Photodissociation dynamics of gaseous CpCo(CO)2 and ligand exchange reactions of CpCoH2 with C3H4, C3H6, and NH3

The photodissociation dynamics of CpCo(CO)(2) was studied in a molecular beam using photofragment translational energy spectroscopy with 157 nm photoionization detection of the metallic products. At 532 and 355 nm excitation, the dominant one-photon channel involved loss of a single CO ligand producing CpCoCO. The product angular distributions were isotropic, and a large fraction of excess energy appeared as product vibrational excitation. Production of CpCO + 2CO resulted from two-photon absorption processes. The two-photon dissociation of mixtures containing CpCo(CO)(2) and H(2) at the orifice of a pulsed nozzle was used to produce a novel 16-electron unsaturated species, CpCoH(2). Transition metal ligand exchange reactions, CpCoH(2) + L → CpCoL + H(2) (L = propyne, propene, or ammonia), were studied under single-collision conditions for the first time. In all cases, ligand exchange occurred via 18-electron association complexes with lifetimes comparable to their rotational periods. Although ligand exchange reactions were not detected from CpCoH(2) collisions with methane or propane (L = CH(4) or C(3)H(8)), a molecular beam containing CpCoCH(4) was produced by photolysis of mixtures containing CpCo(CO)(2) and CH(4).     

Asymmetric synthesis of ring functionalized trans-2,6-disubstituted piperidines from N-sulfinyl delta-amino beta-keto phosphonates. total synthesis of (-)-myrtine

Sulfinimine-derived N-sulfinyl delta-amino beta-ketophosphonates are transformed via the enaminones to the phosphoryl dihydropyridones that selectively give trans-2,6-disubstituted 1,2,5,6-tetrahydropyridines on organocuprate addition and dephosphorylation.     

Synthesis and anion-exchange reactions of a new anionic clay, α-magnesium hydroxide

A new anionic clay, α-magnesium hydroxide, was synthesized by hydrolysis of magnesium acetate in propylene glycol. The structure of this α-hydroxide is similar to that of hydrotalcites. It consists of positively charged magnesium hydroxide layers arising out of partial protonation of the hydroxyl groups of the [Mg(OH)(2)] layers and loosely held anions in the interlayer region. As expected it ages readily in water to give β-magnesium hydroxide, brucite. While anion-exchange reactions of α-magnesium hydroxide could not be carried out in aqueous medium a number of anion-exchange reactions could be carried out successfully in ethanol medium.     

Determination of cocaine in human urine, plasma and red blood cells by gas-liquid chromatography

This paper describes a sensitive and reliable method for the determination of cocaine in human urine, plasma and red blood cells. Cocaine is extracted into cyclohexane from the biological materials at slightly alkaline pH, reduced with lithium aluminium hydride, acylated with pentafluoropropionic anhydride and detected by an electron capture detector. When compared with a gas chromatography-mass spectrometry method the results of cocaine determination correlated highly (r = 0.986). When cocaine was given intravenously to volunteer subjects only 0.2-1.4% of the administered dose was excreted as unmetabolized cocaine in the first 9 h after administration. Plasma and red blood cell levels of cocaine were also determined by this method after intravenous administration.     

Mass spectra of transition metal π-complexes. VI—The metastable ion mass spectrum of (η1-Toluene)-tricarbonylchromium

First field free region metastable fragmentations of (η⁶-PhCH₃)Cr(CO)₃ have been examined by means of the linked scan technique. The molecular ion is shown to fragment exclusively by single and multiple CO loss. The ion [C₇H₈Cr(CO)₂]⁺? also fragments directly to [C₇H₈Cr]⁺?.     

Condensed phase photoelectron asymmetry

Large directional asymmetries were observed in photoelectron distributions from core and valence levels in metals and adsorbate atoms. Intensities varied by factors up to 25 as the angle between A and p was varied. The energy dependence of asymmetry showed atomic behavior similar to that expected for free atoms, modified for the tendency p∥A.     

Dehydrocyclization of 1-heptene-1-14C over chromia on non-acidic alumina

The dehydrocyclization of 1-heptene-1-¹⁴C has been investigated over a chromia on nonacidic alumina catalyst with the aim of determining the¹⁴C distribution in the ring of the toluene product. As high as 80% of the¹⁴C was consistently found in the methyl position as predicted for direct six-carbon ring formation.

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1--1-C¹⁴ , , C¹⁴ . 80%- C¹⁴ , .

     

The use of SO2Cl2 in organometallic chemistry. Convenient high yield syntheses of [Fe(η-C5H5)(CO)3] [FeCl4] and [M(CO5Cl] (M = Mn or Re)

Depending on the substrate and the reaction conditions, SO₂Cl₂ is a useful reagent which brings about either chlorination or the formation of cationic species on reaction with transition metal carbonyl complexes.     

Interfacial energy exchange and reaction dynamics in collisions of gases on model organic surfaces

Molecular beam scattering experiments and molecular dynamics simulations have been combined to develop an atomic-level understanding of energy transfer, accommodation, and reactions during collisions between gases and model organic surfaces. The work highlighted in this progress report has been motivated by the scientific importance of understanding fundamental interfacial chemical reactions and the relevance of reactions on organic surfaces to many areas of environmental chemistry. The experimental investigations have been accomplished by molecular beam scattering from ω-functionalized self-assembled monolayers (SAMs) on gold. Molecular beams provide a source of reactant molecules with precisely characterized collision energy and flux; SAMs afford control over the order, structure, and chemical nature of the surface. The details of molecular motion that affect energy exchange and scattering have been elucidated through classical-trajectory simulations of the experimental data using potential energy surfaces derived from ab initio calculations. Our investigations began by employing rare-gas scattering to explore how alkanethiol chain length and packing density, terminal group relative mass, orientation, and chemical functionality influence energy transfer and accommodation at organic surfaces. Subsequent studies of small molecule scattering dynamics provided insight into the influence of internal energy, molecular orientation, and gas–surface attractive forces in interfacial energy exchange. Building on the understanding of scattering dynamics in non-reactive systems, our work has recently explored the reaction probabilities and mechanisms for O₃ and atomic fluorine in collisions with a variety of functionalized SAM surfaces. Together, this body of work has helped construct a more comprehensive understanding of reaction dynamics at organic surfaces.