PMID: 11925231Apr 2, 2002Paper

Transition-state variation in the nucleophilic substitution reactions of aryl bis(4-methoxyphenyl) phosphates with pyridines in acetonitrile

The Journal of Organic Chemistry
Hai Whang LeeIkchoon Lee

Abstract

The kinetics and mechanism of the reactions of Z-aryl bis(4-methoxyphenyl) phosphates, (4-MeOC(6)H(4)O)(2)P(=O)OC(6)H(4)Z, with pyridines (XC(5)H(4)N) are investigated in acetonitrile at 55.0 degrees C. In the case of more basic phenolate leaving groups (Z = 4-Cl, 3-CN), the magnitudes of beta(X) (beta(nuc)) and beta(Z) (beta(lg)) indicate that mechanism changes from a concerted process (beta(X) = 0.22-0.36, beta(Z) = -0.42 to -0.56) for the weakly basic pyridines (X = 3-Cl, 4-CN) to a stepwise process with rate-limiting formation of a trigonal bipyramidal pentacoordinate (TBP-5C) intermediate (beta(X) = 0.09-0.14, beta(Z) = -0.08 to -0.28) for the more basic pyridines (X = 4-NH(2), 3-CH(3)). This proposal is supported by a large negative cross-interaction constant (rho(XZ) = -1.98) for the former and a positive rho(XZ) (+0.97) for the latter processes. In the case of less basic phenolate leaving groups (Z = 3-CN, 4-NO(2)), the unusually small magnitude of beta(Z) values is indicative of a direct backside attack TBP-5C TS in which the two apical sites are occupied by the nucleophile and leaving group, ap(NX)-ap(LZ). The instability of the putative TBP-5C intermediate leading to a concerted displacement is considered to result f...Continue Reading

References

May 18, 2000·The Journal of Organic Chemistry·A K GuhaI Lee
Apr 28, 2001·The Journal of Organic Chemistry·E A CastroJ G Santos
Oct 24, 2001·The Journal of Organic Chemistry·Enrique A. CastroJosé G. Santos
Oct 25, 2001·The Journal of Organic Chemistry·Enrique A. CastroJosé G. Santos
Oct 25, 2001·The Journal of Organic Chemistry·Han Joong KohIkchoon Lee
Oct 25, 2001·The Journal of Organic Chemistry·Enrique A. CastroJosé G. Santos
Oct 25, 2001·The Journal of Organic Chemistry·Enrique A. CastroJosé G. Santos

❮ Previous
Next ❯

Citations

Nov 29, 2007·Organic & Biomolecular Chemistry·Md Ehtesham Ul HoqueHai Whang Lee
Feb 28, 2006·Luminescence : the Journal of Biological and Chemical Luminescence·Ryu KoikeHiromu Aoyama
Nov 18, 2010·Organic & Biomolecular Chemistry·Nilay Kumar DeyHai Whang Lee
Sep 24, 2015·Acta Crystallographica. Section E, Crystallographic Communications·Tyler A CooleyFelix N Ngassa
Jun 27, 2008·The Journal of Physical Chemistry. a·Boris GalabovHenry F Schaefer
Nov 6, 2007·The Journal of Organic Chemistry·Seok Hwan KimSukbok Chang
Aug 14, 2010·The Journal of Organic Chemistry·Diego M AndradaMiquel Solà
Jun 22, 2007·The Journal of Organic Chemistry·Md Ehtesham Ul HoqueHai Whang Lee
Dec 16, 2005·The Journal of Physical Chemistry. a·Boris GalabovHenry F Schaefer

❮ Previous
Next ❯

Trending Feeds

COVID-19

Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Blastomycosis

Blastomycosis fungal infections spread through inhaling Blastomyces dermatitidis spores. Discover the latest research on blastomycosis fungal infections here.

Nuclear Pore Complex in ALS/FTD

Alterations in nucleocytoplasmic transport, controlled by the nuclear pore complex, may be involved in the pathomechanism underlying multiple neurodegenerative diseases including Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Here is the latest research on the nuclear pore complex in ALS and FTD.

Applications of Molecular Barcoding

The concept of molecular barcoding is that each original DNA or RNA molecule is attached to a unique sequence barcode. Sequence reads having different barcodes represent different original molecules, while sequence reads having the same barcode are results of PCR duplication from one original molecule. Discover the latest research on molecular barcoding here.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.

Evolution of Pluripotency

Pluripotency refers to the ability of a cell to develop into three primary germ cell layers of the embryo. This feed focuses on the mechanisms that underlie the evolution of pluripotency. Here is the latest research.

Position Effect Variegation

Position Effect Variagation occurs when a gene is inactivated due to its positioning near heterochromatic regions within a chromosome. Discover the latest research on Position Effect Variagation here.

STING Receptor Agonists

Stimulator of IFN genes (STING) are a group of transmembrane proteins that are involved in the induction of type I interferon that is important in the innate immune response. The stimulation of STING has been an active area of research in the treatment of cancer and infectious diseases. Here is the latest research on STING receptor agonists.

Microbicide

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections. Here is the latest research on microbicides.