Epoxidation of Alkenes by Peracids: From Textbook Mechanisms to a Quantum Mechanically Derived Curly‐Arrow Depiction

Abstract

Using the intrinsic bond orbital (IBO) analysis based on accurate quantum mechanical calculations of the reaction path for the epoxidation of propene using peroxyacetic acid, we find that the four commonly used curly arrows for representing this reaction mechanism are insufficient and that seven curly arrows are required as a result of changes to σ and π bonding interactions, which are usually neglected in all textbook curly arrow representations. The IBO method provides a convenient quantitative method for deriving curly arrows in a rational manner rather than the normal ad hoc representations used ubiquitously in teaching organic chemistry.

Understanding chemistry: from “heuristic (soft) explanations and reasoning by analogy” to “quantum chemistry”

“…, note the efforts by some theoretical chemists to provide a theoretical underpinning to arrow pushing ( vide infra ). 19–21 Over 25 years ago, Dennis H. Rouvray discussed the necessity of analogies in the development of science, e.g. , “that like structures exhibit like behavior,” 22 in mathematical terms.…”

“…So explanations may, in some cases, be shown to originate in quantum chemistry, e.g., note the efforts by some theoretical chemists to provide a theoretical underpinning to arrow pushing (vide infra). [19][20][21] Over 25 years ago, Dennis H. Rouvray discussed the necessity of analogies in the development of science, e.g., "that like structures exhibit like behavior," 22 in mathematical terms. 23 Indeed, it would be unreasonable if broadly-successful so theoriesgenerated over decades of experimental results and deep thinking by the community of chemistswere not ultimately underpinned by quantum chemistry, although such coincidences are possible, e.g., "the right answer for the wrong reason."…”

An Overview of Self-Consistent Field Calculations Within Finite Basis Sets

“…32 Although localized orbitals are not strictly speaking observables-due to which several localization criteria have been suggested in the literature [33][34][35][36] -they have been shown to offer an effective way to study chemical reactions with ab initio calculations. [37][38][39] In addition to the occupied orbitals, in general there are also a number of unoccupied orbitals, which are commonly known as virtual orbitals. The number of virtual orbitals in any given calculation depends on the size of the basis set: the bigger the basis is, the more virtual orbitals there are.…”

Glutaraldehyde-crosslinked Rhizopus oryzae whole cells show improved catalytic performance in alkene epoxidation

“…An alkene epoxidation reaction is an important approach for obtaining the epoxy compound. Until now, various epoxidation reaction modes have been reported; based on the catalyst, these include metal catalytic epoxidation [ 3 ], Prileshajev epoxidation [ 4 ], enzyme cyclooxidation [ 5 – 8 ], and chemoenzymatic oxidation [ 9 ]. Because biocatalysts have the characteristics of mild reaction, high selectivity, and high purity, the biotransformation processes continually attract interest.…”