Characterization of NIST food-matrix standard reference materials for their vitamin C content

The vitamin C concentrations in three food-matrix Standard Reference Materials (SRMs) from the National Institute of Standards and Technology (NIST) have been determined by liquid chromatography (LC) with absorbance detection. These materials (SRM 1549a Whole Milk Powder, SRM 1849a Infant/Adult Nutritional Formula, and SRM 3233 Fortified Breakfast Cereal) have been characterized to support analytical measurements made by food processors that are required to provide information about their products’ vitamin C content on the labels of products distributed in the United States. The SRMs are primarily intended for use in validating analytical methods for the determination of selected vitamins, elements, fatty acids, and other nutrients in these materials and in similar matrixes. They can also be used for quality assurance in the characterization of test samples or in-house control materials, and for establishing measurement traceability. Within-day precision of the LC method used to measure vitamin C in the food-matrix SRMs characterized in this study ranged from 2.7 % to 6.5 %.     

An Oxidative Approach to a Hydroxypiperidinone Utilizing a Rh‐Catalyzed C‐H Activation Process

C‐H activation and isomerization using a Rh‐catalyst provided quick access to dehydropiperidine derivatives that could be further oxidized to hydroxypiperidinone derivatives.     

Deoxygenation of Aromatic Ketones Using Transfer Hydrogenolysis with Raney Nickel in 2-Propanol

Aryl ketones are readily deoxygenated to their corresponding aryl alkanes upon treatment with Raney nickel catalyst in boiling 2-propanol.

Disassembly Kinetics of Quinone‐Methide‐Based Self‐Immolative Spacers that Contain Aromatic Nitrogen Heterocycles

We prepared several pyridine‐ and pyrimidine‐based self‐immolative spacer groups to evaluate the significance of the resonance energy of the spacer aromatic ring on the kinetics of 1,4‐ and 1,6‐elimination reactions, which govern spacer disassembly. Subsequently, we relied on a photoactivation procedure to accurately analyze the disassembly kinetics. Beyond providing new results that are relevant for deriving quantitative structure–property relationships, herein, we demonstrate that pH value can be used as an efficient parameter to finely control the disassembly time of a self‐immolative spacer after an initial activation.     

Evaluation of the effect of silicon on the carbonization process of Colombian semi-anthracites

The environmental impacts associated with the exploitation and transformation of fossil resources aggravate the planet's situation in terms of climate change. Due to this, this paper studies an alternative use of mineral coal as a precursor to obtaining new materials with different properties to the starting coals. The thermal degradation of two Colombian semi-anthracites is analyzed through the thermogravimetry (TG) technique coupled to a Fourier transform infrared spectroscopy (FTIR) equipment from room temperature (25 °C) to 900 °C, at a heating rate of 10 K min^?1 in an inert atmosphere. The catalytic effect of the addition of silicon to these samples before being subjected to a carbonization process is evaluated during this process. The results indicated that the primary reaction occurs in the temperature range between 400 and 680 °C, where the highest mass loss rate was observed. At the end of the heating process, the TG profile of the samples with silicon addition showed losses between 14.33 and 18.82% in mass, these values being slightly higher compared to the starting and demineralized samples. The release of water, light gases such as CO₂, CH₄, and species such as toluene, phenol and formic acid was identified in most of the samples. The presence of silica seems to favor the release of all these species, being more evident in one of the semi-anthracites studied. According to the results obtained, it is proved that the presence of silicon in samples subjected to carbonization processes has a catalytic effect that improves some characteristics of the new materials obtained, thus contributing to the use of carbon to get new materials.

     

Inherent Ethyl Acetate Selectivity in a Trianglimine Molecular Solid

Ethyl acetate is an important chemical raw material and solvent. It is also a key volatile organic compound in the brewing industry and a marker for lung cancer. Materials that are highly selective toward ethyl acetate are needed for its separation and detection. Here, we report a trianglimine macrocycle ( TAMC ) that selectively adsorbs ethyl acetate by forming a solvate. Crystal structure prediction showed this to be the lowest energy solvate structure available. This solvate leaves a metastable, “templated” cavity after solvent removal. Adsorption and breakthrough experiments confirmed that TAMC has adequate adsorption kinetics to separate ethyl acetate from azeotropic mixtures with ethanol, which is a challenging and energy-intensive industrial separation.     

Rational Development of Remote C−H Functionalization of Biphenyl: Experimental and Computational Studies

A simple and efficient nitrile‐directed meta‐C?H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U‐shaped template to achieve a molecular U‐turn and assemble the large‐sized cyclophane transition state for the remote C?H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta‐C?H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta‐selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand‐containing Pd–Ag heterodimeric transition state (TS) favors the desired remote meta‐selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non‐directed meta‐C?H activation. Substituted 2‐pyridone ligands were found to be key in assisting the cleavage of the meta‐C?H bond in the concerted metalation–deprotonation (CMD) process.     

The Bonebrake Theological Seminary: Top-Secret Manhattan Project Site

We discuss the top-secret Manhattan Project site established at the Bonebrake Theological Seminary in 1943 in Dayton, Ohio, where research on polonium and its production was carried out. The polonium produced there was then transported to Los Alamos to be used in a polonium–beryllium neutron source whose purpose was to ignite the plutonium implosion bomb that would be dropped on Nagasaki, Japan, on August 9, 1945. Our account is based primarily on the recollections of John J. Sopka, research physicist at the Bonebrake laboratory.