bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvolysis of 1‐p‐Methoxyphenyl‐2‐Methylpropen‐1‐Yl Trifluoroacetate and 3,5‐Dinitrobenzoate
Authors: Rappoport Zvi , Kaspi Joseph 
Published: November 2013

AbstractThe reactions of 1‐p‐methoxyphenyl‐2‐methylpropen‐1‐yl trifluoroacetate (I–OCOCF3) and 3,5‐dinitrobenzoate (I–ODNB) in AcOH/NaOAc or with amines in 2,2,2‐trifluoroethanol (TFE) were investigated. In TFE, I–ODNB gives trifluoroethyl 3,5‐dinitrobenzoate (II) and the ketone AnCOCHMe2 (III) in a second order reaction with five amines and with CF3 CH2 ONa, and I–OCOCF3 gives a second order reaction with 2,6‐lutidine. In AcOH/NaOAc, I–OCOCF3 gives the corresponding acetate I–OAc, and I–ODNB gives I–OAc and III. The kAcOH/kAcOD values are 5.5–6.2 for I–OCOCF, and 1.03 ± 0.05 for I–ODNB. It is suggested that the rate determining step in TFE is the attack of CF3 CH2O− (formed from the amine and TFE) on the carbonyl of the ester group in a BAC2 mechanism. In AcOH, an electrophilic addition‐elimination mechanism (AdE–E) for the reaction of I–OCOCF3 is supported by the solvent isotope effect. The solvent isotope effect and the products from I–ODNB in AcOH are consistent with an SN1 mechanism, but since the kCl/kODNB ratio is lower than that in saturated systems, an AAC2 mechanism cannot be unequivocally excluded. The effect of the leaving group in the vinylic SN1 reaction is discussed.
A Thermostat with Short‐ and Long‐Term Stability of ± 1.5×10−4°C
Authors: Priel Z. , Silberberg A. 
Published: November 2013

AbstractThe design of a thermostat which gives a temperature stability of ± 1.5 × 10−4°C over a period of weeks is described. The temperature sensors are thermistors stabilized by heat treatment. Heat input derives mainly from stirring and heat output mainly from losses to the surroundings. Residual heat input is removed by stabilized circulating thermostats. Temperature balance is due to spread out bare wire heaters which carry a current proportional to the state of the control DC Wheatstone bridge. The controlling thermistors are maintained in two oil baths and the state of the current in the control heaters is transmitted to the thermistors by a thermal feedback system involving small heating coils which are placed in the oil baths around the thermistors and which carry a current proportional to the heating current.
Kinetic Study of the Photoexcited Triplet State of Free Base Porphyrins by EPR
Authors: Scherz A. , Orbach N. , Levanon H. 
Published: November 2013

AbstractAn electron paramagnetic resonance (EPR) study of the photoexcited triplet state of four free base porphyrins is presented. The zero field splitting parameters (ZFS) |D| and |E| were calculated from the EPR spectra of the porphyrins dissolved in n‐octane matrices at 80°K. |D| = 0.0359 cm−1, |E| = 0.0079 cm−1 for tetra phenyl porphyrin (H2 TPP), |D| = 0.0432 cm−1, |E| = 0.0037 cm−1 for tetra (per‐fluoro) phenyl porphyrin H2T (per‐F) PP, |D| = 0.0366 cm−1, |E| = 0.0078 cm−1 for tetra (para‐chloro) phenyl porphyrin H2T(P‐Cl)PP, |D| = 0.0369 cm−1, |E| = 0.0076 cm−1 for tetra (para‐methyl) phenyl porphyrin H2T(P‐Me)PP. The transient behavior of the EPR signal intensities in the last two porphyrins is discussed. The depopulation rate constants of the triplet sublevels kp, the ratio between the population rate constants Ap (at zero field, p = x,y,z), and the spin lattice relaxation rate W within the triplet manifold, were calculated.kx = (12 ± 2) × 102 sec−1, ky = (0.5 ± 0.1) × 102 sec−1, kz = (1.2 ± 0.4) × 102 sec−1, Ax:Ay:Az ≃ 0.63:0.01:0.33, W = (0.4 ± 0.1) × 104 sec−1 for H2T(P‐Cl)PP, kx = (7 ± 2) × 102 sec−1, ky = (4 ± 1) × 102 sec−1, kz = (1.5 ± 0.5) × 102 sec−1, Ax:Ay:Az ≃ 0.56:0.31:0.13, W = (1.7 ± 0.4) × 103 sec−1 for H2T(P‐Me)PP.
Modification of the Redox‐Properties of Tetraphenylporphyrin‐Complexes by Bases in Methylene‐Chloride Solution. The Equilibrium of Different Oxidation‐States with Added Base as Measured by Cyclic Voltammetry
Authors: Manassen J. 
Published: November 2013

AbstractThe oxidation half‐wave potentials of Co2+ tetraphenylporphyrin, measured by cyclic voltammetry in methylenechloride solution, are changed by the addition of weak bases like methanol, acetone and dimethylformamide. The wave corresponding to the metal‐oxidation Co2+ ⇄ Co3+ is shifted to lower potential, while the wave, corresponding to the ligand oxidation Co3+(TPP) ⇄ Co3+(TPP)+. is shifted to higher potential. It can be shown, that this is due to a preferential interaction of Co3+(TPP) with the bases, which is stronger than that of the Co2+(TPP) as well as that of the Co3+(TPP)+. Because the shifts are proportional to the concentration of added base, they can be followed quantitatively and the equilibrium constants of the interactions between the different oxidation states and the bases can be calculated. The reduction wave of Co2+(TPP), corresponding to the Co3+ ⇄ Co1+ transition is not changed by the weak bases, but is shifted to lower potential by pyridine and the picolines. The shift is again proportional to the concentration of added base. The reduction wave of Fe3−(TPP)Cl− is not changed by the weak bases, but is shifted to lower potential by pyridine. While the reduction wave of the free Fe3+(TPP)Cl− is irreversible, that of the pyridine‐adduct is reversible. In this case the shift is not proportional to the amount of added base. The voltammetric curves of the Cu, Ni, and Zn tetraphenyl‐porphyrins are not changed by the addition of either the weak or the strong bases.
1‐Phenylcycloalkylamine Derivatives. III
Authors: Kalir A. , Sadeh Shoshana , Karoly Hava , Shirin E. , Balderman D. , Edery H. , Porath Gila 
Published: November 2013

AbstractA series of phencyclidine analogs has been prepared and subjected to pharmacological screening. None of them surpassed the activity of phencyclidine. It was found that trifluoroacetic acid as a solvent favorably influenced the yield of the Ritter reaction.
Nephelometric Measurements by Use of a Spectrofluorometer. Part II
Authors: Gonen L. , Cogan E. 
Published: November 2013

AbstractIn a previous paper the principle of nephelometric measurement using a spectrofluorometer was described. The method has now been extended and applied for the microdetermination of: (1) Chloride in acid and salt solutions, in clays after acid decomposition, in organic solvents containing hydrocarbons and amines and organic chlorides after combustion; (2) Potassium in acid and salt solutions; (3) Barium in acid and salt solutions; and (4) Sulphate in organic solvents containing hydrocarbons and amines. The method is simple and highly sensitive.
Closing the Bromide Cycle in Magnesium Chloride Thermal Hydrolysis Plants
Authors: Zisner Tuvia 
Published: November 2013

AbstractA new process is usually tested in the laboratory and pilot plant after being stripped of most of the ancillary equipment associated with it in the full‐scale plant. When such conventional secondary equipment is then coupled to a well‐investigated new process in order to economize on energy consumption, the two may interact to modify the chemistry of the original process. As an example, we demonstrate the creation of a “closed bromide loop” when a fuel‐saving preconcentrator is attached to a MgCl2 to HCl convertor.
Arylmercury Compounds. Part VI. Asymmetric Diarylmercury Compounds
Authors: Halpern Yuval , Garti Nissim 
Published: November 2013

AbstractAsymmetric diarylmercury compounds were produced together with symmetric products via a symmetrization process. The asymmetric products could not be isolated from the reaction mixture and their existence was indicated through different analyses (mp, IR, PMR, mass spectra, elemental analysis and DTA). The asymmetric products were shown to be unstable and to disproportionate into two symmetric compounds at elevated temperatures, and in organic solvents even at room temperature.
Polymerization of Nitriles by Organotin Catalysts
Authors: Minke Ram , Freireich Shaul , Zilkha Albert 
Published: November 2013

AbstractThe polymerization of the nitrile groups of polyacrylonitrile, polymethacrylonitrile and poly‐α‐cyanoethyl acrylate by organotin compounds was studied. The reaction, which was accompanied by color formation, was found to depend on the concentration and nature of the initiator, temperature, solvent and time of reaction. In the series Pb, Sn and Si, the organometallic derivatives of the former showed the strongest catalyst activity. A series of di‐ and higher nitriles, including benzal malononitrile, 1,1,3,3‐tetracyanopropane, α‐(2‐cyanoethyl) acrylonitrile and Diels Alder adduct of tetracyanoethylene with anthracene, was also polymerized to dark colored polymers. The mechanism of the polymerization is thought to consist of the addition of the organotin compound to the nitrile groups followed by cyclization leading to the formation of conjugated C=N double bonds. Evidence for this mechanism was obtained from the reaction of model compounds, such as 1,3‐dicyanobutane‐1‐carboxylic acid ester, with tributyltin methoxide.
Reactions of Ring C in Glycyrrhetic Acid Derivatives
Authors: Rozen Sh. , Shahak I. , Bergmann E. D. 
Published: November 2013

AbstractThe chemistry of the relatively unreactive glycyrrhetic acid (1) ring C was investigated. The enone group in this ring was reduced by diborane to allylic alcohols (6, 7), which can be readily converted into the corresponding homoannular dienes (2, 5). These dienes were also prepared by NaBH4 reduction of the enone group. The epoxidation of the diene 2 leads to the mono‐(12) and di‐(14) epoxides. A new ring C enone system (13) was also obtained. Treatment of the two different tosylhydrazones derivatives (16, 20) with methyllithium gave the conjugated methylene compounds (17, 21). The NMR spectrum of the latter compound was also studied with a shift reagent — Eu(FOD). The mass spectra of the homoannular dienes (2, 5), allylic alcohols (6, 7) and 11‐methylene compounds (17, 21) were studied and some new types of fragmentation were suggested.
From Quantum Chemistry to Quantum Biochemistry
Authors: Pullman Bernard 
Published: November 2013

AbstractThree periods may be discerned in the development of quantum biochemistry. In the first, simple Hückel theory was applied to conjugated units of biochemical interest. Despite the simplicity of the method, careful analysis has allowed the interpretation of a considerable number of experimental facts, and also a number of predictions. The second stage is linked to the development of all‐valence‐electron and all‐electron theories and techniques. Now the electronic structure of saturated and partially saturated – biomolecules could be investigated, as well as the large field of conformational problems. The third, and present, period is concerned with the study of environmental effects, in particular solvent effects, on molecular structure and properties. Efforts in this field are developing along two lines: one is the “traditional” continuum model which attempts to account for the bulk effect of the medium; the second employs a model that combines the interacting entities as a “supermolecule”. The “dipeptide” protein model, the backbone of nucleic acids, the polar heads of phospholipids, have been subjected to an analysis of the second type. As for proteins, a conclusion of conceptual significance could be arrived at, namely, that the “protein effect” does not create “extraordinary” conformations. In other words sites of attack on biomolecules can be determined through evaluation of molecular electrostatic potentials.
Molecular Structure Information From X‐Ray Photoelectron Spectroscopy
Authors: Shirley David A. 
Published: November 2013

AbstractA discussion is given of the types of molecular structure information available from X‐ray photoelectron spectroscopy. A complete set of atomic charges in a molecule can be deduced from core‐level binding energy shifts. Atomic‐orbital composition of molecular orbitals is derived from relative intensities. Correlation peaks yield information about electron correlation. Relaxation energies are related to basicity for certain functional groups.
Chemical Basis of Memory: Approaches Using Molar and Smaller Systems
Authors: Barondes Samuel H. 
Published: November 2013

AbstractContemporary assumptions about memory storage in the nervous system are that: (1) it is the expression of a change in the efficacy of synaptic transmission in specific pathways in the central nervous system that mediate the behavior that is remembered; (2) this change is the expression of a biochemical change in the neurons in question. The purpose of this brief paper is to: (1) define the nature of the problems of memory storage in more specific terms based on our knowledge of synaptic transmission and general biochemical regulatory processes; (2) describe two approaches to this problem that will ultimately contribute to its understanding in biochemical terms: (a) a molar approach in which the assay of memory is the behavior of an organism and in which certain types of biochemical and pharmacological studies can point to underlying biochemical mechanisms; (b) an approach using smaller systems in which direct physiological, pharmacological and biochemical measurements can be made of the factors regulating changes in the efficacy of synaptic transmission as a function of repetitive stimulation of a specific synapse.
Is There a Chemical Memory Trace?
Authors: Ungar G. 
Published: November 2013

AbstractThe existence of chemical changes in the brain correlated with acquisition and storage of information, and impairment of learning by inhibitors of RNA and protein synthesis suggest that chemical processes are involved in long‐term memory. The main controversy is over the significance of these processes: whether they are merely concerned with increased metabolic needs or represent a molecular code in which neural information would be processed and preserved. The molecular coding hypothesis can neither be proved nor disproved by a purely chemical approach; additional means are necessary for revealing the presence of minute amounts of specific substances. One of these means is the behavioral bioassay which, in the last ten years, has guided the detection of eight learning‐induced substances, all peptides, in the brain. Two of them (scotophobin, ameletin) have been fully identified and synthesized; they can now be determined and studied by chemical methods. Three other peptides have been purified and their structure is being elucidated. Although good correlation has been found between scotophobin and dark avoidance, specificity of each peptide for a given learned behavior requires further study. The nature of the hypothetical coding system is unknown but it operates probably within the framework of neural circuits: it could create new synaptic junctions, mark them and guide the flow of nerve impulses along the new channels induced by learning. This reprogramming may be based on the chemical recognition system that is believed to direct the formation of the genetically programmed pathways.
Dewatering of Dead Sea Brine by Osmosis
Authors: Loeb Sidney , Weintraub Melvin , van Hezel Johanna 
Published: November 2013

AbstractThe first stage in the production of potash from the Dead Sea involves removal of water from Dead Sea Brine by solar evaporation. The pond function can be supplemented by osmosis, utilizing as a dewatering agent End Brine, a high osmotic pressure solution, available in large quantities as a waste stream from the solar evaporation process. For this osmosis service, asymmetric membranes, i.e. those possessing a dense skin surmounting a porous substructure, were examined. These were tubular membranes 16 mm in diameter. The membranes were of cellulose acetate, fabricated by the Loeb‐Sourirajan technique. The principle objective was to obtain a water permeation flux (permeation rate per unit area) sufficiently high for economic operation. Parameters examined included (1) casting solution composition; (2) temperature to which the membrane was heated in the casting process; (3) circulating brine flow characteristics; (4) effect of using diluted End Brine; (5) influence of reinforcing sleeve; (6) total membrane thickness. Of these parameters the last was found to be most important. At 70 microns, the minimum practical thickness, the flux was still too low. The experimental results were supported by a transport analysis of osmotic flow through an asymmetric membrane. This analysis indicated that any asymmetric membrane of the same thickness, regardless of its chemical composition would also have such low flux because flux is limited by the necessary back diffusion rate of dissolved salt in the porous substructure and by the high salt concentrations within it.
New Techniques in Solvent Extraction and in ION‐Exchange
Authors: Baniel A. 
Published: November 2013

AbstractSeparations and reactions achieved through redistribution between a stationary phase and a liquid phase or between two liquid phases pertain to the disciplines of “ion‐exchange” and “solvent extraction” and also to various membrane separations as well as chromatographic techniques involving a stationary phase and a moving liquid phase. A unified view of all techniques and disciplines involved is presented and operationally applicable definitions of ion‐exchange and of solvent extraction proposed. Likely and possible innovations are discussed, in particular: (a) new types of solvent systems with special reference to systems that respond strongly to imposed composition parameters and to temperature changes; (b) solid ion‐exchangers structured on the molecular level so as to separate ion‐exchange from solvent or membrane functions; (c) liquid‐phase to liquid‐phase transfer with the interposition of membranes between the phases.
Hydroboration. 44. Diisopinocampheylborane of High Optical Purity. Asymmetric Synthesis via Hydroboration with Essentially Complete Asymmetric Induction
Authors: Brown Herbert C. , Yoon Nung Min 
Published: November 2013

AbstractThe reaction of borane with α‐pinene in tetrahydrofuran attains equilibrium in 3 days at 0°. With 15% excess (+)‐α‐pinene ([α]D26.5 + 47.99°), the formation of diisopinocampheylborane is essentially quantitative (‐99.5%). The longer reaction time is accompanied by a selective incorporation of the major isomer into the reagent. Thus, (+)‐α‐pinene, dehydroborated from diisopinocampheylborane with triethylamine, exhibits an optical rotation of [α]D23.5 + 51.0°, indicating an optical purity of 99.8%, and the isopinocampheol, obtained following the oxidation of the reagent, showed [α]D23 −35.1° (c 10, benzene), a higher rotation than any realized previously. The hydroboration of cis‐2‐butene with this diisopinocampheylborane in tetrahydrofuran at −25° provided 2‐butanol of high optical purity, [α]D22.5 −13.29°, an optical purity of 98.4%. Thus this reaction proceeds with nearly complete asymmetric induction.
Polarized Electrons and the Origin of Optical Activity
Authors: Bonner William A. , van Dort Mark A. , Yearian Mason R. , Zeman Herbert D. , Li Gloria C. 
Published: November 2013

AbstractThe history of experiments bearing on the origin of optical activity in nature by parity non‐conservation during the β‐decay of radioactive isotopes is briefly reviewed. Following this, we present a more detailed description of our recent published and unpublished data and calculations regarding the generation of optical activity in DL‐leucine by means of artificially produced longitudinally polarized electrons from a linear accelerator.
Transition Metal Carbyne Complexes, XXIX. Metal Carbon Triple Bonds: X‐Ray Studies on Group VIa Metal Carbyne Complexes
Authors: Huttner G. , Frank A. , Fischer E. O. 
Published: November 2013

AbstractStructural results of X‐ray investigations on group VIa metal carbyne complexes are described and the influences of different substituents on the metal carbon triple bond are discussed. From the M‐Ccarbyne distances metal triple bond radii are derived.
The Elplacarnet Tree: A Complement to the Periodic Table for the Organometallic Chemist
Authors: King R. B. 
Published: November 2013

AbstractOnly a limited number of the many possible networks of planar sp2 carbon atoms are sufficiently compact to bond entirely to a single transition metal atom as perhapto ligands. These networks, which are conveniently called elplacarnets, correspond to the vertices of a tree. The edges of this elplacarnet tree correspond to four different types of growth processes which occur at vertices of degree 1, at vertices of degree 2, in rings, and across an edge connecting two vertices of degree 1. For the middle transition metals (e.g. chromium through cobalt) the elplacarnet tree contains 13 vertices and 12 edges. Some applications of the elplacarnet tree in understanding the extensive varieties of structures of transition metal organometallic complexes containing unsaturated hydrocarbon ligands are summarized.
Photonitrosylation of Carbonylmetal Complexes in Chloroform and Carbon Tetrachloride Solution
Authors: Herberhold Max , Klein Reinhard , Alt Helmut G. 
Published: November 2013

AbstractThe photo‐induced reaction of carbonylmetal complexes with gaseous nitric oxide (“photonitrosylation”) in either chloroform or carbon tetrachloride solution is recommended as a synthetic method to prepare nitrosylmetal chlorides. Binary carbonyliron compounds (Fe(CO)5, Fe2(CO)9, Fe3(CO)12) are converted into Fe(NO)3Cl which is also accessible by the cleavage of binuclear [Fe(NO)2Cl]2 with NO in non‐coordinating solvents. Carbonylcobalt complexes (Co2(CO)M, Co(CO)3NO) are photonitrosylated to give binuclear [Co(NO)2Cl]2, while cyclopentadienylcarbonyl‐chormium compounds ([CpCr(CO)3]2, [CpCr(CO)2]2, CpCr(CO)2NO) lead to mononuclear CpCr(NO)2Cl in excellent yields.
Alkyl and Acyl Dicarbonylarenemanganese Complexes: The Reduction of Metal‐Bound Carbonyl Groups
Authors: Munro George A. M. , Pauson Peter L. 
Published: November 2013

AbstractHydride reduction of tricarbonylarenemanganese cations gives, in addition to the known cyclohexadienyl compounds, appreciable yields of dicarbonylarenemethylmanganese by direct reduction of a metal carbonyl group. Alkyllithiums also attack the cations at carbonyl groups as well as at the ring carbons and, in the case of polyalkylbenzene complexes, fair yields of acyl derivatives result. These may be decarbonylated photochemically and may also be converted to cationic carbene complexes by alkylation with triethyloxonium tetrafluoroborate.
Cembranolids from Marine Origin (Red Sea), Survey, and Isolation of a New Sinulariolide Derivative
Authors: Kashman Y. , Bodner M. , Loya Y. , Benayahu Y. 
Published: November 2013

AbstractThe hitherto isolated and identified cembrane derivatives from alcyonarians of the Gulf of Elat (Red Sea) are briefly reviewed, including the thus far unreported isolation of nephtenol and 16‐deoxysarcophine from several soft‐corals. The structure of a new sinulariolide derivative, 11‐episinulariolide acetate, isolated together with 11‐dehydrosinulariolide, from two (out of seven tested) sinularia species is illustrated.
A New Flavolignan of Biogenetic Interest from Aegilops ovata L.—Part I
Authors: Cooper Raymond , Gottlieb Hugo E. , Lavie David 
Published: November 2013

AbstractTwo compounds, tricin and a related new flavolignan have been isolated from Aegilops ovata L. dispersal units. Evidence leading to assignment of structure of this new compound is presented together with 1H and 13C‐NMR chemical shifts of related model compounds. These phenolics found together in the same plant species with a previously discovered lignan possessing activity as a germination inhibitor, raise the possibility of a new biogenetic link.