John H. Penn

FTIR microspectroscopy of particular liptinite- (lopinite-) rich, Late Permian coals from Southern China

Abstract The Late Permian coals from Southern China are unique in their high content of lopinite (liptinite) and elemental hydrogen and typically produce high yields of tar. Typical of the Late Permian coals of Southern China, the coals used in this study show special petrographic and chemical characteristics, as well as significant oil-producing potential. Studies of these coals and of their content of the lopinite maceral will help to explain the genesis of both the lopinite maceral and of the oil-producing potential of the coals. In this study, an FTIR spectrometer was used in the standard transmission mode to generate the IR spectra of the whole coal. An FTIR spectrometer, equipped with a microscope in the reflectance mode, was used to analyze the chemical structure of individual coal macerals, including lopinite, vitrinite, semifusinite and inertinite. The chemical structure of lopinite is characterized by its higher content of longer and less branched aliphatic side chains and distinct C=0 groups. The oil-producing potential of the coals is attributed to their higher content of lopinite.

A de novo approach to the synthesis of glycosylated methymycin analogues with structural and stereochemical diversity.

A divergent and highly stereoselective route to 11 glycosylated methymycin analogues has been developed. The key to the success of this method was the iterative use of the Pd-catalyzed glycosylation reaction and postglycosylation transformation. This unique application of Pd-catalyzed glycosylation demonstrates the breath of α/β- and d/l-glycosylation of macrolides that can be efficiently prepared using a de novo asymmetric approach to the carbohydrate portion.

Validating the use of concept-mapping as a diagnostic assessment tool in organic chemistry: implications for teaching

Science, Technology, Engineering, and Mathematics (STEM) education has become a key focus in the U.S. governments public education agenda. Many STEM degrees require the successful completion of undergraduate introductory organic chemistry (O-Chem), which is notorious for its difficulty and high attrition rate. Concept Maps (CM) have been used as a tool to improve teaching and learning by providing feedback to teacher and students. Although numerous studies have examined the use of concept maps (CMs) as an assessment tool in science classes, none to date has examined such applications of CMs in O-Chem. Furthermore, studies investigating the validity of CMs in post-secondary science courses are rare. Thus, the present study investigated the validity of CMs as an assessment tool and their diagnostic uses in O-Chem by examining the relationship between CM scores and other key performance measures in O-Chem. Results indicated that CM scores were significantly correlated with problem set scores and final course grade. In addition, a mediation analysis revealed that problem solving scores partially mediated the relationship between problem solving and final course grade, confirming the role CMs are expected to play in O-Chem achievement. Implications for using CMs as diagnostic and formative tools in instruction are discussed.

STRUCTURE AND STABILITY OF AMINOIMINOMETHANESULFONIC ACID

Abstract The crystal structure of aminoiminomethanesulfonic acid (AIMSOA), (NH 2 ) 2 CSO 3 , was determined by X-ray crystallography. The molecular geometry about the central C atom of this zwitterionic species was found to be strictly planar. The tetrahedral S atom was characterized by three nearly equivalent S–O bonds. The unusually high value for the calculated density of 1.948 g cm −3 indicated extremely efficient packing of the (NH 2 ) 2 CSO 3 molecules in the crystal lattice. Correlation was made between stability of (NH 2 ) 2 CSO 3 and aminoiminomethanesulfinic acid (AIMSA) (NH 2 ) 2 CSO 2 in aqueous solution. A number of unexpected differences were observed in their reactivities, stabilities and decomposition products.

Pinacol cleavage using iron(III)trisphenanthroline complexes

Abstract Oxidative bond cleavage of benzpinacol and 2,3-diphenyl-2,3- butanediol have been effected with two Fe(III)(1,10-phenanthroline) 3 complexes which are thought to undergo electron transfer reactions by an outer sphere mechanism. The products of these reactions are exclusively the corresponding ketones when 2,6-di-t-butylpyridine is added to the solution. In contrast to the facile oxidations of these aromatic substrates, pinacol is not cleaved under these reaction conditions.

Student Perceptions of Online Homework Use for Formative Assessment of Learning in Organic Chemistry

Use of online homework as a formative assessment tool for organic chemistry coursework was examined. Student perceptions of online homework in terms of (i) its ranking relative to other course aspects, (ii) their learning of organic chemistry, and (iii) whether it improved their study habits and how students used it as a learning tool were investigated. Our students perceived the online homework as one of the more useful course aspects for learning organic chemistry content. We found a moderate and statistically significant correlation between online homework performance and final grade. Gender as a variable was ruled out since significant gender differences in overall attitude toward online homework use and course success rates were not found. Our students expressed relatively positive attitudes toward use of online homework with a majority indicating improved study habits (e.g., study in a more consistent manner). Our students used a variety of resources to remediate incorrect responses (e.g., class materials, general online materials, and help from others). However, 39% of our students admitted to guessing at times, instead of working to remediate incorrect responses. In large enrollment organic chemistry courses, online homework may act to bridge the student-instructor gap by providing students with a supportive mechanism for regulated learning of content.

Carboxylic acid reductions: Insights from mixed anhydrides and thiol esters

Abstract Reduction of thiol esters and mixed anhydrides with lithium has been accomplished. Thiol esters have been found to react exclusively to yield aldehydes. Mixed anhydrides give cleavage in a way that can be rationalized by stability of the incipient anions.

π-Acceptor induced reactions : radicals vs. ions in thermally induced ether cleavage reactions

Abstract The reactions of benzyl ether ( 1a ) and 4,4′-dicyanobenzyl ether ( 1b ) with a wide range of π-acceptors in acetonitrile at 190°C have been studied. The π-acceptors were chosen in order to systematically vary the ΔG° for hydride or electron transfer from the ethers to the π-acceptors. The products of thermal activation of the bond cleavage reaction are the aldehyde and the alcohol derived from the starting ethers. A linear free energy correlation of the relative thermal reaction rates of 1a and 1b with the reduction potentials of the quinones was obtained. This relationship indicates that the rate of radical pair separation becomes increasingly important relative to the rate of the second electron transfer and subsequent product formation through the hydride transfer intermediate as the electron affinity of the quinone decreases.

π-Acceptor induced thermal reactions: Bond cleavage reactions

TCNQ, TCNQF4, and DDQ have been found to initiate unusual bond breakage reactions. Benzylphenyl sulfide (BPS) and benzylphenyl ether (BPE) undergo cleavage of their interaryl bonds while bibenzyl (BB) does not cleave the interaryl bond and forms only trans-stilbene (TS) when reacted under the same conditions.

Introduction to Complexation and Masking Within a Computer-Enriched Module for Analytical Chemistry

A web-based course was developed in order to improve pre-service teachers’ knowledge concerning complexation and masking in analytical chemistry. This course was designed to enhance students’ achievement by promoting individual and student-centered learning through the use of a series of web-based modules in the subject area. A chemistry achievement test of 10 questions was developed and administered as a pre-test to assess student knowledge in the general area of complexation and masking. Eighty-four students were randomly divided into two groups. One group, referred to hereafter as the experimental group, learned about the specified material within the Web-based course that was developed for this study. The control group was traditionally taught using a lecture format. The increase in the achievement of the control and experimental groups was then assessed through the administration of the chemistry achievement test of 10 questions which was used as a post-test. Significant differences in group achievement scores, favoring the experimental group, were observed between the post-test achievement averages of the control group and the treatment group.