Micellar Catalysis of Nitric Oxide Dissociation from Diazeniumdiolates
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Abstract:
The effect of surfactant micelles on the acid-catalyzed dissociation of NO from diazeniumdiolate ions of structure R1R2N[N(O)NO]- has been examined in phosphate-buffered solutions at 37 °C. The reaction behavior of zwitterionic substrates [2, R1 = R2 = H2N(CH2)2; 3, R1 = R2 = H2N(CH2)3; 4, R1 = n-Pr, R2 = H2N(CH2)3; 5, R1 = H2N(CH2)3, R2 = H2N(CH2)3NH(CH2)4] and anionic substrates [1, R1 = R2 = Et; 6, R1 = R2 = n-Pr] has been compared. All but DEA/NO (1) are catalyzed by anionic micelles of sodium dodecyl sulfate (SDS) but are unaffected by the presence of cationic cetyltrimethylammonium bromide or the zwitterionic surfactant 3-(N-dodecyl-N,N-dimethylammonio)-1-propanesulfonate (lauryl sulfobetaine). Catalysis by sodium decylphosphonate micelles has also been demonstrated for 2 (DETA/NO). The surfactant-mediated catalysis is discussed in terms of a distribution model with simultaneous reaction in the water and micellar pseudophases. Binding constants (Ks) for diazeniumdiolate association with the surfactant micelles have been obtained, and a comparison of second-order rate constants, k2m and k2w, for their acid-catalyzed dissociation in the micellar and aqueous phases, respectively, has been made. For the zwitterionic polyamine diazeniumdiolates 2−5, the Ks values show good correlation with the number of positively charged nitrogen centers in the substrates, consistent with micellar association between protonated nitrogens in the zwitterions and the anionic headgroups of the micelle. The Coulombic interaction of zwitterionic substrates with SDS micelles is compared with the weak hydrophobic association which was found with the anionic diazeniumdiolate 6.Keywords:
Sodium dodecyl sulfate
Cationic polymerization
Dissociation constant
Acid dissociation constant
Acid dissociation constant
Dissociation constant
Phenol red
Catechol
Carboxylate
Succinic acid
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Acid dissociation constant
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In this paper, the dissociation constants (pKa1, pKa2) of five anthraquinones were determined from the relation between the effective mobility at different pH values and the buffer pH value, which was derived from the basic electrophoresis theory and the dissociation equilibrium of a binary acid. In addition, the changes of pKa values of the five compounds were also investigated when organic modifiers were added to the buffer system.
Acid dissociation constant
Dissociation constant
Anthraquinones
Anthraquinones
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Buffer (optical fiber)
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Micelles in the Physical/Analytical Chemistry Laboratory. Acid Dissociation of Neutral Red Indicator
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMicelles in the Physical/Analytical Chemistry Laboratory. Acid Dissociation of Neutral Red IndicatorKathryn R. Williams and Loretta H. Tennant View Author Information Department of Chemistry, University of Florida, Gainesville, FL 32611-7200Cite this: J. Chem. Educ. 2001, 78, 3, 349Publication Date (Web):March 1, 2001Publication History Received3 August 2009Published online1 March 2001Published inissue 1 March 2001https://pubs.acs.org/doi/10.1021/ed078p349https://doi.org/10.1021/ed078p349research-articleACS PublicationsRequest reuse permissionsArticle Views2230Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Dissociation,Micelles,Pharmacology,Sodium dodecyl sulfate,Surfactants Get e-Alerts
Acid dissociation constant
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Sodium dodecyl sulfate
Cationic polymerization
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Acid dissociation constant
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Microscale chemistry
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The acid dissociation constants, Ka, of nine biologically active 2-amino-4-(x-pyridyl)-thiazole, 2-methylimino-3-methyl-4-(x-pyridyl)-2,3-dihydrothiazole, and 2-methylamino-4-(x-pyridyl)-2,3-dihydrothiazole were determined using UV−vis spectroscopic technique.The acidity constants for the first protonation, pKa1, of parent molecules and their fixed model molecules are found to be associated with the protonation of aza or imino nitrogen atom. The acidity constants for the second proton uptake, pKa2, are found to correspond to aza, imino, or amino nitrogen atom protonation. The contribution of the imino tautomeric form to tautomeric equilibria was found to be considerably important.
Thiazole
Acid dissociation constant
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Nitrogen atom
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The first dissociation constant of 1,2,3-benzothiadiazole is pKa= 2·84 ± 0·04 at 25°. The protonation site is the 3-position but the presence of a smaller amount of the 2-protonated species cannot be ruled out. The di-cation is absent. A violet-blue coloration, previously attributed to 1,2,3-benzothiadiazolium salts, is due to thianthren impurity.
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The acid dissociation constants of twelve novel drug precursor N-substituted-6-acylbenzothiazolone derivatives were determined by using the UV–vis spectroscopic technique. The protonation and deprotonation behaviors of the investigated molecules were researched from the super basic to super acid regions (i.e., 8 mol·L–1 KOH to 98% H2SO4) including the pH region. It is observed that all of the molecules are protonated in the super acidic region. The calculated relative stability values of possible tautomer structures indicate that the keto form of investigated molecules is favored over the enol form. It was predicted that protonation occurs at the amide (oxo) group found in the keto form.
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Dissociation constants of the protonated form of imidazole base have been measured from 0 to 50° at 5° intervals. The use of different formulæ for the extrapolation of data to zero ionic strength is discussed, and the results are compared with the available literature values. The acid dissociation constant of the imidazolium ion is given by the equations pKa= 472·269/T+ 15·1061 – 0·0487442T+ 0·00005440T0, or pKa= 1906·884/T+ 0·6225 – 0·0000848T; the thermodynamic quantities derived from the first equation are discussed.
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Imidazole
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