Guy Waddington

Bio: Guy Waddington is an academic researcher from United States Bureau of Mines. The author has contributed to research in topics: Enthalpy & Vapor pressure. The author has an hindex of 24, co-authored 42 publications receiving 1753 citations.

Combustion Calorimetry of Organic Fluorine Compounds by a Rotating-Bomb Method

Abstract: A rotating-bomb method was developed for the combustion calorimetry of organic fluorine compounds. Conventional methods of handling volatile samples could not be used, and a special technique with sealed, fused-quartz ampoules was devised. Some auxiliary data necessary for reduction of the calorimetric results to standard states were lacking: this difficulty was circumvented by use of suitable comparison or ''blank'' experiments. The following values, in kcal. mole/sup -1/, are reported for the standard heats of formation, ..delta..Hf/sup 0//sub 298.16/, of some organic fluorine compounds from graphite and gaseous hydrogen, oxygen and fluorine: o-fluorobenzoic acid (c), -134.3/sub 8/; m-fluorobenzoic acid(c), -137.8/sub 4/; p-fluorobenzoic acid (e), -138.9/sub 5/; fluorobenzene (liq.), -34.7/sub 5/; benzotrifluoride (liq.), -147.8/sub 5/ and polytetrafluoroethylene (granular, no heat treatment), -193./sub 5/. The samples of fluorobenzoic acids were purified by zone melting. p-Fluorobenzoic acid is proposed as a reference substance for intercomparison of bomb-calorimetric data for fluorine compounds among different laboratories.

A Rotating Combustion Bomb for Precision Calorimetry. Heats of Combustion of Some Sulfur-Containing Compounds

Abstract: To obtain accurate heat of formation data for organic sulfur compounds, a heat of combustion calorimeter has been developed in which it is possible to rotate the bomb after the combustion. Rotation of the bomb tends to produce a thermodynamically defined final state for the combustion process, because the stirring action hastens the attainment of (a) homogeneity of the bomb solution and (b) equilibrium with respect to solution of the bomb gases in the solution. Uncertainties inherent in the use of conventional calorimeters for heat of combustion studies of sulfur compounds are thereby minimized. Results, comparable in precision to those possible in similar studies of hydrocarbons, have been obtained. The indications are that the rotating bomb will have many other applications in combustion calorimetry, particularly in cases in which it is advisable to add a large amount of liquid to the bomb. The following values in kcal. mole/sup -1/ are reported for the standard heats of formation, ..delta..H/sup 0//sub f/(25/sup 0/), of some organic sulfur compounds from graphite, hydrogen gas and rhombic sulfur: 1-pentanethiol, (1) -36.1, (g) -26.2; 3-thiapentane, (1) -28.9, (g) -20.4; 2-methyl-2-propanethiol, (1) -33.7, (g) -26.3; thiacyclopentan, (1) -17.3, (g) -8.0; thiacyclobutane, (1) +6.2, (g) +14.7; and thianthrene,more » (s) +43.6.« less

Thermochemistry and Vapor Pressure of Aliphatic Fluorocarbons. A Comparison of the C–F and C–H Thermochemical Bond Energies

Abstract: The heat of formation of four organic fluorine compounds, including three completely fluorinated aliphatic compounds, was determined by a rotating-bomb method of combustion calorimetry. An earlier technique that used fused quartz ampoules for containing samples of volatile fluorine compounds was replaced by an improved technique that used sealed bags of a polyester film. For three of the compounds vapor pressure measurements were made by an improved method of comparative ebulliometry. The following values, in kcal. mole/sup -1/, are reported for the standard heat of formation, ..delta..Hf/sup 0//sub 296.16/, of these compounds from graphite and gaseous fluorine and hydrogen; m-fluorobenzotrifluoride(g), -184.17; perfluoromethylcyclohexane(g), -675.3; perfluoroethylcyclohexane(g), -769.7; and perfluoro-n-heptane(g), -789.0. These values were used with other thermochemical data to obtain a direct comparison of the C-F and C-H thermochemical bond energies in aliphatic compounds.

Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals

Abstract: VOLUME I Introduction The Incentive Physical-Chemical Properties Experimental Methods Quantitative Structure-Property Relationships (QSPRs) Mass Balance Models of Chemical Fate Data Sources and Presentation Illustrative QSPR Plots and Fate Calculations References Aliphatic and Cyclic Hydrocarbons Lists of Chemicals and Data Compilations Summary Tables and QSPR plots References Mononuclear Aromatic Hydrocarbons Lists of Chemicals and Data Compilations Summary Tables and QSPR plots References Polynuclear Aromatic Hydrocarbons (PAHs) and Related Aromatic Hydrocarbons Lists of Chemicals and Data Compilations Summary Tables and QSPR plots References VOLUME II * Halogenated Aliphatic Hydrocarbons Chlorobenzenes and Other Halogenated Mononuclear Aromatics Polychlorinated Biphenyls (PCBs) Chlorinated Dibenzop-dioxins Chlorinated Dibenzofurans VOLUME III * Ethers Alcohols Aldehydes and Ketones Carboxylic Acids Phenolic Compounds Esters VOLUME IV Nitrogen and Sulfur Compounds Lists of Chemicals and Data Compilations Summary Tables References Herbicides Lists of Chemicals and Data Compilations Summary Tables References Insecticides Lists of Chemicals and Data Compilations Summary Tables References Fungicides Lists of Chemicals and Data Compilations Summary Tables References APPENDICES List of Symbols and Abbreviations Alphabetical Index CAS Registry Index Molecular Formula Index * Each chapter contains lists of chemicals and data compilations, summary tables, QSPR plots, and references

The melting behavior of organic materials confined in porous solids

Abstract: The solid–liquidphase transition temperatures and heats of fusion ΔH f of nonpolar organic solids confined in the pores of controlled pore glasses were measured by differential scanning calorimetry. The pore diameters d were in the range of 40–730 A and the organics studied were cis‐decalin, trans‐decalin, cyclohexane, benzene, chlorobenzene, naphthalene, and heptane. In accordance with previous reports on studies of primarily inorganic materials, the melting point of the pore solidT(d) decreased with decreasing pore diameter. In addition, a large reduction in the bulk enthalpy of fusion ΔH f of the pore solid was measured, which apparently has not been studied in detail by other workers. A linear correlation was found between the melting point depression (ΔT m ) and the reciprocal diameter, as predicted by theories of solidification in a capillary. The calculated values of the solid–liquid interfacial energy σsl were in reasonable agreement with values reported in the literature based on other methods of measurement.

Merck molecular force field. IV. conformational energies and geometries for MMFF94

Abstract: This article describes the parameterization and performance of MMFF94 for conformational energies, rotational barriers, and equilibrium torsion angles. It describes the derivation of the torsion parameters from high-quality computational data and characterizes MMFF94's ability to reproduce both computational and experimental data, the latter particularly in relation to MM3. The computational data included: (i) ∼ 250 comparisons of conformational energy based on “MP4SDQ/TZP” calculations (triple-zeta plus polarization calculations at a defined approximation to the highly correlated MP4SDQ level) at MP2/6-31G* geometries; and (ii) ∼ 1200 MP2/TZP comparisons of “torsion profile” structures at geometries derived from MP2/6-31G* geometries. The torsion parameters were derived in restrained least-squares fits that used the complete set of available computational data, thereby ensuring that a fully optimal set of parameters would be obtained. The final parameters reproduce the “MP4SDQ/TZP” and MP2/TZP computational data with root mean square (rms) deviations of 0.31 and 0.50 kcal/mol, respectively. In addition, MMFF94 reproduces a set of 37 experimental gas-phase and solution conformational energies, enthalpies, and free energies with a rms deviation of 0.38 kcal/mol; for comparison, the “MP4SDQ/TZP” calculations and MM3 each gives a rms deviation of 0.37 kcal/mol. Furthermore, MMFF94 reproduces 28 experimentally determined rotational barriers with a rms deviation of 0.39 kcal/mol. Given the diverse nature of the experimental conformational energies and rotational barriers and the clear indications of experimental error in some cases, the MMFF94 results appear excellent. Nevertheless, MMFF94 encounters somewhat greater difficulty in handling multifunctional compounds that place highly polar functional groups in close proximity, probably because it, like other commonly used force fields, too greatly simplifies the description of electrostatic interactions. Some suggestions for enhancements to MMFF94's functional form are discussed. © 1996 John Wiley & Sons, Inc.

Diffusion characteristics of substrates in Ca-alginate gel beads.

Abstract: The diffusion characteristics of several substrates of varying molecular sizes into and from Ca-alginate gel beads in well-stirred solutions were investigated. The values of the diffusion coefficient (D) of substrates such as glucose, L-tryptophan, and alpha-lactoalbumin [with molecular weight (MW) less than 2 x 10(4)] into and from the gel beads agreed with those in the water system. Their substrates could diffuse freely into and from the gel beads without disturbance by the pores in the gel beads. The diffusion of their substrates into and from the gel beads was also not disturbed by increasing the Ca-alginate concentration in the beads and the CaCl(2) concentration used in the gel preparation. In the case of higher molecular weight substances such as albumin (MW = 6.9 x 10(4)), gamma-globulin (MW = 1.54 x 10(5)) and fibrinogen (MW = 3.41 x 10(5)), the diffusion behaviors of the substrates into and from the gel beads were very different. No diffusion of their substrates into the gel beads from solutions was observed, and only albumin was partly absorbed on the surface of the gel beads. The values of D of their substrates from the gel beads into their solutions were smaller than their values in the water system, but all their substrates could diffuse from the gel beads. The diffusion of high molecular weight substrates was limited more strongly by the increase of Ca-alginate concentration in the gel beads than by the increase of the CaCl(2) concentration used in the gel preparation. Using these results, the capacity of Ca-alginate gel as a matrix of immobilization was discussed.