand components and, moreover, though fractionation may narrow the MMD to some extent it can never lead to fractions that truly consist of a single component (see Chapter 14).
Miscellaneous phase transitions
Authors: Koningsveld R , Stockmayer W H , Nies E
Published: November 2023

This chapter gives a brief description of phase transitions not fully covered in the preceding discussions but that need attention if only because the phase diagrams in which they appear show similarities with the more familiar types and may therefore be confusing.
Monolayer Structures
Authors: Bruch L W , Cole Milton W , Zaremba Eugene
Published: November 2023

Physically adsorbed layers are readily compressed by increasing the pressure of the coexisting 3D gas.* The lattice constants of the monolayer solids are on the scale of a few angstroms, the compressions are on the scale of tenths of angstroms, and the lengths derived in high resolution diffraction experiments typically have precisions 0.002-0.02 õ. A small number of lattice classes suffices to describe the average lattices of most monolayer solids. As for 3D solids, the primitive vectors, basis vectors, and reciprocal lattice vectors provide a convenient set of coordinates with which to express the periodicity of the lattice. Further, the spatial periodicity of the potential arising from the substrate is conveniently formulated with such coordinates.
Prologue
Authors: Mukaiyama Teruaki
Published: November 2023

Vigorous evolution of gas, quick coloration to brown, and the formation of precipitates; there, hidden, was the treasure of possibility in the bubbles of foam on the surface, which were observed in the reaction vessel in a corner of our small laboratory! For organic chemists, facing such an unpredictable phenomenon is not uncommon. In flasks, that which can never be predicted by thought or discussion with co-workers often happens. This unpredictability is a prominent characteristic of chemical research. Frank acceptance of what is witnessed will lead one to find the very hint of a major breakthrough in the researcher’s knowledge.
Ring-opening polymerization
Authors: Mukaiyama Teruaki
Published: November 2023

In Chapter 3, I have described the chemistry in which compounds with cumulated double bonds (X=Y=Z) or an unsaturated carbon-carbon bond (e.g. isocyanate, carbodiimide, alkoxyacetylene, vinyl ether, and ketene acetal) undergo reaction with aldoximes, primary nitroalkanes, hydroxamic acids, etc. to give intramolecular dehydration products (e.g. nitriles, nitrile oxides, isocyanates, etc.) in high yields. In order to broaden the scope of such dehydration reactions, we examined the dehydration of aldoximes with diethyl N-phenyliminocarbonate, which can be regarded as the acetal of isocyanate. At that time, I assumed simply that the iminocarbonate is an equivalent of isocyanate, as an acetal is the equivalent of a ketone. Contrary to my expectation, however, aldoximes were completely unreactive to the iminocarbonate under various reaction conditions using a basic or Lewis acid catalyst, in contrast to the reaction with isocyanate. A protic acid was then added to promote the reaction. Although aldoximes were unreactive under these conditions, the iminocarbonate was found to react with acid vigorously to produce ethyl N-phenylcarbamate and the corresponding ester of the added acid, as shown in eqn (4.1).1 The reaction probably proceeds as follows: first, the iminium salt is formed by protonation of the nitrogen-carbon double bond, and then the carboxylate anion attacks the iminium salt to give urethane and the carboxylic ester.
New synthetic reactions with titanium compounds
Authors: Mukaiyama Teruaki
Published: November 2023

In Chapter 8, the general use of the oxidation-reduction condensation reaction using triphenylphosphine and 2,2’-dipyridyl disulfide has been illustrated in the synthesis of peptides and nucleotides. We now focused our attention on the application of such a condensation reaction to intramolecular dehydration reactions, specifically to the dehydration of alcohols to olefins. The initial trial consisted of the following reactions: preparation of the phosphonium salt from phosphine and disulfide, followed by addition of an alcohol and AgC104, the latter being expected to serve as a thiol captor. The reaction produced the expected olefin, albeit in very low yield, and detailed studies revealed that the presence of the silver salt is enough to effect the dehydration reaction1 ( eqn (9.1)).
Synthetic control
Authors: Mukaiyama Teruaki
Published: November 2023

In the preceding chapters, I described our main efforts devoted to the development of new methods for bond formations, such as carbon-carbon bonds, amide and phosphate linkages, etc. At that time, the accumulation of experience within our group, along with rapid progress in synthetic organic chemistry, led me to believe that the development of reactions where bond formation is achieved with a high degree of selectivity would become not only possible but a prerequisite in the near future. What follows is an account of one of my first attempts to realize such selectivity in synthetic organic reactions.
Oscillatory Behaviour In The Isothermal Cstr: Autocatalytic Systems
Authors: Gray Peter , Scott Stephen K
Published: November 2023

The previous chapters focused on the existence and locus of stationary states. Here their stability to small perturbations is outlined, together with the systematic study of the onset of oscillations in isothermal, autocatalytic open systems. After careful study the reader should be able to:
Heterogeneous Reactions
Authors: Gray Peter , Scott Stephen K
Published: November 2023

The previous chapters have dealt at some length with the wide range of non-linear kinetic behaviour which can arise when there is autocatalysis, either because of chemical intermediates or through self-heating. Reactions involving more conventional catalysts, such as heterogeneous surfaces or enzymes, are also known as a good source of multiple stationary states and oscillations. Many simple oxidation processes, including those of H2, CO, and NH3, show ignition and extinction (hysteresis loops) and periodic reaction.
Experimental Systems 1: Solution-Phase Reactions
Authors: Gray Peter , Scott Stephen K
Published: November 2023

Although this is a text expounding the value of simplified models of chemical instabilities and oscillations, its techniques would not command conviction if they could not bridge the gap between observation of real systems and quantitative interpretation. In this chapter the BelousovZhabotinskii reaction and its currently proposed chemical mechanistic steps are related. All schemes build on the classic work of Field, Koros, and Noyes (FKN) (1972) and the simplified three-variable oregonator condensed scheme is the model. The techniques expounded earlier, especially for dealing with relaxation oscillations and chaos, can be used with much success. After a careful study the reader should be able to.
Electrodissolution reactions
Authors: Scott Stephen K
Published: November 2023

Electrodissolution reactions provide perhaps some of the strongest evidence for the widespread applicability of the non-linear principles presented in previous sections. At first sight an experimental situation that can be uncharitably described as ‘dangling a rusty nail in a vat of acid’ might not be expected to be in anyway regular let alone sufficiently deterministic to hold to the complex but ordered sequences discussed above. Even though the experiments are actually somewhat more sophisticated they might still not be a priori an obvious choice for quantitative experimental investigation. But subtle is the Lord, and these do in fact provide some of the best examples of the order within classical bifurcation theory and chaos.
Biochemical systems
Authors: Scott Stephen K
Published: November 2023

No book dealing with chemical non-linearities, oscillations, and chaos would be complete without some mention of biochemical systems. On the other hand, a thorough treatment of this part of the subject would double the length of the book. As some form of compromise, this chapter will make a highly selective (probably somewhat random) foray mainly to indicate some of the scope.
Spin And Magnetic Moment
Authors: Goldman Maurice
Published: November 2023

NMR deals solely with the motion of nuclear magnetic moments and their detection. In quantum mechanics, the nuclear magnetic moment is an operator proportional to another operator, called the spin. For a quantum description of NMR it is therefore essential to have a thorough knowledge of the properties of spin operators.
Wavepackets
Authors: Child M S
Published: November 2023

The discussion in previous chapters has centred on the use of trajectorybased information to add quantum corrections to the classical picture, in a mainly time-independent picture. This chapter takes an explicitly timedependent standpoint by examining the relevance of various types of wavepacket to classical mechanics and vice versa; Littlejohn (1986) gives a much fuller mathematical account. The intuitive connection is obvious, in the sense that a unit normalized wavepacket corresponds most nearly to a single quantum mechanical particle, but the associated uncertainty relations imply a closer connection with a classical ensemble. Analysis of this connection is one of the main concerns of the first half of the chapter.
Introduction
Authors: Procter Garry
Published: November 2023

Organic compounds play an important part in modern life, not least in the area of pharmaceuticals, agrochemicals, and other materials which possess useful biological activity. Often such biological activity arises through the interaction of the organic compound with a ‘biomolecule’ such as an enzyme or a receptor. Such sites of action are constructed from chiral building blocks such as amino acids or carbohydrates, which means that these sites of action are themselves chiral. Being natural chiral compounds, these building blocks are present as single enantiomers, and it follows of course that the resulting biomolecules are single enantiomers. If the organic compound itself is chiral, then one consequence of this is that the two enantiomers are likely to interact differently with a given biomolecule of the type described above. In general, when considering the interaction of two such chiral systems, the stereochemistry of both systems can have a profound effect on the magnitude of the interaction, and therefore on the biological response.
Asymmetric aldol reactions
Authors: Procter Garry
Published: November 2023

The addition of an enolate to a ketone or aldehyde, often :referred to as an aldol reaction, bas a long pedigree, having been studied for many years from both the synthetic and mechanistic points of view. Throughout this volume, the term ‘aldol reaction’ will be used to denote the formation of a β-bydroxycarbonyl system S.2, thereby distinguishing it from an ‘aldol condensation’ which refers to the formation of an α, β-unsaturated carbonyl compound S.3 by P-elimination of an intermediate β-hydroxycarbonyl system. These relationships and definitions are illustrated in Fig. 5.1.
On Direct-Methods Phase Information from Differences between Isomorphous Structure Factors
Authors: Kyriakidis Christos E , Peschar René
Published: November 2023

The crystal structure of relatively small molecules of up to 100 independent atoms are readily determined from the diffraction intensities by means of Direct-Methods (DM) techniques relying on the mathematical application of the joint probability distribution (jpd) of complex-valued structure factors (SFs). DM estimate phases from the intensities. When these phases are approximately correct the Fourier summation based upon measured magnitudes and estimated phases produces an image of the structure. However an increase in the size of the structure reduces the reliability of the phase estimates and consequently obstructs the structure determination via traditional DM(e.g. Woolfson, 1987).
Order-disorder phenomena and biologically active compounds
Authors: Kutschabsky Leo
Published: November 2023

Disorder is a frequently observed effect in crystal structures. Often disorder is connected with the existence of a special kind of symmetry in the crystal, the so-called partial symmetry (Domberger-Schiff, 1966b) which leads to the Order-Disorder (OD) phenomenon. OD structures may be considered as consisting of layers periodic in two dimensions, of rods periodic in one dimension or of finite blocks.
Practical aspects of isomorphous replacement
Authors: Böocskei Zsolt
Published: November 2023

Crystallography is becoming a routine tool m protein structure determinations. The number of structures in Brookhaven Protein Database is over 500 and the number of undeposited structures may be in the same order. Data collection methods, processing software and molecular modelling are developing steadily (Wyckoff, Hirs and Timasheff 1985; Eisenberg and Hill, 1989; Moras, Podjarny and Thierry, 1991). However, mostab initio protein structures are still determined by the old method of isomorphous replacement (Blundell and Johnson, 1976).
Pressure generation
Authors: Besson J M
Published: November 2023

The instruments and methods which have been used for the generation of high pressures are probably more diverse than those in any other field of instrumentation. Since the high-pressure field has long been considered as a closed domain, devoted to the study of matter under extreme or exotic conditions, it has frequently progressed under the impulse of highly dedicated individuals, or schools of thought, who drove to its ultimate limits one given technology or one given concept and more or less ignored alternative solutions. Thus, high-pressure technology seems to have evolved in the present century in a completely irrational way, in sharp contrast to low-temperature technology, which, since Kamerlingh Onnes at least, has followed a logical pattern of improvement. A few examples will illustrate this. About half a century ago, P. W. Bridgman devised and operated an intricate two-stage system to compress large volumes of gas (fluid) to 10 GPa. At the present time, no laboratory could repeat this feat. By contrast, the diamond-anvil cell (DAC), which is now the dominant device for high-pressure studies, was perfected in its complete form, that is, as a gasketed device, with a rubyfluorescence scale only in the 1970s, following work by S. Block and G. J. Piermarini. Nevertheless, all the necessary know-how and materials existed a century ago, and it is strange that no one thought of it before.
Introduction: techniques, transformations, correlations, and conformation
Authors: Jones D W
Published: November 2023

Given an amenable, preferably centrosymmetric, single crystal of an organic compound, then the determination of an individual crystal structure by X-ray diffraction well enough to establish connectivity can often be a near routine business. Of course, as mentioned in the final chapter, there are still many crystal structures that are, if not intractable, then extremely difficult to solve satisfactorily. In recent decades the interest of many crystallographers has focussed more on the structural correlations and interactions revealed by measurements on the structures of a series of compounds, both specifically determined and extracted from the database. There remain very many cases, for example powdery materials, or those with low melting point or with multiple or amorphous phases, for which a satisfactory crystal is not available and for which, therefore, a straightforward X-ray single-crystal analysis is not feasible at room temperature. In Part I are presented two kinds of experimental approach to structure determination applicable in some of these cases, together with a reminder that diffraction measurements yield data about the motions as well as the positions of atoms.
Crystal chemical design of prototropic systems with intra-and inter-molecular transfer of protons: results and prospects for practical application
Authors: Aldoshin S M , Chuev I I
Published: November 2023

In recent years the study of crystal chemical aspects of solid phase transformations was one of the main topics of investigation for the Institute of Chemical Physics (Chernogolovka). Investigations of such reactions are preferred to those in the liquid phase because: a) the initial state of the system can be determined by X-rays; b) in suitable cases the crystal structure of the solid matrix stabilizes intermediates which can be studied by X-ray or spectroscopic methods; c) if a reaction does not occur on the macro-or micro-defects, correlation between the character of the reaction and the crystal structure of the reagents can be deduced. In this case, topochemical principles of control for solid phase reactions can be formulated and this opens vast possibilities for “engineering of crystal structure” which is favourable for such reactions.
Long-range consequences of hydrogen bonding: a partial correlation approach to relationships among structural parameters
Authors: Wozniak K , Krygowski T M
Published: November 2023

Computer-assisted searches of the literature databases indicate that a paper on hydrogen (H)bonding is published every half hour (1). In most cases (1,2] these papers deal with the H-bonding itself - its geometry and energy of interactions - or with changes in physicochemical or biochemical properties.
Spherands, hemispherands and calixspherands
Authors: Verboom Willem , Reinhoudt David N
Published: November 2023

In 1979 Cram reported the synthesis of a novel class of macrocyclic host molecules composed of anisyl units that have rigid preorganized cavities. These so-called spherands, the prototype of which is 1, form very stable complexes with small alkaline cations (Li+, Na+). The high thermodynamic stabilities (Ka > 1013 L mol−1) are due to the rigidity of the molecular framework which creates a high electron density directed in the cavity, generated by the oxygen lone pairs of anisyl moieties. Upon cbmplexation, the electronelectron repulsion of neighbouring oxygen lone pairs is relieved. This is a fundamentally different concept when compared with the complexation of cations by more flexible macrocyclic ligands, which require reorganization of the ligand prior to or during complexation, although in the complexation of cations by crown ethers, relief of oxygen-oxygen repulsions may also contribute. The concept of preorganization has been further extended by Cram and his group, for example by variation of the ring size and by substitution of one or more anisyl units by methoxycyclohexyl, urea or phenanthroline subunits.
Synthons derived from aspartic and glutamic acids
Authors: Moloney Mark G
Published: November 2023

Glutamic and aspartic acids are both proteinogenic amino acids widely distributed in nature. They are amongst the cheapest commercially available amino acids, obtainable as either enantiomer in homochiral form, and because of their side-chain functionality, make useful starting materials for stereoselective organic synthesis.11-5 However, because of the presence of three functional groups in these amino acids, and because of the potentially epimerizable a centre, suitable protection is generally required in order to obtain a synthetically useful intermediate, and this is particularly true for reactions involving deprotonations. Protection must be achieved in a manner which also enables convenient and efficient deprotection, to enable the manipulation of the functionalized intermediates into amino acid and other products.
Synthetic uses of methionine
Authors: Meffre Patrick , Vo-Quang Liliane , Vo-Quang Yen , Goffic Francois Le
Published: November 2023

The synthetic utility of amino acids for the generation of chiral reagents, intermediates and final products is now well documented. Naturally occurring L-methionine is an interesting source of chiral starting material. After appropriate amino and carboxy-protection, side-chain modifications provide chiral protected vinylglycine 11 and aspartic acid j3-semialdehyde 2, two attractive a-amino acid chiral building blocks.
Diastereocontrolled functionalization of enantiomerically pure 5-phenyl-11,4-oxazin-2-ones by azomethine ylid generation and trapping
Authors: Harwood L M , Lilley i. A , Cox g. G , Williams c. E
Published: November 2023

The conformational rigidity of the 1,4-oxazin-2-one ring makes it an ideal template for diastereocontrolled reactions and several groups have profited from this property in the area of asymmetric synthesis of enantiomerically pure a-amino acids.
Reactions at the a-carbon atom of a-amino acid derivatives
Authors: Barrett Graham c.
Published: November 2023

For the common a-amino acids, racemization is the classic example of a reaction under this heading. a,a-Disubstituted glycines H3N+-CR11R2-Co2-, prepared through C-alkylation of a glycine synthon (another classic example of a reaction at the a carbon atom), are stable towards racemization because they lack an a proton. Removal of the a proton and a leaving group at the (3 position (simple a,(3-elimination leading to a-aminoacrylates R11NH-C( =CHR2)-CO2R3; alias 𠄘dehydro-amino acids𠄙) represents the remaining major category of reaction
The Theory of Intermolecular Forces
Authors: Stone A J
Published: November 2023

There have been many developments in the theory of intermolecular forces over the last twenty years or so that have not so far been collected together in book form. After many years of effort, practical methods have emerged for the accurate calculation of intermolecular interactions by perturbation theory. Increasing computer power is making it possible to pension off the Lennard-Jones potential after 75 years of valuable service and to use more realistic models; similarly point-charge models are giving way to more so phisticated multipole descriptions. This has come at a time when experimental methods for determining intermolecular potentials are becoming more and more powerful and re liable, and when interest in accurate models of intermolecular interactions is greater than ever before, not least because of the increasing use of computer modelling for simulating systems of biological interest and for designing biologically active molecules for use as drugs and pesticides and the like.
Circular Dichroism and Linear Dichroism
Authors: Rodger Alison , Norden Bengt
Published: November 2023

This book provides an introduction to all those who wish to use the complementary spectroscopic techniques of optical activity (circular dichroism, CD) and optical anisotropy (linear dichroism, LD) for the study of the structure of molecules and interactions between molecules in solution. It emphasizes these techniques and how to use them for both low and high molecular weight molecules. The book begins by describing the principles behind CD and LD and how these techniques can be used in the laboratory without using advanced maths or quantum mechanics. The next chapters describe how both techniques may be applied to the study of biological macromolecules and give a detailed description of how they may be used on small molecules to investigate molecular and electronic structure. The final part contains theoretical derivations of all the equations required for the applications described previously. Specific molecular examples are used to illustrate concepts and to show the reader how to use the techniques in chemical and biological systems. Circular Dichroism and Linear Dichroism is an easy guide to what a prospective user of CD needs to know and explains how LD is not merely an exotic technique only to be practiced by experienced spectroscopists, but may be routinely and usefully employed as an aid to molecular structure determination.
Circular dichroism of biomolecules
Authors: Rodger Alison , Norden Bengt
Published: November 2023

It is probably true that CD is now more widely used to study biological systems than non-biological systems. This is despite the fact that the molecules concerned are usually very large and therefore detailed structural analysis of their CD data is not yet possible. In this chapter we shall focus on the CD of proteins, nucleic acids, and nucleic acid-ligand systems. What is written here is by no means the last word on these subjects as the increasing interest in structural details of biological molecules means that all techniques that can be used to study these systems are the focus of active research.
Linear dichroism of biomolecules
Authors: Rodger Alison , Norden Bengt
Published: November 2023

In this chapter we shall see how LD can be used to study macromolecules of biological interest. In contrast to the previous chapter, we shall deal with proteins fairly quickly as LD has been less widely used for these molecules than for DNAs. Our main concern will be with DNA since LD, particularly flow and electric field LD, has been used to great effect in the study of the conformation of DNA and binding geometries of DNA-drug systems. Since LD is conceptually quite simple (much simpler than CD) the reader will be able to follow easily the deduction of structural information for biopolymers in the examples of this chapter. The formal mathematical framework for LD is presented in Chapter 4 for more general cases of LD spectroscopic applications.