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  • 1
    Online Resource
    Online Resource
    Wiley ; 2011
    In:  Israel Journal of Chemistry Vol. 51, No. 10 ( 2011-11), p. 997-1006
    In: Israel Journal of Chemistry, Wiley, Vol. 51, No. 10 ( 2011-11), p. 997-1006
    Abstract: The genesis of enantiopurity in nature, as exemplified by terrestrial amino acids and sugars, has fascinated scientists for more than 150 years. This is a field where we know what we do not know. Starting from theoretical treatments postulated more than 50 years ago, numerous hypotheses, theories, and experiments have been formulated to claim niches of logic and truth. Such arguments vary from purely speculative, often bizarre, to sound enough in terms of reproducibility and feasible generation of mirror symmetry breaking. Although we cannot exclude a biotic origin (i.e,. homochirality was an a posteriori event where one enantiomer tripped and the other survived and evolved, in close resemblance to a Darwinian‐like process), most data and models available are consistent with an abiotic origin that amplified small and stochastic imbalances to produce enantiopure homogeneity prior to life. This analysis revisits recent theoretical background and experiments, which appear to be prebiotically credible, and focuses on primordial molecules such as amino acids. This by no means implies a recreation of the origin of life on Earth, as this task will likely be a surmise forever. These strategies reveal a high degree of robustness and prove how home‐made enantiopurity can be accomplished. Such routes should, in addition, be of enormous practical interest for the production of chiral materials and drugs.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2011
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  • 2
    Online Resource
    Online Resource
    Wiley ; 1985
    In:  Israel Journal of Chemistry Vol. 26, No. 3 ( 1985-01), p. 243-247
    In: Israel Journal of Chemistry, Wiley, Vol. 26, No. 3 ( 1985-01), p. 243-247
    Abstract: The position of the equilibrium in the PTC exchange reaction of alkyl chloride with metal bromide salts RCl + MBr ⇌ RBr + MCI under various condtions is utilized for calculation of the selectivity constant K sel Cl/Br . This constant is found to be dependent on the nature of the metal cation and the inorganic phase composition. K sel Cl/Br can be defined for any point on the phase diagram MCl—MBr—H 2 O at a given temperature, solvent and quaternary cation.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 1985
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  • 3
    In: Israel Journal of Chemistry, Wiley, Vol. 29, No. 2-3 ( 1989-01), p. 131-135
    Abstract: A stereospecific 18 O‐labelling study shows that the syn ‐hydroxy group is preferentially lost from the syn, anti ‐title diol upon i ‐C 4 H 10 chemical ionization, indicating occurrence of a stereoelectronic effect in this process. A collision‐induced dissociation study of deuterium‐ and 18 O‐labelled analogs shows that a symmetrical ether structure is not formed in the above process by an S N i mechanism. This result leads to the conclusion that the stereoelectronic assistance of the anti ‐OH group in the loss of the syn ‐hydroxyl is expressed either in a weak transition state interaction or by other processes such as β‐elimination via hydrogen transfer with concomitant double bond formation.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 1989
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  • 4
    Online Resource
    Online Resource
    Wiley ; 2014
    In:  Israel Journal of Chemistry Vol. 54, No. 5-6 ( 2014-06), p. 642-649
    In: Israel Journal of Chemistry, Wiley, Vol. 54, No. 5-6 ( 2014-06), p. 642-649
    Abstract: The astounding electronic performance of acenes such as tetracene and pentacene (and their heteroaromatic counterparts) stands to revolutionize the field of organic electronics, promising novel consumer electronics for power generation and information display in lightweight, flexible form factors. These results have rekindled interest in acenes larger than pentacene, to determine how electronic properties are further altered by extending conjugation. This research has had to encompass many fundamental studies, as even the simple nature of aromaticity in larger acenes is still a controversial topic. Further, the reactivity of acenes toward oligomerization or oxidation becomes significant in larger acenes, while the diminishing solubility complicates isolation and characterization. This article surveys recent works describing the nature of aromaticity and reactivity in larger acenes, methods used to prepare parent acenes larger than pentacene, and functionalization approaches to soluble, reasonably stable large acenes.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2014
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2019
    In:  Israel Journal of Chemistry Vol. 59, No. 1-2 ( 2019-02), p. 41-51
    In: Israel Journal of Chemistry, Wiley, Vol. 59, No. 1-2 ( 2019-02), p. 41-51
    Abstract: Chemical biology and drug discovery are instrumental sciences to address unmet medical needs and to gain a deeper understanding of normal and disease state biology in mammalian systems. Unlike most genetic tools, the small molecule modulation of biology is reversible, controllable in space, time and quantity, avoids the removal of gene products from cellular systems and thus enables perturbation of biology in its native state. Natural products, their derivatives as well as small molecules based on the core‐scaffolds of natural products including natural product fragments allow targeting unique, biologically relevant fractions of chemical space that may deliver quality tool compounds. In this essay, we discuss various synthesis approaches inspired by natural products to deliver biologically active small molecules. We argue and provide evidence that inspiration by natural product structure remains a powerful guiding principle for the development of novel approaches to the study biology by means of novel bioactive small molecules.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 6
    Online Resource
    Online Resource
    Wiley ; 2022
    In:  Israel Journal of Chemistry Vol. 62, No. 3-4 ( 2022-03)
    In: Israel Journal of Chemistry, Wiley, Vol. 62, No. 3-4 ( 2022-03)
    Abstract: Semiconducting transition metal dichalcogenides can be synthesized in a wide range of structures and geometries, including closed cage nanostructures, such as nanotubes or fullerene‐like nanoparticles (NSs). The latter is especially intriguing due to the stability, enhanced light‐matter interactions, and ability to sustain exciton‐polaritons (EPs) in ambient conditions, i. e., strong coupling of excitonic resonances to the optical cavity. Here we investigate the dynamics of EPs formation in WS 2 NPs in the time domain using femtosecond transient extinction spectroscopy. We develop a gamut of analytical methods and models with time‐dependent parameters to extract the underlying non‐equilibrium dynamics of EPs formation. We find that the formation of EPs in WS 2 NPs is not instantaneous but a gradual process that occurs only after several picoseconds. Specifically, for the short delay times, the light‐matter interaction is guided by excitonic absorption, whereas for the long delay times, the process is controlled by polaritonic scattering. We discover that the coupling strength is a time‐dependent entity and not a constant as is usually defined. Namely, there is a nonlinear coupling between excitonic and external modes and a notable transition from weak to strong coupling limit. Our results show that the time‐dependent phenomenological dynamical model quantitatively reproduces the nonlinear dynamical coupling as well as the effects of the pump fluence on the coupling strength.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 7
    Online Resource
    Online Resource
    Wiley ; 1979
    In:  Israel Journal of Chemistry Vol. 18, No. 1-2 ( 1979-01), p. 110-117
    In: Israel Journal of Chemistry, Wiley, Vol. 18, No. 1-2 ( 1979-01), p. 110-117
    Abstract: The adsorption and electrochemical surface reactions of 1‐naphthol on platinum in 0.5 M sulfuric acid were investigated by optical and electrochemical methods. At low anodic potentials (up to 0.65 V vs. dhe) monolayer adsorption of the organic molecule was observed with a significant extent of charge transfer. At more anodic potentials electrochemical polymerization occurs with films reaching several hundred Angstroms in thickness. Film growth is halted if the potential is decreased below 0.65 V. A parabolic rate of growth is observed and is attributed to slow, rate determining migration of electrons from the film/solution interface to the metal via the π electron systems of the polymeric film. At higher anodic potentials (above ca. 1.00 V) the parabolic growth law is no longer followed due to the occurrence of side reactions. The polymeric film is microporous, allowing passage of water molecules and ions at a low rate (low diffusion coefficient in the film). As a result the rate of electrochemical reactions on the film‐covered surface is diffusion controlled and depends mainly on bulk concentration, resulting with an apparent selectivity with respect to oxidation or reduction of the solvent.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 1979
    detail.hit.zdb_id: 2066481-3
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  • 8
    Online Resource
    Online Resource
    Wiley ; 2016
    In:  Israel Journal of Chemistry Vol. 56, No. 11-12 ( 2016-11), p. 1067-1075
    In: Israel Journal of Chemistry, Wiley, Vol. 56, No. 11-12 ( 2016-11), p. 1067-1075
    Abstract: A new approach to resolve and quantify the effect of temperature on both the average, as well as the instantaneous, structure of generally symmetric molecules is presented. The method employs the efficient continuous symmetry measure, which is shown here to be capable of separating temperature‐induced instantaneous disorders from other sources of distortion, such as the Jahn−Teller effect. We demonstrate the potential of the method by studying two highly symmetric molecules: adamantane and the cyclopentadienyl anion and their cationic states. Our results show that although the distortive effect of temperature is significant, it does not mask other distortion effects. Symmetry analysis provides means to quantify the extent of the distortion in each case, and is investigated from a statistical point of view. A major experimental and theoretical challenge is to resolve the Jahn−Teller effect from other environmental effects, such as solvent, solid matrix, concentration, etc. Our results provide a step forward in this direction.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2016
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  • 9
    Online Resource
    Online Resource
    Wiley ; 1979
    In:  Israel Journal of Chemistry Vol. 18, No. 1-2 ( 1979-01), p. 125-130
    In: Israel Journal of Chemistry, Wiley, Vol. 18, No. 1-2 ( 1979-01), p. 125-130
    Abstract: Electropolished Ni(110) electrodes have a highly epitaxed 4 to 6 Å thick NiO surface film which is cathodically reduced in pH 2.8 Na 2 SO 4 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.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 1979
    detail.hit.zdb_id: 2066481-3
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  • 10
    Online Resource
    Online Resource
    Wiley ; 1981
    In:  Israel Journal of Chemistry Vol. 21, No. 2-3 ( 1981-01), p. 145-150
    In: Israel Journal of Chemistry, Wiley, Vol. 21, No. 2-3 ( 1981-01), p. 145-150
    Abstract: In order to study the stereochemistry of thiirane oxide decomposition, syn ‐ and anti ‐2,3‐dideuterothiirane‐1‐oxides and trans ‐2,3‐dideutero‐thiirane‐1‐oxide have been synthesized in three steps from cis ‐ and trans ‐dideuteroethylene via stereospecific formation of the corresponding oxiranes and thiiranes. The presence of the deuterium label was used so as not to perturb the course of the decomposition from that of the parent thiirane oxide. Pyrolysis of the labeled thiirane oxides in both gas and solution phase proceeded with greater than 90% retention of stereochemistry. Analyses were performed by comparison of the infrared spectra of the product mixtures with standard calibrated samples. Attempts to trap possible biradical intermediates with di(p‐anisyl)thioketone gave a low yield of products, possibly derived from addition to thiirane oxide. These results suggest a possible partial contribution of a biradical mechanism to the thiirane oxide decomposition. If bond rotation in the biradical is slow, this mechanism could be the sole mode of sulfur monoxide extrusion.
    Type of Medium: Online Resource
    ISSN: 0021-2148 , 1869-5868
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 1981
    detail.hit.zdb_id: 2066481-3
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