George M. Bodner

PROBLEM-SOLVING IN CHEMISTRY

W hen the first au tho r be gan work in chem ical edu cation , he be cam e inte rested in researchon problem solving for several reasons. First, problem solving is what chemists do,regardless of whether they work in the area of synthesis, spectroscopy, theory, analysis,or the characterization of compounds. Second, it was clear that individuals who weresuccessful in chemistry courses either developed good problem solving skills — more orless on their own —or brought these skills to their chemistry courses. Finally, it wasobvious that we weren’t doing as good a job as we could in helping less successfulstudents learn how to build problem solving skills.This chapter provides a review of the research literature devoted to the study of problemsolving in chemistry, including research on instructional strategies that might lead toimprovements in students’ problem solving ability. This literature runs the gamut fromstudies of high-school students working on stoichiometry or gas law problems throughstudies of problem solv ing by advanced graduate st udents in chemis try. Our primar y goalin writing this chapter is to point the reader toward appropriate literature, that can (andshould) be read for further details. We will also provide our biased perspective on someof this work.

Making sense of the arrow-pushing formalism among chemistry majors enrolled in organic chemistry

This paper reports results of a qualitative study of sixteen students enrolled in a second year organic chemistry course for chemistry and chemical engineering majors. The focus of the study was student use of the arrow-pushing formalism that plays a central role in both the teaching and practice of organic chemistry. The goal of the study was to probe how students made sense of the arrow-pushing formalism by examining their responses to seven organic chemistry problems that required the use of this formalism. This paper discusses common barriers to students’ understanding of the arrow-pushing formalism, the concepts and ideas students apply when they use this formalism to solve mechanism problems, and implications of the observation that they used this formalism in a meaningless, mechanical manner.

What can we do about ‘Parker’? A case study of a good student who didn't ‘get’ organic chemistry

This paper is based on a qualitative study of seven students enrolled in a two-semester organic chemistry course for chemistry and chemical engineering majors that focused on the reasoning the students had used to answer questions on the course exams. Narrative analysis was applied to create case records for each participant that were then subjected to a cross-case analysis of similarities and differences among the participants. The data were found to be consistent with a theoretical framework that differentiates between instrumental and relational learning. The intense speed with which material was covered and the complexity of the material was found to drive even those students who valued a relational understanding towards functioning as instrumental learners. Particular attention is paid to one participant in the study, Parker, who had been a successful chemistry major until he entered the second year organic course.

A Study of the boron-11 nuclear magnetic resonance spectra of the (3)-1,2-B9C2H-12 and [(3)-1,2-B9C2H11]2Co- ions

Abstract The 70.6 MHz 11 B NMR spectrum of(3)-1,2-B 9 C 2 H - 12 consists of five doublets of relative intensities 2/3/2/1/1 reading upfield. The proposed assignment of these doublet resonances is B(4, 7); B(6) and B(9, 12); B(5, 11); B(8) and B(10) respectively. The 11 B NMR spectrum of [(3)-1,2-B 9 C 2 H 11 ] 2 Co - contains five doublets of relative intensities 1/1/4/2/1 reading upfield. The proposed assignment of these doublets is B(8); B(10); B(9, 12) and B(4, 7); B(5, 11) and B(6) respectively.

A fourier transform carbon-13 NMR study on trivalent compounds of phosphorus, arsenic, antimony and bismuth and their LNi(CO)3 complexes

Abstract 13 C NMR chemical shift data are reported for a number of trivalent derivatives of P, As, Sb and Bi and their LNi(CO) 3 complexes. Data for EMe 3 and EPh 3 (E = P, As, Sb and Bi), EEt 3 and EBu 3 (E = P, As and Sb) and PhEX 2 and Ph 2 EX (E = P, As; X = Cl, Me, Et, Bu) are presented, as well as data for many of the corresponding metal carbonyl complexes. The spectra of AsBu 3 and SbBu 3 are assigned using T 1 (spin-lattice) relaxation time measurements. The effect of variations in the Group VA atom and the effect of complexation on the chemical shifts of alkyl- and aryl-carbon resonances are discussed. Resonance substituent constants of the aryl derivatives are analyzed.

Studies in boron hydrides—V: Assignment of the 11B NMR spectrum of the tridecahydro decaborate(1−) ion

Abstract The 70·6 MHz 11B NMR spectrum of B10H13− consists of four doublets of relative intensities 2:1:5:2 which are assigned to B(6, 9); B(1 or 3): B(5, 7, 8, 10 and 1 or 3); and B(2,4) respectively. This data is consistent with a 3630 model for the solution structure.

An NMR study of icosahedral heteroatom borane derivatives

Abstract An extensive study of 13C and 11B shielding values of icosahedral heteroatom boranes is described. Shielding effects on polyhedral atoms due to variations (a) in directly bonded exopolyhedral groups, (b) in ortho cage groups, (c) in meta cage groups, and (d) in para cage groups are outlined. A linear relationship between 13C and 11B shielding values of isoelectronic and isostructural icosahedral molecules is demonstrated.

High-resolution 1H and 11B NMR studies of 1,2- and 1,7-B10C2H12

Abstract The 70.6-MHz 11B NMR spectrum of 1,2-B10C2H12 has been assigned by use of labeled derivatives. The assignments are, in order of increasing field, B(9,12), B(8,10), B(4,5,7,11) and B(3,6). Resonances in 1,7-B10C2H12 are due, in order of increasing field, to B(5,12), B(9,10), B(4,6,8,11) and B(2,3). The 1H NMR spectrum of 1,2-D2-1,2-B10C2H10 in C6D6 contains four quartets at −2.7, −2.5, −2.1, and −1.7 ppm due to H(8,10), H(9,12), H(4,5,7,11) and H(3,6), respectively. Confirmation of the assignment was achieved by double-resonance experiments.

Assignment of the 13C NMR resonances in trialkylphosphines from spin-lattice relaxation time measurements

Abstract Analysis of the 13C NMR chemical shift and coupling constant data for a number of straight-chain aliphatic trialkylphosphines and their transition metal carbonyl complexes suggests that complexation leads to: (1) a deshielding of C(1) and an increase in 1J(13C31P), (2) a slight shielding of C(2) and a decrease in 2J(13C31P), and (3) little or no change in the chemical shift for C(3) and a slight increase in 3J(13C31P). Application of these rules to the assignment of the 13C NMR spectrum of P(butyl)3 led to conflict with prior work. A study of segmental motion in these derivatives via spin-lattine (T1) relaxation time measurements was therefore performed, and these data are in complete agreement with the proposed assignments. These generalizations must be applied with care, however, since the presence of either unsaturation or branching near the phosphorus can interfere with this pattern.

A variable temperature NMR study of carbonyldiphenylacetylene tris(π-cyclopentadienylrhodium) and its bis(pentafluorophenyl) derivative

Abstract The temperature-dependent 1H and 13C NMR spectra of (h5-C5H5)3Rh3 (CO)C6H5CCC6H5 support the view that this molecule is fluxional in solution at room temperature but is in a frozen conformation at −88°; NMR data of (h5-C5H5)3Rh3 (CO) C6F5CCC6F5 indicate that this molecule appears to be static at room temperature and fluxional at elevated temperatures. The NMR data are consistent with structures, which have been determined by X-ray methods.