No abstract

Alginic acid was converted to a variety of ammonium alginate derivatives carrying diverse chemical cargo such as analgesics, antibiotics, and enzymes. These functional polymers could be fashioned into nanofibrous mats by electrostatic spinning. The therapeutic payload could be released in functional form by a simple ion exchange mechanism. Prospects in wound healing are discussed.

Thionyl chloride (Cl 2 SO) serves as a common Cl atom source in widespread applications of chlorine chemistry though little is known about the reactivity and spectroscopy of the ClSO radical after a Cl−S bond cleavage. We performed a Pulsed Laser Photolysis experiment to detect ClSO from Cl 2 SO photolysis at 248 nm in a gas-flow reactor by timeresolved UV−vis transient absorption spectroscopy. A few chemical tests, using I 2 and NO 2 , suggested the structured absorption band between 260 and 320 nm belonged to ClSO radical and that the termolecular ClSO + Cl + M → Cl 2 SO association reaction occurred. From EOMIP-CCSD/ano-pVQZ calculations, the ClSO band was assigned to the 1 2 A″ ← X 2 A″ transition involving the π* ← π transition of the SO bond and the vibrational progression to the SO stretching mode of the 1 2 A″ state, with a maximum cross-section = (2.0 ± 0.5) × 10 −18 cm 2 near 286 nm (1σ uncertainty) and an average spacing of vibrational structure of 658 cm −1 . The rapid decay of the ClSO signal monitored near 303 nm could be fit to a second-order kinetic model over 10−90 Torr, which yields an effective bimolecular rate coefficient k Cl+ClSO = (1.48 ± 0.42) × 10 −11 cm 3 molecule −1 s −1 at 292 K and 90 Torr (1σ uncertainty). This fast recombination reaction suggests that Cl-containing SO x species might act as significant Cl atom reservoirs in sulfur oxide-rich environments such as Venus' atmosphere. Moreover, the reported UV spectrum provides a new means for monitoring the ClSO radicals.

Although kinetics forms a foundational part of the chemical curriculum, laboratory experiences with the subject are often limited and lack relevance to the actual practice of chemistry. Presented is an inquiry-based lab focused on Michaelis− Menten kinetics, implemented in an upper-level, university physical chemistry laboratory. Student learning was assessed over the course of three years via a pre-and post-test scheme that evaluated student understanding of Michaelis−Menten concepts and experimental design. Results indicate improvement in both domains, in line with previous results in the inquiry-based laboratory literature.

The concentration of formic acid in Earth’s troposphere is underestimated by detailed chemical models compared to field observations. Phototautomerization of acetaldehyde to its less stable tautomer vinyl alcohol, followed by the OH-initiated oxidation of vinyl alcohol, has been proposed as a missing source of formic acid that improves the agreement between models and field measurements. Theoretical investigations of the OH + vinyl alcohol reaction in excess O2 conclude that OH addition to the α carbon of vinyl alcohol produces formaldehyde + formic acid + OH, whereas OH addition to the β site leads to glycoaldehyde + HO2. Furthermore, these studies predict that the conformeric structure of vinyl alcohol controls the reaction pathway, with the anti-conformer of vinyl alcohol promoting α OH addition, whereas the syn-conformer promotes β addition. However, the two theoretical studies reach different conclusions regarding which set of products dominate. We studied this reaction using time-resolved multiplexed photoionization mass spectrometry to quantify the product branching fractions. Our results, supported by a detailed kinetic model, conclude that the glycoaldehyde product channel (arising mostly from syn-vinyl alcohol) dominates over formic acid production with a 3.6:1.0 branching ratio. This result supports the conclusion of Lei et al. that conformer-dependent hydrogen bonding at the transition state for OH-addition controls the reaction outcome. As a result, tropospheric oxidation of vinyl alcohol creates less formic acid than recently thought, increasing again the discrepancy between models and field observations of Earth’s formic acid budget.