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This report describes rapid changes to instructional materials, assessment, and technology use in a flipped college-level organic chemistry course in response to the sudden COVID-19 campus closures and midsemester transition to remote learning. The instructors modified in-class instructional materials to accommodate students' preference for text-based over audiovisual engagement in the remote environment. The pros and cons of three approaches to administering remote organic chemistry exams are presented. Issues related to equitable incorporation of technology and maintaining academic integrity are discussed.

MIDA boronates (N-methylimidodiacetic boronic acid esters) serve as an increasingly general platform for small-molecule construction based on building blocks, largely because of the dramatic and general rate differences with which they are hydrolysed under various basic conditions. Yet the mechanistic underpinnings of these rate differences have remained unclear, which has hindered efforts to address the current limitations of this chemistry. Here we show that there are two distinct mechanisms for this hydrolysis: one is base mediated and the other neutral. The former can proceed more than three orders of magnitude faster than the latter, and involves a rate-limiting attack by a hydroxide at a MIDA carbonyl carbon. The alternative 'neutral' hydrolysis does not require an exogenous acid or base and involves rate-limiting B-N bond cleavage by a small water cluster, (H2O)n. The two mechanisms can operate in parallel, and their relative rates are readily quantified by 18O incorporation. Whether hydrolysis is 'fast' or 'slow' is dictated by the pH, the water activity and the mass-transfer rates between phases. These findings stand to enable, in a rational way, an even more effective and widespread utilization of MIDA boronates in synthesis.

Monodeuterated methyl groups have previously been demonstrated to provide access to long-lived nuclear spin states. This is possible when the CH 2 D rotamers have sufficiently different populations and the local environment is chiral, which foments a non-negligible isotropic chemical shift difference between the two CH 2 D protons. In this article, the focus is on the N- CH 2 D group of N- CH 2 D -2-methylpiperidine and other suitable CH 2 D -piperidine derivatives. We used a combined experimental and computational approach to investigate how rotameric symmetry breaking leads to a 1 H CH 2 D chemical shift difference that can subsequently be tuned by a variety of factors such as temperature, acidity and 2-substituted molecular groups. [ABSTRACT FROM AUTHOR]

Methanol titrations of partially deuterated 1,4- and 1,3-diols dissolved in nonpolar solvents such as CD 2 Cl 2 and benzene- d 6 have provided 1 H NMR measurements of OH/OD isotope shifts, diagnostic for intact intramolecular hydrogen bonds, under conditions of increasing protic solvent concentration. 1,4- and 1,3-diols with conformationally favored intramolecular OH/OH hydrogen bonds can be titrated to constant isotope shift values, albeit with variable sign, in the presence of excess methanol equivalents, providing evidence for intact intramolecular hydrogen bonds under these conditions. Conversely, the isotope shift in a 1,3-diol with a conformationally labile intramolecular hydrogen bond titrated to zero when in the presence of excess equivalents methanol, consistent with intramolecular hydrogen bond rupture under these conditions. Additionally, the titration behavior of hydroxyl chemical shifts in diols and protected derivatives has revealed significant OH/OD isotope shifts in the absence of chemical shift differences (δOH in = δOH out ) that are necessary for an equilibrium isotope effect, lending evidence for an intrinsic contribution to the isotope effect. OH/OD isotope shift titration thus provides a means for understanding the origins of these isotope effects and for probing the intact or nonintact nature of intramolecular OH/OH hydrogen bonds in response to intermolecular hydrogen bonds provided by a protic solvent.