- Excited-State Proton-Transfer Kinetics: A Theoretical Model
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The intersecting-state model is applied to excited state proton-transfer reactions.The results are consistent with those previously obtained for the analogous ground-state reactions.The transition-state bond order n* is similar in the ground and excited states: carbon acids have lower n* than nitrogen or oxygen acids.The mixing entropy parameter λ is found to be lower for excited-state than ground-state reactions.The mechanistic implications of this are discussed.
- Arnaut, Luis G.,Formosinho, Sebastiao J.
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- Dynamics of Excited-State Reactions in Reversed Micelles. 2. Proton Transfer Involving Various Fluorescent Probes according to Their Sites of Solubilization
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Reversed micelles of bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane were investigated with three acid fluorescent probes: 2-naphtol (NOH), sodium 2-naphtol-6-sulfonate (NSOH), and potassium 2-naphtol-6,8-disulfonate (NDSOH).These probes, which tend to undergo protolysis in the excited state, are well suited to the investigation of the acid-base reacitvity of water molecules forming the aqueous core.The rate constants for deprotonation and back-recombination were determined by phase fluorometry as a function of the water content w=/.These rate constants together with the spectroscopic properties of the probes provide information on their localization and the corresponding ability of the microenvironment to accept a proton. (i) NDSOH is localized around the center of the water pool and, at water contents, w, greater than about 10, its behavior regarding protolysis is identical with that in bulk water. (ii) NSOH resides in the vicinity of the interface and an amount of water of w 40 is required for observing the same deprotonation rate as in bulk water whereas the rate of back-recombination is still much faster. (iii) NOH is localized at the interface and does not undergo deprotonation in the excited state whatever the water content.Efficiency and kinetics of proton transfer are thus strongly dependent on localization.The ability of water to accept a proton is related to is H-bonded structure and its protolytic reactivity is an image of its structure which changes as a function of the distance with respect to the interface.
- Bardez, Elisabeth,Monnier, Eric,Valeur, Bernard
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- Production method of K acid
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A production method of a K acid comprises the following steps: 1, mixing 2-naphthol (I) with 92-98% sulfuric acid, introducing a gas, and carrying out a primary sulfonation reaction to obtain a compound (II); 2, reacting the compound (II) with a potassium salt and an ammonium salt, and carrying out an ammonification reaction and sulfuric acid acidifying to obtain a compound (III); and 3, mixing the compound (III) with 95-98% sulfuric acid, introducing a gas, and carrying out a secondary sulfonation reaction to obtain a compound (IV) that is the K acid. The chemical equation of the method is shown in the description. The method effectively increases the utilization rate of sulfuric acid in the sulfonation process, greatly reduces the production amount of waste sulfuric acid and even industrial sulfates, avoids production operating inconvenience brought by use of 20% nicotinic acid and 65% nicotinic acid, improves the operability of the process, and also has the advantages of small sulfuric acid use amount, low production cost, high product quality and small environmental pollution.
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Paragraph 0023; 0027; 0031; 0035
(2017/07/20)
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