Brian P. Coppola

Intermolecular 1,3-dipolar cycloadditions of müchnones with acetylenic dipolarophiles: Sorting out the regioselectivity

Abstract A series of 1,3-dipolar cycloadditions of munchnones with acetylenic dipolarophiles was studied, wherein factors related to regioselectivity were investigated. The results from munchnones with electronically divergent thioaryl substituents compared with others bearing alkyl substituents suggest that an unsymmetrical transition state structure, rather than FMO perturbation, plays a significant role in regioselection. If eclipsing interactions preclude a highly unsymmetrical transition state however, then minimizing steric interactions becomes important. A pair of complementarily substituted munchnones, differing only in the position of isotopic labels, establishes an inherently symmetrical electronic nature of the mesoionic heterocycle.

The neuronal NOS inhibitor L-MIN, but not 7-NINA, reduces neurotoxic effects of chronic intrastriatal administration of quinolinic acid

Rat striata were exposed to 15 mM quinolinic acid (QUIN), or QUIN plus the nitric oxide synthase inhibitors S-methyl-L-thiocitrulline dihydrochloride (L-MIN) or 7-nitroindazole monosodium salt (7-NINA) for 21 days. Co-administration of 100 microM or 1 mM L-MIN with QUIN significantly reduced lesion volume compared to QUIN alone. Co-administration of 1 microM or 10 microM L-MIN with QUIN had no significant effect. There was no significant effect of 7-NINA co-administered with QUIN compared to QUIN alone. L-MIN reduction of lesion volume supports the contention that neuronal nitric oxide synthase is a mediator of excitotoxic injury.

Student Learning in Science Classrooms: What Role Does Motivation Play?

One of the major goals of science education today is the attainment of scientific literacy, which includes deeper conceptual understanding of key scientific principles and ideas, the ability to apply scientific knowledge in real-life contexts, as well as the ability to identify problems and conduct scientific inquiry (American Association for the Advancement of Science, 1994; Marx et al, 1997). In examining the antecedents of scientific literacy, one fruitful avenue of research has been the work on student cognition. In particular, this work has underscored the affordances and constraints of prior knowledge influencing conceptual change. These cognitive models of learning have focused mainly on factors such as encoding, automatization, and metacognitive strategies, which have been found in laboratory studies to play a critical role in the conceptual change process. However, there is a need to also consider noncognitive factors such as students’ motivational beliefs, especially when examining students’ cognitive engagement in academic classrooms (Pintrich et al., 1993; Zusho et al, 2003). Accordingly, the purpose of this chapter is to discuss the value of motivation within science education. It is important to note that we conceptualize motivation in this chapter more as a process, rather than as a product. Drawing on recent research from social–cognitive and situated perspectives, we stress the multidimensional nature of motivation and examine how motivational processes are influenced by classroom contextual factors. In short, we do not consider motivation to be a general trait, with some students more and others less motivated along a general quantitative continuum. Rather, we assume student motivation to be situated and changeable as a function of instruction, tasks, and activities that take place in a classroom. In considering the relation between motivation and achievement, we propose two general ways in which motivational beliefs can influence positive academic outcomes (Linnenbrink & Pintrich, 2002). First, motivational beliefs can be thought to “mediate” the relation between certain instructional strategies and achievement (see Figure 1a). For example, the implementation of a new inquiry-based curriculum can result in students becoming more interested in science, which ultimately could lead to higher levels of achievement. In short, this view assumes that “good” instruction should lead to more adaptive motivational processes, which should in turn lead to positive academic outcomes (Stipek, 2001).

Regiocontrol in the 1,3-dipolar cycloaddition reactions of mesoionic compounds with acetylenic dipolarophiles

Abstract The regioselectivity of 1,3-dipolar cycloaddition reactions between mesoionic compounds with singly-tethered substituents is examined. The results with propiolate dipolarophiles are compared with other singly and doubly-tethered examples according to a model using an asynchronous, concerted transition state. The isolation and reaction of a novel, nonaryl substituted mesoionic compound 7 is reported. A regiodirected synthesis starting with N -(2-thiazolinyl)proline gives a complementary dihydropyrroline compared with the reaction between N -formylproline and alkyl propiolates.

Substituent effects on 13C NMR chemical shifts in dialkylaminophenylchlorophosphines

Abstract The relative chemical shifts and 2J(PC) coupling constants in the low-temperature limiting spectra of a series of Ph(R2N)PCl compounds [R  Me, Et, PhCH2, iPr and c-Hex] differ for R  primary or secondary. For primary alkyl substituents, the more downfield signal exhibits a large, positive coupling and the more upfield resonance shows a small, negative coupling. These observations are reversed for secondary alkyl substituents. Calculated minimum-energy molecular structures indicate that the source of this reversal does not lie in differences in conformation about the PN bond. Analysis of the high- and low-temperature limiting spectra of a series of Ph(RR′N)PCl compounds [R, R′  Me, Et, Bz, iPr and c-Hex] suggests that the NC carbon syn to the phosphorus lone-pair is subject to a relatively constant deshielding effect from the phosphorus-lone pair and a shielding contribution from the anti substituent that increases with increasing bulk of that anti substituent. Conversely, the chemical shift of the carbon anti to the phosphorus lone-pair is relatively insensitive to changes in the syn substituent, giving rise to the observed chemical shift reversal.

The Relationship Between Subject Matter Knowledge and Teaching Effectiveness of Undergraduate Chemistry Peer Facilitators

Use of peer instruction and facilitation has surged in undergraduate education at large colleges and universities in recent years. Studies on peer instruction have been directed primarily at student learning gains and affective outcomes among the facilitators. For peer instructors, the relationship between their teaching effectiveness and their foundational content knowledge is assumed but understudied. In an effort to promote instructional coherence (i.e., instructional same-pageness) in the introductory organic chemistry program at the University of Michigan, we observed peer-led study group facilitators’ involvement in their study groups (as teachers of groups of 6–12 students) and in a companion course (as learners) designed to reinforce and enhance their content knowledge. Audiovisual recordings of the facilitators in both the companion course and, for ten of them, leading their study groups, were captured over each of the two week periods covering the topics of stereochemistry and also conformational analysis. Recordings were subsequently coded for topic and correctness in presentation of subject matter. Errors made in either study group or the companion course were investigated for error resolution (corrected or uncorrected), source of error, and propagation of corrected errors. Analysis of recordings revealed that facilitators who have their own errors corrected in the companion course, or observe their peers’ errors corrected in the companion course, correctly describe these concepts in study groups. On examining errors made by facilitators when they are leading study group sessions, a backwards analysis showed consistently that either the topics had not been addressed in the antecedent companion course, or the facilitator was not actively engaged with the discussion when the topics were being discussed. These findings have implications to inform not only our own implementation of peer-led study groups, but also those interested in designing subject matter companion courses for peer leaders in other instructional settings.

Book and Media Recommendations: Enlightenment (Lather, Rinse, Repeat)

Under the surface of new narratives, we tell and retell the same stories and relearn the same lessons. From the reasons we teach in the first place, to recalling that progress is not always made linearly, openly, or transparently, and on through to the daily decisions we face as educators, we are in the business of providing enlightenment to the next group that comes through the door, over and over again. This selection of book and media recommendations visits (and revisits) the theme of how we need to learn (and relearn) the important lessons we wish to convey.