Kinetic acidity function Hc.thermod.. 1. Definition of the function in aqueous sulfuric acid and its applicability to acid-catalyzed hydrogen exchange of the ring protons of aromatic molecules, and protonation of carbon-carbon double and triple bonds

Linear Pfluger plots of unit slope are obtained from logarithmic rate constants for acid–catalysed hydration of phenylacetylene and its substituted derivatives p‐OCH3, p‐CH3, m‐CH3, p‐Br, m‐Cl, m‐NO2, p‐NO2 in aqueous sulphuric acid solution. This direct experimental observation of absence of any dependence on selectivity gives evidence for the applicability of the kinetic acidity function in these systems.

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Isotope effects in acid‐catalyzed aromatic hydrogen exchange

Cox

1991

J of Physical Organic Chem

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Deuterium‐ or tritium‐substituted aromatics undergo isotope exchange in fairly concentrated aqueous sulfuric acid media. The rate constant for this process is complex, being composed of that for the slow electrophilic attack, and the isotope effect on the breakup of the Wheland intermediate. Using experimental rate constant data for both deuterium and tritium exchange on the same substrate, the excess acidity method and the Swain–Schaad relationship, true protonation rate constants and isotope effects have been separated out for several positions in several simple aromatic substrates. Most of the electrophilic attack rate constants are described by a Hammett‐type linear free energy relationship with a ρ+ of − 6.5. The average observed deuterium isotope effect on Wheland intermediate breakup was 5.3. Using rate constants obtained at different temperatures, enthalpies and entropies of activation were also obtained for benzene, naphthalene and thiophene; the activation entropy averaged − 8 cal mol−1 K−1. Some evidence was found for general acid catalysis at the higher acidities.

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Kinetic acidity function Hc.thermod.. 1. Definition of the function in aqueous sulfuric acid and its applicability to acid-catalyzed hydrogen exchange of the ring protons of aromatic molecules, and protonation of carbon-carbon double and triple bonds

Cited by 10 publications

References 20 publications

ChemInform Abstract: KINETIC ACIDITY FUNCTION HC.THERMOD.. 1. DEFINITION OF THE FUNCTION IN AQUEOUS SULFURIC ACID AND ITS APPLICABILITY TO ACID‐CATALYZED HYDROGEN EXCHANGE OF THE RING PROTONS OF AROMATIC MOLECULES, AND PROTONATION OF CARBON‐CARBON DOUBLE AND TRIPLE BONDS

ChemInform Abstract: KINETIC ACIDITY FUNCTION HC.THERMOD.. 1. DEFINITION OF THE FUNCTION IN AQUEOUS SULFURIC ACID AND ITS APPLICABILITY TO ACID‐CATALYZED HYDROGEN EXCHANGE OF THE RING PROTONS OF AROMATIC MOLECULES, AND PROTONATION OF CARBON‐CARBON DOUBLE AND TRIPLE BONDS

Constant Selectivity in Proton Exchange Reactions Between Aqueous Sulphuric Acid and Acetylenes

Isotope effects in acid‐catalyzed aromatic hydrogen exchange

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