If it won't explode, hit it with a hammer: Facilitating chemical reactions at a liquid surface

Abstract only availableCollisional energy transfer at a gas-liquid interface may play an important role in the initial decomposition of multiphase combustibles. The energy feedback of hot, energetic, gaseous atoms, in this case Ar, striking the liquid surface can potentially impart enough energy to break one of the liquid's bonds in a homolytic fashion thus creating radicals necessary for a resulting explosive chain reaction. Liquid nitromethane (CH3NO2) is a prototypical explosive and is modeled here as a simple diatomic consisting of one methyl (CH3) and one nitro (NO2) groups. The methyl and nitro groups are shown through MP2 6-311+G (2d, 2p) calculations to be the most likely resulting decomposition fragments; as such, focus is placed on the breaking of the C-N bond. For this study, the attractive term of the gas-liquid interaction potential is assumed to be zero to find the limit of Ar-nitromethane interaction. The energy transfer is studied by running simulations, using the DL_Poly_2 program, of Ar impinging the liquid nitromethane from zero degrees to the surface normal and over multiple incident energies. The results are then analyzed for energy transfer and C-N bond breakage.Stevens' Chemistry Progra

The Energetics of Halogenated Ethylenes (Ethynes) and 1,3-Butadienes (Butadiynes): A Computational and Conceptual Study of Substituent Effects and “Dimerization”

The energetics of ethylenes and 1,3-butadienes may be interrelated by the reaction: RHC=CH2 + H2C=CHR\u27 → RHC=CH−CH=CHR\u27 + H2. Shown earlier to be nearly enthalpically thermoneutral for a variety of hydrocarbon cases, we are now interested in the related energetics of halogenated alkenes and alkynes. Using quantum chemical calculations, we have studied this as recast as the isodesmic reactions: 2(H2C=CHX) + H2C=CH−CH=CH2 → p,q-di-X-1,3-butadiene + 2H2C=CH2 2(HC≡CX) + HC≡C−C≡CH → di-X-butadiyne + 2HC≡CH. Here p,q- = 1,3-; 1,4- and 2,3- with X = F, Cl, Br, and I. The halogen and location-dependent deviations from near enthalpic thermoneutrality are discussed

Experimental and theoretical study of the structures and enthalpies of formation of the synthetic reagents l,3-thiazolidine-2-thione and l,3-oxazolidine-2-thione

This paper reports an experimental and a theoretical study of the structures and standard (po = 0.1 MPa) molar enthalpies of formation of the synthetic reagents 1,3-thiazolidine-2-thione [CAS 96-53-7] and 1,3-oxazolidine-2-thione [CAS 5840-81-3]. The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry, and the Knudsen effusion technique and gas-phase enthalpies of formation values at T = 298.15 K of (97.1 ± 4.0) and −(74.4 ± 4.6) kJ·mol−1 for 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in reasonable agreement with the experimental values. In the solid state, 1,3-thiazolidine-2-thione exists in two polymorphic forms (monoclinic and triclinic) and 1,3-oxazolidine-2-thione exits in the triclinic form. The isostructural nature of these compounds and comparison of their molecular and crystal structures have been analyzed. The experimental X-ray powder diffractograms have been compared with the calculated patterns from their structures for identification of the polymorphic samples used in this study. A comparison of our results with literature thermochemical and structural data for related compounds is also reported.M.T. would like to thank MEC/SEUI, FPU AP2002-0603, Spain, for financial support. A.V.D. thanks the National Science Foundation (CHE-0547566) and the American Heart Association (0855743G) for financial support of this research. The support of the Spanish Ministerio de Educación y Ciencia under Projects CTQ2007-60895/BQU and CTQ2006-10178/BQU is gratefully acknowledged

Experimental and Theoretical Study of the Structures and Enthalpies of Formation of the Synthetic Reagents 1,3-Thiazolidine-2-thione and 1,3-Oxazolidine-2-thione

This paper reports an experimental and a theoretical study of the structures and standard (p o ) 0.1 MPa) molar enthalpies of formation of the synthetic reagents 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione . The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry, and the Knudsen effusion technique and gas-phase enthalpies of formation values at T ) 298.15 K of (97.1 ( 4.0) and -(74.4 ( 4.6) kJ · mol -1 for 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in reasonable agreement with the experimental values. In the solid state, 1,3-thiazolidine-2-thione exists in two polymorphic forms (monoclinic and triclinic) and 1,3-oxazolidine-2-thione exits in the triclinic form. The isostructural nature of these compounds and comparison of their molecular and crystal structures have been analyzed. The experimental X-ray powder diffractograms have been compared with the calculated patterns from their structures for identification of the polymorphic samples used in this study. A comparison of our results with literature thermochemical and structural data for related compounds is also reported

Using Isoelectronic Reasoning to Examine the Constancy of Bond Dissociation Enthalpy Ratios [abstract]

Abstract only availableFaculty Mentor: Dr. Carol Deakyne, ChemistryIt has been shown both computationally and experimentally that the bond dissociation enthalpy ratio , where X= O, S, Se (group 16) and Y= C, Si, Ge (group 14) is nearly constant at 0.8. Computations also show that the corresponding ratios when Y= N+, P+, As+ (group 15) or Y= B-, Al-, Ga- (group 13) are nearly constant at 0.7 and 0.9 respectively. We have extended these calculations to the isoelectronic systems HXYXH, where X= N, P, As (group 15) and Y=C, Si, Ge (group 14) or Y= N+, P+, As+ (group 15) to determine whether our earlier observations or the constancy and relative magnitudes of the bond dissociation enthalpy of the ratios still hold. The dependency of the ratios on the geometries of the HXYXH and HXY molecules is also being examined. It would be particularly advantageous if our isoelectronic reasoning is valid because many of the systems that we are now examining computationally are difficult to study in the laboratory.Missouri Academ

Dimeric nanocapsule induces conformational change

An induced cis–trans–trans (rctt) chair to cone structural rearrangement is forced by the addition of a pentacoordinate zinc(II) complex, overcoming thermodynamic and kinetic factors to produce the first phenyl-substituted zinc dimeric nanocapsule