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Journal articles on the topic 'Protonation'

Author: Grafiati

Published: 4 June 2021

Last updated: 6 September 2023

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1

Perez, G., E. Possagno, and E. Lilla. "Influence of Protonation Exothermicity on Gas-Phase Concurrent Dealkylation and Isomerization of p-Cymene." Australian Journal of Chemistry 45, no. 3 (1992): 623. http://dx.doi.org/10.1071/ch9920623.

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The gas-phase protonation is reported of p-cymene (p- isopropyltoluene ) by different radiolytically formed protonating agents (O2H+, N2H+, CH5+, COH+). The characteristics of the reactions vary with the protonation exothermicity . Both dealkylation and isomerization are observed with O2H+ or N2H+ ions. Only dealkylation occurs when the protonating agent is the CH5+ ion. Formation of products is not observed when the less energetic COH+ ions are employed. The results show that in the competition between isomerization and dealkylation the dealkylation reaction becomes favoured as the protonation exothermicity decreases.

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2

Jankovska, Katica, Lidija Soptrajanova, and Ilinka Spirevska. "Protonation of maleic and fumaric acid in aqueous sulfuric acid solutions." Journal of the Serbian Chemical Society 65, no. 10 (2000): 695–708. http://dx.doi.org/10.2298/jsc0010695j.

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The protonations of maleic and fumaric acid in an acidic medium (aqueous solutions of sulfuric acid) were followed spectrophotometrically at room temperature. The acid-base equilibria were characterised qualitatively and quantitatively. The pKBH+ values were determined using the Hammett equation, employing several acid functions in order to determine which of them describes best the protonation process of the studied organic acids. The thermodynamic pKBH+ values as well as those of the solvation parameters m, m* and ? and of the thermodynamic protonation constants (or, rather, the pKa,p values) were also defermined. The method of characteristic vector analysis (CVA) was used to reconstruct the experimental spectra.

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3

Singh, Anil K., Camille Sandorfy, and Janos H. Fendler. "Retinylidene Schiff bases in surfactant-solubilized water pools in heptane." Canadian Journal of Chemistry 68, no. 9 (September 1, 1990): 1514–22. http://dx.doi.org/10.1139/v90-233.

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All-trans-retinal (1) was reacted with n-butylamine in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles in heptane to form all-trans-N-retinylidene–n-butylamine Schiff bases (2). The extent of protonation of 2 by 3-chloropropionic acid (CPA) to give 3 in AOT reverse micelles in heptane was found to depend on the ratio of [CPA] to [2], as well as on [H2O]/[AOT] (i.e., on the ω value). At any given [2] and ω values, increasing amounts of CPA increased the protonation and at any given constant [2] and [CPA], increasing ω values also increased the protonation. Over a period of 24 hours, there was only 4% decomposition of 2 in AOT reverse micelles in heptane at ω = 24. Conversely, in three hours, 23% of 3 decomposed in the same system. The trans to cis photoisomerization of 2 in heptane occurred at a much faster rate in the presence of AOT reverse micelles than in their absence. The appearance of carboxylate peaks (FTIR, 1400–1500 cm−1) indicated that the larger the AOT solubilized water pools, the greater the CPA dissociation. 1 also reacted with the α-NH2 group of l-lysine (4) in AOT reverse micelles in heptane to give the corresponding Schiff base 6. Protonation of 6 occurred either intramolecularly or by reaction with unreacted 4. These results were discussed in terms of rhodopsin protonations. Keywords: retinylidene Schiff bases, reverse micelles, protonation of Schiff bases, trans to cis photoisomerization.

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4

Perisic-Janjic, Nada, Jevrem Janjic, and Marija Lazarevic. "A spectrophotometric study of the protonation processes of some N-[1-(benzimidazol)-1-yl]methylbenzamide derivatives." Journal of the Serbian Chemical Society 65, no. 1 (2000): 37–45. http://dx.doi.org/10.2298/jsc0001037p.

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The protonation of N-[1-(benzimidazol)-1-yl]methylbenzamide derivatives in aqueous acids (H2SO4) media was investigated, using a spectrophotometric method. The investigated compounds have two protonation processes. The first protonation process occurs in weakly acidic aqueous solutions (pH range) and refers to the protonation of the benzimidazole part of the molecule. The second protonation process occurs in concentrated sulfuric acid solutions and refers to protonation of the amide group. The protonation constants of the second process were calculated by the Hammett and Cox-Yates method. The effect of chemical structure on the ionisation constants is discussed. A correlation between the protonation constants and antimicrobial activity was established.

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5

Mohr, Justin T., Allen Y. Hong, and Brian M. Stoltz. "Enantioselective protonation." Nature Chemistry 1, no. 5 (July 24, 2009): 359–69. http://dx.doi.org/10.1038/nchem.297.

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6

Chandrasekaran, Maruthai, Michael Noel, and Venkatasubramanian Krishnan. "Glassy carbon surface effects on the electroreduction of aromatic carbonyl compounds. II Benzophenone." Collection of Czechoslovak Chemical Communications 56, no. 10 (1991): 2055–66. http://dx.doi.org/10.1135/cccc19912055.

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Results of the voltammetric study of benzophenone reduction in dimethylformamide and aqueous media on GCE are presented together with the comparative discussion of the data for mercury and other electrodes available in the literature. The formation and stability of anion radicals and dianions and their reactivity with protonating agents on GCE are similar to those on mercury electrodes. A new surface prewave noticed in aprotic and neutral aqueous solutions on GCE has not so far been reported on any other electrode. All experimental evidences support the view that this prewave is due to the surface protonation by the acidic functional groups on GCE. The surface protonation is found to be a slow time-dependent process requiring 3-4 minutes for completion. The surface concentration evaluated from the faradaic response of the surface process is found to be around 30% or even less if the surface roughness factor is considered,. The importance of this finding to the general concept of surface acidity effects on electrocatalysis is also emphasised.

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7

Sharma, Sangita, Mayur C. Shah, Neha Patel, Dipika Dalwadi, and J. J. Vora. "Potentiometric Studies on the Protonation Constants and Protonation Energies of Some Diamines in Methanol + Water Mixtures." E-Journal of Chemistry 4, no. 3 (2007): 313–19. http://dx.doi.org/10.1155/2007/978639.

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The protonation constants of diamines such as ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane,o-phenylenediamine,m-phenylene-diamine,p-phenylenediamine were determined on the basis of Bjerrum and Calvin method in methanol-water mixtures. A pH metric method was used for calculation of protonation constants. The effects of solvents on protonation constant have been determined at ionic strength 0.2 M dm-3(NaClO4) and temperature 30±0.1oC under nitrogen atmosphere. FORTRAN (IV) programs were used for calculation of protonation constants and distribution of species like H2L, HL, L in equilibrium state. The logarithm of the protonation constants decrease in aliphatic diamines and increase in aromatic diamines with increase in methanol content in mixed equilibria. The verification of constants are explained on the basis of solute-solvent interaction, solvation, proton transfer processes and dielectric constant of equilibria. Protonation energies have been calculated theoretically using computational methods and these protonation energies for aromatic diamines are higher than aliphatic diamines.

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8

Men, Yi, Srinivas R. Korupoju, Masato Kurihara, Jun Mizutani, and Hiroshi Nishihara. "Protonation, Deprotonation, and Protonation: Conjugated Photochemical Reactions of Ferrocenylazophenol." Chemistry - A European Journal 11, no. 24 (December 9, 2005): 7322–27. http://dx.doi.org/10.1002/chem.200500713.

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9

Karlsson, Annika, Anders Broo, and Per Ahlberg. "Regioselective protonation of ferrocene in superacid and formation of a CHFe bond. An experimental and theoretical study of the structure and dynamics of the ferrocenonium ion." Canadian Journal of Chemistry 77, no. 5-6 (June 1, 1999): 628–33. http://dx.doi.org/10.1139/v99-053.

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Protonation of ferrocene has been suggested to take place on carbon (exo-protonation) or iron (endo-protonation). However, experiments have not been conclusive because of interfering exchange reactions. Now low-temperature protonation of ferrocene and [2H10]-ferrocene in superacid and direct observation of the carbocation by 1H NMR at low temperature shows only primary protonation and that it exclusively takes place in an endo-fashion. Studies by DFT calculations using B3LYP hybrid functional indicate the presence of an intramolecular nonlinear CHFe bond and that the proton might be delocalized between carbon and iron. Potential energy barriers for degenerate rearrangements of the hydride bridged carbocation are low, suggesting that the proton might be delocalized between all 10 carbons and iron. The NMR results are consistent with such an interpretation.Key words: regioselective, protonation, superacid, ferrocenonium ion.

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10

Tóth, Jaroslav, Milan Remko, and Milan Nagy. "Structural Study of Flavonoids and Their Protonated Forms." Zeitschrift für Naturforschung C 51, no. 11-12 (December 1, 1996): 784–90. http://dx.doi.org/10.1515/znc-1996-11-1204.

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The highly successful semiempirical quantum chemical methods AM1 (Austin Model 1) and PM3 (a reparametrization of AM1) were applied to an investigation of the conformational properties of flavone, 3-hydroxyflavone, isoflavone and 2-hydroxyisoflavone. The most stable structures correspond to the non-planar forms with an angle of phenyl ring rotation out of the chromone moiety from a relatively narrow interval (28° - 38°). The mono- and diprotonation of these compounds was also investigated. The prominent site of protonation is the oxygen of the carbonyl group with a protonation enthalpy from the interval of about 900 -920 kJ.mol-1. The protonation enthalpy for protonation of the ether oxygen was computed to be about 200 kJ.mol-1 lower. Adding a second proton to monoprotonated species studied resulted in much lower protonation enthalpies compared to monoprotonation. The geometry of the studied compounds upon protonation changed considerably.

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11

Rao, P. Srinivasa, B. Srikanth, V. Samba Siva Rao, C. Kamala Sastry, and G. Nageswara Rao. "Protonation Equilibria of L-Aspartic, Citric and Succinic Acids in Anionic Micellar Media." E-Journal of Chemistry 6, no. 2 (2009): 561–68. http://dx.doi.org/10.1155/2009/705976.

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The impact of sodium lauryl sulphate (SLS) on the protonation equilibria ofL-aspartic acid, citric acid and succinic acid has been studied in various concentrations (0.5-2.5%w/v) of SLS solution maintaining an ionic strength of 0.16 mol dm-3at 303 K. The protonation constants have been calculated with the computer program MINIQUAD75 and the best fit models have been calculated based on statistical parameters. The trend of log values of step-wise protonation constants with mole fraction of the medium has been explained based on electrostatic and non-electrostatic forces operating on the protonation equilibria. The effects of errors on the protonation constants have also been presented.

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12

Kalydi, Eszter, Milo Malanga, Dóra Ujj, Gábor Benkovics, Zoltán Szakács, and Szabolcs Béni. "Fully Symmetric Cyclodextrin Polycarboxylates: How to Determine Reliable Protonation Constants from NMR Titration Data." International Journal of Molecular Sciences 23, no. 22 (November 21, 2022): 14448. http://dx.doi.org/10.3390/ijms232214448.

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Acid-base properties of cyclodextrins (CDs), persubstituted at C-6 by 3-mercaptopropionic acid, sualphadex (Suα-CD), subetadex (Suβ-CD) and sugammadex (Suγ-CD, the antidote of neuromuscular blocking steroids) were studied by 1H NMR-pH titrations. For each CD, the severe overlap in protonation steps prevented the calculation of macroscopic pKa values using the standard data fitting model. Considering the full symmetry of polycarboxylate structures, we reduced the number of unknown NMR parameters in the “Q-fitting” or the novel “equidistant macroscopic” evaluation approaches. These models already provided pKa values, but some of them proved to be physically unrealistic, deceptively suggesting cooperativity in carboxylate protonations. The latter problem could be circumvented by adapting the microscopic site-binding (cluster expansion) model by Borkovec, which applies pairwise interactivity parameters to quantify the mutual basicity-decreasing effect of carboxylate protonations. Surprisingly, only a single averaged interactivity parameter could be calculated reliably besides the carboxylate ‘core’ microconstant for each CD derivative. The speciation of protonation isomers hence could not be resolved, but the optimized microscopic basicity parameters could be converted to the following sets of macroscopic pKa values: 3.84, 4.35, 4.81, 5.31, 5.78, 6.28 for Suα-CD; 3.82, 4.31, 4.73, 5.18, 5.64, 6.06, 6.54 for Suβ-CD and 3.83, 4.28, 4.65, 5.03, 5.43, 5.81, 6.18, 6.64 for Suγ-CD. The pH-dependent charge of these compounds can now be accurately calculated, in support of designing new analytical methods to exploit their charge-dependent molecular recognition such as in cyclodextrin-aided chiral capillary electrophoresis.

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13

Lakshminarayanan, Abirami, and Narayanaswamy Jayaraman. "Successive outermost-to-core shell directionality of the protonation of poly(propyl ether imine) dendritic gene delivery vectors." Canadian Journal of Chemistry 95, no. 9 (September 2017): 965–74. http://dx.doi.org/10.1139/cjc-2017-0153.

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The protonation behaviour of polycationic compounds has direct relevance to their ability to condense and deliver nucleic acids. This report pertains to a study of the protonation behaviour of polycationic poly(propyl ether imine) (PETIM) dendritic gene delivery vectors that are constituted with tertiary amine core moiety and branch sites, n-propyl ether linkages, and primary amine peripheries. The ability of this series of dendrimers to condense nucleic acids and mediate endosomal escape was studied by unravelling the protonation behaviour of the dendrimers aided by pH metric titrations and 1H and 15N NMR spectroscopies. The results demonstrate protonation of the primary and tertiary amines of outermost-to-core shells occurring in a successive stepwise fashion, in contrast to other polycationic vectors. Theoretical calculations based on the Ising model rationalize further the finer details of protonation at each shell. The protonation pattern correlates with the endosomal buffering and nucleic acid condensation properties of this PETIM-based dendritic gene delivery vectors. The study establishes that the protonation behaviour is a critical and essential parameter to assess the gene condensation and delivery vector properties of a polycationic compound.

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14

Hou, Meimei, Lu Lin, Xiangpei Chai, Xiaowei Zhao, Baokun Qiao, and Zhiyong Jiang. "Enantioselective photoredox dehalogenative protonation." Chemical Science 10, no. 27 (2019): 6629–34. http://dx.doi.org/10.1039/c9sc02000d.

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15

Ballerat-Busserolles, Karine, Mickaël R. Simond, Yohann Coulier, and Jean-Yves Coxam. "Protonation of alkanolamines and cyclic amines in water at temperatures from 293.15 to 373.15 K." Pure and Applied Chemistry 86, no. 2 (February 1, 2014): 233–43. http://dx.doi.org/10.1515/pac-2014-5017.

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Abstract The protonation properties of amines are of particular interest for the development of thermodynamic models representative of CO2 dissolution in aqueous solutions. This paper reports experimental equilibrium constants of protonation of alkanolamines (2-aminoethanol, 2,2′-iminodiethanol, 2-[bis(2-hydroxyethyl)amino]ethanol, 2-amino-2-methylpropan-1-ol, 2,2′-(methylimino)diethanol and cyclic amines (morpholine, 4-methylmorpholine, pyridine, 1-methyl-piperidine, 2-methyl-piperidine, 2,6-dimethylpiperidine). The equilibrium constants of protonation were determined by potentiometric technique up to 353.15 K and extrapolated up to 373.15 K using experimental enthalpies of protonation.

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16

Alcarás, José Renato, Hugo J. N. P. D. Mello, and Marcelo Mulato. "Polyaniline Protonation and Deprotonation Process as the Main Mechanism for Ionic Field Effect Sensors." MRS Proceedings 1795 (2015): 41–46. http://dx.doi.org/10.1557/opl.2015.674.

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ABSTRACTIn this work, Polyaniline (PANI) was used as a sensing film for pH measures due to its characteristic of switching protonation states under acid and alkaline solutions. Equally produced films had their sensitivity (electric response versus pH) measured before and after being under the influence of a constant electric potential (from 3.5 to 6 V, one for each film) for the analysis on how the electric potential influenced the sensitivity. Then, the protonation caused by the application of the first potential was reversed by applying a constant 5 V reverse potential and the sensitivity was then evaluated again. The results show, on average, a constant relation between intensity of protonation and the potential applied and that the process of protonation is reversible by applying a higher opposite potential then the protonation one.

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17

Chang, Do Ren, Sara Harden, and Nick Loverro. "Protonation of Polyethylenimine." Journal of Macromolecular Science: Part A - Chemistry 23, no. 6 (June 1986): 801–4. http://dx.doi.org/10.1080/00222338608063425.

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18

Yu, Yuan, Esmir Gunic, and Larry L. Miller. "Protonation of Oligothiophenes." Chemistry of Materials 7, no. 2 (February 1995): 255–56. http://dx.doi.org/10.1021/cm00050a004.

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19

Diana, Patrizia, Paola Barraja, Antonino Lauria, Anna Maria Almerico, Gaetano Dattolo, and Girolamo Cirrincione. "Protonation of Aminoindoles." Tetrahedron 56, no. 29 (July 2000): 5177–83. http://dx.doi.org/10.1016/s0040-4020(00)00180-0.

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20

Cho, Seung Joo, Chunzhi Cui, Jin Yong Lee, Jong Keun Park, Seung Bum Suh, Jaiwook Park, Byeang Hyean Kim, and Kwang S. Kim. "N-Protonation vs O-Protonation in Strained Amides: Ab InitioStudy." Journal of Organic Chemistry 62, no. 12 (June 1997): 4068–71. http://dx.doi.org/10.1021/jo962063z.

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21

Fujiki, Ryo, Toru Matsui, Yasuteru Shigeta, Haruyuki Nakano, and Norio Yoshida. "Recent Developments of Computational Methods for pKa Prediction Based on Electronic Structure Theory with Solvation Models." J 4, no. 4 (December 10, 2021): 849–64. http://dx.doi.org/10.3390/j4040058.

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The protonation/deprotonation reaction is one of the most fundamental processes in solutions and biological systems. Compounds with dissociative functional groups change their charge states by protonation/deprotonation. This change not only significantly alters the physical properties of a compound itself, but also has a profound effect on the surrounding molecules. In this paper, we review our recent developments of the methods for predicting the Ka, the equilibrium constant for protonation reactions or acid dissociation reactions. The pKa, which is a logarithm of Ka, is proportional to the reaction Gibbs energy of the protonation reaction, and the reaction free energy can be determined by electronic structure calculations with solvation models. The charge of the compound changes before and after protonation; therefore, the solvent effect plays an important role in determining the reaction Gibbs energy. Here, we review two solvation models: the continuum model, and the integral equation theory of molecular liquids. Furthermore, the reaction Gibbs energy calculations for the protonation reactions require special attention to the handling of dissociated protons. An efficient method for handling the free energy of dissociated protons will also be reviewed.

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22

Sudhakar, Ch, Allabakshu Shaik, M. Ramanaiah, and Ch Nageswara Rao. "Effect of Solvent on Protonation Equilibria of L-Serine and L-Tryptophan in Ethylene Glycol-Water Mixtures." Research Journal of Chemistry and Environment 25, no. 7 (June 25, 2021): 124–29. http://dx.doi.org/10.25303/257rjce12421.

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Protonation equilibria of L-serine and L-tryptophan in varying compositions (0.0-50.0 % v/v) of ethylene glycol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1 using sodium chloride. The protonation constants have been calculated with the computer program MINIQUAD 75 and are selected based on statistical parameters. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, χ2, skewness and kurtosis. The protonation constants of L-serine and L-tryptophan change linearly with increasing ethylene glycol content. This is attributed to the dielectric constant of the medium.

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23

Ishii, Yosuke, Keisuke Kurimoto, Kento Hosoe, Remi Date, Itta Yamada, and Shinji Kawasaki. "Photo-rechargeable fuel cell using photo-hydrogenation reactions of quinone molecules." New Journal of Chemistry 44, no. 6 (2020): 2275–80. http://dx.doi.org/10.1039/c9nj04782d.

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24

Alex, S., P. Turcotte, R. Fournier, and D. Vocelle. "Study of the protonation of simple Schiff bases in solvents of various polarity by means of Raman spectroscopy." Canadian Journal of Chemistry 69, no. 2 (February 1, 1991): 239–45. http://dx.doi.org/10.1139/v91-038.

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In this study, the protonation of simple Schiff bases by organic acids in various solvents is investigated by Raman spectroscopy and the spectral response of the C=N+ stretching mode is correlated with the macroscopic properties of the medium surrounding the imine. Upon protonation, the unperturbed C=N stretch increases in frequency due to the combination of the coupling with the C=N+H bend and a partial rehybridization of the C=N bond. Depending on the proton location relative to that of its counterion, one mechanism may prevail over the other. Intensity measurements show that protonation is mostly controlled by the hydrogen bonding properties of the solvent and by the polarity of the medium. However, whatever the solvent, full proton transfer cannot be achieved with organic acids with pKa similar to the COOH of amino acids found in visual or bacterial pigments, meaning that the protonation mechanism may depend upon particular properties of the protein. Key words: imines, protonation, Raman spectroscopy, rhodopsin, Schiff base.

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25

Le, Minh Tam, Hung Thanh Le, and Tien Giang Nguyen. "Computational dertermination of protonation for aromatic derivatives." Journal of Technical Education Science, no. 77 (June 28, 2023): 35–39. http://dx.doi.org/10.54644/jte.77.2023.1401.

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Protonation is an important process relating to various fields, such as biological reactions, and organic chemical synthesis. The determining position of protonation has been involved many challenging issues which are usually impossible to directly predict the positions of attaching protons from structures of molecules. However, predicting positions of protonation for aromatic rings is particularly important since it decides which form is preferred in the main products. For this reason, solving this task has been interesting for chemists since last decades with various studies carried out. Many results have been achieved in this field from both experimental and computational efforts. In the present work, protonation of three aromatic derivatives were investigated via the computational approach in which geometry configuration of relevant protonated molecules were optimized using the molecular modeling method. The results showed that protonation was strongly influenced when groups OH-, CH3-, and NH2- appear in aromatic derivatives with three cases studied including phenol, aniline and toluene.

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26

Gan, Shenglong, Longbin Chen, Yancong Feng, Yong Deng, Rui Zhou, Yingying Dou, Biao Tang, et al. "Protonation-induced molecular permeation at the oil/water interface in an electric field." Physical Chemistry Chemical Physics 20, no. 46 (2018): 29012–17. http://dx.doi.org/10.1039/c8cp04028a.

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27

Priyanka, K. P., V. Anita, P. Shyamala, and Rao G. Nageswara. "Solvent Effect on Protonation Equilibria of L-Histidine and 1,10- Phenanthroline in 1-Propanol-Water Mixtures." Research Journal of Chemistry and Environment 25, no. 10 (September 25, 2021): 132–37. http://dx.doi.org/10.25303/2510rjce132137.

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Solute-solvent interactions of L-Histidine and 1,10- Phenanthroline have been studied in varying compositions (0-60% v/v) of 1-propanol-water mixtures using pH-metric technique. The ionic strength of 0.16 mol. L-1 is maintained at 303±0.1 K and protonation constants were calculated by using the computer program MINIQUAD75. The best suited chemical model of protonation equilibria was selected based on the statistical parameters. The solvent effect on log K values increased with the inverse of dielectric constants of 1-proponol-water mixtures and the trend was explained based on operation of electrostatic forces on protonation equilibria. This study also discusses the distribution of species and effect of influential parameters on the protonation constants.

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28

Jankulovska, Mirjana, Vesna Dimova, Ilinka Spirevska, and Milena Jankulovska. "Comparison of theoretical and experimental investigation of protonation process of some thiones in acid media." Zastita materijala 62, no. 1 (2021): 9–21. http://dx.doi.org/10.5937/zasmat2101009j.

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PM3 semiempirical method was used for quantum chemical investigation in order to investigate the electronic properties and to determine the protonation centre in 1,2,4-triazoline-3-thione molecule. Confirmation of protonation center in acid media of investigated compounds was made using the values of atomic charges, as well as, proton affinity values. The results from semiempirical calculations indicated that the protonation center in the thione molecule was the sulphur atom. The behavior of thiones was investigated in mineral acid media using UV spectroscopy. The influence of the strength of the acid and its anion on the protonation process was discussed using three different mineral acids (perchloric, hydrochloric and phosphoric acid) for protonation. The protonation process in perchloric and hydrochloric acid took place in one step, while in phosphoric acid was not finished even when its concentration was to the highest degree. The dissociation constants of protonated forms (pKBH + ) and the solvation parameter m* values were calculated in accordance with "excess acidity" function method (Cox and Yates) using the absorbance data from the experimental and reconstructed spectra (Characteristic Vector Analysis (CVA)). The determined pKBH + values in hydrochloric acid had more negative value than those obtained in perchloric acid media. The pKBH + values were in agreement with the literature data for this class of compounds.

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29

Fuentes-Martínez, Yanet, Carolina Godoy-Alcántar, Felipe Medrano, Alexander Dikiy, and Anatoly K. Yatsimirsky. "Protonation of kanamycin A: Detailing of thermodynamics and protonation sites assignment." Bioorganic Chemistry 38, no. 4 (August 2010): 173–80. http://dx.doi.org/10.1016/j.bioorg.2010.04.003.

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30

Henderson, Richard A., and Kay E. Oglieve. "Single protonation labilises but double protonation inhibits substitution of [Fe4S4Cl4]2−." Journal of the Chemical Society, Dalton Transactions, no. 11 (1998): 1731–34. http://dx.doi.org/10.1039/a802303d.

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31

Ogunsipe, Abimbola O., Mopelola A. Idowu, Taofeek B. Ogunbayo, and Isaac A. Akinbulu. "Protonation of some non-transition metal phthalocyanines — spectral and photophysicochemical consequences." Journal of Porphyrins and Phthalocyanines 16, no. 07n08 (July 2012): 885–94. http://dx.doi.org/10.1142/s1088424612500988.

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The photophysics and photochemistry of phthalocyanine complexes of magnesium (MgPc), aluminum chloride (ClAlPc) and zinc (ZnPc) are studied in N,N′-dimethylformamide (DMF). The values obtained for the photophysical and photochemical parameters are normal for simple metallophthalocyanine (MPc) complexes. Protonation of the azomethine bridges reduced the photoactivities of the complexes considerably; however the excited triplet states of the protonated species are more stable towards ground state oxygen. The interaction of the non-protonated MPcs with ground state oxygen is shown to be diffusion-assisted, with bimolecular rate constant values of the order of 1010 M-1.s-1. MgPc could not be protonated; it was easily demetalated by the protonating acid. The kinetics of the demetalation yielded the rate equation: Rate = 0.1[MgPc][H+]2/3

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32

Seliger, Piotr, Danuta Tomczyk, Grzegorz Andrijewski, and Ewa Tomal. "The Determination of Protonation Constants of Peptidomimetic Cyclophanes in Binary Methanol-Water Mixtures." Journal of Analytical Methods in Chemistry 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/1721069.

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The protonation constants of new group of peptidomimetic cyclophanes with valine or phenylalanine moieties incorporated into the macrocyclic skeleton as well as their linear analogues were determined by potentiometric measurements in solutions of methanol-water mixtures at 25°C and constant ionic strength. The influence of cavity size, location of protonation sites, and attached substituents of the macrocyclic ligands on the protonation constants were discussed on the basis of potentiometric measurement as well as H1-NMR results.

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33

Li, Lianwei, Wai-Yip Lo, Zhengxu Cai, Na Zhang, and Luping Yu. "Proton-triggered switch based on a molecular transistor with edge-on gate." Chemical Science 7, no. 5 (2016): 3137–41. http://dx.doi.org/10.1039/c6sc00152a.

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The effect of protonation on the molecular electronic properties of five pyridinoparacyclophane (PPC)-based molecular wires was investigated. The protonation/deprotonation process can reversibly switch the electronic properties of the molecules.

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34

Klyukin, Ilya N., Anastasia V. Kolbunova, Alexander S. Novikov, Aleksey V. Nelyubin, Nikita A. Selivanov, Alexander Yu Bykov, Alexandra A. Klyukina, Andrey P. Zhdanov, Konstantin Yu Zhizhin, and Nikolay T. Kuznetsov. "Protonation of Borylated Carboxonium Derivative [2,6-B10H8O2CCH3]−: Theoretical and Experimental Investigation." International Journal of Molecular Sciences 23, no. 8 (April 10, 2022): 4190. http://dx.doi.org/10.3390/ijms23084190.

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The process of protonation of [2,6-B10H8O2CCH3]− was investigated both theoretically and experimentally. The most suitable conditions for protonation of the derivative [2,6-B10H8O2CCH3]− were found. The process of protonation was carried out in the presence of an excess of trifluoromethanesulfonic acid CF3SO3H at room temperature in dichloromethane solution. The structure of the resulting complex [2,6-B10H8O2CCH3*Hfac]0 was established using NMR data and the results of DFT calculations. An additional proton atom Hfac was found to be localized on one of the facets that was opposite the boron atom in a substituted position, and which bonded mainly with one apical boron atom. The main descriptors of the B-Hfac bond were established theoretically using QTAIM and NBO approaches. In addition, the mechanism of [2,6-B10H8O2CCH3]− protonation was investigated.

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35

Halder, Antarip, Sukanya Halder, Dhananjay Bhattacharyya, and Abhijit Mitra. "Feasibility of occurrence of different types of protonated base pairs in RNA: a quantum chemical study." Phys. Chem. Chem. Phys. 16, no. 34 (2014): 18383–96. http://dx.doi.org/10.1039/c4cp02541e.

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How the thermodynamic barrier associated with the protonation of a nucleobase is overcome in the context of RNA may be understood by considering protonation induced charge redistribution in the nucleobases and base pairs.

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36

Henderson, Richard A. "Protonation mechanisms of Nickel Complexes Relevant to Industrial and Biological Catalysis." Journal of Chemical Research 2002, no. 9 (September 2002): 407–11. http://dx.doi.org/10.3184/030823402103172554.

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The sites of protonation and the subsequent rearrangement reactions of simple nickel complexes containing hydride, thiolate and alkyl ligands are reviewed, and the relevance of these reactions to the action of certain nickelbased catalysts are discussed. Summary Protonation at the metal and ligand is central to the understanding of how both enzymes and industrial catalysts operate at the molecular level. The recurring theme in studies on the protonation of all metal complexes is that the ultimate residence of the proton is not necessarily the initial binding site, and the movement of proton between sites can occur by a variety of mechanisms. These features are also evident in the reactions of simple nickel complexes and mechanistic studies are revealing the subtle interplay between ligand and metal which are the basis of the kinetic and thermodynamic control of protonation reactions at these sites.

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37

Bhushanavathi, P., B. Veeraswamy, G. Nageswara Rao, and U. Viplavaprasad. "Effect of Solvent on Protonation Equilibria ofL-Proline andL-Valine in 1, 2-Propanediol-Water Mixtures." E-Journal of Chemistry 9, no. 2 (2012): 517–24. http://dx.doi.org/10.1155/2012/289074.

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Protonation equilibria ofL-proline and L-valine in varying compositions (0.0-60.0% v/v) of 1, 2-Propanediol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1using sodium chloride. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, Χ2, skewness, and kurtosis. All the protonation constants of proline and valine increased with increasing propanediol content. This is attributed to the dielectric constant of the medium.

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38

Stoltz, B., J. Mohr, T. Nishimata, and D. Behenna. "Catalytic Enantioselective Decarboxylation-Protonation." Synfacts 2006, no. 12 (December 2006): 1239. http://dx.doi.org/10.1055/s-2006-949497.

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39

Mohr, Justin T., Toyoki Nishimata, Douglas C. Behenna, and Brian M. Stoltz. "Catalytic Enantioselective Decarboxylative Protonation." Journal of the American Chemical Society 128, no. 35 (September 2006): 11348–49. http://dx.doi.org/10.1021/ja063335a.

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40

Shainyan, B. A., and T. V. Raskulova. "Protonation of N-alkenylacrylamides." Russian Journal of General Chemistry 74, no. 6 (June 2004): 921–25. http://dx.doi.org/10.1023/b:rugc.0000042428.35918.4c.

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41

Leigh, G. J. "Protonation of coordinated dinitrogen." Accounts of Chemical Research 25, no. 4 (April 1992): 177–81. http://dx.doi.org/10.1021/ar00016a001.

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42

Yeagle, P. "Protonation by "Newton's cradle"." Science 349, no. 6250 (August 20, 2015): 838–39. http://dx.doi.org/10.1126/science.349.6250.838-g.

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43

Cirrincione, Girolamo, Gaetano Dattolo, Anna Maria Almerico, Enrico Aiello, R. Alan Jones, and Werner Hinz. "Protonation of 3-aminopyrroles." Tetrahedron 43, no. 22 (January 1987): 5225–28. http://dx.doi.org/10.1016/s0040-4020(01)87697-3.

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44

Morrison, Emma A., Anne E. Robinson, Yongjia Liu, and Katherine A. Henzler-Wildman. "Asymmetric protonation of EmrE." Journal of General Physiology 146, no. 6 (November 16, 2015): 445–61. http://dx.doi.org/10.1085/jgp.201511404.

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The small multidrug resistance transporter EmrE is a homodimer that uses energy provided by the proton motive force to drive the efflux of drug substrates. The pKa values of its “active-site” residues—glutamate 14 (Glu14) from each subunit—must be poised around physiological pH values to efficiently couple proton import to drug export in vivo. To assess the protonation of EmrE, pH titrations were conducted with 1H-15N TROSY-HSQC nuclear magnetic resonance (NMR) spectra. Analysis of these spectra indicates that the Glu14 residues have asymmetric pKa values of 7.0 ± 0.1 and 8.2 ± 0.3 at 45°C and 6.8 ± 0.1 and 8.5 ± 0.2 at 25°C. These pKa values are substantially increased compared with typical pKa values for solvent-exposed glutamates but are within the range of published Glu14 pKa values inferred from the pH dependence of substrate binding and transport assays. The active-site mutant, E14D-EmrE, has pKa values below the physiological pH range, consistent with its impaired transport activity. The NMR spectra demonstrate that the protonation states of the active-site Glu14 residues determine both the global structure and the rate of conformational exchange between inward- and outward-facing EmrE. Thus, the pKa values of the asymmetric active-site Glu14 residues are key for proper coupling of proton import to multidrug efflux. However, the results raise new questions regarding the coupling mechanism because they show that EmrE exists in a mixture of protonation states near neutral pH and can interconvert between inward- and outward-facing forms in multiple different protonation states.

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45

Kirmse, Wolfgang. "ChemInform Abstract: Carbene Protonation." ChemInform 33, no. 7 (May 22, 2010): no. http://dx.doi.org/10.1002/chin.200207290.

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46

Jagur-Grodzinski, Joseph. "Protonation of Macrocyclic Polyethers." Israel Journal of Chemistry 25, no. 1 (1985): 39–42. http://dx.doi.org/10.1002/ijch.198500007.

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47

Bouchoux, Guy, Jean-Claude Guillemin, Nadège Lemahieu, and Terrance B. McMahon. "Protonation thermochemistry of aminoacetonitrile." Rapid Communications in Mass Spectrometry 20, no. 8 (2006): 1187–91. http://dx.doi.org/10.1002/rcm.2437.

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48

Cirrincione, Girolamo, Anna Maria Almerico, Patrizia Diana, Paola Barraja, Francesco Mingoia, Stefania Grimaudo, Gaetano Dattolo, and Enrico Aiello. "Reactivity of aminopyrroles: Protonation." Journal of Heterocyclic Chemistry 33, no. 1 (January 1996): 161–68. http://dx.doi.org/10.1002/jhet.5570330128.

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49

Potin, Dominique, Kevin Williams, and Julias Rebek. "Asymmetric Protonation of Enolates." Angewandte Chemie International Edition in English 29, no. 12 (December 1990): 1420–22. http://dx.doi.org/10.1002/anie.199014201.

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50

Soman, Rahul, Subramaniam Sujatha, and Chellaiah Arunkumar. "Protonation and axial ligation intervened fluorescence turn-off sensing of picric acid in freebase and tin(iv) porphyrins." RSC Advances 5, no. 113 (2015): 93243–47. http://dx.doi.org/10.1039/c5ra18310c.

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Protonation and axial ligation: selective sensing of picric acid using freebase and tin(iv) meso-tetraarylporphyrins occurs through protonation and axial ligation which is evident from UV-visible, fluorescence, ¹H NMR titrations and X-ray crystallography.

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