Marc Whalen | Dalhousie University (original) (raw)
Papers by Marc Whalen
Journal of Fluorine Chemistry, 1995
least-squares cycle, the largest parameter shift was 0.02 times its estimated Phenyl hydrogen ato... more least-squares cycle, the largest parameter shift was 0.02 times its estimated Phenyl hydrogen atom Positions were calculated (~c-H set at 0.95 A) and included in structure factor calculations but were not refined. The final difference Fourier map revealed an electron density peak in the region where the q2-H2 ligand was expected. The maximum to o1 (O1-Os-peak = 1700), Other relevant angles about os to this peak were 860 to PI, 800 to p2, 880 p3 and 1290 to 02, Attempts to refine this oeak as a hvdroaen atom or as a n2-H, ligand were un
Journal, 2010
PURPOSE To determine the effect of operator, curing light and preparation location, as well as an... more PURPOSE To determine the effect of operator, curing light and preparation location, as well as any correlations among these variables, on the amount of light energy delivered to simulated cavity preparations. MATERIALS AND METHODS Each of 10 dentists and 10 fourth-year dental students light-cured a Class I preparation in tooth 26 and a Class V preparation in tooth 37 in a dental mannequin head. The operators exposed each preparation for 10 seconds with each of 3 LED-based curing lights (Bluephase G2 on high power, Demi and VALO on standard power). Each operator also used the VALO unit in the plasma mode for 2 sequential 3-second curing cycles. For each combination of operator, curing light and preparation, the irradiance (mW/cm(2)) received at the base of the preparation was measured with a laboratory-grade spectroradiometer, and software was used to calculate the energy density delivered in real time. The statistical analysis included 3-way analysis of variance (ANOVA) and the Fish...
Journal of Chemical Education
The flow of materials and energy through society is an integral but poorly visible element of glo... more The flow of materials and energy through society is an integral but poorly visible element of global sustainability agendas such as the Planetary Boundaries Framework and the UN Sustainable Development Goals (UNSDG). Given that the primary activities of chemistry are to analyze, synthesize, and transform matter, the practice of chemistry has a great deal to contribute to sustainability science, which in turn should play an increasingly important role in reshaping the practice of chemistry. Success in integrating sustainability considerations into the practice of chemistry implies a substantial role for chemistry education to better equip students to address the sustainability of earth and societal systems. Building on the framework of the IUPAC Systems Thinking in Chemistry Education (STICE) project, we develop approaches to using systems thinking to educate students about the molecular basis of sustainability, to assist chemistry to contribute meaningfully and visibly toward the attainment of global sustainability agendas. A detailed exemplar shows how ubiquitous coverage in general chemistry courses of the Haber−Bosch process for the synthesis of ammonia could be extended using systems thinking to consider the complex interplay of this industrial process with scientific, societal, and environmental systems. Systems thinking tools such as systems thinking concept map extension (SOCME) visualizations assist in highlighting inputs, outputs, and societal consequences of this large-scale industrial process, including both intended and unintended alterations to the planetary cycle of nitrogenous compounds. Strategies for using systems thinking in chemistry education and addressing the challenges its use may bring to educators and students are discussed, and suggestions are offered for general chemistry instructors using systems thinking to educate about the molecular basis of sustainability.
Physics and Chemistry of Glasses
ABSTRACT
Kirk-Othmer Encyclopedia of Chemical Technology, 2000
Journal of the American Chemical Society
We report a comprehensive and systematic experimental and computational assessment of the P-P bon... more We report a comprehensive and systematic experimental and computational assessment of the P-P bond in prototypical molecules that represent a rare series of known compounds. The data presented compliments the existing solid-state structural data and previous computational studies to provide a thorough thermodynamic and electronic understanding of the P-P bond. Comparison of homolytic and heterolytic bond dissociation for tricoordinate-tricoordinate, tricoordinate-tetracoordinate and tetracoordinate-tetracoordinate P-P bonds frameworks 1-6 provides fundamental insights into covalent bonding. For all types of P-P bond discussed, homolytic dissociation is favoured over heterolytic dissociation, although the distinction is small for 21+ and 61+. The presence of a single cationic charge in a molecule substantially strengthens the P-P bond (relative to analogous neutral frameworks) such that it is comparable with the C-C bond in alkanes. Nevertheless, P-P distances are remarkably independ...
Journal (Canadian Dental Association), 2010
To determine the effect of operator, curing light and preparation location, as well as any correl... more To determine the effect of operator, curing light and preparation location, as well as any correlations among these variables, on the amount of light energy delivered to simulated cavity preparations. Each of 10 dentists and 10 fourth-year dental students light-cured a Class I preparation in tooth 26 and a Class V preparation in tooth 37 in a dental mannequin head. The operators exposed each preparation for 10 seconds with each of 3 LED-based curing lights (Bluephase G2 on high power, Demi and VALO on standard power). Each operator also used the VALO unit in the plasma mode for 2 sequential 3-second curing cycles. For each combination of operator, curing light and preparation, the irradiance (mW/cm(2)) received at the base of the preparation was measured with a laboratory-grade spectroradiometer, and software was used to calculate the energy density delivered in real time. The statistical analysis included 3-way analysis of variance (ANOVA) and the Fisher protected least significant...
Journal (Canadian Dental Association), 2011
To quantify the effect of distance on the irradiance and beam homogeneity from 4 curing lights. F... more To quantify the effect of distance on the irradiance and beam homogeneity from 4 curing lights. Four light-emitting diode curing lights were evaluated: Fusion, Bluephase 16i, Demi and FlashLite Magna. The irradiance at the centre of the light beam (ICB) was measured at 1.0 to 9.0 mm from the emitting tip using a 3.9-mm diameter probe connected to a spectrometer. The uniformity of the beam from each curing light was characterized by means of the "top hat factor" at 2.0, 4.0, 6.0 and 8.0 mm from the emitting tip. The useful beam diameter, within which irradiance values were greater than 400 mW/cm2, was calculated. The ICB, top hat factor and useful beam diameter were compared by analysis of variance and Fisher's protected least significant difference test at α = 0.01. At all distances, the ICB was lowest for the FlashLite Magna and highest for the Fusion. Only the Fusion maintained an ICB above 1000 mW/cm2 at the 8.0 mm distance. For distances between 2.0 and 8.0 mm, the...
![Research paper thumbnail of Syntheses of [F5TeNH3][AsF6], [F5TeN(H)Xe][AsF6], and F5TeNF2 and Characterization by Multi-NMR and Raman Spectroscopy and by Electronic Structure Calculations: The X-Ray Crystal Structures of α- and β-F5TeNH2, [F5TeNH3][AsF6], and [F5TeN(H)Xe][AsF6]](https://attachments.academia-assets.com/79683186/thumbnails/1.jpg)
](ChemInform, 2006
Tellurium I 0053 Syntheses of [F 5 TeNH 3 ][AsF 6 ], [F 5 TeN(H)Xe][AsF 6 ], and F 5 TeNF 2 and C... more Tellurium I 0053 Syntheses of [F 5 TeNH 3 ][AsF 6 ], [F 5 TeN(H)Xe][AsF 6 ], and F 5 TeNF 2 and Characterization by Multi-NMR and Raman Spectroscopy and by Electronic Structure Calculations: The X-Ray Crystal Structures of αand β-F5TeNH2, [F5TeNH3][AsF6], and [F5TeN(H)Xe][AsF6].-[F5TeN(H)Xe][AsF6] is synthesized by reactions of [F5TeNH3][AsF6] with XeF2 (in HF and BrF5 solvents) and F5TeNH2 with [XeF][AsF6] (HF solvent) and characterized in solution by 129 Xe, 19 F, 125 Te, 1 H, and 15 N NMR spectroscopy at-60 to-30°C. The crystal structures of the low-temperature phase α-F5TeNH2 (space group P21, Z = 2;-113°C), the high-temperature phase β-F5TeNH2 (I43m, Z = 2;-5°C), [F5TeNH3][AsF6] (P21/m, Z = 6;-109°C), and [F5TeN(H)Xe][AsF6] (P1, Z = 2;-109°C) as well as the vibrational frequencies of these compounds are reported. HF and DFT calculations are used to calculate the gas-phase geometries, charges, Mayer bond orders, and Mayer valencies and to assign the experimental vibrational frequencies.-(FIR, B.; WHALEN,
Phosphorus, Sulfur, and Silicon and the Related Elements, 1992
ABSTRACT
[
…, 1992
... Engl. 1974,13,742. Quast, H.; Kees, F. Chem. Ber. 1981,114,774. ... 1988, C44,1033, and refer... more ... Engl. 1974,13,742. Quast, H.; Kees, F. Chem. Ber. 1981,114,774. ... 1988, C44,1033, and references therein. CNSI: Brook, AG; Kong, Y. K.; Saxena, AK; Sawyer, J. F. Organometallics 1988, 7,2245. CSiP: Schaefer, A.; Weidenbruch, M.; Sank, W.; Pohl, S. Angew. Chem., Int. Ed. ...
…, 1990
... synthetic pathways are responsible for the now extensive series of stable nonmetal heterocy-c... more ... synthetic pathways are responsible for the now extensive series of stable nonmetal heterocy-cles.' However, examples of "genuine" heterocycles (that ... Development Department, Experimental Station, E. I. du Pont de Nemours & Co., PO Box 80356, Wilmington, Deia ware 19880 ...
Inorganic Chemistry, 1994
The salt CF&(OH)N&+AsF6-reacts with XeF2 in BrF5 solvent by means of an HF elimination reaction t... more The salt CF&(OH)N&+AsF6-reacts with XeF2 in BrF5 solvent by means of an HF elimination reaction to give the novel xenon-oxygen-bonded CF3C(OXeF)NH2+ cation. Both CF3C(OH)NH2+ and CF3C(OXeF)NH2+ have been characterized in BrF5 solvent using 129Xe, 19F, 13C, and 'H NMR spectroscopy. Hindered rotation about the C-N bonds in both cations results in chemical inequivalence of the amido protons in the 'H NMR spectra. Assignment of the amido proton resonances was made using the two-dimensional heteronuclear ('H-19F) NOESY technique. The CF3C(OXeF)NH2+ cation is not observed in anhydrous HF solution, but complete removal of the HF solvent in vacuo results in the isolation of CF3C(OXeF)NH2+AsF6-as a white powder which has been characterized by Raman spectroscopy. The Xe-0 bond of the CF&(OXeF)NH2+ cation is interpreted as having substantial covalent character on the basis of trends among lZ9Xe and 'v NMR chemical shifts, 1J(19F-129Xe), and Xe-F stretching frequencies for related xenon(II) species. The substantial covalent character of the Xe-0 bond is attributed, in great measure, to n-bonding between carbon and nitrogen. An intermediate HF solvate, CF~C(OH)NH~+ASF~-.X~F~XHF, has also been isolated from anhydrous HF at low temperature. Raman spectroscopy indicates that the XeF2 molecule is weakly coordinated to the CF3C(OH)NH2+ cation, possibly through hydrogen-bonding interactions with the protonated carbonyl and/or amino groups. This solvate represents the first example of an isolated intermediate in an HF elimination reaction involving XeF2.
Journal of Fluorine Chemistry, 1995
least-squares cycle, the largest parameter shift was 0.02 times its estimated Phenyl hydrogen ato... more least-squares cycle, the largest parameter shift was 0.02 times its estimated Phenyl hydrogen atom Positions were calculated (~c-H set at 0.95 A) and included in structure factor calculations but were not refined. The final difference Fourier map revealed an electron density peak in the region where the q2-H2 ligand was expected. The maximum to o1 (O1-Os-peak = 1700), Other relevant angles about os to this peak were 860 to PI, 800 to p2, 880 p3 and 1290 to 02, Attempts to refine this oeak as a hvdroaen atom or as a n2-H, ligand were un
Journal, 2010
PURPOSE To determine the effect of operator, curing light and preparation location, as well as an... more PURPOSE To determine the effect of operator, curing light and preparation location, as well as any correlations among these variables, on the amount of light energy delivered to simulated cavity preparations. MATERIALS AND METHODS Each of 10 dentists and 10 fourth-year dental students light-cured a Class I preparation in tooth 26 and a Class V preparation in tooth 37 in a dental mannequin head. The operators exposed each preparation for 10 seconds with each of 3 LED-based curing lights (Bluephase G2 on high power, Demi and VALO on standard power). Each operator also used the VALO unit in the plasma mode for 2 sequential 3-second curing cycles. For each combination of operator, curing light and preparation, the irradiance (mW/cm(2)) received at the base of the preparation was measured with a laboratory-grade spectroradiometer, and software was used to calculate the energy density delivered in real time. The statistical analysis included 3-way analysis of variance (ANOVA) and the Fish...
Journal of Chemical Education
The flow of materials and energy through society is an integral but poorly visible element of glo... more The flow of materials and energy through society is an integral but poorly visible element of global sustainability agendas such as the Planetary Boundaries Framework and the UN Sustainable Development Goals (UNSDG). Given that the primary activities of chemistry are to analyze, synthesize, and transform matter, the practice of chemistry has a great deal to contribute to sustainability science, which in turn should play an increasingly important role in reshaping the practice of chemistry. Success in integrating sustainability considerations into the practice of chemistry implies a substantial role for chemistry education to better equip students to address the sustainability of earth and societal systems. Building on the framework of the IUPAC Systems Thinking in Chemistry Education (STICE) project, we develop approaches to using systems thinking to educate students about the molecular basis of sustainability, to assist chemistry to contribute meaningfully and visibly toward the attainment of global sustainability agendas. A detailed exemplar shows how ubiquitous coverage in general chemistry courses of the Haber−Bosch process for the synthesis of ammonia could be extended using systems thinking to consider the complex interplay of this industrial process with scientific, societal, and environmental systems. Systems thinking tools such as systems thinking concept map extension (SOCME) visualizations assist in highlighting inputs, outputs, and societal consequences of this large-scale industrial process, including both intended and unintended alterations to the planetary cycle of nitrogenous compounds. Strategies for using systems thinking in chemistry education and addressing the challenges its use may bring to educators and students are discussed, and suggestions are offered for general chemistry instructors using systems thinking to educate about the molecular basis of sustainability.
Physics and Chemistry of Glasses
ABSTRACT
Kirk-Othmer Encyclopedia of Chemical Technology, 2000
Journal of the American Chemical Society
We report a comprehensive and systematic experimental and computational assessment of the P-P bon... more We report a comprehensive and systematic experimental and computational assessment of the P-P bond in prototypical molecules that represent a rare series of known compounds. The data presented compliments the existing solid-state structural data and previous computational studies to provide a thorough thermodynamic and electronic understanding of the P-P bond. Comparison of homolytic and heterolytic bond dissociation for tricoordinate-tricoordinate, tricoordinate-tetracoordinate and tetracoordinate-tetracoordinate P-P bonds frameworks 1-6 provides fundamental insights into covalent bonding. For all types of P-P bond discussed, homolytic dissociation is favoured over heterolytic dissociation, although the distinction is small for 21+ and 61+. The presence of a single cationic charge in a molecule substantially strengthens the P-P bond (relative to analogous neutral frameworks) such that it is comparable with the C-C bond in alkanes. Nevertheless, P-P distances are remarkably independ...
Journal (Canadian Dental Association), 2010
To determine the effect of operator, curing light and preparation location, as well as any correl... more To determine the effect of operator, curing light and preparation location, as well as any correlations among these variables, on the amount of light energy delivered to simulated cavity preparations. Each of 10 dentists and 10 fourth-year dental students light-cured a Class I preparation in tooth 26 and a Class V preparation in tooth 37 in a dental mannequin head. The operators exposed each preparation for 10 seconds with each of 3 LED-based curing lights (Bluephase G2 on high power, Demi and VALO on standard power). Each operator also used the VALO unit in the plasma mode for 2 sequential 3-second curing cycles. For each combination of operator, curing light and preparation, the irradiance (mW/cm(2)) received at the base of the preparation was measured with a laboratory-grade spectroradiometer, and software was used to calculate the energy density delivered in real time. The statistical analysis included 3-way analysis of variance (ANOVA) and the Fisher protected least significant...
Journal (Canadian Dental Association), 2011
To quantify the effect of distance on the irradiance and beam homogeneity from 4 curing lights. F... more To quantify the effect of distance on the irradiance and beam homogeneity from 4 curing lights. Four light-emitting diode curing lights were evaluated: Fusion, Bluephase 16i, Demi and FlashLite Magna. The irradiance at the centre of the light beam (ICB) was measured at 1.0 to 9.0 mm from the emitting tip using a 3.9-mm diameter probe connected to a spectrometer. The uniformity of the beam from each curing light was characterized by means of the "top hat factor" at 2.0, 4.0, 6.0 and 8.0 mm from the emitting tip. The useful beam diameter, within which irradiance values were greater than 400 mW/cm2, was calculated. The ICB, top hat factor and useful beam diameter were compared by analysis of variance and Fisher's protected least significant difference test at α = 0.01. At all distances, the ICB was lowest for the FlashLite Magna and highest for the Fusion. Only the Fusion maintained an ICB above 1000 mW/cm2 at the 8.0 mm distance. For distances between 2.0 and 8.0 mm, the...
ChemInform, 2006
Tellurium I 0053 Syntheses of [F 5 TeNH 3 ][AsF 6 ], [F 5 TeN(H)Xe][AsF 6 ], and F 5 TeNF 2 and C... more Tellurium I 0053 Syntheses of [F 5 TeNH 3 ][AsF 6 ], [F 5 TeN(H)Xe][AsF 6 ], and F 5 TeNF 2 and Characterization by Multi-NMR and Raman Spectroscopy and by Electronic Structure Calculations: The X-Ray Crystal Structures of αand β-F5TeNH2, [F5TeNH3][AsF6], and [F5TeN(H)Xe][AsF6].-[F5TeN(H)Xe][AsF6] is synthesized by reactions of [F5TeNH3][AsF6] with XeF2 (in HF and BrF5 solvents) and F5TeNH2 with [XeF][AsF6] (HF solvent) and characterized in solution by 129 Xe, 19 F, 125 Te, 1 H, and 15 N NMR spectroscopy at-60 to-30°C. The crystal structures of the low-temperature phase α-F5TeNH2 (space group P21, Z = 2;-113°C), the high-temperature phase β-F5TeNH2 (I43m, Z = 2;-5°C), [F5TeNH3][AsF6] (P21/m, Z = 6;-109°C), and [F5TeN(H)Xe][AsF6] (P1, Z = 2;-109°C) as well as the vibrational frequencies of these compounds are reported. HF and DFT calculations are used to calculate the gas-phase geometries, charges, Mayer bond orders, and Mayer valencies and to assign the experimental vibrational frequencies.-(FIR, B.; WHALEN,
Phosphorus, Sulfur, and Silicon and the Related Elements, 1992
ABSTRACT
[
…, 1992
... Engl. 1974,13,742. Quast, H.; Kees, F. Chem. Ber. 1981,114,774. ... 1988, C44,1033, and refer... more ... Engl. 1974,13,742. Quast, H.; Kees, F. Chem. Ber. 1981,114,774. ... 1988, C44,1033, and references therein. CNSI: Brook, AG; Kong, Y. K.; Saxena, AK; Sawyer, J. F. Organometallics 1988, 7,2245. CSiP: Schaefer, A.; Weidenbruch, M.; Sank, W.; Pohl, S. Angew. Chem., Int. Ed. ...
…, 1990
... synthetic pathways are responsible for the now extensive series of stable nonmetal heterocy-c... more ... synthetic pathways are responsible for the now extensive series of stable nonmetal heterocy-cles.' However, examples of "genuine" heterocycles (that ... Development Department, Experimental Station, E. I. du Pont de Nemours & Co., PO Box 80356, Wilmington, Deia ware 19880 ...
Inorganic Chemistry, 1994
The salt CF&(OH)N&+AsF6-reacts with XeF2 in BrF5 solvent by means of an HF elimination reaction t... more The salt CF&(OH)N&+AsF6-reacts with XeF2 in BrF5 solvent by means of an HF elimination reaction to give the novel xenon-oxygen-bonded CF3C(OXeF)NH2+ cation. Both CF3C(OH)NH2+ and CF3C(OXeF)NH2+ have been characterized in BrF5 solvent using 129Xe, 19F, 13C, and 'H NMR spectroscopy. Hindered rotation about the C-N bonds in both cations results in chemical inequivalence of the amido protons in the 'H NMR spectra. Assignment of the amido proton resonances was made using the two-dimensional heteronuclear ('H-19F) NOESY technique. The CF3C(OXeF)NH2+ cation is not observed in anhydrous HF solution, but complete removal of the HF solvent in vacuo results in the isolation of CF3C(OXeF)NH2+AsF6-as a white powder which has been characterized by Raman spectroscopy. The Xe-0 bond of the CF&(OXeF)NH2+ cation is interpreted as having substantial covalent character on the basis of trends among lZ9Xe and 'v NMR chemical shifts, 1J(19F-129Xe), and Xe-F stretching frequencies for related xenon(II) species. The substantial covalent character of the Xe-0 bond is attributed, in great measure, to n-bonding between carbon and nitrogen. An intermediate HF solvate, CF~C(OH)NH~+ASF~-.X~F~XHF, has also been isolated from anhydrous HF at low temperature. Raman spectroscopy indicates that the XeF2 molecule is weakly coordinated to the CF3C(OH)NH2+ cation, possibly through hydrogen-bonding interactions with the protonated carbonyl and/or amino groups. This solvate represents the first example of an isolated intermediate in an HF elimination reaction involving XeF2.