Acid-catalyzed cleavage of 2-pyridyl and 4-pyridyl derivatives of aminomethylphosphonic acid. Kinetic and chemical arguments for a mechanism with A-SE2 character

Article abstract of DOI:10.1080/10426500008076325

Studies of the acid-catalyzed cleavage of 2-pyridyl and 4-pyridyl(amino)methylphosphonic acids demonstrate that protonation has a profound effect on the cleavage of C-P bonds. In H₂SO₄, and other strong mineral acids the cleavage of aminophosphonic acids 1 and 4 exhibits a kinetic depedence on Zucker-Hammett acidity function (h₀), with rate law, v = k[phosphonate]·h₀, and also fulfil the Bunnett approach on acidity function. The measured solvent isotope effect k_H/k_D is small, and varied from 1.46 for 1b to 1.18 for 4b. The isotope effect shows that protons are involved on the rate determining step of the cleavage. All of this evidence indicates that the cleavage of 1 or 4 shows A-S_E2 character substitution reaction. Calculated activation parameters and some chemical experiments indicate that the protonated phosphonate molecule is split by a dissociative mechanism, combined with formation of a positive-charged phosphorus moiety.

Full text of DOI:10.1080/10426500008076325

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Phosphorus, Sulfur, and
Silicon and the Related
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Acid-Catalyzed Cleavage
Of 2-Pyridyl and 4-
Pyridyl Derivatives Of
Aminomethylphosphonic
Acid. Kinetic And Chemical
Arguments For A Mechanism
With A-SE2 Character
Bogdan Boduszek a c , Rafał Latajka a &
Wojciech Leśniak b
a Institute of Organic Chemistry, Biochemistry
and Biotechnology , Wroctaw University of
Technology , 50–370 Wroctaw, Poland
b Faculty of Chemistry , University of Wroctaw ,
50–383 Wroctaw, Poland
c E-mail:
Published online: 19 Dec 2006.
To cite this article: Bogdan Boduszek , Rafał Latajka & Wojciech Leśniak
(2000) Acid-Catalyzed Cleavage Of 2-Pyridyl and 4-Pyridyl Derivatives Of
Aminomethylphosphonic Acid. Kinetic And Chemical Arguments For A Mechanism
With A-SE2 Character, Phosphorus, Sulfur, and Silicon and the Related Elements,
165:1, 53-75, DOI: 10.1080/10426500008076325
To link to this article: http://dx.doi.org/10.1080/10426500008076325

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