3922-28-9Relevant academic research and scientific papers
Electrostatic Control of Macrocyclization Reactions within Nanospaces
Wang, Kaiya,Cai, Xiaoyang,Yao, Wei,Tang, Du,Kataria, Rhea,Ashbaugh, Henry S.,Byers, Larry D,Gibb, Bruce C.
supporting information, p. 6740 - 6747 (2019/05/06)
The intrinsic structural complexity of proteins makes it hard to identify the contributions of each noncovalent interaction behind the remarkable rate accelerations of enzymes. Coulombic forces are evidently primary, but despite developments in artificial nanoreactor design, a picture of the extent to which these can contribute has not been forthcoming. Here we report on two supramolecular capsules that possess structurally identical inner-spaces that differ in the electrostatic potential (EP) field that envelops them: one positive and one negative. This architecture means that only changes in the EP field influence the chemical properties of encapsulated species. We quantify these influences via acidity and rates of cyclization measurements for encapsulated guests, and we confirm the primary role of Coulombic forces with a simple mathematical model approximating the capsules as Born spheres within a continuum dielectric. These results reveal the reaction rate accelerations possible under Coulombic control and highlight important design criteria for nanoreactors.
Direct Reduction of 1-Bromo-6-chlorohexane and 1-Chloro-6-iodohexane at Silver Cathodes in Dimethylformamide
Rose, John A.,McGuire, Caitlyn M.,Hansen, Angela M.,Karty, Jonathan A.,Mubarak, Mohammad S.,Peters, Dennis G.
, p. 311 - 317 (2016/10/05)
Cyclic voltammetry and controlled-potential (bulk) electrolyses have been employed to probe the electrochemical reductions of 1-bromo-6-chlorohexane and 1‐chloro-6-iodohexane at silver cathodes in dimethylformamide (DMF) containing 0.050?M tetra-n-butylammonium tetrafluoroborate (TBABF4). A cyclic voltammogram for reduction of 1-bromo-6-chlorohexane shows a single major irreversible cathodic peak, whereas reduction of 1-chloro-6-iodohexane gives rise to a pair of irreversible cathodic peaks. Controlled-potential (bulk) electrolyses of 1-bromo-6-chlorohexane at a silver gauze cathode reveal that the process involves a two-electron cleavage of the carbon–bromine bond to afford 1-chlorohexane as the major product, along with 6-chloro-1-hexene, n‐hexane, 1‐hexene, and 1,5-hexadiene as minor species. In contrast, bulk electrolyses of 1-chloro-6-iodohexane indicate that the first voltammetric peak corresponds to a one-electron process, leading to production of a dimer (1,12-dichlorododecane) together with 1-chlorohexane and 6-chloro-1-hexene as well as 1‐hexene and 1,5-hexadiene in trace amounts. At potentials corresponding to the second cathodic peak, reduction of 1-chloro-6-iodohexane is a mixture of one- and two-electron steps that yields the same set of products, but in different proportions. Mechanistic schemes are proposed to explain the electrochemical behavior of both 1‐bromo-6-chlorohexane and 1-chloro-6-iodohexane.
Chemical control of double barrier tunnelling in α,ω- dithiaalkane molecular wires
Leary, Edmund,Higgins, Simon J.,Van Zalinge, Harm,Haiss, Wolfgang,Nichols, Richard J.
, p. 3939 - 3941 (2008/09/21)
Single molecule conductance measurements on 1,4-bis-(6-thia-hexyl)-benzene derivatives reveal (i) that benzene rings serve as an effective indentation in the tunnelling barrier, and (ii) that more electron-rich benzene rings give higher conductances, cons
A safe and efficient procedure to prepare alkyl and alkoxyalkyl chlorides and dichlorides by catalytic decomposition of the corresponding alkyl and alkoxyalkyl chloroformates and bischloroformates with hexabutylguanidinium chloride
Violleau,Thiebaud,Borredon,Le Gars
, p. 367 - 373 (2007/10/03)
Small amounts of hexabutylguanidinium chloride (0.01 mol%) decomposes pure chloroformates or bischloroformates with different lengths of carbon chains by a semicontinuous process to diminish run-away risk, leading to chloride compounds with high yield and purity.
Mechanism of dichlorination of n-dodecane and chlorination of 1-chlorododecane adsorbed on ZSM-5 zeolite molecular sieves. A supramolecular structural interpretation
Turro, Nicholas J.,Han, Nianhe,Lei, Xue-Gong,Fehlner, James R.,Abrams, Lloyd
, p. 4881 - 4893 (2007/10/02)
The product distributions produced by the photoinduced dichlorination of n-dodecane (nD) and the photoinduced monochlorination of 1-chlorododecane (1CD) adsorbed on two pentasil zeolites (silicalite and LZ-105) have been investigated. The results are explained in terms of a supramolecular model for which the mobile and diffusing chlorination reagents (Cl?/Cl2) enter the zeolite particle from the external surface and diffuse preferentially along the linear channels of the zeolite internal surface that contain immobile adsorbed nD (or 1CD) molecules. The model assumes that the outermost layer of adsorbed substrates is attacked preferentially, that the attack occurs at the proximal end of adsorbed nD molecules closest to the external surface, and that, after the first chlorination, the substrate molecules in an inner layer are protected from chlorination by "blocking" molecules parked in the outer layer. The model describes each substrate molecule adsorbed on the internal surface in terms of supramolecular isomeric structures that are capable of characterizing the specific void space sites occupied by the substrate. A detailed analysis of the results allows the conclusion that the compensating cations tend to be preferentially located in the zigzag channels rather than in the linear channels or intersections and that the variation of selectivity of chlorination with experimental conditions results from redistribution of the isomeric supramolecular structures.
Electrochemical Reduction of 1,6-Dihalohexanes at Carbon Cathodes in Dimethylformamide
Mubarak, Mohammad S.,Peters, Dennis G.
, p. 681 - 685 (2007/10/02)
Cyclic voltammograms for the reduction of 1,6-dibromo-, 1,6-diiodo-, 1-bromo-6-chloro-, and 1-chloro-6-iodohexane at glassy carbon electrodes in dimethylformamide containing tetramethylammonium perchlorate exhibit single irreversible waves that correspond to the reductive cleavage of carbon-bromine or carbon-iodine bonds.When large-scale controlled-potential electrolyses of either 1,6-dibromo- or 1,6-diiodohexane are performed at reticulated vitreous carbon, the principal products are n-hexane (30-45percent), 1-hexene (28-34percent), 1,5-hexadiene (6-16percent), and cyclohexane (7percent), with n-dodecane being another significant species obtained from 1,6-diiodohexane.Because a carbon-chlorine bond is not directly reducible, 1-bromo-6-chloro- and 1-chloro-5-iodohexane give rise mainly to 1-chlorohexane (47-64percent), 6-chloro-1-hexene (20-33percent), and 1,12-dichlorododecane (2-25percent).From these product distributions, and with the aid of experiments done in the presence of deuterium-labeled reagents, we conclude that the electrolytic reduction of 1,6-diiodo- and 1-chloro-6-iodohexane involves both radical and carbanion intermediates, whereas only carbanionic pathways are important for electrolyses of 1,6-dibromo- and 1-bromo-6-chlorohexane.
Photochlorination of n-Alkanes Adsorbed on Pentasil Zeolites
Turro, Nicholas J.,Fehlner, James R.,Hessler, Diane P.,Welsh, Kevin M.,Ruderman, Warren,et al.
, p. 3731 - 3735 (2007/10/02)
The photochlorination of n-alkanes adsorbed on pentasil zeolites proceeds with up to a 20-fold greater selectivity for the monochlorination of terminal methyl groups compared to the selectivity observed when the reaction is carried out in a homogeneous solution.This enhanced selectivity, which provides a novel means of synthesizing terminally functionalized linear alkanes, was found to be a function of the percent loading of the alkane on the zeolite, the zeolite's silicon to aluminum ratio, the percent conversion of the starting material, and the water content of the zeolite.
