Solvation Effect on Proton Transfer Complex Formation between 2,4-Dinitro-1-naphthol and Amines

Hamed, Ezzat A.; Habeeb, Moustafa M.; El-Hegazy, Fatma M.; Shehata, Aziza K.

doi:10.1021/je00021a002

Cited by 7 publications

(6 citation statements)

References 7 publications

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“…Note, however, this acid−base reaction is in equilibrium between a soft (porphyrin) and a hard (NaOH) base and therefore solvent effects can be used to alter the relative strength of the bases − Changing the solvent from water to a polar, aprotic medium such as DMSO or DMF will increase the base strength of the NaOH but will hardly affect the porphyrin. Thus, a solvent like DMF effectively weakens the basicity of the porphyrin relative to that of the NaOH.…”

Section: Discussionmentioning

confidence: 99%

Sequential Deprotonation of meso-(p-Hydroxyphenyl)porphyrins in DMF: From Hyperporphyrins to Sodium Porphyrin Complexes

et al. 2005

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Sequential deprotonations of meso-(p-hydroxyphenyl)porphyrins (p-OHTPPH2) in DMF + H2O (V/V = 1:1) mixture have been verified to result in the appearance of hyperporphyrin spectra. However, when the deprotonations of these p-OHTPPH2 are carried out in DMF, the spectral changes differ considerably from those in the mixture mentioned above. At low [OH-], the optical spectra in the visible region are still considered to have characteristics of hyperporphyrin spectra. Further deprotonation at much higher basicity makes the optical spectra form three-banded spectra similar to those in the acidic solution. To clarify the molecular origins of these changes, UV-vis, resonance Raman (RR), proton nuclear magnetic resonance (1H NMR) experiments are carried out. Our data give evidence that p-OHTPPH2 in DMF can be further deprotonated of pyrrolic-H by higher concentrated NaOH, due to an aprotic medium like DMF effectively weakening the basicity of the porphyrin relative to that of the NaOH, and coordinates with two sodium ions (except the sodium ions that interact with the peripherial phenoxide anions) to form the sodium complexes of p-OHTPPH2 (Na2P, to lay a strong emphasis on the sodium ions that coordinate with the central nitrogen atom), which can be regarded as the porphyrin anions being perturbed by the sodium cations due to their highly ionic character. The negative centers generated by deprotonation of pyrrolic-H and phenolic-H are not thoroughly delocalized between the substituents and the porphyrin ring. Thus the negative centers generated by deprotonation of pyrrolic-H only act as electron-donating groups on the porphyrin pi system, and the negative charges of the phenoxide anion are also mainly localized on the peripheral substituents. As a result, the porphyrin pi orbitals cross over the phenoxide anion pi orbital and turn into HOMOs, which turns hyperporphyrin spectra of deprotonated phenolic-H of p-OHTPPH2 into three-banded spectra of regular metalloporphyrins.

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Section: Discussionmentioning

confidence: 99%

Sequential Deprotonation of meso-(p-Hydroxyphenyl)porphyrins in DMF: From Hyperporphyrins to Sodium Porphyrin Complexes

et al. 2005

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“…The equilibrium constants of 1 : 1 proton transfer complex formation for the investigated systems were calculated at a given wavelength by applying the minimum-maximum method, where the composition of the CA-aniline mixture was calculated directly from the known concentrations of the reactants and the minimum-maximum absorptivities of the CA and the formed complex [16][17][18][19][20].…”

Section: Methods Of Calculationmentioning

confidence: 99%

Proton transfer equilibria, temperature and substituent effects on hydrogen bonded complexes between chloranilic acid and anilines

Gohar

Habeeb

2000

Journal of Spectroscopy

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The proton transfer equilibrium constants (KPT) for 1 : 1 complex formation between Chloranilic Acid (CA) and a series ofp- andm‒substituted anilines have been measured in 1,4-dioxane spectrophotometrically. The results supported the concept of amine-solvent hydrogen bond formation (short range solvation effect). Beside, this effect, theKPTvalues were apparently affected by the electron donation power of the aniline ring substituent, which was transmitted to the interaction center via resonance and inductive effects. Linear relationships betweenKPTand σ-Hammett substituent constants, or pKvalues formandpanilines,were obtained verifying the above conclusions. The solute-solvent hydrogen bond formation might increase the reactivity of the aniline nitrogen than would the inductive effect of the alkyl group, in case of CA-N-alkyl aniline complexes. The thermodynamic parameters for the proton transfer complex formation were estimated and it was indicated that the solvent–aniline hydrogen bond formation was preferred in the case ofp-substituted aniline complexes more than in the case of the correspondingm‒isomer. It has been found that the proton transfer process was enthalpy and entropy controlled.

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“…This electron withdrawing capacity of the nitro-groups of these compounds which make them electron deficient is tested and used by screening some selected NACs as charge transfer reagents (electron acceptors) with some drug substances possessing excess π-or n-electrons. As at present, the literature survey revealed the use of few nitroaromatic derivatives as charge transfer reagents, and involved 2, 4-dinitro-1-naphthol, besides their use in chemical synthesis [31][32][33][34].…”

Section: Introductionmentioning

confidence: 97%

Potentials of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol as novel charge transfer acceptors in pharmaceutical analysis of some quinolones and cephalosporins

2022

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Background Quinolones and cephalosporins are antibiotic agents with activity against Gram-positive and Gram-negative bacteria. They contain chromophores and amine groups which are electron-rich centres capable of donating electrons to electron-deficient compounds. A survey of the literature revealed that 2, 4-dinitro-1-naphthol, a nitroaromatic useful in chemical synthesis, can accept electrons in charge transfer reactions. This work investigates N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol in the formation of charge transfer complexes by accepting electrons from selected quinolones and cephalosporins. Five other nitroaromatics (i.e. 4-nitro-1-naphthylamine, 2-nitro-1-naphthol, 2,4-dinitro-1-naphthylamine, 1-nitronaphthalene and 1,4-dinitronaphthalene) were screened in addition to the aforementioned and compared for charge transfer complexes formation. Spot test was used to establish charge transfer complex formation at room and elevated temperatures with determination done by visual inspection and thin layer chromatographic analysis of the reaction mixture. Ultraviolet visible absorption spectroscopy was used to estimate the extent of complexes. Results Only solutions of adducts of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol gave instant and distinct colour with each drug used at room and elevated temperature. While the former gave deep golden yellow, the latter gave golden yellow against their blank reagent solutions which were, lemon and greenish yellow respectively. Visual inspections of 2-nitro-1-naphthol adduct solutions showed no colour change from the yellow colour of the blank reagent solution, even though the Ultraviolet visible absorption spectra revealed the formation of charge transfer complexes. The adducts solutions of 4-nitro-1-naphthylamine, 2,4-dinitro-1-naphthylamine, 1-nitronaphthalene and 1,4-dinitronaphthalene showed no colour change from their blank reagent solutions and their Ultraviolet visible absorption spectra revealed no formation of charge transfer complexes. Conclusion Ultraviolet visible absorption spectral analysis shows superiority of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol in charge-transfer complex formation over other nitroaromatics screened. N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol are good acceptors of electrons from these drugs, hence could be useful as charge transfer reagents in ultraviolet visible spectrophotometric analysis of these drugs.

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Solvation Effect on Proton Transfer Complex Formation between 2,4-Dinitro-1-naphthol and Amines

Cited by 7 publications

References 7 publications

Sequential Deprotonation of meso-(p-Hydroxyphenyl)porphyrins in DMF: From Hyperporphyrins to Sodium Porphyrin Complexes

Sequential Deprotonation of meso-(p-Hydroxyphenyl)porphyrins in DMF: From Hyperporphyrins to Sodium Porphyrin Complexes

Proton transfer equilibria, temperature and substituent effects on hydrogen bonded complexes between chloranilic acid and anilines

Potentials of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol as novel charge transfer acceptors in pharmaceutical analysis of some quinolones and cephalosporins

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