bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Course of N‐Alkylation of 6‐Methylmercaptopurines
Authors: Neiman Z. , Bergmann F. 
Published: November 2013

AbstractReaction of a 6‐methylmercaptopurine with methyl iodide in an aprotic solvent gives only a single methylation product. Both the 7‐ and the 9‐methyl derivatives are alkylated at N‐3. 3‐Methyl‐6‐methylmetcaptopurine is attacked at N‐7, while the 1‐methyl isomer is substituted at position 9. The course of the latter reaction depends markedly on the reaction conditions, as in the presence of an alkali carbonate alkylation takes place at N‐7. The mechanism of these methylations is discussed.
Organic Reactions in Melts and Solids. Part III: Hydrogenolysis by Neat Acyloins
Authors: Goldberg O , Michman M. , Patai S. 
Published: November 2013

AbstractAcyloins were investigated as hydrogen donors in thermal reactions. With neat materials, satisfactory yields were obtained when weak oxidants such as mercuric cyanide and other mercuric salts were used as hydrogen acceptors. The reactions show a high degree of selectivity: acyloins alone are oxidized by mercuric cyanide while compounds of related structure do not react. The reactions of neat materials, in the molten state, yield results which clearly differ from those previously obtained in various solvents.
Electrodialytic Determination of the Capacity of Permselective Membranes
Authors: Kertész D. , De Körösy F. 
Published: November 2013

AbstractThe determination of exchange capacities of permselective membranes has been speeded up from 1–2 weeks to 1–2 days by use of electrodialytic methods for all exchange and washing processes. The total and the non‐quaternary capacities of anionic membranes are determined in a single operation. Capacities in general agree well with analytical data of the membranes.
6‐Trifluoromethylindole
Authors: Kalir A. , Pelah Z. 
Published: November 2013

Abstract6‐Trifluoromethylindole was prepared by reductive cyclization of 2‐nitro‐4‐trifluoromethylbenzyl cyanide. The indole was converted into the corresponding 3‐aldehyde and 3‐carboxylic acid.
Infrared Study of the Adsorption of Benzoic Acid and Nitrobenzene in Montmorillonite
Authors: Yariv S. , Russell J.D. , Farmer V.C. 
Published: November 2013

AbstractNitrobenzene and benzoic acid are coordinated through water molecules to the more highly polarizing exchangeable cations in the interlayer space of montmorillonite, but are directly coordinated to NH4+ and possibly also K+: On dehydration of the adsorption complexes the nitrobenzene and benzoic acid become directly coordinated to all of the exchangeable cations investigated. Benzoate ion was also formed in amounts which were dependent on the exchangeable cations.
Organic Fluorine Compounds. Part XXXVII the Preparation of ω‐Amino‐α‐Fluroacids
Authors: Bergmann E.D. , Cohen Amnon 
Published: November 2013

Abstractγ‐Amino‐α‐fluorobutyric acid (V) and ϵ‐amino‐α‐fluorocaproic acid (VII) have been prepared from the corresponding phthalimido‐α‐bromo‐acid anilides (or other amides) through reaction with potassium fluoride and subsequent hydrolysis.
Amperometric Determination of Cerium and Vanadium, and Cerium and Molybdenum in Their Binary Mixtures Using Two Indicator Electrodes
Authors: Singh D. , Bhatnagar Uma 
Published: November 2013

AbstractIn recent studies in this laboratory, the amperometric method has been applied for the successive determination of cerium and iron [1] and a number of other elements in their binary mixtures [2–3]. In the present investigation this method has been extended for the estimation of mixtures of cerium and vanadium or cerium and molybdenum, using ascorbic acid as titration reagent.
The Reaction of N‐Bromoacetamide with α, β‐Unsaturated Carbonyl Compounds. I. Formation of Bromohydrins from 2‐Hydroxy‐ and 2′‐Hydroxychalcones
Authors: Bien S. , Ber M. , Flohr E. 
Published: November 2013

AbstractThe reaction of N‐bromoacetamide with 2‐hydroxy‐ and 2′‐hydroxychalcones and some transformations of the resulting bromohydrins are described.
Products of the Reaction Between Alcohols and Phosphorus Pentoxide. III. Identification by Infrared Spectrophotometry
Authors: Zangen M. , Bergmann E. D. , Marcus Y. 
Published: November 2013

AbstractThe various compounds obtained by the reaction P4O10 + 4ROH (where R represents hydrocarbon radicals of various length and structure) were identified by infrared spectrophotometry of the fractions separated by column chromatography. The identification was made possible by a comparison between the relative values of the integrated absorption for the P = O, P‐O‐P, P‐O‐C and O‐H bands with those of known standards. For the reaction of phosphorus pentoxide with ethanol, the compounds formed were found to be: mono‐, di‐ and triethyl phosphate, mono‐, (1, 2) di‐ and triethyl‐pyrophosphate; (1, 3) di‐ and (1, 2, 3) triethyl triphosphate; mono‐ and diethyl trimetaphosphate. With other alcohols, only homologs of these compounds were found, but always fewer compounds. Uncertainty between possible isomers was resolved by identification of their acid hydrolysis products.
Substituent Effects on the N. M. R. Signals of the Angular Methyl Groups in Steroids
Authors: Lavie D. , Greenfield S. , Kashman Y. , Glotter E. 
Published: November 2013

AbstractThe chemical shifts of the angular methyl groups in 131 steroids are tabulated and discussed. Additivity increments of substituents mainly at positions 1, 4, 5 and 6 are derived.
On the U. V. Spectrum of O2−
Authors: Czapski G. , Halperin B. 
Published: November 2013

AbstractThe spectrum of O2− ion was measured in several media. The absorption spectra of O2− in KCl discs, in acetonitrile and the reflection spectrum of KO2 showed the maximum absorption in the range of 240 mμ.Solutions of KO2 in liquid ammonia and ethylene diamine are characterized by an absorption band in the range of 370–380 mμ.It is shown that the latter absorption was misinterpreted and is due to the nitrite ion which is formed as a by‐product, rather than to the O2− ion.
Tautomerism and Geometric Isomerism in Arylazo‐Phenols and Naphthols. Part III. Orthohydroxy Derivatives and their Reversible Photochemical Reactions
Authors: Gabor Gavriella , Frei Yael , Gegiou Dina , Kaganowitch M. , Fischer E. 
Published: November 2013

AbstractSolutions of o‐hydroxy or o‐methoxy azobenzene and phenylazonaphthalenes were studied spectroscopically and photochemically in a wide range of temperatures and solvents. All the hydroxy derivatives exist in solution in the azo form, except for (I) and (IV) which show an equilibrium between the azo and hydrazone forms. The latter predominates in (IV), and in (I) and (IV) is responsible for the so‐called luminescence of o‐hydroxy azo compounds. Luminescence was absent in the other compounds. All compounds except (IV) undergo distinct spectral changes when irradiated with ultraviolet or visible light at temperatures sufficiently low to prevent thermal reversion. In the methoxy derivatives the changes are due to cis‐trans isomerization, as shown also by the activation energy of 23 kcal/mole for the thermal reversion. The same explanation is assumed for the hydroxy compounds. The detailed involvement of the hydrazonic form of (I) in these spectral changes is not clear. In rigid media at −187°C, irradiation of (I) with visible light causes a different spectral change, tentatively ascribed to a “hydrazone” → “azo” conversion. Heating the solutions reverts the changes caused by irradiation. The kinetics of this reversion in the hydroxy compounds are complex, showing that the reactions are either catalyzed or else pass through a hydrazonic form, thereby proceeding with much smaller activation energies and frequency factors. It is suggested that several of the eight possible configurations of the “hydroxy” compounds serve as intermediates in the photochemical and thermal conversions, while others coexist in thermal equilibrium.
2‐Nitro‐4‐Methoxyphenylsulfenyl—A New Protecting Group for the Amino Nitrogen
Authors: Wolman Y. 
Published: November 2013

AbstractThe use of 2‐nitro‐4‐methoxy‐phenylsulfenyl‐(I) as an amino protecting group which is extremely sensitive towards electrophilic attack in the synthesis of amino penicillins (amino‐penicillin and DL‐α‐amino‐benzylpenicillin) is described. Synthesis of few protected dipeptides (2‐nitro‐4‐methoxyphenylsulfenyl‐L‐phenylalanyl‐L‐valine, 2‐nitro‐4‐methoxyphenylsulfenyl‐L‐phenylalanyl‐L‐phenylalanine and 2‐nitro‐4‐methoxyphenylsulfenyl‐L‐valyl‐L‐phenylalanine) demonstrates the use of the protecting group in peptide synthesis.
Benzylation of 6‐Alkylthiopurines in Aprotic Solvents
Authors: Neiman Z. , Bergmann F. 
Published: November 2013

AbstractBenzylation of 6‐methylthiopurine (I) and its N‐alkyl derivatives in an aprotic solvent usually leads to a single reaction product. Both (I) and its 7‐benzyl derivative are attacked at N‐3, in analogy to the behavior of the corresponding 7‐methylpurine. Reaction of the 9‐benzyl derivative of (I), followed by thiohydrolysis of the thioether group, gives 7, 9‐dibenzyl‐6‐thiopurine betaine. This result is in disagreement with an earlier report that the 9‐methyl derivative is substituted by methyl iodide at N‐3. Re‐investigation shows, however, that in this case too, the 9‐alkyl group directs further attack toward N‐7. Methylation and benzylation of (I) thus obey the same general rules.
The Influence of Supporting Electrolytes on Ionic Equilibria. The Hydrolysis of the Dichromate Ion
Authors: Perlmutter‐Hayman Berta , Weissmann Yael 
Published: November 2013

AbstractThe influence of supporting electrolytes on the equilibrium Cr2O72− + H2O ⇄ 2 HCrO4− has been investigated with a view to comparing this influence with that exerted on the rates of reactions of similar charge‐types. Neither the influence on the equilibrium constant nor that on the rate constant of the back reaction was found to be uniquely determined by the principle of ionic strength. These results, together with examples from the literature, show that there seems to be nothing special about environmental influence on the kinetics of reactions. It is suggested that what makes prediction difficult is the fact that in both cases activity coefficients appear in a combination which is different from that encountered in the mean activity coefficient.A spectrophotometric method is employed. The value of the equilibrium constant at zero ionic strength has been found equal to 4.4 × 10−2; the heat of reaction is 3.8 Kcal mol−1. The discrepancies between these values and those reported in the literature are discussed.
Some Pseudohalide Derivatives of Perfluoralkyl Selenides
Authors: Welcman N. , Wulf M. 
Published: November 2013

AbstractSeveral new pseudohalide derivatives of perfluoralkyl selenides have been prepared and characterized. Their properties are discussed in relation to the analogous alkyl and aryl selenides and perfluoralkyl sulphides. The trends in the properties of these compounds have been found to be in accordance with the expected influence of the strongly electron‐withdrawing perfluoroalkyl groups.
The Diffusion of Divalent Europium into Single Crystals of Potassium Chloride
Authors: Reisfeld Renata , Honigbaum A. 
Published: November 2013

AbstractThe diffusion of europium was studied in single crystals of potassium chloride by the spectrophotometric method. Measurements were carried out in the temperature range 418–550†C. The absorption spectra as well as the fluorescence spectra of crystals showed that europium diffused in its divalent state, being reduced by the crystal field of potassium chloride. The diffusion of europium can be represented by the equation D = 6.45. 10−2exp(‐29.400/RT). It is concluded that the activation energy consists of the sum of the jump energy of Eu2+ and of the enthalpy of solution of EuCl2 in KCl.
The Influence of Counter‐Ions on the Properties of a Polyethylene Phosphonic Acid Membrane
Authors: Kertész D. , De Körösy F. 
Published: November 2013

AbstractPermselective polyethylene‐phosphonate membranes have been prepared from polyethylene, both by topochemical reaction and by casting from solution. At capacities around 1–2 meq/g these membranes change their electric resistance by more than four orders of magnitude and deswell in acid solutions. The jump in resistance values takes place at different pH according to capacity and cross‐linking of the membrane. The influence of different alkali ions and some tetraalkyl‐ammonium ions on conductivity, swelling and hysteresis of these membranes has been determined. The Li+ ion deswells the membrane and increases its resistance nearly as much as the H+ ion while swelling and conductivity increase in hydroxide solutions with increasing atomic weight of the alkali metals. In non‐alkaline solutions the K+ form has lower conductivity than the Na+ form. Physiological implications of the findings are discussed.
A New Method for Measurement of the Electrical Conductivity of Unsaturated Soils
Authors: Mokady R. S. , Majdan A. 
Published: November 2013

AbstractA method for the measurement of the electrical conductivity of unsaturated soils is presented. A low frequency A.C. is passed through a soil sample and the consequent voltage drop in the soil is measured potentiometrically. The measurement is carried out at different frequencies and by extrapolating to zero, the electrical conductance of the sample is obtained. The results were in good agreement with those obtained using the D. C. technique. Yet, in the proposed method, difficulties due to electro‐osmosis and polarization are avoided and it is possible to carry out measurements over extended periods of time as there occur only negligible changes in the medium measured. The internal resistance of the differential potentiometer is not great enough; therefore, there still does exist a certain influence of contact‐resistance. The proposed method enables us to make reliable and accurate measurements (relative error — 0.3%) of electrical conductivity even in relatively dry soils because the contact resistance does not interfere in this set‐up.
Calculation of the Standard Free Energy of Cation Exchange in Clay Systems
Authors: Bolt G. H. , Winkelmolen C. J. G. 
Published: November 2013

AbstractThe paper deals with methods for calculation of the standard free energy of cation exchange on clays, by assuming certain models for the distribution of the cations between the adsorbed phase and the equilibrium solution. From a comparison of the results calculated with the help of a hypothetical discharging/charging process of the exchanger in the respective homoionic forms, with those found from graphical integration of In K(exchange) over the equivalent fraction adsorbed (method of Gaines and Thomas), the free energy change of the “associated‐solvent” appearing in the latter procedure is identified with that of the “salt‐free” solvent present in the system. The calculated values of ΔG0 (exchange) corresponding to the chosen models are given for the purpose of comparison with experimental values that are found in, or could be derived from, the relevant literature.
Sorption of Methylene Blue by Montmorillonite Saturated with Different Cations
Authors: Bodenheimer W. , Heller Lisa 
Published: November 2013

AbstractSorption of methylene blue by montmorillonite is a cation exchange reaction, but the replacement is not stoichiometric. The degree of dispersion of the clay and the interlayer cations initially present influence the amount of dye sorbed and the nature of the reaction products.
Spectroscopic and Conductance Effects of Conjugated Double‐Bond Systems in Permselective Membranes
Authors: Forgacs C. , Stein G. 
Published: November 2013

AbstractChanges in the absorption spectrum due to different gegen‐cations of colored cation‐exchange membranes were found and explained by direct interaction between the gegen‐ion and conjugated double‐bond chains in the matrix of the membranes. The decoloration of these membranes as a result of current transfer through them was determined. Tracer experiments showed that during current transfer, Cl− ions become covalently bound to the matrix of the membrane. A theory for the electronic conductance through conjugated double‐bond chains in ionic environment was developed, in consistency with the experimental results.
Rapid Spectrographic Determination of Beryllium in Biological Samples
Authors: Schoenfeld Irena 
Published: November 2013

AbstractA direct spectrochemical method for the determination of beryllium in biological samples is described. Charred samples are mixed with dilute HCl and used directly for excitation by the rotating‐disc spark technique. Chemical separation of Be is eliminated, simplifying the estimation and increasing the speed at which the analysis can be performed. The limit of detection is 1 ppb of Be in urine samples, 20 ppb in lung and other tissues. The coefficient of variation ranges from 15% to 25%. This precision is sufficient when the determination is intended for rapid diagnostic purposes.
The Condensation of 2‐Aminofluorene with α, ω‐Dibromoalkanes
Authors: Barak S. 
Published: November 2013

AbstractN, N′‐(2‐fluorenyl) derivatives of piperazine, azetidine, pyrrolidine, piperidine and hexamethyleneimine are formed in the condensation of 2‐aminofluorene with α,ω‐dibromoalkanes in the presence of calcium hydroxide or sodium ethoxide. The same products have been prepared also by other routes.
The Preparation and Acid‐Catalyzed Decomposition of N‐Triphenylmethyl Amides
Authors: Dayagi S. 
Published: November 2013

AbstractAliphatic and aromatic primary amides react with triphenyl methanol in the presence of small amounts of sulfuric acid in acetic acid, and N‐triphenylmethyl amides are obtained in good yields. The products are cleaved by acids. The decomposition of four N‐trityl amides was studied in various mixtures of acetic acid‐sulfuric acid, and the correlations between the logarithms of the observed first‐order rate coefficients, the concentration of the sulfuric acid, and the acidity functions HO and HA were studied. The kinetic data support a unimolecular rate‐determining step for the solvolysis.
Acylation of Nitrogen Heterocycles under the Conditions of the Schotten‐Baumann Reaction I: Benzimidazoles
Authors: Ben‐Ishai D. , Babad E. , Bernstein Z. 
Published: November 2013

AbstractThe acylation of N‐monosubstituted benzimidazoles with various acid chlorides in ethyl acetate — aqueous bicarbonate mixture was investigated. The reaction, which leads to the fission of the imidazole ring, was found to be strongly dependent on the substitution on both the benzimidazole and the acid chloride used. Electron withdrawing groups in the benzimidazoles were found to facilitate the reaction. Carbobenzoxy chloride and ort ho substituted benzoyl chloride gave the highest yields of the fission products. The carbobenzoxylation and benzoylation of unsubstituted, 2‐monosubstituted and 1,2‐disubstituted benzimidazoles were also investigated.
The Cyclization of Cis‐ and Trans‐ Methoxybenzaldoximes to Methoxy‐3,1,4‐Benzoxadiazepines and Methoxy‐Quinazoline‐3‐Oxides Respectively
Authors: Brown D. J. , England B. T. 
Published: November 2013

AbstractCis and trans forms of 2‐amino‐3(4, 5, and 6)‐methoxybenzaldoximes were separated chromatographically and distinguished by their spectra. The trans‐isomers, with triethyl orthoformate, gave 5(6, 7, or 8)‐methoxyquinazoline‐3‐oxide whereas appropriate cis‐isomers gave 7‐ or 9‐methoxy‐3,1,4‐benzoxadiazepine. The structures of the bicyclic products were confirmed by their mass spectra.
Pyrimidines, Part XXII Synthesis and Properties of 5, 6‐Dihalogenouracils
Authors: Pfleiderer W. , Deiss H. 
Published: November 2013

AbstractThe synthesis of various 6‐mono‐ and 5,6 dihalogeno‐uracils is described. It is shown by ultraviolet absorption spectral comparisons in aqueous solutions that the neutral species of all synthesized compounds exist in the dilactam form. The monoanions are formed by loss of a proton from N‐1. pKa values and ultraviolet absorption spectra are reported and the influence of the different halogen substituents are on these properties discussed.
Approach to the Controlled Synthesis of Nucleopeptides I. Nε‐(6‐Purinoyl‐L‐Lysine and β‐(5‐Uracilyl)‐Dl‐Alanine
Authors: Vincze A. , Lachman Ch. , Cohen S. 
Published: November 2013

AbstractNε‐(6‐purinoyl)‐L‐lysine has been prepared by acylation of L‐lysine copper complex or Nα‐carbobenzoxy‐L‐lysine with 6‐trichloromethylpurine followed by the removal of the protecting group. β‐(5‐uracilyl)‐DL‐alanine has been prepared by condensation of 5‐chloro‐methyluracil with diethyl acetamidomalonate, followed by acid hydrolysis.
Hydroboration. XXIX. The Hydroboration of Allylic Chlorides a Study of Directive Effects and the Elimination Reaction
Authors: Brown H. C. , Knights E. F. 
Published: November 2013

AbstractA series of representative allylic chlorides was hydroborated with borane‐tetrahydrofuran and disiamylborane. Hydroboration of allylic chlorides containing a symmetric double bond placed the boron exclusively at the β‐position. Dissymmetric double bonds having more β‐substitution than γ‐substitution react to place the boron predominantly on the γ‐carbon with borane‐tetrahydrofuran and almost exclusively on the γ‐carbon with disiamylborane. In the hydroboration of crotyl chloride with diborane, the rate of elimination of the β‐chloroorganoborane slows markedly after 80% elimination. The 20% of slow elimination reflects the amount of dihydroboration which occurs before elimination. The dialkylborane thus formed probably dimerizes and the dimer undergoes elimination at a reduced rate. The slow elimination is subject to Lewis acid catalysis.
Secondary Isotope Effects Part IV Complex Formation Between Aromatic Hydrocarbons and HCl,
Authors: Halevi E. A. , Ravid B. 
Published: November 2013

AbstractThe isotope effects on complex formation between HCl and variously deuterated benzenes and toluenes have been measured at −80°C, using a differential solubility technique. Both methyl and nuclear deuteration increase the basicity of the hydrocarbon, the two effects being additive in toluene. All the results can be fit with values of: δ FM° = −3.15− cal / g. atom D for methyl deuteration of toluene, and δ FN° = −3.56− cal/g. atom D for nuclear deuteration of either benzene or toluene. The implications of these results for the theory of secondary isotope effects are discussed.
Interaction Dipole Moments in 3‐Arylcycloalkenones
Authors: Meyer A. Y. , Bergmann E. D. 
Published: November 2013

AbstractThe dipole moments of several 3‐aryl‐cycloalk‐2‐en‐1‐ones have been measured and found to deviate from values calculated by summation of the “group moments”. It is shown how such deviations can be used in structural studies.
Structure Determination of Derivatives of α‐Amino‐α, α‐Diphenylacetamide by Mass Spectrometry
Authors: Breuer E. , Sarel S. , Taube Aviva , Sharvit J. 
Published: November 2013

AbstractThe mass spectral fragmentation pattern of a series of derivatives of α‐amino‐α,α‐diphenylacetamide of the types A and B is described. The fragmentation of some related benzhydryl ureas (C) is also included.