bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereospecific Syntheses of Isomeric [Mn(CO)6‐n(CNMe)n]+ Complexes and Study of their Electrochemical Oxidations
Authors: Treichel P. M. , Mueh H. J. , Bursten B. E.
Published: November 2013

The reactions of Mn(CO)5‐n(CNMe)nBr (n = 2, 3, 4) with either CO or CNMe in the presence of a halide acceptor are found to be stereospecific, with incoming ligand replacing the halide ion. These reactions were used in the syntheses of mer‐ and fac‐[Mn(CO)3(CNMe)3]PF6 and cis‐ and trans‐[Mn(CO)2(CNMe)4]PF6. A cyclic voltammetric study showed that the isomeric complexes had different E1/2 values. The difference in eases of oxidation was rationalized qualitatively based on the abilities of CO and CNMe to serve as π acceptors. This suggestion was supported quantitatively by theoretical calculations which defined the degree of stabilization of the HOMO levels in these complexes through π bonding.
Aromatic Substitution of Olefins. Reactions of 1‐Octene and Phenyl‐Substituted Butadienes with Benzene or Toluene, and the Inter‐ and Intramolecular Substitutions of Triphenylethylene in the Presence of Palladium(II) Salts
Authors: Fujiwara Y. , Asano R. , Teranishi S.
Published: November 2013

The reactivities of 1‐octene, 1‐phenyl‐1,3‐butadiene and 1,4‐di‐phenyl‐1,3‐butadiene toward benzene or toluene in the presence of palladium salts were examined. 1‐octene and benzene gave trans‐1‐phenyl‐1‐octene (1) as a major product with its cis‐isomer (2), 2‐phenyl‐1‐octene (3) and 2‐phenyl‐2‐octene (4). 1‐phenyl‐1,3‐butadiene and 1,4‐diphenyl‐1,3‐butadiene react with benzene to give phenyl‐substituted butadienes predominantly. The inter‐ and intramolecular aromatic sub‐situations of triphenylethylene occurred to give p‐β,β‐diphenylvinyl‐tetraphenylethylene (9) and 9‐phenylphenanthrene (10) when treated without aromatic compounds.
Novel Decomposition Modes of Transition Metal Metallocycles Containing the Silicon–Silicon Bond: 1‐Nickela‐ and 1‐Platina‐3,4‐Disilacyclopentane Ring Systems
Authors: Tamao Kohei , Yoshida Jun‐Ichi , Okazaki Satoshi , Kumada Makoto
Published: November 2013

Reaction of 1,2‐bis(bromomethyl)tetramethyldisilane with magnesium in ether gave 1,1,3,3‐tetramethyl‐1,3‐disilacyclobutane (3) (∼ 20%) together with ca. 60% yield of the di‐Grignard reagent (5). Treatment of 5 with [Ni(PPh3)2Cl2] (7) in refluxing ether formed 3 in ca. 20% yield. Decomposition of 1‐nickela‐3,4‐disilacyclopentane intermediate, prepared from 7 with 5 at low temperatures, in the presence of 1‐naphthyl bromide, triphenylphosphine or 2,3‐dimethyl‐1,3‐butadiene also formed 3 in 12–20% yields. Reaction of 5 with Pt(COD)Cl2 (COD = 1,5‐cyclooctadiene) gave a 1‐platina‐3,4‐disilacyclopentane derivative as stable crystals, which gave 3 in quantitative yield when heated with PPh3 in benzene. Mechanisms for the formation of 3 have been discussed.
Correlation of Emotional Stress and Physical Exertions with Urinary Metabolite Profiles
Authors: Ludwig Helga , Spiteller Michael , Egger Hermann Josef , Spiteller Gerhard
Published: November 2013

Changes in human metabolism caused by physical or mental stress were examined by monitoring the rate of excretion of metabolites via the urine. Gas liquid chromatography and mass spectra analysis of urine revealed differences in the rate of metabolite excretion between mental stressed and unstressed persons: Emotional stress causes an increase in the DHEA excretion for a factor up to twenty. Physical stress does not change the steroid pattern, but is manifested in respect to a much greater increase in excretion of citric acid and isocitric acid and decrease in excretion of amino acid conjugates in untrained persons as compared to trained athletes.
Studies on Warburganal, Muzigadial and Related Compounds
Authors: Nakanishi Koji , Kubo Isao
Published: November 2013

Warburganal and muzigadial are two new sesquiterpenes isolated from a medicinal plant. They are two of the strongest antifeedants against the monophagous African army worm; in addition they possess potent molluscicidal activity and other antibiotic properties. A general account is given on these aspects as well as the spectral data leading to determination of their structures.
I. Basic Concepts of Quantum Chemistry for Electron Density Studies
Authors: Smith Vedene H. , Absar Ilyas
Published: November 2013

A systematic treatment of those concepts of quantum chemistry relevant to electron‐density studies is given. The discussion is at an elementary level and encompasses not only the familiar concepts but more modern developments as well.
V. One‐Electron Density Functions and Many‐Centered Finite Multipole Expansions
Authors: Stewart Robert F.
Published: November 2013

The one‐electron density function, ρ(r), (in principle deduced from elastically scattered X‐ray intensities) is the probability distribution function of an electron, averaged over the positions of all other electrons. A partitioning of ρ(r) into constituent parts is an intellectual exercise that does not lend itself to unique measurement from elastic X‐ray scattering experiments. It is shown that in the limit of perfect data and an infinite Ewald sphere, a least‐squares fit with a many‐centered finite multipole expansion of the charge density about the N nuclei will necessarily satisfy the q‐centered multipoles of the molecule for q = 1, 2,…, N. This means that a large number of static‐charge physical properties (averages over ρ(r)) are correctly given. Several expressions for averages of ρ(r) or over FH are given. It is shown that outer moments, such as atomic charges, dipole moments and quadrupole moments, always depend on a shape function. On the other hand, inner moments such as potentials, electric forces, and electric field gradients, may be represented by direct Fourier analysis of FH (obs) (suitably phased, of course). Nuclear vibrations have been neglected throughout the discussion.
VI. Charge Deformation Models
Authors: Kurki‐Suonio Kaarle
Published: November 2013

Basic construction principles of charge‐density models based on independent deformed atoms are presented. The asymptotic validity of the rigid free‐atom model in reciprocal space; mathematical properties of possible radial bases of multipole expansions; requirements put by symmetry, by regularity, by approximate free‐atom nature, by approximate harmonicity of motion and by N‐representability on the deformation models; and the connection between orthogonality and independence of model parameters are discussed together with consequent conclusions about the analysis of diffraction data in terms of deformation models.
VII. Vibrational Averaging of X‐Ray Scattering Intensities
Authors: Stewart Robert F.
Published: November 2013

The adiabatic potential for vibrational wavefunctions is given in a Preface. The vibrational average of ℐXRel(K;Q) is studied by taking a canonical‐ensemble average of the states of motion for the nuclei. A simple example for an oriented diatomic molecule (one vibration) is used to illustrate the sin θ/Λ dependence of ℐBragg and ℐTDS. The averaged X‐ray intensity, ℐav, is then fully developed (as done by Born) within the harmonic‐oscillator and rigid‐pseudoatom approximations for molecules and a crystal lattice. It is shown that generalized X‐ray scattering factors, characteristic of static charge properties, cannot in general be extracted from FOBSBragg. With the rigid‐pseudoatom model, relationships betweeen the dynamical matrix and electric‐field gradients and charge densities are given. In this way self‐consistency between Born's scattering matrix and pseudoatoms can be imposed on charge‐density models.
XII. The Combination of Aspherical‐Atom Least‐Squares Refinements with Fourier Methods in the Study of Electron Distributions
Authors: Coppens Philip , Hansen Niels K.
Published: November 2013

Since electron density fitting in real and reciprocal space are equivalent, the convergence of aspherical‐atom least‐squares refinements may be judged from Fourier density maps. Residual densities, least‐squares model densities and X–N or X–X difference densities are defined and used in the analysis. A further criterion is provided by comparison of atomic parameters from multipolar refinements with neutron or X‐ray high‐order results. Derived molecular properties such as dipole moments can be obtained from the least‐squares results and compared with quantities from direct‐space integration. Expressions for both methods of integration are presented.
XIX. Nuclear Quadrupole Resonance Spectroscopy in Solids
Authors: Vega Shimon
Published: November 2013

In these lecture notes some basic aspects of Nuclear Quadrupole Resonance (NQR) spectroscopy are presented. The parameters of the Electric Field Gradient (EFG) tensor which are obtained from NQR experiments are discussed. The theory of Townes and Dailey is used for the derivation of the expressions for the occupation numbers of electronic wave function of spn hybridized atoms in terms of the asymmetry parameter η and the nuclear quadrupole coupling constant eq. The point‐charge model is applied in order to obtain the possible sp2 and sp3 configurations for which η = 1.
Appendix 2. A Deformation Density Refinement Program
Authors: Hirshfeld F. L.
Published: November 2013

A computer program is described that permits the refinement of the static charge deformation in a flexible atom‐centered multipole expansion, together with positional and vibrational parameters, against X‐ray and neutron data. Other options allow for rigid‐body constraints on some or all of the atomic vibration tensors and the imposition of local symmetry on a set of atoms such as a methyl group.
Exciplex Formation between Indole Derivatives and Polar Solutes
Authors: Lasser N. , Feitelson J. , Lumry R.
Published: November 2013

The interaction between 3‐methylindole (3‐MeI) in cyclohexane with the polar molecules ethyl acetate (EA) and dimethylacetamide (DMA) was studied. The kinetic analysis of the fluorescence data shows that 3‐MeI forms an excited state complex with EA in a diffusion controlled process. The temperature dependence of the exciplex formation indicates that its dissociation rate constant too is of appreciable magnitude. UV, IR and fluorescence measurements all indicate that DMA forms complexes with 3‐MeI both in the ground and in the excited states. The latter complex is rather strong i.e. its dissociation rate is negligibly small. The findings imply that the fluorescence properties of tryptophan residues within a protein often must be determined by their interaction with neighboring polar groups rather than by the degree to which they are exposed to the ambient solution.
Photochemical Studies. XV. Photochemistry of 1,2‐Dihydrophthalic Anhydride and Related Compounds
Authors: Fuchs Benzion , Scharf Gad
Published: November 2013

Irradiation induced fragmentation of 1,2‐dihydrophthalic anhydride (2) as well as of its precursor, 7‐oxonorbornen‐2,3‐dicarboxylic anhydride (1) yields benzene as the major product, accompanied by bicyclo[2.2.0]hex‐5‐ene‐2,3‐dicarboxylic anhydride (3) and tropone (5), in wave‐length dependent chemical‐ and quantum‐yields. It is shown that (2) is the key compound in the sequence, reacting from a singlet excited state and a biradical intermediate.
Reactions of Electropositive Chlorine Compounds with Fluorocarbons
Authors: Schack Carl J. , Christe Karl O.
Published: November 2013

The reactions of simple chlorine containing compounds of the general composition XCl are reviewed and discussed. The compounds included for review are ClF, RfOCl, SF5OCl, CF3OOCl, SF5OOCl, ClOSO2F, ClOClO3 and ClONO2. It is concluded that most of the known reaction chemistry of electropositive chlorine compounds can be rationalized in terms of either addition of Cl‐X across multiple bonds or oxidative addition to atoms, such as iodine or sulfur in their lower oxidation states. The observed variety of final reaction products can be explained by a multitude of secondary reactions which can involve either eliminations, further additions or degradations. The observed reactions are easily moderated and controlled and only seldom is no reaction encountered.
On High Pressure Synthesis in Inorganic Solid State Fluorine Chemistry
Authors: Hoppe Rudolf
Published: November 2013

Results of high pressure fluorination (300–3000 bar F2) are given and discussed, e.g. fluorides of CrIV, MnIV, NiIV, CuIV, PtIV, PrIV, NdIV(?), DyIV(?) and RhV, AuV. Newly prepared were BaNiF6 (monoclinic, a = 9.465 Å, b = 4.950 Å, c = 6.655 Å, β = 103.3O), Cs2‐xRbxNiF6, Rb2‐xKxNiF6 (K2PtCl6‐type) all carmine‐red; BaPrF6 (RbPaF6‐type, a = 8.027 Å, b = 11.593 Å, c = 5.617 Å), SrPrF6 (LaF6‐type, a = 7.090 Å, c = 7.290 Å), both colourless powders; Cs2KNdF7 (a = 9.605 Å), Cs2KDyF7 (a = 9.479 Å), both cubic, orange‐yellow powders, (NH4)3, ZrF7‐type; MnF4 (trig., a = 19.53 Å, c = 12.59 Å), ultramarine‐blue single crystals, O+2[MnF5]− (monoclinic, a = 17.55 Å, b = 8.43 Å, c = 9.10 Å, β = 101.8°), bright‐red single crystals, and yellow single crystals, O+2[AuF6]−, which decomposed even under F2 during X‐ray radiation.
Intramolecular Nucleophilic Displacement of Fluorine
Authors: Hudlicky M.
Published: November 2013

Intramolecular nucleophilic displacement in organic fluorine compounds takes place if a fluorine atom is located in the molecule at such a distance from a nucleophilic functional group as to allow cyclization to three‐membered rings (in aliphatic compounds only), five‐membered rings, six‐membered rings, and, exceptionally, seven‐ and polymembered rings (in aromatic series only). The nucleophilic functions can be hydroxyl groups of alcohols, enols, phenols and carboxylic acids, sulfhydryl groups, primary or secondary amino groups, and carbanionic carbon atoms. The reaction is common with aliphatic monofluorides and aromatic polyfluorides, and rare with geminal and trigeminal fluorides. Whereas in the aliphatic series it is usually an undesirable side‐reaction, in the aromatic series it is useful as a means of synthesizing carbocyclic and heterocyclic polynuclear compounds.
Reactions Involving Fluoride Ion. Part XV. Oligomers From Chlorotrifluoroethylene
Authors: Chambers Richard D. , Lindley Andrew A. , Philpot Paul D. , Fielding Harold C. , Hutchinson John
Published: November 2013

Reaction of chlorotrifluoroethylene with caesium fluoride in tetraglyme gives CF3CFCl2 and higher molecular weight compounds which do not contain chlorine, C8F16, C10F18, C12F22, etc. The mechanism of this process, including the production of additional unsaturated sites, is discussed. Chlorotrifluoroethylene also reacts with perfluorobut‐2‐ene, giving mainly C6F12, C8F16 and C10F18, and with C8F16, giving mainly C10F18, C12F22 and C14F24. It is now established that reaction of perfluorobut‐2‐ene with caesium fluoride gives C8F16 and C12F22 and it is proposed that this fluoride‐ion induced defluorination is promoted by the formation of caesium polyfluorides.
Field Desorption of Oligosaccharides and Glycolipids by the Cationization Method
Authors: Prome Jean‐Claude , Puzo Germain
Published: November 2013

In the FD–MS of oligosaccharide derivatives by the cationization method, the influence of the nature of the cation was studied so as to observe either monomeric doubly or singly charged ions. Trehalose was used as a model for this study. The use of alkaline‐earth salts does not allow the desorption of doubly charged monomeric ions. These ions are formed during the desorption of mixtures of trehalose and NaI, but the narrowness of their desorption temperature range limits the applicability of the method. Monomeric cationized ions are formed with alkaline cations: cesium iodide seems to be a suitable cationizing reagent as regards the appearance‐emitter temperature, the width of the desorption temperature range, and the sensitivity. The FD/Cs spectra of several diacyl trehaloses are presented. The desorption of a synthetic “cord factor” (dimycoloyl trehalose) containing 100 carbon atoms produces an intense peak at the expected m/e value for the (M + Cs) ions. The spectrum of the natural “cord factor” from Corynebacterium diphtheriae is presented.
Mass Spectrometry of Steroid Systems. XXVII. Mass Spectrometry and Stereochemisty of Vitamin D3 and its Analogs
Authors: Zaretskii Ze'ev V. I.
Published: November 2013

The relative stabilities of stereoisomers in the vitamin D3 series were established using the appearance — ionization energies differences obtained for the main fragmentation processes characteristic of these compounds. The influence of (Z)‐and (E)‐configurations of the 5,6‐double bonds in vitamin D3 stereoisomers on the previtamin D ‐ vitamin D equilibrium in gas phase, have been also studied.
Sex Pheromones of the American Cockroach, Periplaneta americana
Authors: Talman E. , Verwiel P. E. J. , Ritter F. J. , Persoons C. J.
Published: November 2013

Two sex pheromones, periplanone A and periplanone B were isolated from the American cockroach Periplaneta americana. The technique is described for collecting periplanone B from the alimentary tracts of virgin females. Periplanone A was extracted from the excreta of the insects. Mass spectral analysis of the pheromones and related compounds were performed and the results are reported here. Evidence is presented suggesting that periplanone A is in fact a degradation product of periplanone B. A reaction scheme is considered for the pathway: periplanone B → periplanone A → (stable, but inactive) PA 22–VII.
Preparation and Properties of tert‐Butyloxycarbonylaminoacyl‐4‐(oxymethyl) phenylacetamidomethyl‐(Kel F‐g‐styrene) Resin, an Insoluble, Noncrosslinked Support for Solid Phase Peptide Synthesis
Authors: Kent Stephen B. H. , Merrifield R. B.
Published: November 2013

The Boc‐aminoacyl‐OCH2‐Pam‐ derivative of Kel F‐g‐styrene resin has been synthesized by a chemically unambiguous route. Direct amidoalkylation of the unsubstituted resin followed by hydrazinolysis gave the aminomethyl‐resin. The loaded resin was obtained by reaction with a Boc‐aminoacyl‐OCH2‐phenylacetic acid and DCC. The stability of this resin derivative towards acidolysis in trifluoroacetic acid was determined. Only 0.01–0.02 mol% loss of chains will occur in a single deprotection cycle in solid phase peptide synthesis. The peptidyl‐ and aminoacyl‐OCH2‐Pam‐(Kel F‐g‐styrene) resins were cleaved with anhydrous HF‐anisole at 0°C in near‐quantitative yield. Simultaneous syntheses of the model peptide Leu‐Ala‐Gly‐Val on this resin and on Val‐OCH2‐Pam‐poly(styrene‐co‐1% divinylbenzene) resin gave the same low levels of byproducts. No (<0.1%) intersite aminolysis was observed on treatment of Leu‐Ala‐Gly‐Val‐OCH<2‐Pam‐(Kel F‐g‐styrene) resin with 5% diisopropylethylamine in dichloromethane for 22 h.
The Use of Polymer Supports in Organic Synthesis. 17. The Synthesis of Unsymmetrical Diamides and Monoamide Monotosylamides from Symmetrical Diamines
Authors: Dixit Dilip M. , Leznoff Clifford C.
Published: November 2013

A 1 or 2% crosslinked divinylbenzene‐styrene copolymer, incorporating benzyl alcohol groups (1) was treated with p‐nitrophenyl chloroformate to give a polymer‐bound benzyl p‐nitrophenyl carbonate (2). The reaction of (2) with an excess of the symmetrical diamines 1,4‐diaminobutane (3a), 1,6‐diaminohexane (3b), 1,8‐diaminooctane (3c), 1,10‐diaminodecane (3d) and 1,12‐diaminododecane (3e) gave the respective monoprotected polymer‐bound aminocarbamates (4a‐e). Benzoylation or tosylation of (4a‐e) gave the polymer‐bound N‐benzoyl or N‐tosyl carbamates (7a‐e) or (8a‐e) respectively. Cleavage of (7a‐e) with trifluoroacetic acid liberated the N‐benzoyl‐N'‐trifluoroacetyl‐1, ω‐diaminoalkanes (9a‐e) in 80% yield. Cleavage of (8a‐e) with HCl in benzene, followed by acetylation yielded N‐acetyl‐N'‐tosyl‐1, ω‐diaminoalkanes (11a‐e) in 80% yield. From both cleavage reactions about 20% of the symmetrical diamines were recovered as their N,N'‐ditrifluoroacetyl or N,N'‐diacetyl derivatives (10a‐e) or (12a‐e) respectively.
Synthesis of Polymers Containing Lipoic Acid Structure and Study of the Acyl Transfer Reaction
Authors: Okawara Makoto , Fujimoto Atsuko , Endo Takeshi
Published: November 2013

Several S‐acetyl and S,S‐diacetyl derivatives of dihydrolipoic acid and amide were prepared as model compounds to examine acyl transfer reactions similar to those in living systems. A macromolecule bearing the lipoic acid (1,2‐dithiolane) structure was synthesized by polymer reaction of polyacrylamide. The acyl transfer from these S‐acetates to nucleophiles such as amine, alcohol and thiol as well as the catalytic behavior of silver ion in these reactions was studied.
Insoluble Polymer‐Supported Conjugate Bases of Thiazolium Ions As Catalysts in Organic Chemistry
Authors: Castells J. , Dunach E. , Geijo F. , Pujol F. , Segura P. M.
Published: November 2013

The synthetic possibilities of the generalized benzoin condensation are examined: benzoin condensation in its strict sense and closely related reactions, Michael type additions of aldehydes to activated double bonds, and oxidative benzoin condensation. In solid phase chemistry, comments are made on cyanide resins and details are given on the preparation of insoluble 5‐(2‐hydroxyethyl)‐4‐methyl‐3‐(polystyrylmethyl)thiazolium chloride and of 4‐methyl‐3‐(polystyrylmethyl)thiazolium chloride. Examples of the use of polymer thiazolium salts in the three types of reactions mentioned are presented and information on the stability of these salts is presented.
Polymeric Carriers as Immobilizing Media — Fact and Fiction
Authors: Kraus Menahem A. , Patchornik A.
Published: November 2013

The use of crosslinked polymers as immobilizing media in chemical and biochemical processes is reviewed. Numerous successful immobilization experiments are described. A considerable number of unsuccessful attempts are also presented. In an attempt to settle the recent controversy as to the applicability of polymers as immobilizing matrices, a unified view is given of the subject, explaining both successful and unsuccessful results.
The Nature of Oxide Films on Ni(110) Electrodes
Authors: Macdougall B. , Mitchell D. F. , Graham M. J.
Published: November 2013

Electropolished Ni(110) electrodes have a highly epitaxed 4 to 6 Å thick NiO surface film which is cathodically reduced in pH 2.8 Na2SO4 solution with a current efficiency of ∼ 60%. This oxide breaks down rapidly on open circuit in the same solution giving an arrest structure which, in conjunction with surface activity measurements, indicates localized removal of a very defective film. The open‐circuit breakdown characteristics of anodically formed passive oxide films indicate that these films contain a localized distribution of defects within the oxide. The number of defects and their stability is found to be highly dependent upon the condition of anodization. With increasing time of anodization at potentials in the passive region, the number of defect sites decreases and/or their stability increases, i.e. the film becomes more perfect The corresponding decrease in anodic current with increasing time of anodization indicates a correlation between this current and the electrochemical reactions at the defect sites. The anodic current is due mainly to nickel dissolution which occurs after breakdown and during inefficient repair of the defect oxide. Analysis of the passive oxide film indicates the presence of 9 to 12 Å of NiO. The time and potential of anodization has little effect on the average thickness or stoichiometry of the passive film, the condition of anodization only influencing the small (≦2%) coverage of defect sites on the surface. The passive film can be cathodically reduced but with only a very low current efficiency. The results obtained with the Ni(110) surface are in general agreement with those previously obtained for Ni(111) and Ni(100) electrodes.
Deposition of Palladium on Platinum in Hydrochloric Acid Media
Authors: Szabó S. , Nagy F.
Published: November 2013

Palladium adsorbed on platinum has been shown to decrease the amount of adsorbed hydrogen because the site requirement of Pdads is about 1.5 times higher than that of adsorbed hydrogen. Metal adsorption via the ionization of adsorbed hydrogen occurs in two steps: the first leading to bulk deposition. This is followed by bulk ionization and repeated reduction, producing the adsorbed metal layer. The electrosorption valency of the adsorbed Pd layer thus formed is about 1.8. The Pdads does not desorb in Cl−‐free media.
Di‐(trans‐4‐Alkylcyclohexyl)‐α‐Diketones A New Class of Liquid Crystal Compounds
Authors: Praefcke Klaus , Schmidt Dietmar , Heppke Gerd
Published: November 2013

Up to the present time it was assumed that the properties of liquid crystal compounds arise not only from the presence of long chain molecules, but that these molecules must further contain at least two phenyl rings. However recent work has shown that complete hydrogenation of derivatives of alkylbenzoic acids,2,3 as well as of alkylcyanobiphenyls,4 leads to compounds with liquid crystal properties. Continuing our work on liquid crystals,1 we report here on di‐(trans‐4‐alkylcyclohexyl)‐1,2‐ethanediones 6a–c, which are the first representatives of a further class of saturated liquid crystal compounds.
Liquid Crystalline 4′‐Pentylphenyl 4‐Alkyloxydithiobenzoates
Authors: Kohne B. , Praefcke K. , Heppke G.
Published: November 2013

The 4′‐pentylphenyl‐4‐alkyloxydithiobenzoates (1a–e), prepared for the first time, form enantiotropic nomatic phases. Thus, the –CS.S– linking unit qualifies as a central group in the construction of new classes of liquid crystals. The compounds investigated are red in colour and exhibit only a slight tendency to form smectic phases.
Copolymerization in Liquid Crystalline Media
Authors: Hardy G. , Cser F. , Nyitrai K.
Published: November 2013

The data at our disposal on the copolymerization of potentially mesogenic monomers either in mesomorphic or in isotropic phases are reviewed. There are only very few convincing data concerning the effect of the mesophase on the ratio of kinetic constants of the monomer (ri = kij/kij). The p‐ethoxy‐p'‐acryloyloxy‐azobenzene (EOA) and cholesteryl acrylate (CA) gave different r values in cholesteric and in isotropic state copolymerizations (rCA,i = 0.28, rEOA,i = 0.57, rCA,m = 0.16, rEOA,m = 1.10). r values were determined in other systems consisting of p‐methyl‐p'‐acryloyloxyazoxybenzene (MAAB), phenyl‐p‐acryloyloxybenzoate (PAB), N‐acryloylpiperidine (AP), cholesterylvinylsuccinate (CUS) and cholesterylsuccinyl‐diglycoylacrylate (CSDA) as well as CA. (rCA = 0.58, rPAB = 0.62, rCA = 0.16; rAP = 1.14; rPAB = 0.16; rAP = 0.81; rCVS = 0.01, rPAB = 2.36, rCSDA = 0.20, rPAB = 1.26, rMAAB = 2.40; rCVS = 0.02). These data were obtained in isotropic phase reactions and they do not satisfy the generally accepted concepts of reactivity. The structure of the copolymers were invesitgated by X‐ray diffraction and by thermal treatment. The copolymer/comonomer state diagram for the MAAB/CVS system were also used to determine the structural features of this system.

Copolymers consisting of potentially mesogenic vinyl‐monomers are macromolecules with anisotropic properties. Their transition temperatures (Tg, Tf, Ta→i) have minimal values at a given composition. The copolymers show different X‐ray Bragg periods before and after this composition. They can be regarded as anisotropic two phase systems, although they are not block copolymers.

The data published in recent literature together with those obtained in our current work suggest that both the chemical and the physical structures of the copolymers built up from potentially mesogenic vinyl‐monomers are more dependent on topochemical than on pure chemical conditions.
Aromatic Guest Molecules Enclathrated in Hofmann‐Type and Analogous Clathrates
Authors: Iwamoto Toschitake
Published: November 2013

The structural features of the clathrate compounds with a general formula M(diam)M'(CN)4. 2G (M = a divalent metal in six‐coordination, diam = (NH3)2 or a diamine, M'(CN)4 = a square‐planar or tetrahedral teracyanometallate(II), G = an aromatic guest such as C4H5N, C4H4S, C6H6, C6H5NH2, etc.) are discussed from the viewpoint of the arrangement and orientation of the guest molecules in relation to the structure of the metal complex hosts. The layer structure of the Hofmann‐type host M(NH3)2M'(CN)4 (M'(CN)4 = a square‐planar moiety) enclathrates the guest molecules with a fixed orientation, but the three‐dimensional host structures built up of tetrahedral M'(CN)4 moieties provide considerably flexible and expanded cavities for guest molecules. The cavity in the three‐dimensional host may be seen as a container of a guest molecule with a chemically inactive wall and with a volume slightly larger than that of the molecule; in the container the guest molecule has freedom of motion to a certain extent. It can be expected that appropriate selection of the host constituents will afford the host lattice a stereospecific function and/or a function of keeping chemically‐active species stable in the cavity of the clathrate structure.
Alumina‐Catalyzed Alcoholysis of Cyclohexene Oxide
Authors: Posner Gary H. , Rogers Donald Z. , Romero Arthur
Published: November 2013

Alcoholysis of cyclohexene oxide by methanol and allyl alcohol, catalyzed by chromatographic γ‐alumina, was studied. Two procedures were used: (1) passing a mixture of the epoxide and alcohol through a column of alumina at 25° and (2) stirring a mixture of epoxide and alcohol over alumina at 100°. The 25° column procedure allowed conversion of ca 2 mmol of epoxide per 1 g of alumina, and the 100°‐reaction allowed catalytic conversion of ca 100 mmol of epoxide per 1 g of alumina. These results are compared with those reported for zeolite catalysts.
Topotactic and Topochemical Conversions of Distyrylpyrazine
Authors: Nakanishi H. , Parkinson G. M. , Jones W. , Thomas J. M. , Hasegawa M.
Published: November 2013

The γ‐form of distyrylpyrazine, hitherto regarded as photostable, is shown to undergo an unusual, thermally stimulated, topotactic phase transformation \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {(010)_{\rm \gamma } ||(\bar 101)_{\rm \alpha } ;[001]_{\rm \gamma } ||[010]_{\rm \alpha } } \right) $\end{document} into the α‐form which, in turn, undergoes photostimulated topochemical reaction into the single‐crystal polymer.
Liquid Crystalline Solvents as Mechanistic Probes. IV. The Influence of Ordered Media on the Norrish Type II Photoprocesses in α‐Diketones
Authors: Nerbonne Jeanne M. , Weiss Richard G.
Published: November 2013

The Norrish II photoreactions of octane‐4,5‐dione (1) and 1,6‐diphenylhexane‐3,4‐dione (2) have been investigated at several temperatures and in isotropic and ordered (liquid crystalline) media. The sole photoproducts detected in all solvents are 1/1 diastereomeric mixtures of α‐hydroxycyclobutanones. The quantum yields for disappearance of 1 and 2 tend to decrease as the temperature increases in all media investigated. Whereas the quantum yield ratio for disappearance of 1 in cholesteric mesophases and hexane is greater than one, the ratio for disappearance of 2 is less than one. Possible explanations for these observations, based upon the influence of solvent order on solute conformational lability, are advanced.
Synthesis and Reactivity of a Surfactant Ferrocene. Environmental Effects on Oxidation of Ferrocene in Organized Media
Authors: Seiders Reginald P. , Brookhart M. , Whitten David G.
Published: November 2013

This paper reports on the synthesis of a surfactant ferrocene, 16‐ferrocenylhexadecanoic acid, (1), which can readily be incorporated into monolayer films and assemblies, micelles and vesicles. The reactivity of this ferrocene towards potential oxidants and complexing agents has been investigated in the different media under a variety of conditions. In the monolayer assemblies (1) was readily oxidized by I2 but inert towards exposure to aqueous Ag+, aqueous TCNE or TCNO vapor. The inertness of (1) under the latter conditions suggests the chromophore is oriented in a highly hydrophobic site. In contrast, (1) is readily oxidized by I2 and Fe3+ in lecithin vesicles and anionic SDS micelles. In cationic CTAB micelles iodine is reactive as an oxidant but Fe3+ is not, presumably due to charge effects. The results suggest that the ferrocene moiety in (1) is not rigidly oriented in the hydrophobic core of the vesicles or micelles but spends sufficient time near the hydrophobic interface to be oxidized by polar reagents.
Ab Initio Calculation of One‐Center Integrals of Semiempirical Theories of Valence
Authors: Freed Karl F. , Sun Hosung
Published: November 2013

In order to highlight some of the apparent contradictions between semiempirical and ab initio theories of valence, a brief review of some facets of the two approaches is presented. The recently developed effective valence shell Hamiltonian, , is then briefly introduced to bridge the gap. Results of purely ab initio Hv calculations for atoms and simple molecules are mentioned. The ab initio one‐center integrals are quantitatively much different from those of semiempirical theories. However, the exact contains extra terms, three‐ (or higher) electron interactions, which are totally absent in semiempirical theories. This paper shows that the nonclassical, three‐electron terms are incorporated into semiempirical one‐ and two‐electron integrals, and a parametrization scheme illustrating this is presented. As an example, the carbon system is chosen and the one‐center carbon semiempirical integrals are calculated from the results of ab initio calculations for C and CH. This enables discussions of questions of the degree of transferability of semiempirical one‐center integrals. The one‐center one‐ and two‐electron integrals obtained from ab initio calculations by including the effects of three‐electron terms are found to be close to the traditional semiempirical values.
Gauge Invariance — A Brief Review
Authors: Epstein Saul T.
Published: November 2013

The gauge properties of exact solutions, and of optimal variational solutions for static magnetic fields are reviewed. Also various other topics are discussed, including the optimal choice of gauge, gauge factors, gauge invariance and current conservation, minimal variance gauges, and the Thomson bound.
On the Dependence of Total Energy on Occupation Numbers
Authors: Gopinathan M. S. , Whitehead M. A.
Published: November 2013

An equation is developed for describing the pairwise interactions of q electrons, when q is integer or non‐integer. This expression is compared with the usual equation. It is found to give lower total energies, different ionization and transition energies in the Slater Transition State theory, different values for the atomic energies calculated by the Hyper‐Hartree–Fock method, but numerically identical results for the Mulliken Electronegativity.
Approximate Electron Densities for Atoms and Molecules
Authors: Hall George G. , Martin David
Published: November 2013

Approximate electron densities for atoms and molecules can be calculated from some given electron density by minimizing the total energy of their error‐fields. Results are presented for some simple systems using one or two term expansions. A conical function and a Gaussian function give comparable results. Electrostatic potentials calculated from the results are of good accuracy while the Coulomb self‐energy begins to converge quickly.
Analytical Functions for the Potential Energy Surfaces of Small Polyatomic Molecules
Authors: Murrell J. N.
Published: November 2013

A review is given of a recently developed method of constructing analytical functions to represent the potential energy surfaces of small polyatomic molecules.
Affinities of Ammonia and Methylamine for H+, Li+, K+ and CH3+ An Ab Initio SCF Study with Large Basis Sets
Authors: Berthod Hélène , Pullman Alberte
Published: November 2013

Computations of Li+‐affinities of NH3 and NH2CH3 performed with the SCF ab initio method, using the 4‐31G, 6‐31G*, 6‐31G** basis sets as well as Dunning's (9s, 5p/4s) basis contracted to double‐zeta without and with polarization functions, show that only the last basis is able to reproduce the experimental order of the gas‐phase affinities. A study is made of the evolution of the various components of the binding energy upon methylation, and of the modifications observed upon improvement of the basis sets: reversal of the order of the binding energies to the correct order occurs when the decrease of the Coulomb term becomes smaller than the increase of the delocalization term upon methylation. The best of the previous sets is shown to account in a satisfactory way for the H+ and CH3+ affinities of the same compounds. For K+‐affinities, the same basis still yields an incorrect ordering upon methylation. A further improvement of the basis is seen to work in the right direction. The K+‐affinities of H2O and NH3 computed with the most extended basis are in numerical agreement with the gas‐phase values.
Ab Initio Study of Inner Solvent Shell Reorganization in the Fe2+–Fe3+ Aqueous Electron Exchange Reaction
Authors: Jafri J. A. , Logan J. , Newton M. D.
Published: November 2013

Ab initio RHF molecular orbital calculations are carried out for several hydrate clusters of Fe2+ and Fe3+, using a double‐zeta valence atomic orbital basis set and an effective core potential for inner shell electrons, and comparison is made with all‐electron results at the monohydrate level. The calculations are shown to give a good quantitiative account of the solvent shell radii and breathing vibration frequencies for the hexahydrates. The large decrease (∼0.15 Å) in going from Fe2+(H2O)6 to Fe3+(H2O)6 is related to the interaction of the ag (4s) and ϵg (3d) Fe valence orbitals with the ligand 2p‐orbitals, with little π antibonding character found for the tg orbitals. The expansion of the 3d orbitals in the Fe2+ ion, relative to the Fe3+, is also noted and discussed in connection with the change in solvent shell size for the two complexes. The charge transfer from the ligands involves mainly a depletion of the hydrogen atom electrons, implying increased acidity for the first‐shell water molecules.
The Conformation of Free and Complexed Oligoethers
Authors: Dale Johannes
Published: November 2013

Recent X‐ray and 13C NMR results on macrocyclic compounds containing oxyethylene units (1,4 dioxa groupings) are reviewed. When such “saturated” crown ethers and related compounds form complexes with cations and uncharged protonacidic molecules, they adopt conformations which contain chiefly ag± a units or g± g± a units (genuine corners) and are thus of the types encountered, or conceived for corresponding cycloalkanes. Uncomplexed or incompletely complexed crown ethers, on the other hand, adopt as a rule unusual conformations never encountered in cycloalkanes. These latter crown ethers contain g± g± a units (pseudo corners) characterized by close 1,5 CH … O interactions. Such conformational units are also found in uncomplexed cryptands. In open chains, there is no evidence of this type of chain folding, except in the gas phase for 1,2‐dimethoxyethane. It is concluded that pseudo‐corner formation is resorted to only when solvation of ether oxygen is excluded, such as in the gas phase or in the inaccessible interior of macrocyclic compounds.
Stereochemistry in the Coordination Chemistry of Metal Surfaces
Authors: Muetterties E. L.
Published: November 2013

The stereochemistry of metal surface coordination chemistry is discussed with respect to the chemisorption states of hydrogen, carbon monoxide, nitriles, isocyanides, pyridine, benzene, acetylenes and olefins. A stereochemical comparison is made of the binding of such species on metal surfaces with the binding in discrete molecular clusters.
Stereochemistry of Perhydrocrysene
Authors: Farina Mario , Silvestro Giuseppe Di , Mantica Enrico , Botta Donatella , Morandi Francesco , Brückner Sergio
Published: November 2013

The five most stable stereoisomers of perhydrocrysene were prepared and identified by 13C‐NMR analysis. Their relative stability was determined by epimerization on Pd/C at 508°K and compared with the results obtained by molecular mechanics calculations. As expected, isomer TATAT is the stablest. Of particular interest is the considerable stability of compounds with central cis junction (TACAT and TSCST), practically identical with that of TATAC and TATSC. Both analogies and differences between perhydrocrysene and steroids are briefly discussed from a conformational point of view.
Radical Anions of Some Dehydro[n]annulene‐diones with n = 16 and 18
Authors: Gerson Fabian , Beckhaus Hans‐Dieter , Sondheimer Franz
Published: November 2013

Radical anions of 10,15‐dimethyl‐2,4,11,13‐tetrakisdehydro[18]annulene‐1,6‐dione (syn‐18 ), 6,15‐dimethyl‐2,4,11,13‐tetrakisdehydro[18]annulene‐1,10‐dione (anti‐18 ) and 8,13‐dimethyl‐2,9,11‐trisdehydro[16]annulene‐1,4‐dione (syn‐16 ) have been investigated by ESR and, in part, by ENDOR spectroscopy. The hyperfine patterns of these radical anions depend on the rate of intramolecular interconversion between two equivalent ion pairs in which the counterion is associated with one oxygen atom. It is found that the polarity of the solvent, which is an important factor influencing such a rate, does not affect the spectra of syn‐16⊕. quite in the same way as those of syn‐18⊕. and anti‐16⊕. This behavior, together with the lower stability of the former radical anion as compared to the two latter ones, points to substantial differences in physico‐chemical properties. Simple MO models indicate that the electronic structures of syn‐16⊕., syn‐18⊕. and anti‐16⊕. can be related to those of the corresponding 16π‐ and 18π‐perimeters. One is thus tempted to interpret the observed differences in terms of Hückel's rule of “aromaticity” and “antiaromaticity”.
Chemistry of the Homophenalenyl Systems
Authors: Murata Ichiro , Nakasuji Kazuhiro
Published: November 2013

The perturbational molecular orbital theory by Haddon suggested the interesting possibility that introduction of homoconjugate linkages as a perturbation of the parent phenalenyl systems at 1,2‐, 1,10‐, and 10,11‐positions leads to the most unfavorable, medium, and most favorable energy changes, respectively. In order to prove this prediction, formation of 1,2‐, 1,10‐, and 10,11 ‐homophenalenyl systems were examined by employing the possible precursors such as the ketone 5,29, the alcohol 8, as well as the hydrocarbons 16, 22, and 37. In contrast to the prediction by PMO theory, these systems have no homoaromatic stabilization even in the 10,11 ‐homophenalenyl cation and anion. In further extension of this study, the synthesis of the hitherto unknown parent 8,16‐methano[2.2]metacyclophane‐1,9‐diene 45 has been achieved recently.
Structure‐Resonance Theory. A Review of Applications to π ‐Hydrocarbon Systems
Authors: Herndon William C.
Published: November 2013

Studies of structure‐resonance theory applied to π‐hydrocarbon systems are reviewed. The theory leads to quickly obtainable quantitative predictions of bond orders, charge distributions, and relative stabilities of ground state species or reaction intermediates. Numerical results correlate precisely with experimental properties, and with results of LCAO‐MO‐SCF calculations.
Structure‐Resonance Theory for π‐Hydrocarbon Iron Tricarbonyl Complexes
Authors: Herndon William C.
Published: November 2013

Structure‐resonance theory is applied to transition metal π ligand complexes. This theory leads to specific, quantitative predictions of bond orders, charge distributions in ions, and relative stabilities of ground state species or reaction intermediates. In applications to hydrocarbon systems, numerical results correlate precisely with experimental properties, and with results of LCAO‐MO‐SCF calculations. Initial extensions to iron tricarbonyl derivatives are described herein. A unique advantage of structure‐resonance theory is that it can be applied rapidly by hand calculation, allowing numerous applications with little labor. The orbital basis for describing iron complexes allows one to use graph‐theoretical algorithms to further simplify the theoretical formulism.
Effects on Cyclopropane Geometry of Aromatic Substituents in the Bisected Conformation. The Structures of Spiro[cyclopropane‐1,9′‐[9H]fluorene] and 2,2‐Dichlorospiro[cyclopropane‐1,9′‐[9H]fluorene]
Authors: Jason Mark E. , Gallucci Judith C. , Ibers James A.
Published: November 2013

The structures of spiro[cyclopropane‐1,9′‐[9H]fluorene] (1) and 2,2‐ dichlorospiro[cyclopropane‐1,9′‐[9H]fluorene] (2) have been determined by conventional single‐crystal X‐ray diffraction techniques. Compound 1 crystallizes with 32 molecules in the unit cell in space group C212v–Iba 2 of the orthorhombic system in a cell of dimensions a = 42.228(23), b = 27.318(17) and c = 7.664(8) Å. Compound 2 crystallizes with four molecules in the unit cell in space group C52h–P21/c of the monoclinic system in a cell of dimensions a = 8.451(3), b = 8.960(3), c = 15.882(5) Å and β = 97.31(1)°. The structures of 1 and 2 have been refined by full‐matrix least‐squares techniques to conventional R indices of 0.055 and 0.049, respectively. Relative to the bridgehead position, the cyclopropane ring in 1 contains a short distal bond of average value 1.496(9)Å and lengthened vicinal bonds averaging 1.531(11)Å. This geometry agrees qualitatively with a simple molecular orbital model for charge transfer from cyclopropane to an aromatic π‐system held in the bisected conformation. The cyclopropane ring in compound 2 contains C–C bond lengths of 1.537(3), 1.517(3) and 1.475(3) Å. These values cannot be explained by summing the expected changes induced by the aromatic and halogen substituents.
Small and Strained Ring Compounds via Unsaturated Carbenes
Authors: Stang Peter J.
Published: November 2013

Unsaturated carbenes, provide a ready means of entry into numerous, diverse small ring systems. They have been employed to prepare strained alkylidenecyclopropanes that open up to the corresponding trimethylenemethanes or in one case m‐xylylene. Triafulvenes, [3]‐radialenes as well as [4]‐radialenes and cyclynes have been prepared by addition of unsaturated carbenes to appropriate π‐systems. They show great potential for the simple preparation of novel small ring heterocycles. Potential formation of allene oxides, allene episulfides, α‐lactams and heterocumulene oxides are discussed.
The Chemistry of Silylcyclopropanes
Authors: Paquette Leo A.
Published: November 2013

The synthesis and reactions of silylcyclopropanes are reviewed. From the preparative viewpoint, these strained systems can be obtained by the addition of silyl‐substituted carbenes to olefins and of carbenes or carbenoids to vinylsilanes, by condensation of cyclopropyllithiums with chlorosilanes, by ring opening of silyl‐substituted bicyclobutanes and by trimethylsilylmethylenesulfurane addition to α,β‐unsaturated ketones. The susceptibility of this class of molecules to acid‐ and base‐promoted ring openings, electrophilic substitution and thermal rearrangement is detailed. These latter topics and a summary of the use of silylcyclopropanes as cyclopropene precursors are presented in a manner which stresses the unique synthetic utility conveyed by the presence of the silicon atom.
Reactions of 3‐Amino‐2H‐Azirines with NH–Acidic Compounds
Authors: Heimgartner Heinz
Published: November 2013

3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine (1) reacts with a number of NH–acidic compounds to give adducts of interesting structural variety. In analogy to the reaction of OH‐acidic substrates, the reaction mechanism can be understood to proceed via initial protonation of the aminoazirine, subsequent attack of the nitrogen nucleophile on the iminiumaziridine and ring expansion of the three‐membered ring to form a zwitterionic intermediate. Depending very much on the charge‐distribution delivered by the variety of substituents, this zwitterionic intermediate is going to be stabilised by different routes, e.g. water elimination, ring enlargement or rearrangement, to yield new N‐heterocyclic compounds.