Electronic structure and direct dynamics calculations were used to study the potential energy surface atomic-level for OH– + CH3I reactions. The results are compared with crossed molecular beam, ion imaging experiments. DFT/B97-1/ECP/d level of theory gives reaction energetics in good agreement experiment higher calculations, it was simulations that performed reactant collision energies 2.0, 1.0, 0.5, 0.05 eV. Five different pathways observed simulations, forming CH3OH I–, CH2I– H2O, CH2 I–...

Intramolecular [2 + 2] cycloaddition reactions of allene−ynes offer a quick and efficient route to fused bicyclic ring structures. Insights into the mechanism regiochemical preferences this reaction are provided herein on basis results quantum chemical calculations (B3LYP/6-31+G(d,p)) select experiments; both indicate that likely proceeds through stepwise diradical pathway where one radical center is stabilized allylic delocalization. The influences length tether connecting alkyne allene...

Abietic acid, a constituent of pine resin, is naturally derived from abietadiene — process that requires four enzymes: one (abietadiene synthase) for conversion the acyclic, achiral geranylgeranyl diphosphate to polycyclic, chiral (a complex involving copalyl intermediate) and then three oxidize single methyl group corresponding carboxylic acid. In previous work (Nature Chem.2009, 1, 384), electronic structure calculations on carbocation rearrangements leading abietadienyl cation revealed an...

We describe accommodations that we have made to our applied computational–theoretical chemistry laboratory provide access for blind and visually impaired students interested in independent investigation of structure–function relationships. Our approach utilizes tactile drawings, molecular model kits, existing software, Bash Perl scripts written in-house, three-dimensional printing a process allows or student satisfy her his curiosity about relationships with minimal assistance from sighted...

We present a study of the different product channels in reactions OH− and OH−(H2O) with methyl iodide over range collision energies. Direct dynamics classical trajectory simulations are employed to obtain an atomistic comparison experimental results. For experiments we have combined crossed beam ion imaging setup multipole rf trap. The trap allows us prepare molecular cluster ions controlled internal temperature thus provides well-defined initial conditions for reaction at low energy....

The biosynthesis of abietadiene is the first biosynthetically relevant process shown to involve a potential energy surface with bifurcating reaction pathway. Herein, we use gas-phase, enzyme-free direct dynamics simulations study behavior key (bifurcating) step, which conversion C20 pimaradienyl cation abietadienyl cation. In previous (J. Am. Chem. Soc.2011, 133, 8335), truncated C10 model was used investigate this reaction. current work finds that complete gives similar reported for model....

Direct dynamics simulations are a very useful and general approach for studying the atomistic properties of complex chemical systems, since an electronic structure theory representation system's potential energy surface is possible without need fitting analytic function. In this paper, recently introduced compact finite difference (CFD) schemes approximating Hessian [J. Chem. Phys.2010, 133, 074101] tested by employing monodromy matrix equations motion. Several including carbon dioxide...

Herein we use quantum chemical methods (B3LYP/LANL2DZ) to chronicle the path of Pd(II)-promoted Cope rearrangement. It was discovered that although mechanism can proceed through a stepwise associative pathway (forming cyclohexyl cation-like intermediateif appropriately substituted with an electron-donating group), simple change in substituent position or nature (e.g., aptly placed electron-withdrawing group) makes concerted energetically favorable. The origins rate acceleration these systems...

The cycloaddition of (Z)-7-(prop-1-enyl)-7-azabicyclo[4.1.0]heptane with dimethyl acetylene dicarboxylate (DMAD) was reported previously to proceed complete stereoselectivity. Quantum chemical calculations (B3LYP) were used evaluate the mechanism cyclization process, and it discovered that a stepwise pathway is preferred. subsequent electrocyclic ring opening reaction cyclobutene also studied, found "methyl-in" dienamine preferred "methyl-out" product by some 4−5 kcal/mol.

Direct dynamics trajectory simulations were performed for two examples of the thiolate-disulfide exchange reaction, that is, HS(-) + HSSH and CH(3)S(-) CH(3)SSCH(3). The trajectories computed PBE0/6-31+G(d) potential energy surface using both classical microcanonical sampling at ion-dipole complex quasi-classical Boltzmann (T = 300 K) central transition state. these reactions involves a hypercoordinate sulfur intermediate. Despite fact intermediate resides in shallow well (less than 5...

Certain room-temperature ionic liquids exhibit hypergolic activity as liquid bipropellants. Understanding the chemical pathways and reaction mechanisms associated with ignition is important for designing new fuels. It has been proposed (J. Phys. Chem. A 2008, 112, 7816) that an step bipropellant system of dicyanamide/nitric acid activation dissociation 1,5-dinitrobiuret anion DNB(-). For work reported here, a quasiclassical direct dynamics simulation, at DFT/M05-2X level theory, was...

[structure: see text] Quantum chemical calculations (B3LYP and Moeller-Plesset second-order perturbation theory) on carbonium ions containing hypercoordinated carbon atoms in distorted square-pyramidal geometries are described. The importance of overall charge (in addition to the delocalization a certain number electrons) for stability such structures is explored through isoelectronic systems boron atoms. effects alkyl substitution as well variations structure linker attached C(5) core...

A series of sandwich compounds transition metals (M=Ni, Fe, Cr) with cyclic hydrocarbon (M(CH)(n)) and borane (M(BH(2))(n)), ligands (including mixed hydrocarbon/borane sandwiches) has been studied using density functional theory (B3LYP/6-311+G(df,p)). Multicenter bonding between the central metal atom basal cycloborane rings provides stabilization to planar species. Large negative NICS values allude aromatic character in cycloboranes similar analogous hydrocarbons. The ability sandwiches...

Herein we describe our exploration, using density functional theory calculations, of a conjugate addition-rearrangement sequence that leads to medium-ring cyclic amines. On the basis results conclude rearrangement step is rate determining. In addition, analyze role carbanion lone pair in step, concluding it functions as substituent on [3,3] sigmatropic shift, rather than nucleophile; thus, Woodward-Hoffmann rules are not circumvented this reaction via involvement orthogonal orbitals an atom...

The world depends on petroleum for everything from the plastics that contain our food to natural gas heats homes gasoline feed cars' engines. With rising prices of reflecting demand this finite resource, attention has been turned alternative sources energy. Biodiesel, which exhibits many same properties as conventional diesel but is derived biological sources, an attractive alternative. Fats and oils are converted biodiesel, fatty acid methyl esters (FAMEs), by transesterification. FAMEs...

N-Allylhydrazones are reported to undergo an elaborate [3,3]-sigmatropic shift/N2 extrusion sequence. Both concerted and radical cation pathways for the shift of several N-allylhydrazones were investigated using B3LYP/6-31+G(d,p) calculations. It was discovered that, assuming facile formation N-allylhydrazone cation, rearrangement takes place through a series low barrier steps energetically preferred alternative available neutral N-allylhydrazones. Subsequent N2 extrusions forming...

Abstract B3LYP and MP2 quantum chemical calculations on cyclopropylcarbinyl cations fused to various cyclic polycyclic architectures are described. ‘Competition’ for delocalization between the cyclopropane other cyclopropanes and/or π ‐systems incorporated into (poly)cyclic framework which it is was assessed, primarily through use of characteristic geometric perturbations substructure. For example, a linear correlation orientation ‘empty p‐orbital’ at carbocationic center, affected by nature...

Previous experiments [J. Phys. Chem. A 116, 2833 (2012)] have studied the dissociation of 1,2-diiodoethane radical cation () and found a one-dimensional distribution translational energy, an odd finding considering most product relative energy distributions are two-dimensional. The goal this study is to obtain accurate understanding potential surface (PES) topology for unimolecular decomposition reaction → C2H4I+ + I•. This done through comparison many single-reference electronic structure...

The bicyclo[4.1.0]heptane substructure, featured in a number of natural products, is economically formed via gold(III)-mediated cycloisomerization 5-acetoxy-1,6-enyne. This Ohloff–Rautenstrauch rearrangement takes place with high regio- and stereocontrol purportedly proceeds through either two pathways that differ the order major events: cyclization followed by ester migration ("cyclization first") or its transpose ("migration first"). Implicit solvent-phase (dichloroethane) electronic...

The sophomore organic chemistry sequence (Organic I and II) has a reputation: one that prospective students worried. Their anxiety is well-founded, given estimates of the national success rate (defined as grade "C" or better) 50–75%. In an attempt to improve both student opinions about chemistry, we implemented one-week "boot camp" (preparatory) course called Preparing for Organic Chemistry. This reviewed concepts general required in Chemistry II. We found improvements opinion (both before...

Quantum mechanical (QM) + molecular mechanics (MM) models are developed to represent potential energy surfaces (PESs) for the HBr(+) CO2 → Br HOCO(+) reaction with in (2)Π3/2 and (2)Π1/2 spin-orbit states. The QM component is spin-free PES coupling each state represented by a MM-like analytic fit electronic structure calculations. Coupled-cluster single double perturbative triple excitation (CCSD(T)) calculations performed obtain "benchmark" energies without coupling. With zero-point...

Abstract A multitude of challenges facing modern synthesis have an enamine component as part a solution. Transition‐metal‐catalyzed rearrangement allylamines to enamines has occupied prominent place among catalytic transformations. Similar more conventional synthetic approaches intermediates, this chemistry typically leads the formation ( E ) isomers. Recently, Rh I ‐catalyzed N ‐allylaziridines Z )‐ ‐alkenylaziridines was reported with kinetic stereoselectivities between 75:25 and 95:5 / )....

Dependence on petroleum and petrochemical products is unsustainable; it both a finite resource an environmental hazard. Biodiesel has many attractive qualities, including sustainable feedstock; however, its complications. The pyrolysis (a process already in common use the industry) of biodiesel demonstrated formation smaller hydrocarbons comprising but experiments suffer from difficulty quantifying myriad reaction pathways followed formed. A computational simulation using “ab initio...