Determination of acidic dissociation constants of several vic-dioximes

Banks, Charles V.; Carlson, A.B.

doi:10.1016/s0003-2670(01)83338-9

Cited by 25 publications

(6 citation statements)

References 7 publications

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“…The pKa values were then obtained by introducing this ratio into the Henderson-Hasselbalch equation corrected for the ionic strength. 16 The brackets denote molar concn and µ is the ionic strength, pKa = pH + log 10 [oxime]/[oximate ion] + (0.509µ1/2)/ (1 + µ1/2). The pAa's listed on Table II are the mean of four detn at different pH or wavelength and are believed to be accurate to 0.05 pK& units.…”

Section: Methodsmentioning

confidence: 99%

Acetylcholinesterase reactivators. Pyridyl and anilyl trifluoromethyl ketoximes

Salvador¹,

Saucier²,

Simon³

et al. 1972

J. Med. Chem.

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Section: Methodsmentioning

confidence: 99%

Acetylcholinesterase reactivators. Pyridyl and anilyl trifluoromethyl ketoximes

Salvador¹,

Saucier²,

Simon³

et al. 1972

J. Med. Chem.

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“…Both the above pathways shown in Scheme S1 (see Supplementary Materials) seem to be the probable chemical transformation. Indeed, the pK a1 value for methylboronic acid and those for the initial α-dioximes H 2 Nx and H 2 Ox, which have been measured in aqueous solutions, are known from the literature [ 30 , 31 , 32 , 33 ] to be almost equal and to fall in the ranges 10.4–10.7 [ 30 , 31 ], 10.6 [ 33 ] and 10.5–10.7 [ 32 ], respectively. So, at the maximal concentrations of the corresponding α-dioximes and CH 3 B(OH) 2 equal to 3 × 10 −3 and 3 × 10 −1 mol L −1 , respectively, and pH = 3.75, those of their monoanionic forms do not exceed 5 × 10 −10 and 7 × 10 −8 mol L −1 , while the initial concentration of Fe 2+ ions is close to 10 −5 mol L −1 .…”

Section: Resultsmentioning

confidence: 99%

Dramatic Effect of A Ring Size of Alicyclic α-Dioximate Ligand Synthons on Kinetics of the Template Synthesis and of the Acidic Decomposition of the Methylboron-Capped Iron(II) Clathrochelates

et al. 2021

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Kinetics and thermodynamics of the template synthesis and of the acidic decomposition of the methylboron-capped iron(II) tris-1,2-dioximates—the clathrochelate derivatives of six (nioxime)- and eight (octoxime)-membered alicyclic ligand synthons—were compared. In the case of a macrobicyclic iron(II) tris-nioximate, the plausible pathway of its formation contains a rate-determining stage and includes a reversible formation of an almost trigonal-antiprismatic (TAP) protonated tris-complex, followed by its monodeprotonation and addition of CH3B(OH)2. Thus, the formed TAP intermediate undergoes a multistep rate-determining stage of double cyclization with the elimination of two water molecules accompanied by a structural rearrangement, thus giving an almost trigonal-prismatic (TP) iron(II) semiclathrochelate. It easily undergoes a cross-linking with CH3B(OH)2, resulting in the elimination of H+ ion and in the formation of a macrobicyclic structure. In contrast, the analogous scheme for its macrobicyclic tris-octoximate analog was found to contain up to three initial stages affecting the overall synthesis reaction rate. The rates of acidic decomposition of the above clathrochelates were found to be also affected by the nature of their ribbed substituents. Therefore, the single crystal XRD experiments were performed in order to explain these results. The difference in the kinetic schemes of a formation of the boron-capped iron(II) tris-nioximates and tris-octoximates is explained by necessity of the substantial changes in a geometry of the latter ligand synthon, caused by its coordination to the iron(II) ion, due to both the higher distortion of the FeN6-coordination polyhedra, and the intramolecular sterical clashes in the molecules of the macrobicyclic iron(II) tris-octoximates.

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“…Then, either a deprotonation of one oxime group of the aforementioned adduct occurs, followed by its coordination to the Lewis-acidic trigonal boron atom of CH 3 B(OH) 2 , thus giving a tetrahedral O 3 BC group, or the molecule of methylboronic acid forms the corresponding diester, undergoing a further deprotonation. pK a1 values for methylboronic acid and those for the initial alicyclic α-dioximes, which have been measured [13][14][15][16] in aqueous solutions at room temperature, are known to be almost equal. They fall in the range 10.4-10.7 for CH 3 B-(OH) 2 , [13,14] are equal to 10.7 for H 2 Gx, [16] to 10.6 for H 2 Nx and is in the range 10.5-10.7 for H 2 Ox.…”

Section: Chemistryselectmentioning

confidence: 99%

Kinetics of the Template Synthesis and Acidic Decomposition of the Methylboron‐Capped Iron(II) Tris‐heptoximate: Dramatic Changes in a Series of Alicyclic α‐Dioximate Ligand Synthons

et al. 2022

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Reaction of the template synthesis of the methylboron-capped iron(II) tris-heptoximate clathrochelate on Fe 2 + ion as a matrix was found to proceed in the quantitative yield in diluted aqueous-organic solutions. This complex is intensively colored in the visible range, whereas the initial ligand synthons are optically silent, thus allowing to photometric study the kinetics of its synthesis and acidic decomposition reactions. Template condensation of the corresponding chelating and capping ligand synthons gave a solid form of this macrobicyclic complex, which was characterized using modern spectral methods and by the single-crystal X-ray diffraction (XRD) experiment. Kinetic schemes and parameters of the aforemen-tioned reactions for the methylboron-capped clathrochelates, the derivatives of six-(H 2 Nx), seven-(H 2 Gx) and eight(H 2 Ox)membered alicyclic α-dioximes, are dramatically affected by their alicyclic ring size. If the general schemes of their formation persist, those for H 2 Nx and H 2 Gx contain a rate-determining stage, whereas that for H 2 Ox has three initial consecutive stages with close rates. Passing from H 2 Nx to H 2 Gx caused a decrease in the synthesis reaction rates of their macrobicyclic derivatives by approximately three orders of magnitude. These kinetic effects were explained using the XRD data for the initial α-dioximes and for their methylboron-capped macrobicyclic derivatives.

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Determination of acidic dissociation constants of several vic-dioximes

Cited by 25 publications

References 7 publications

Acetylcholinesterase reactivators. Pyridyl and anilyl trifluoromethyl ketoximes

Acetylcholinesterase reactivators. Pyridyl and anilyl trifluoromethyl ketoximes

Dramatic Effect of A Ring Size of Alicyclic α-Dioximate Ligand Synthons on Kinetics of the Template Synthesis and of the Acidic Decomposition of the Methylboron-Capped Iron(II) Clathrochelates

Kinetics of the Template Synthesis and Acidic Decomposition of the Methylboron‐Capped Iron(II) Tris‐heptoximate: Dramatic Changes in a Series of Alicyclic α‐Dioximate Ligand Synthons

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