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Teaching laboratories are designed to educate students on basic theories and techniques through guided laboratory experiments. As advances in automation revolutionize research chemistry laboratories, teaching tools can advance to reflect these changes. In this study, we integrated several programmable instruments, including automated pumps for liquid transfer, into an augmented titration setup that can be operated remotely. Our setup empowers students to learn the conceptual, technical, and practical aspects of titration by leveraging laboratory automation tools. Our system uses Siri as a speech recognition tool and the Python programming language to develop action routines for titration uses. The application of Siri provides a smooth user-to-instrument experience, and the use of Python allows coders to effectively develop and maintain the workflow. Three chemistry professors were invited to participate in usability tests of the system using a mobile device. Their positive feedback highlights the promise of our system as a valuable addition to undergraduate chemistry teaching laboratories. This titration setup addresses accessibility challenges and distance learning requirements for chemical education. Further, our tool introduces students to the type of automated experimentation that is emerging as the modern standard in chemistry research laboratories.

We have used the quantitative polymerase chain reaction (qPCR) to measure the extent of oxidative DNA damage under varying reaction conditions used for copper(I)-catalyzed click chemistry. We systematically studied how the damage depends on a number of key reaction parameters, including the amounts of copper, ascorbate, and ligand used, and found that the damage is significant under nearly all conditions tested, including those commonly used for bioconjugation. Furthermore, we discovered that the addition of dimethyl sulfoxide, a known radical scavenger, into the aqueous mixture dramatically suppresses DNA damage during the reaction. We also measured the efficiency of cross-linking two short synthetic oligonucleotides via click chemistry, and found that the reaction could proceed reasonably efficiently even with DMSO present. This approach for screening both DNA damage and reactivity under a range of reaction conditions will be valuable for improving the biocompatibility of click chemistry, and should help to extend this powerful synthetic tool for both in vitro and in vivo applications.

This article describes the aza-Piancatelli rearrangement with hydroxylamines to 4-aminocyclopentenones and subsequent transformations that highlight the versatility of the cyclopentene scaffold and the value of the hydroxylamine nucleophile in this transformation.

Continuing developments in the elucidation techniques of complex catalytic processes is of foremost importance to modern synthetic chemistry, and the identification of efficient synthetic techniques relies on precise, reliable, and adaptable methods to dissect the mechanism of a given transformation. Currently, methods of reaction development are grounded upon the systematic modification of specific variables - such as temperature, time, concentration, etc. - to account for and control the dynamic series of coupled equilibria within a catalytic environment. On the other hand, tandem reaction analytical methods that involve the concomitant use of different instruments to probe a reaction can provide time-resolved information regarding active chemical species and facilitate the interrogation and optimization of the system. Herein, we report our study applying tandem in situ ReactIR and HPLC-MS monitoring to the dysprosium(III) triflate-catalyzed aza-Piancatelli rearrangement of 2-furylcarbinols, a reaction that grants access to trans-4,5-disubstituted cyclopentenones - common motifs in important biologically relevant and natural compounds. With a prototype automated sampling apparatus, information was obtained about the intrinsic chemoselectivity of the reaction, and previously unseen intermediates were observed, allowing for a more detailed reaction mechanism to be substantiated. The advantages of applying this type of tandem measurement to study these types of systems are also discussed. (Figure Presented).

A current goal in nanotechnology focuses on the assembly of different nanoparticle types into 3D organized structures. In this paper we report the use of a liquid crystal host phase in a new process for the generation of micron-scale vesicle-like nanoparticle shells stabilized by ligand-ligand interactions. The constructs formed consist of a robust, thin spherical layer, composed of closely packed quantum dots (QDs) and stabilized by local crystallization of the mesogenic ligands. Ligand structure can be tuned to vary QD packing within the shell and made UV cross-linkable to allow for intact shell extraction into toluene. The assembly method we describe could be extended to other nanoparticle types (metallic, magnetic etc.), where hollow shell formation is controlled by thermally sorting mesogen-functionalized nanoparticles in a liquid crystalline host material at the isotropic to nematic transition. This process represents a versatile method for making non-planar 3D nano-assemblies.

We present a novel method that covalently and sequence-specifically attaches long DNA molecules to a surface that is compatible with high-resolution atomic force microscopy (AFM) imaging. Surfaces prepared with this approach are ideally suited for performing biophysical experiments on single DNA molecules.

Mesogenic ligands have the potential to provide control over the dispersion and stabilization of nanoparticles in liquid crystal (LC) phases. The creation of such hybrid materials is an important goal for the creation of soft tunable photonic devices, such as the LC laser. Herein, we present a comparison of isotropic and mesogenic ligands attached to the surface of CdSe (core-only) and CdSe/ZnS (core/shell) quantum dots (QDs). The mesogenic ligand's flexible arm structure enhances ligand alignment, with the local LC director promoting QD dispersion in the isotropic and nematic phases. To characterize QD dispersion on different length scales, we apply fluorescence microscopy, X-ray scattering, and scanning confocal photoluminescent imaging. These combined techniques demonstrate that the LC-modified QDs do not aggregate into the dense clusters observed for dots with simple isotropic ligands when dispersed in liquid crystal, but loosely associate in a fluid-like droplet with an average interparticle spacing >10 nm. Embedding the QDs in a cholesteric cavity, we observe comparable coupling effects to those reported for more closely packed isotropic ligands.

The ability for nuclear magnetic resonance (NMR) spectroscopy to provide quantitative, structurally rich information makes this spectroscopic technique an attractive reaction monitoring tool. The practicality of NMR for this type of analysis has only increased in the recent years with the influx of commercially available benchtop NMR instruments and compatible flow systems. In this study, we aim to compare 19F NMR reaction profiles acquired under both on‐line continuous‐flow and stopped‐flow sampling methods, with modern benchtop NMR instrumentation, and two reaction systems: a homogeneous imination reaction and a biphasic activation of a carboxylic acid to acyl fluoride. Reaction trends with higher data density can be acquired with on‐line continuous‐flow analyses, and this work highlights that representative reaction trends can be acquired without any correction when monitoring resonances with a shorter spin–lattice relaxation time (T1), and with the used flow conditions. On‐line stopped‐flow analyses resulted in representative reaction trends in all cases, including the monitoring of resonances with a long T1, without the need of any correction factors. The benefit of easier data analysis, however, comes with the cost of time, as the fresh reaction solution must be flowed into the NMR system, halted, and time must be provided for spins to become polarized in the instrument's external magnetic field prior to spectral measurement. Results for one of the reactions were additionally compared with the use of a high‐field NMR. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique with the ability to acquire both quantitative and structurally insightful data for multiple components in a test sample. This makes NMR spectroscopy a desirable tool to understand, monitor, and optimize chemical transformations. While quantitative NMR (qNMR) approaches relying on internal standards are well‐established, using an absolute external calibration scheme is beneficial for reaction monitoring as resonance overlap complications from an added reference material to the sample can be avoided. Particularly, this type of qNMR technique is of interest with benchtop NMR spectrometers as the likelihood of resonance overlap is only enhanced with the lower magnetic field strengths of the used permanent magnets. The included study describes a simple yet robust methodology to determine concentration conversion factors for NMR systems using single‐ and multi‐analyte linear regression models. This approach is leveraged to investigate a pharmaceutically relevant amide coupling batch reaction. An on‐line stopped‐flow (i.e., interrupted‐flow or paused‐flow) benchtop NMR system was used to monitor both the 1,1′‐carbonyldiimidazole (CDI) promoted acid activation and the amide coupling. The results highlight how quantitative measurements in benchtop NMR systems can provide valuable information and enable analysts to make decisions in real time. [ABSTRACT FROM AUTHOR]

The observed rate of reaction in the dysprosium triflate catalyzed aza-Piancatelli rearrangement is controlled by a key off-cycle binding between aniline and catalyst. Deconvoluting the role of these ancillary species greatly broadens our understanding of factors affecting the productive catalytic pathway. We demonstrate that the rate of reaction is controlled by initial competitive binding between the furylcarbinol and nitrogen nucleophile using either a Brønsted or Lewis acid catalyst and that the resulting rearrangement proceeds without involving the Brønsted and Lewis acid catalyst. This shows conclusively that the rate-controlling step and selectivity of reaction are decoupled.

Advances in 3D printing technology over the past decade have led to its expansion into all subfields of science, including chemistry. This technology provides useful teaching tools that facilitate communication of difficult chemical concepts to students and researchers. Presented here is the use of 3D printing technology to create tangible models of reaction progress surfaces. Easy-to-follow step-by-step instructions are provided for the creation of these surfaces from IR, NMR, and HPLC data. More generally, this procedure enables conversion of any arrayed data set into a 3D-printable STL file. The general utility of these 3D-printed models is highlighted with three unique case studies.

A facile and efficient resolution of omeprazole as the monopotassium salt diethanol solvate using coupled preferential crystallization has been developed. This approach uses small perturbations in solution-phase concentration to control the competing process of selective crystal growth while suppressing unwanted primary nucleation. The result is a selective crystallization technique that replaces the traditional batch-type isolation with a continuous process amenable to scale, which provides easy access to enantiopure conglomerate crystals.