Substituted naphthalene reaction rates with peroxy-acid treatment: prediction of reactivity using PEST

Persistent organic contaminants in the environment pose an environmental risk due to widespread occurrence and toxic properties. Advanced oxidation processes (AOPs) are treatment methods that have been used to successfully degrade organic contaminants in water, soil, sediments and sludge. Reaction rate constants (k) for peroxy acid treatment of 10 substituted naphthalene compounds were determined. The treatment method utilized acetic acid, hydrogen peroxide and a sulphuric acid catalyst to degrade the polyaromatic structures found in the compounds. Molecular structures of the selected compounds were derived at the B3LYP/6-31G* level of theory. Property-encoded surface translator (PEST) descriptors were calculated from B3LYP/6-31G* optimized structures and were found to have significant levels of correlation with k. Models using minimum local ionization potential (PIP.MIN) and a histogram [bin] of the gradient of the K electronic kinetic energy normal to the isosurface (DKN) were evaluated and found to agree within 10% of experimentally derived values of k in most instances. Results show that a combination of PEST descriptors could be used to predict reactivity by the peroxy-acid process. The PEST technology could prove to be a valuable asset for effective remediation design by predicting reaction outcomes for substituted naphthalene compounds and possibly other hydrophobic organic compounds (HOCs).

Discovery of Highly Potent Liver X Receptor β Agonists

Introducing a uniquely substituted phenyl sulfone into a series of biphenyl imidazole liver X receptor (LXR) agonists afforded a dramatic potency improvement for induction of ATP binding cassette transporters, ABCA1 and ABCG1, in human whole blood. The agonist series demonstrated robust LXRβ activity (>70%) with low partial LXRα agonist activity (<25%) in cell assays, providing a window between desired blood cell ABCG1 gene induction in cynomolgus monkeys and modest elevation of plasma triglycerides for agonist 15. The addition of polarity to the phenyl sulfone also reduced binding to the plasma protein, human α-1-acid glycoprotein. Agonist 15 was selected for clinical development based on the favorable combination of in vitro properties, excellent pharmacokinetic parameters, and a favorable lipid profile.

Polycyclic aromatic hydrocarbon reaction rates with peroxy-acid treatment: prediction of reactivity using local ionization potential

Property-Encoded Surface Translator (PEST) descriptors were found to be correlated with the degradation rates of polycyclic aromatic hydrocarbons (PAHs) by the peroxy-acid process. Reaction rate constants (k) in hr(-1) for nine PAHs (acenaphthene, anthracene, benzo[a]pyrene, benzo[k]fluoranthene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) were determined by a peroxy-acid treatment method that utilized acetic acid, hydrogen peroxide, and a sulphuric acid catalyst to degrade the polyaromatic structures. Molecular properties of the selected nine PAHs were derived from structures optimized at B3LYP/6-31G(d) and HF/6-31G(d) levels of theory. Properties of adiabatic and vertical ionization potential (IP), highest occupied molecular orbitals (HOMO), HOMO/lowest unoccupied molecular orbital (LUMO) gap energies and HOMO/singly occupied molecular orbital (SOMO) gap energies were not correlated with rates of peroxy-acid reaction. PEST descriptors were calculated from B3LYP/6-31G(d) optimized structures and found to have significant levels of correlation with k. PIP Min described the minimum local IP on the surface of the molecule and was found to be related to k. PEST technology appears to be an accurate method in predicting reactivity and could prove to be a valuable asset in building treatment models and in remediation design for PAHs and other organic contaminants in the environment.

Determination of 3,3'-dichlorobenzidine and its degradation products in environmental samples with a small low-field Fourier transform ion cyclotron resonance mass spectrometer

3,3'-Dichlorobenzidine (DCB) and its degradation products, 3-chlorobenzidine (MCB) and benzidine, are of environmental concern because of their carcinogenic nature. The suitability of a small Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer for the analysis of these environmental contaminants in different types of matrices was explored. All the measurements were carried out by depositing the sample solution directly on a disk that was introduced into the mass spectrometer. This approach is very fast and simple because it requires no prior chromatographic separation or derivatization. Calibration curves determined by collecting 70-eV electron ionization mass spectra of neat samples yielded lower limits of detection of 29 and 17 pg (total amount on the solids probe) for DCB and benzidine, respectively (based on a signal to noise ratio of > or = 2:1), while chemical ionization with ammonia resulted in lower limits of detection of 21 pg for DCB and 9 pg for benzidine (total amount on the solids probe). FT-ICR analysis of sediments collected from Lake Macatawa (Holland, MI) verified the presence of DCB in this complex, environmentally significant sample matrix. Laboratory experiments designed to probe biodegradation and photodegradation pathways showed that DCB undergoes sequential dehalogenation to yield MCB and then benzidine under exposure to microorganisms and under simulated tropospheric solar radiation. The ability of the FT-ICR to determine elemental compositions of compounds introduced as described above was demonstrated for one of the degradation products.