21st Rocky Mountain Conference on Analytical Chemistry

Abstracts and meeting program from the 21st annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, July 30 - August 1, 1979

Solid State \u3csup\u3e13\u3c/sup\u3eC NMR and Thermal Analysis of Conformational Motion and Disorder in Small and Large Molecules

In this work it is attempted to explore the conformational motion and disorder through a large number of examples of molecular systems differing in shape, rigidity, and molecular weight: a series of tetra-n-alkylammonium bromides and iodides, a liquid-crystal-forming molecule, N,N\u27-bis(4-n-octyloxybenzal)-1,4-phenylenediamine (OOBPD), and polymers, poly[oxy-1,4-(3-methylphenylene)ethylene-1,4-phenyleneoxynonamethylene] (MBPE-9) and poly[oxy-1,4-(3-methylphenylene)ethylene-1,4-phenyleneoxypentamethylene] (MPBE-5). The techniques used to study the conformational motion and disorder are mainly solid state 13C nuclear magnetic resonance (NMR) spectroscopy and thermal analysis. The results of this work show that conformational disordered states (condis crystals) exist indeed in these molecules containing flexible chemical bonds (single bonds) or more than one accessible conformer. The unique characteristics of the condis crystal and the phase transitions to a condis crystal and to isotropic state have been studied in detail. It could be show that motifs in condis crystals show only conformational disorder but maintaining orientational and positional order, while liquid and plastic crystals show conformational motion in addition to their characteristic positional and orientational disorder and motion, respectively. The molecular motion in the condis state is slow compared to well-known plastic and liquid crystals. Besides the large-amplitude motion in a first-order transition, it is documented that gradual start of motion is possible increasing the conformational entropy over a broad temperature range

Chemical dynamics

CHEMICAL EDUCATION is changing rapidly, not only because of the explosive growth of knowledge but also because the new knowledge has stimulated reformulation of working principles in the science. Undergraduate curricula and individual courses are in constant flux. Nowhere is the change and challenge greater than in freshman chemistry. Teachers of freshmen must meet the intellectual needs of students who have had more sophisticated and stimulating high school courses than those given a decade ago. At the same time, the freshman teacher must be aware of the constant modification of the more advanced courses in chemistry and other fields that his students will study later. Continuous reformulation of courses sometimes results in the inclusion of valuable new material at the expense of other equally valuable material. We believe that this has happened in some of the sophisticated courses in freshman chemistry. Structural chemistry often receives far greater emphasis than chemical dynamics. In 1965, the Westheimer Report (Chemistry: Opportunities and Needs, National Academy of Sciences, 1965) identified the three major fields of chemistry as structure, dynamics, and synthesis. We firmly believe that a balanced course in general chemistry should reflect the outlook of this report. The study of modern chemical synthesis is too demanding to be covered in depth in an introductory course. However, chemical dynamics -- the systematic study of reactions and reactivity -- can and should be studied at the freshman level. The study of changing chemical systems is the most fascinating part of the field for many students, and its early introduction forms a solid foundation for later study. This small volume is our attempt to answer the need. The book is intended for students who have had introductory stoichiometry, energetics, and structure at the level of a modern freshman textbook (for example, Basic Principles of Chemistry, by H. B. Gray and G. P. Haight, Jr., W. A. Benjamin, Inc., New York, 1961). Chemical Dynamics is designed to accompany approximately 20-25 lectures to be given as the concluding section of a freshman chemistry course. We have chosen topics for their fundamental importance in dynamics and then tried to develop a presentation suitable for freshman classes. Discussion of each topic is limited, because chemistry majors will inevitably return to all the subject matter in more advanced courses. We hope that the following ideas have been introduced with a firm conceptual basis and in enough detail for the student to apply them to chemical reality. 1. Thermodynamics and kinetics are two useful measures of reactivity. 2. Characteristic patterns of reactivity are systematically related to molecular geometry and electronic structure. 3. Reaction mechanisms are fascinating in their own right and indispensable for identification of significant problems in reaction rate theory. 4. The concepts underlying experiments with elementary reaction processes (molecular beams) are simple, even though the engineering of the experiments is complicated. 5. Application of theories of elementary reaction rates to most reactions (slow reactions, condensed media, etc.) provides enough challenge to satisfy the most ambitious young scientist. The book includes exercises at the end of each chapter except the last. Their purpose is didactic, inasmuch as most have been written with the aim of strengthening a particular point emphasized in the chapter, or of introducing an important topic which was not developed in the text for reasons of space and which would normally be taken up in greater detail in later courses. The material in this volume has been adapted primarily from a portion of the lectures given by H.B.G. and G.S.H. to the Chemistry 2 students at the California Institute of Technology during the academic years 1966-1967 and 1967-1968. These lectures were taped, written up by J.B.D., and distributed to the students in the form of class notes. The final manuscript was written after class-testing of the notes. Our decision to revise the Chemistry 2 notes in the form of an introductory text was made after H.B.G. and G.S.H. participated in the San Clemente Chemical Dynamics Conference, held in December 1966 under the sponsorship of the Advisory Council of College Chemistry. At San Clemente we found we were not the only group concerned over the exclusion of significant reference to chemical reactions and reactivity relationships in freshman courses. In addition to their general encouragement, which provided the necessary additional impetus, these colleagues prepared a series of papers for publication in an issue of the Journal of Chemical Education. It is a pleasure to acknowledge here the direct contribution these papers made in shaping the final form of our volume; specifically, in preparing Chapter 6, we have drawn examples from the San Clemente papers of Professors R. Marcus, A. Kuppermann and E. F. Greene, and J. Halpern. The concluding chapter of this book was developed from the lectures given by Professors E. F. Greene (dynamics in simple systems), Richard Wolfgang (atomic carbon), John D. Roberts (nuclear magnetic resonance), and F. C. Anson (electrochemical dynamics) to the students of Chemistry 2 in May 1967. These colleagues have kindly given us permission to use their material. We are grateful to Professors Ralph G. Pearson and Paul Haake, who read the entire manuscript and offered valuable criticism. It is a special pleasure to acknowledge the enormous contribution our students in Chemistry 2 made to the project. Their enthusiastic, critical attitude helped us make many improvements in the manuscript. Thanks are also due to four very special members of the staff of W. A. Benjamin, Inc., for seeing this project through with infectious vigor. Finally, and not the least, we acknowledge the role Susan Brittenham and Eileen McKoy played in preparing the final manuscript. JOSEPH B. DENCE HARRY B. GRAY GEORGE S. HAMMOND Pasadena, California January 196

20th Annual Rocky Mountain Conference on Analytical Chemistry

Abstracts and program from the 20th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 7-9, 1978

34th Rocky Mountain Conference on Applied Spectroscopy

Program and registration information for the 34th annual meeting of the Rocky Mountain Conference on Applied Spectroscopy, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 2-6, 1992

Structural and Spectroscopic Studies of Transition Metal Organometallic and Coordination Complexes with Reference to Catalysis

Inorganic chemistry encompasses a variety of topics and in many ways, these advances affect a wider sphere of chemists than purely inorganic and progress in this field is interesting to many scientists. The developments presented in this dissertation are significant as they affect three issues: catalytic reactivity, ligand fluxionality, and catalyst development. Catalysis affects industrial profit, pharmaceutical development, agrochemical synthesis, spectroscopy, enzymatic activity, and polymerization. Progress in certain areas such as the [Cp*Rh(TsDPEN)] (TsDPEN = p-toluenesulfonyldiphenylethylenediamine) has lead to a moiety that is a powerful and efficient catalyst for the reduction of C=N bonds. The precise mechanism of the reaction has been illuminated through a combination of isolation and detection of key intermediates in the catalytic cycle, independent synthesis under non-catalytic conditions, isotopic labeling in combination with in situ 2-dimensional VT NMR. The intermediacy of a fugative Rh-H is strongly supported, and the 16 electron species [Cp*(p-toluenesulfonyldiphenylethylenediamido)Rh] also appears to play a role, implying that there is more than one mechanistic cycle that is important. Understanding this catalyst cycle explains and predicts the stereospecific reductive ability of this catalyst. Improvement upon the understanding of the fluxional structure of polycyclic tetramines in solution allows for a better knowledge of how these species will act as ligands in solution. They are an interesting ligand-type that is likely to bind with unusual properties to a metal center. A series of these molecules were measured and modeled using 1D and 2D VT NMR spectroscopy. Correlations with the electronic structure, using group theoretical methods, supported by density functional calculation, lead to a full picture of the behavior of these proton sponges in solution. Amido ligands, when complexed to transition metals have been the subject of intense interest in recent years and have been shown to promote new and unusual reactivity. This chemistry is often a result of both s and p donation to the metal center. In order to understand this bonding scheme and the donation involved, as well as to study the reaction chemistry, several novel amido complexes, containing both p basic and non-basic ligands, have been synthesized. The ligands and their zirconium complexes have been characterized extensively using both 2D and VT NMR techniques. The synthesis and characterization of a series of metal carbazolyl complexes by X-ray and NMR techniques is reported

Applications of Gas Chromatography-Mass Spectrometry to Organic Chemistry

The work described in this thesis was based on applications of the combined technique of gas chromatography-mass spectrometry (GC-MS) to a variety of topics in organic chemistry and biochemistry. The research included studies of the scope of the technique (based on model compounds) and applications to actual analytical problems. Following the introduction, a section of the thesis is devoted to work on steroids. Results obtained with progesterone and testosterone analogues confirm The value of GC-MS in distinguishing isomers. The use of trimethylsilyl (TMS) ether derivatives in GC-MS is well established, but the advantages of (chloromethyl)dimethylsilyl ethers as derivatives for GC-MS have been little explored. The utility of these derivatives is illustrated and discussed for the example of 1/alpha-alkyl-17beta-hydroxy steroids. The mass spectral fragmentations of TMS ether derivatives of androst-5-en-3beta-ol analogues and of other unsaturated 3beta-hydroxy steroids have been investigated. The results of this survey have been applied to the characterisation of yeast sterols, sterols from a bacterium (Methylococcus capsulatus) grown on methane, steroidal drug metabolites, and a steroidal enzyme-reduction product. Corticosteroids cannot be examined directly by GC-MS because of References cited in this summary are restricted to publications incorporating work described in the thesis. the low thermal stability of the side chain. Earlier work has shown that their boronate derivatives are quite stable. The mass spectra (recorded by GC-MS) of representative corticosteroid boronates are discussed in respect of their use in structural assignments. Similar difficulties are encountered in GC-MS of beta-hydroxy amines because of their relatively high polarity and low thermal stability. The use of boronate derivatives in the characterisation of catecholamines and related beta-hydroxy amines by GC-MS is discussed, and a more detailed investigation of the mass spectral fragmentations of the derived 1,3,2-oxazaborolidines has been carried out. O-methyloxime (MO) derivatives are of value in the analysis by GC-MS of aldehydes and ketones. Salient features of the spectra of MO derivatives of aliphatic aldehydes and ketones are enumerated. Aldehydes from the cuticular leaf waxes of Chenopodium album L. and Lolium perenne L. have been identified by GC-MS of their MO derivatives. Unsaturated aliphatic hydrocarbons from the green form of the freshwater alga Botryococcus braunii have been ozonised and cleaved to form aldehydes which have been identified as their MO derivatives. The structures of the hydrocarbons have thus been inferred. An exploratory study of the use of GC-MS in the analysis of air pollutants has been carried out. The gas chromatographic and mass spectrometric properties of some polycyclic aromatic hydrocarbons have been surveyed and a number of these compounds have been tentatively identified in dust collected from air conditioner filters. Perfluorodecalin has been found to be a convenient mass calibration standard for low resolution mass spectra. The need for, and problems associated with, computer-assisted data handling in GC-MS are discussed. The development of an on-line real-time data acquisition system is described