Barrier to pyramidal inversion in ethylmethylphenylarsine

Senkler, G. H.; Mislow, Kurt

doi:10.1021/ja00756a059

Cited by 35 publications

(11 citation statements)

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“…The fact that there are three 1 H NMR signals is due to the axial and equatorial signals from the protons on C1 and C(1A) and a multiplet due to the protons on C2. Pyramidal inversion is possible at the arsenic but with a high energetic barrier (25-42 kcal/mol), the inversion is slow [20,21]. This explains the three distinct multiplets seen in the 1 H NMR.…”

Section: Resultsmentioning

confidence: 96%

Structural characteristics of 2-halo-1,3,2-dithiarsenic compounds and tris-(pentafluorophenylthio)-arsen

Shaikh

Bakus

Parkin

et al. 2006

Journal of Organometallic Chemistry

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Section: Resultsmentioning

confidence: 96%

Structural characteristics of 2-halo-1,3,2-dithiarsenic compounds and tris-(pentafluorophenylthio)-arsen

Shaikh

Bakus

Parkin

et al. 2006

Journal of Organometallic Chemistry

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“…While these reactions may proceed without bond breaking, as suggested for ethylmethylphenylarsine,27 an alternative is a dissociative mechanism, in which one of the bonds to As is broken and reformed 20. 24, 32 The case for such a mechanism is bolstered by the existence of arsenium cations,33, 34 which would be intermediates in the process.…”

Section: Rate Constants[a] For the Formation (Kon) Of Ass Adducts Wimentioning

confidence: 99%

Prospective study of biliary cytology in suspected perihilar cholangiocarcinoma

Hattori

Nagino

Kato

et al. 2011

British Journal of Surgery

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“…Pyrimidal inversion at an arsenic center with three carbon substituents is presumed to occur without bond breaking and is extremely slow; [27][28][29] for example, ethylmethylphenylarsine has a half-life for racemization in decalin of about 6 days at 218 8C. [27] In contrast, As III compounds with Si substituents isomerize faster; for example, C 6 H 5 As[SiH(CH 3 ) 2 ] 2 has a solvent-independent barrier to inversion of 74 kJ mol À1 , which corresponds to a half-life for racemization of about 1 s at 25 8C.…”

Section: -Sulfophenylarsonousmentioning

confidence: 99%

“…[27] In contrast, As III compounds with Si substituents isomerize faster; for example, C 6 H 5 As[SiH(CH 3 ) 2 ] 2 has a solvent-independent barrier to inversion of 74 kJ mol À1 , which corresponds to a half-life for racemization of about 1 s at 25 8C. [30] Although detailed kinetic studies are lacking, As III compounds with S substituents also isomerize faster; for example, stereoisomers of the cyclic 1:1 adducts of phenyldichloroarsine with 1,3-dimercapto-2-propanol and 1,2-dimercaptopropane interconvert with rate constants in the range of 0.42 to 3.1 s À1 at about 25 8C in acidic CD 3 OD, [20] in contrast with earlier measurements in neutral apolar solvents.…”

Section: -Sulfophenylarsonousmentioning

confidence: 99%

“…[31] The cyclic diastereomeric adducts between phenylarsonous acid and a dicysteine peptide isomerized in acetonitrile-water (pH % 2) with t 1/2 % 40 h. [32] The diastereomeric adducts between methylphenylarsinous acid and glutathione could be separated by means of high-performance liquid chromatography (HPLC), but were interconverted upon removal of the solvent. [22] While these reactions may proceed without bond breaking, as suggested for ethylmethylphenylarsine, [27] an alternative is a dissociative mechanism, in which one of the bonds to As is broken and reformed. [20,24,32] The case for such a mechanism is bolstered by the existence of arsenium cations, [33,34] which would be intermediates in the process.…”

Section: -Sulfophenylarsonousmentioning

confidence: 99%

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Formation of a Chiral Center and Pyrimidal Inversion at the Single‐Molecule Level

et al. 2007

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The recent development of single-molecule techniques has been largely targeted at solving biological problems; [1][2][3][4][5] for example, protein folding has been examined by means of force spectroscopy, and enzyme kinetics have been investigated by single-molecule fluorescence. These approaches provide insight into individual trajectories that might be obscured in ensemble measurements. In contrast, bondforming and bond-breaking reactions of small molecules in solution have rarely been observed at the single-molecule level. We have developed an approach through which the covalent chemistry of individual molecules can be monitored in an aqueous environment inside a "nanoreactor", that is, the transmembrane protein pore formed by a-hemolysin.[6-9] By monitoring an ionic current driven through the pore by a transmembrane potential, subtle changes in the structures of individual reactants tethered within the lumen can be detected. We now use this approach to follow both the formation of a chiral center at As III (through the making of an As À S bond) and the inversion taking place at that center. The nanoreactor also serves to isolate the relatively short-lived As III adduct and thereby prevent additional reaction steps that would complicate the chemistry. AsÀS bond making and breaking are important reactions in pharmacology, toxicology, [10][11][12][13] and experimental cell biology. [14,15] We earlier reported reversible covalent As À S bond formation between the side chain of a cysteine residue at position 117 in the a-hemolysin pore and 4-sulfophenylarsonous acid (Figure 1 a).[9] Herein, we examine the same reaction at a different position within the nanoreactor (residue 137) and observed two distinct conductance levels, which corresponded to the formation of two As À S adducts at the wall of the protein (see Figure 1 b). Re-examination of the earlier data from the reaction at position 117 also revealed two current levels, but they were very closely spaced. The unitary conductance of P 137-SH -a heteromeric pore with just one of the seven subunits containing a cysteine residue at position 137-in 2 m KCl at À50 mV is (1.71 AE 0.04) nS (this is Figure 1. Two adducts are formed when 4-sulfophenylarsonous acid reacts with the side chain of Cys-137 in the P 137-SH pore. a) Structure of 4-sulfophenylarsonous acid and schematic of the P 137-SH pore. In aqueous solution, the dehydrated form, that is, 4-sulfophenylarsane oxide, may exist in equilibrium with 4-sulfophenylarsonous acid. The P 137-SH pore consists of six cysteine-free wild-type subunits (green) and one mutated subunit (blue) in which Gly 137 is substituted by Cys. The sulfur atom of the Cys residue is shown in yellow, the carboxy oxygen of residue 137 in red. b) Single-channel recording at À50 mV and 23 8C with a buffer containing 2 m KCl, 80 mm 3-(4-morpholinyl)-1-propanesulfonic acid (MOPS), 100 mm ethylenediaminetetraacetate (EDTA) (pH 8.4) in both chambers. 4-Sulfophenylarsonous acid (100 mm) was in the trans chamber. The current levels corresponding ...

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Barrier to pyramidal inversion in ethylmethylphenylarsine

Cited by 35 publications

References 0 publications

Structural characteristics of 2-halo-1,3,2-dithiarsenic compounds and tris-(pentafluorophenylthio)-arsen

Structural characteristics of 2-halo-1,3,2-dithiarsenic compounds and tris-(pentafluorophenylthio)-arsen

Prospective study of biliary cytology in suspected perihilar cholangiocarcinoma

Formation of a Chiral Center and Pyrimidal Inversion at the Single‐Molecule Level

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