bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-ray structure refinement with X-PLOR
Authors: Bhat T N 
Published: November 2023

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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).
Monolayer Structures
Authors: Bruch L W , Cole Milton W , Zaremba Eugene 
Published: November 2023

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
Heterogeneous Reactions
Authors: Gray Peter , Scott Stephen K 
Published: November 2023

Abstract
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

Abstract
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

Abstract
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.
Wavepackets
Authors: Child M S 
Published: November 2023

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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).