Analytical solution for transient partitioning and reaction of a condensing vapor species in a droplet

We present the exact analytical solution of the transient equation of gas-phase diffusion of a condensing vapor to, and diffusion and reaction in, an aqueous droplet. Droplet-phase reaction is represented by first-order chemistry. The solution facilitates study of the dynamic nature of the vapor uptake process as a function of droplet size, Henry's law coefficient, and first-order reaction rate constant for conversion in the droplet phase

A general, modular method for the catalytic asymmetric synthesis of alkylboronate esters

Alkylboron compounds are an important family of target molecules, serving as useful intermediates, as well as end points, in fields such as pharmaceutical science and organic chemistry. Facile transformation of carbon-boron bonds into a wide variety of carbon-X bonds (where X is, for example, carbon, nitrogen, oxygen, or a halogen), with stereochemical fidelity, renders the generation of enantioenriched alkylboronate esters a powerful tool in synthesis. Here we report the use of a chiral nickel catalyst to achieve stereoconvergent alkyl-alkyl couplings of readily available racemic α-haloboronates with organozinc reagents under mild conditions. We demonstrate that this method provides straightforward access to a diverse array of enantioenriched alkylboronate esters, in which boron is bound to a stereogenic carbon, and we highlight the utility of these compounds in synthesis

Substituent Effects on Energetics of Peptide-Carboxylate Hydrogen Bonds as Studied by ^1H NMR Spectroscopy: Implications for Enzyme Catalysis

Substituent effects in N–H···O hydrogen bonds were estimated by comparing the acidities of two series of model compounds: N-benzoylanthranilic acids (A) and 4-benzoylamidobenzoic acids (B). Intramolecular N–H···O hydrogen bonds were found to be present in the A series of compounds, while B acids were used as control models. The respective pK_a values for A and B acids were determined experimentally in DMSO solution using proton NMR spectroscopy. With X = H, the pK_a for A and B acids were observed to be 7.6 and 11.6, respectively, a difference of 4.0 units (ΔpK_a). However, with X = p-NO_2, the ΔpK_a value between A and B acids increased to 4.7 units: the pK_a values for A and B acids were determined as 6.7 and 11.4, respectively. The ΔpK_a values between A and B acids as a function of the X substituents were studied in 10 other examples. The effects of X substituents in A acids could be predicted on the basis of the observed linear Hammett correlations, and the sensitivity of each substituent effect was found to be comparable to those observed for the ionization of substituted benzoic acids (ρ = 1.04 for A acids, and ρ = 1.00 for benzoic acids)

Colloidal Electronics

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, September, 2020Cataloged from the official PDF of thesis. "July 2020."Includes bibliographical references.Arming nano-electronics with mobility extends artificial systems into traditionally inaccessible environments. Carbon nanotubes (1D), graphene (2D) and other low-dimensional materials with well-defined lattice structures can be incorporated into polymer microparticles, granting them unique electronic functions. The resulting colloidal electronic 'cells', comprised of microscopic circuits connecting artificial 'organelles' (e.g., generators, sensors, logic gates, etc.), combine the modularity of modern electronics with the characteristic mobility found in dispersive colloidal systems. Fundamental to colloidal electronics lie two challenges: (1) providing electrical energy to a microscopic system with limited footprint; and (2) developing energy efficient electronic devices and circuitries with low power consumption. In this context, my thesis introduces two concepts - Autoperforation and Asymmetric Chemical Doping - as means to fabricate and power electronic circuit elements on top of colloidal particles. These advances allow us to build the first colloidal electronic system that perform autonomous functions integrating energy harvesting, chemical detection and digital memory recording - all within a form-factor no larger than biological cells.by (Albert) Tianxiang Liu.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineerin

Conformational Equilibria of N,N-Dimethylsuccinamic Acid and Its Lithium Salt as a Function of Solvent

The conformational preferences of N,N-dimethylsuccinamic acid and its Li^+ salt were estimated by comparing the respective experimental NMR vicinal proton–proton coupling constants to semiempirical coupling constants for each staggered conformer as derived by the Haasnoot–De Leeuw–Altona method. The strong gauche preferences for the Li^+ salts clearly depended more on the solvents’ hydrogen-bond donating strength (α) than on their hydrogen-bond accepting (β) counterpart, where α and β are the corresponding Kamlet–Taft parameters

Substituent Effects on Energetics of Peptide-Carboxylate Hydrogen Bonds as Studied by ¹H NMR Spectroscopy: Implications for Enzyme Catalysis

Substituent effects in N–H···O hydrogen bonds were estimated by comparing the acidities of two series of model compounds: <i>N</i>-benzoylanthranilic acids (<b>A</b>) and 4-benzoylamidobenzoic acids (<b>B</b>). Intramolecular N–H···O hydrogen bonds were found to be present in the <b>A</b> series of compounds, while <b>B</b> acids were used as control models. The respective p<i>K</i>_a values for <b>A</b> and <b>B</b> acids were determined experimentally in DMSO solution using proton NMR spectroscopy. With X = H, the p<i>K</i>_a for <b>A</b> and <b>B</b> acids were observed to be 7.6 and 11.6, respectively, a difference of 4.0 units (Δp<i>K</i>_a). However, with X = <i>p</i>-NO₂, the Δp<i>K</i>_a value between <b>A</b> and <b>B</b> acids increased to 4.7 units: the p<i>K</i>_a values for <b>A</b> and <b>B</b> acids were determined as 6.7 and 11.4, respectively. The Δp<i>K</i>_a values between <b>A</b> and <b>B</b> acids as a function of the X substituents were studied in 10 other examples. The effects of X substituents in <b>A</b> acids could be predicted on the basis of the observed linear Hammett correlations, and the sensitivity of each substituent effect was found to be comparable to those observed for the ionization of substituted benzoic acids (ρ = 1.04 for <b>A</b> acids, and ρ = 1.00 for benzoic acids)