Comment on “The role of electrostatic induction in secondary isotope effects on acidity” by E. A. Halevi, New J. Chem., 2014, <b>38</b>, 3840

Perrin, Charles L.

doi:10.1039/c4nj01887g

Cited by 6 publications

(5 citation statements)

References 16 publications

(33 reference statements)

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“…Its numerical value depends on the method used to estimate how the atomic charges are distributed among the atoms. The wide variation between these distributions is evident in Perrin's Table 1, 5 as it is in my Tables 1, 6 and 10. 1 I agree that Dm/Dr e is not the same as dm/dr, the derivative of the dipole moment of a bond with respect to the distance as it vibrates about its equilibrium length, though -if the same charge distribution scheme is used -I would expect it to be similar.…”

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confidence: 62%

“…Perrin prefaces his rebuttal as follows: 5 ''To keep the discussion to its essentials, we ignore various aspects of Halevi's calculations, including acetic acid, hydration, and calculations that separate enthalpy from entropy''. He also disregards the theoretical discussion (Section 2) and the accompanying Appendix (Section 5), so I will limit my response to Perrin's comments on what he regards as the essentials.…”

Section: The Objectives Of My Paper 1 Arementioning

confidence: 99%

“…Specifically for the vibrational ground state, À r H o , the expectation value of the X-H bond length is larger than both r e and À r D o , the corresponding length of the X-D bond, which lies below it in the potential well. In Perrin's model, 5 eqn (4) identifies the isotope effect on potential energy as the difference between values of the potential energy curve computed at À r H o and À r D o , which he finds negligible for hydrocarbons. This is not surprising; it is also minuscule in the case of formic acid, as shown in Table 5 of my paper.…”

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confidence: 99%

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Reply to the ‘Comment on “The role of electrostatic induction in secondary isotope effects on acidity”’ by C. L. Perrin, New J. Chem., 2015, 39, DOI: 10.1039/C4NJ01887G

Halevi

2015

New J. Chem.

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Reply to the ‘Comment on “The role of electrostatic induction in secondary isotope effects on acidity”’ by C. L. Perrin, New J. Chem., 2015, 39, DOI: 10.1039/C4NJ01887G

Halevi

2015

New J. Chem.

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“…The harmonic and anharmonic frequencies calculated for formic acid and formate anion do differ. Nevertheless, the IE calculated from harmonic frequencies is the same as from anharmonic . We therefore conclude that if harmonic frequencies can account for the IEs, it is not necessary to invoke an inductive origin for the IEs arising from anharmonicity.…”

Section: Other Secondary Deuterium Isotope Effects On Aciditymentioning

confidence: 99%

The Logic behind a Physical–Organic Chemist’s Research Topics

Perrin

2016

J. Org. Chem.

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Abstract. Although my research has no common theme or defining area, a coherence connects the diverse topics, insofar as one project leads logically to another. Thus studies on mechanisms of hydrogen exchange in amides and amidines led to the influence of hydrogenbonding and to NMR methods for chemical kinetics, including 2D-EXSY spectroscopy.Another connection was the OH --catalyzed NH exchange in amines that had supported the hypothesis of stereoelectronic control. We therefore analyzed that hypothesis critically, tested it, found counterexamples, and proposed an alternative hypothesis. We next addressed one-bond NMR coupling constants in ethers and the reverse anomeric effect. The latter studies required a highly accurate NMR titration method that we developed to measure the additional steric bulk resulting from protonation of a substituent. This method is also applicable to measuring secondary isotope effects on acidity, and we could demonstrate that they arise from n-* delocalization, not from an inductive effect. Other studies included kinetic isotope effects for both dissociation and H exchange of aqueous NH 4 + , for C-N rotation in amides, and for a hydride transfer. The role of hydrogen-bonding led us to the rotation of NH 4 + within its solvent cage and then to the symmetry of hydrogen bonds. This review article is based on an address presented at the 249th National Meeting of the American Chemical Society in Denver CO, on the occasion of the James Flack Norris Award in Physical-Organic Chemistry. 1 It demonstrates the ways whereby one physicalorganic chemist, and physical-organic chemists in general, have investigated how molecular structure affects chemical reactivity. It also seeks to confirm my claim that "In my opinion, 2 physical organic chemistry represents the intellectual basis of organic chemistry. It asks (and answers!) fundamental questions about how chemical substances behave, and it rationalizes that behavior." 2 The reason that I won the James Flack Norris Award was for my "insight, rigorous analysis, and understanding of mechanisms and reactive intermediates", rather than any distinctive area of research with which I am associated. Instead of choosing one area to review here, I have tried to describe the path of my research for the past 40 years, as an expansion of an earlier article on this topic. 3 Each area seems to have engendered additional questions, leading to additional areas. Often those questions are marked by an intense skepticism, and the answers to those questions are supported by a logical analysis that I am proud of. I hope that this article will be as interesting, informative, and enjoyable to the reader as the research described here has been for me. A Beginner's ResearchMy Ph.D. thesis research was on mercuration of benzene, an electrophilic aromatic substitution that is accelerated by strong acid, and where we measured the H/D kinetic isotope effect. 4 To understand the origin of the acceleration it was necessary to consider acidity functions, including a new one, H...

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“…5 The same point was recently reiterated 6 in response to an assertion that there is no contribution of an inductive effect to secondary deuterium isotope effects upon acidity, 7 and it sparked a controversy. 8,9 (CH 3 + ) 1 + (CD 3 + ) e " (CH 3 + ) 1 + (CD 3 ) e…”

Section: Introductionmentioning

confidence: 99%

Critical evaluation of anharmonicity and configurational averaging in QM/MM modelling of equilibrium isotope effects

Roca

Upfold

Williams

2020

Phys. Chem. Chem. Phys.

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Comment on “The role of electrostatic induction in secondary isotope effects on acidity” by E. A. Halevi, New J. Chem., 2014, 38, 3840

Abstract: We reject Halevi's interpretation and reaffirm our conclusion that secondary deuterium isotope effects on acidity are due to n–σ* delocalization.

Cited by 6 publications

References 16 publications

Reply to the ‘Comment on “The role of electrostatic induction in secondary isotope effects on acidity”’ by C. L. Perrin, New J. Chem., 2015, 39, DOI: 10.1039/C4NJ01887G

Reply to the ‘Comment on “The role of electrostatic induction in secondary isotope effects on acidity”’ by C. L. Perrin, New J. Chem., 2015, 39, DOI: 10.1039/C4NJ01887G

The Logic behind a Physical–Organic Chemist’s Research Topics

Critical evaluation of anharmonicity and configurational averaging in QM/MM modelling of equilibrium isotope effects

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