Efficient and selective catalysis lies at the heart of much of chemistry, enabling the synthesis of molecules and materials with enormous societal and technological impact. Modern in silico tools should allow us to develop new catalysts faster and better than ever before; this contribution discusses the feasibility and potential of computational catalyst design.
Alkylidene carbenes undergo rapid inter-and intra-molecular reactions and rearrangements, including 1,2-migrations of β-substituents to generate alkynes. Their propensity for substituent migration exerts profound influence over the broader utility of alkylidene carbene intermediates, yet prior efforts to categorize 1,2-migratory aptitude in these elusive species have been hampered by disparate modes of carbene generation, ultrashort carbene lifetimes, mechanistic ambiguities, and the need to individually prepare a series of 13 C-labelled precursors. Herein we report on the rearrangement of 13 C-alkylidene carbenes generated in situ by the homologation of carbonyl compounds with [ 13 C]-Li-TMS-diazomethane, an approach that obviates the need for isotopically labelled substrates and has expedited a systematic investigation ( 13 C{ 1 H} NMR, DLPNO-CCSD(T)) of migratory aptitudes in an unprecedented range of more than 30 alkylidene carbenes. Hammett analyses of the reactions of 26 differentially substituted benzophenones reveal several counterintuitive features of 1,2-migration in alkylidene carbenes that may prove of utility in the study and synthetic application of unsaturated carbenes more generally.
Materials science research has expanded significantly
in recent
years; a multidisciplinary field, home to an ever-growing number of
chemists. However, our general chemistry degree courses have not changed
to reflect the rise in interest in this topic. In this paper, we propose
a laboratory experiment for the undergraduate chemistry practical
course, which may serve as a hands-on introduction to this field.
The experiment involves the synthesis and characterization of magnetic
materials via commonly employed techniques in materials science. Students
begin by producing three metal ferrite spinels using a sol–gel
combustion synthesis. They must then characterize the differing magnetic
properties across their three samples using a magnetic susceptibility
balance. In the second part of the experiment, students must create
a ferrofluid via coprecipitation, from which they may observe the
phenomenon of “spiking” in response to an external magnet.
Additional data such as X-ray diffraction (XRD) patterns and transmission
electron microscopy (TEM) images corresponding to these materials
are also provided, and students are tasked with the interpretation
of these data in their writeup report. Upon completion, students should
gain a new-found understanding of materials science and its fundamental
overlap with chemistry.
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