A systematic entropy relationship for the general-base catalysis of the deprotonation of a carbon acid. A quantitative probe of transition-state solvation

Bunting, John W.; Stefanidis, Dimitrios

doi:10.1021/ja00158a043

Cited by 47 publications

(29 citation statements)

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“…This is likely due to the higher hydrophobic character brought by the ethyl substituent. The p K a values ranged from 4.3 (compound 17 ) to 5.07 (compound 11 ) and are in excellent agreement with the values determined for adequate models such as aniline (p K a = 4.72 [ 54 ] in 0.1 M KCl versus compound 7 p K a = 4.74 ± 0.05 or compound 17 p K a = 4.30 ± 0.02) or N -phenyldiethanolamine (p K a = 4.13 [ 55 ] in 0.4 M KCl versus compound 3 p K a = 4.87 ± 0.03 or compound 18 p K a = 4.60 ± 0.04). This feature emphasizes the absence of any electronic effect of the menadione core on the acido-basic properties of the benzylamine subunit due to the presence of the methylenic moiety which can be regarded as a poor electronic relay.…”

Section: Resultssupporting

confidence: 76%

Pharmacomodulation of the Antimalarial Plasmodione: Synthesis of Biaryl- and N-Arylalkylamine Analogues, Antimalarial Activities and Physicochemical Properties

et al. 2017

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With the aim of increasing the structural diversity on the early antimalarial drug plasmodione, an efficient and versatile procedure to prepare a series of biaryl- and N-arylalkylamines as plasmodione analogues is described. Using the naturally occurring and commercially available menadione as starting material, a 2-step sequence using a Kochi-Anderson reaction and subsequent Pd-catalyzed Suzuki-Miyaura coupling was developed to prepare three representative biphenyl derivatives in good yields for antimalarial evaluation. In addition, synthetic methodologies to afford 3-benzylmenadione derivatives bearing a terminal -N(Me)2 or -N(Et)2 in different positions (ortho, meta and para) on the aryl ring of the benzylic chain of plasmodione were investigated through reductive amination was used as the optimal route to prepare these protonable N-arylalkylamine privileged scaffolds. The antimalarial activities were evaluated and discussed in light of their physicochemical properties. Among the newly synthesized compounds, the para-position of the substituent remains the most favourable position on the benzyl chain and the carbamate -NHBoc was found active both in vitro (42 nM versus 29 nM for plasmodione) and in vivo in Plasmodium berghei-infected mice. The measured acido-basic features of these new molecules support the cytosol-food vacuole shuttling properties of non-protonable plasmodione derivatives essential for redox-cycling. These findings may be useful in antimalarial drug optimization.

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Section: Resultssupporting

confidence: 76%

Pharmacomodulation of the Antimalarial Plasmodione: Synthesis of Biaryl- and N-Arylalkylamine Analogues, Antimalarial Activities and Physicochemical Properties

et al. 2017

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“…First, the stepwise protonation constants of the ligand were determined to be 10.00(9), 4.63(3), 3.42(5) and 2.3(1) in 0.1 M KCl, 298 K. The first two protonation constants correspond to the protonation of the amine functions. log K H2 is significantly lower than log K H1 due to the vicinity of the aromatic benzene, and is consistent with the pKa of an aniline group (4.72) . The last two protonation constants refer to the protonation of carboxylate functions; further protonation constants are too low to be observed.…”

Section: Resultssupporting

confidence: 74%

A Bishydrated, Eight–Coordinate Gd(III) Complex with Very Fast Water Exchange: Synthesis, Characterization, and Phantom MR Imaging

et al. 2018

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We report here the physical-chemical characterization of a highly water-soluble Gd(III) complex (complex 1) formed with the asymmetric hexadentate ligand H 4 bedik (2,2'-((2-(bis (carboxymethyl)amino)benzyl)azanediyl)diacetic acid). The number of water molecules directly coordinated to the metal, q = 2.2, was assessed by measuring luminescence lifetimes of the Tb(III) analogue (complex 2) in H 2 O and D 2 O and it further was confirmed by 17 O chemical shift measurements on the Gd(III) complex. The complex has moderate thermodynamic stability and remains insensitive to physiological anions [biphosphate (HPO 4 2À ), bicarbonate (HCO 3 À )] and pH variation (in the range 5-10) of the medium as evidenced by negligible changes in longitudinal relaxivity (r 1 ) at 1.41 T, 25 8C. The Gd(III) complex exhibits very fast water exchange, among the fastest reported for Gd(III) chelates, and high relaxivity at high magnetic fields (r 1 = 7.47 mM -1 s -1 at 9.4 T, pH~7 and 25 8C). Interestingly, the very high positive value of the activation entropy indicates a dissociatively activated water exchange for this eight-coordinate complex.

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“…The third H-bond is to the O atom of the adjacent Fe 2 OH group, however. Recent work by Nangia et al [43] has demonstrated the importance of surface H-bonding networks on influencing the structure of the mineral-water interface, so this factor should be considered in models of mineral surfaces.…”

Section: Discussionmentioning

confidence: 99%

Periodic density functional theory calculations of bulk and the (010) surface of goethite

2008

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BackgroundGoethite is a common and reactive mineral in the environment. The transport of contaminants and anaerobic respiration of microbes are significantly affected by adsorption and reduction reactions involving goethite. An understanding of the mineral-water interface of goethite is critical for determining the molecular-scale mechanisms of adsorption and reduction reactions. In this study, periodic density functional theory (DFT) calculations were performed on the mineral goethite and its (010) surface, using the Vienna Ab Initio Simulation Package (VASP).ResultsCalculations of the bulk mineral structure accurately reproduced the observed crystal structure and vibrational frequencies, suggesting that this computational methodology was suitable for modeling the goethite-water interface. Energy-minimized structures of bare, hydrated (one H2O layer) and solvated (three H2O layers) (010) surfaces were calculated for 1 × 1 and 3 × 3 unit cell slabs. A good correlation between the calculated and observed vibrational frequencies was found for the 1 × 1 solvated surface. However, differences between the 1 × 1 and 3 × 3 slab calculations indicated that larger models may be necessary to simulate the relaxation of water at the interface. Comparison of two hydrated surfaces with molecularly and dissociatively adsorbed H2O showed a significantly lower potential energy for the former.ConclusionSurface Fe-O and (Fe)O-H bond lengths are reported that may be useful in surface complexation models (SCM) of the goethite (010) surface. These bond lengths were found to change significantly as a function of solvation (i.e., addition of two extra H2O layers above the surface), indicating that this parameter should be carefully considered in future SCM studies of metal oxide-water interfaces.

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A systematic entropy relationship for the general-base catalysis of the deprotonation of a carbon acid. A quantitative probe of transition-state solvation

Cited by 47 publications

References 0 publications

Pharmacomodulation of the Antimalarial Plasmodione: Synthesis of Biaryl- and N-Arylalkylamine Analogues, Antimalarial Activities and Physicochemical Properties

Pharmacomodulation of the Antimalarial Plasmodione: Synthesis of Biaryl- and N-Arylalkylamine Analogues, Antimalarial Activities and Physicochemical Properties

A Bishydrated, Eight–Coordinate Gd(III) Complex with Very Fast Water Exchange: Synthesis, Characterization, and Phantom MR Imaging

Periodic density functional theory calculations of bulk and the (010) surface of goethite

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