Molecular Modeling of an Electrophilic Addition Reaction with “Unexpected” Regiochemistry

Abstract

The electrophilic addition of a hydrohalic acid (HX) to an alkene is often one of the first reactions learned in second-year undergraduate organic chemistry classes. During the ensuing discussion of the mechanism, it is shown that this reaction follows Markovnikov’s rule, which states that the hydrogen atom will attach to the carbon with fewer substituents while the halogen atom will attach to the carbon with more substituents. However, in the preparation of tropic acid, the reaction of HCl with atropic acid (2-phenylpropenoic acid) does not follow this rule because it is a conjugated system. Molecular modeling of the possible carbocation intermediates suggests that the reaction follows a conjugate addition mechanism involving a 1,4-addition of HCl across the conjugated alkene and carboxyl group rather than addition across the alkene as students often first propose. PM3 semiempirical calculations are used to determine the energies of three possible carbocation intermediates. The energies obtained from the modeling suggest that the carbocation intermediate produced by the 1,4-addition is the most stable.

Heat‐Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low‐Power Organic Soft Electronics

“…The water contact angles was higher (i.e., closer to those of a hydrophobic surface and low efficiency) when the reaction was conducted i) without heat, ii) without UV illumination during the reaction, and iii) using only strong acids without heat or UV light. These results strongly suggest that the HAPO reaction consists of a complicated photochemical modification of alkenes (i.e., π−π* singlet states), in addition to a typical electrophilic addition reaction . We surmise that it proceeds via biradical formation from singlet states and subsequent electrophilic reactions with hydronium ions because the global electrophilicity index of 2‐hydroxybut‐2‐yl has been found to be relatively low and the whole reaction time is relatively short …”

Computational Chemistry in the Undergraduate Classroom – Pedagogical Considerations and Teaching Challenges

“…A third approach, which is apparent from the vast majority of publications on CC in education, is to include CC modules or exercises in various courses such as organic chemistry, [63,64] general chemistry, [65,66] or physical chemistry. [67,68] Many examples of such modules, not listed here, were published in the Journal of Chemical Education throughout the years, and in the recent ACS symposium book on the topic.…”

The Computational Design of Two-Dimensional Materials

“…In addition to the mandatory experiments, students are required to design an independent computational project in consultation with the instructor. They may choose an experiment that has already been published in this journal (e.g., refs − ), design a project that is relevant to research projects they have carried out in experimental groups, or explore technical aspects of first-principles calculations. This allows students to focus on topics that are interesting to them and is relevant to their diverse backgrounds.…”