Gas‐Phase Structure Determination of Dihydroxycarbene,One of the Smallest Stable Singlet Carbenes

Carbenes are reactive molecules of the form R¹? C?? R² that play a role in topics ranging from organic synthesis to gas‐phase oxidation chemistry. We report the first experimental structure determination of dihydroxycarbene (HO? C?? OH), one of the smallest stable singlet carbenes, using a combination of microwave rotational spectroscopy and high‐level coupled‐cluster calculations. The semi‐experimental equilibrium structure derived from five isotopic variants of HO? C?? OH contains two very short CO single bonds (ca. 1.32 Å). Detection of HO? C?? OH in the gas phase firmly establishes that it is stable to isomerization, yet it has been underrepresented in discussions of the CH₂O₂ chemical system and its atmospherically relevant isomers: formic acid and the Criegee intermediate CH₂OO.     

Synthesis of PEG–iridium conjugates and their use as hydrogenation catalysts in a water/substrate two-phase medium

New syntheses of PEG-(OCH₂C₅H₄N)₂ and PEG-(OC₆H₄PPh₂)₂ (PEG: poly(ethylene glycol)) conjugates are reported. An iridium hydrogenation catalyst 1, is shown to catalyze hydrogenation in a water/substrate two-phase system. Attachment of 1 to PEG to make 2 and 3 succeeds in making the complex water-soluble and allows it to retain some of its catalytic ability, but leads to micelle formation that inhibits the separation of organic and aqueous phases.     

Experimental determination of magnetic landau parameters in ErRh4B4

From d.c. magnetization data obtained between 0.45 and 13 K we derive the bare Curie temperature, the temperature dependence of the paramagnetic susceptibility, and the coefficients of the higher order terms in the Landau expansion of the magnetic free energy for ErRh₄B₄. We find the unexpected result that the fourth order term is small or zero. Consequently the sixth order term plays the dominant role in stabilizing the magnetic phase.     

Research in the olfactory detection of chemical agents

This paper describes in a review fashion research on the olfactory detection of various electrophiles including toxic organophosphorus compounds. The method involves rapid formation of an odoriferous alkyl isocyanide from reaction of the electrophile with N-alkylformamides. Concepts of using olfactory sensing and a colorimetric procedure as subjective and objective methods, respectively, for isocyanides are discussed.     

RCARM: Reaction classification using automated reaction mapping

Detailed chemical kinetic modeling of gas‐phase reactions can result in automatically generated mechanisms that contain thousands of reactions. In this paper, we describe the development of a rule‐based expert system tool that organizes these reactions into classes such as hydrogen abstraction and beta scission. We have developed 29 simple classification rules, 20 complex (well‐skipping) classification rules, and four second‐stage classification rules. This greatly simplifies the task of the chemical kineticist who wishes to verify, analyze, and gain insights into the reactions comprising the mechanism. This system, which is based on the automated identification of the bonds that break and form in a chemical reaction (the reaction mapping problem), is used to classify reactions in three different mechanisms. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 125–139, 2013     

The photochemistry of 4-azidopyridine-1-oxide

Laser flash photolysis of 4-azidopyridine-1-oxide at 266 or 308 nm yields triplet 4-nitrenopyridine-1-oxide as the dominant reactive intermediate species, with k(ISC) of approximately 2 x 10(7) s(-1). No evidence of products arising from the singlet nitrene was observed, indicating a slow rate of cyclization to the benzazirine and didehydroazepine species. The slow rate of cyclization is postulated to be due to the aminoxyl-like electronic configuration of this species, which withdraws spin density from sites for potential cyclization.