An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The Math-Up Skills Tests (MUST) has been used in multiple research projects conducted by the Networking for Science Advancement (NSA) team to determine how automaticity skills (what can be done without a calculator) in arithmetic can be used to predict if students will be successful (course average = 69.5%+) in general chemistry. This study expands our investigations to include how students' quantitative literacy/quantitative reasoning (QL/QR) abilities influence their success. The NSA team studied multiple classes at eight universities (n = 1,915) within a broad geographic setting in one large, majority-minority southwestern US state. In a short amount of required classroom time, it is possible to identify students at the beginning of the semester who will struggle in first- and second-semester general chemistry (Chem I and Chem II). Results show a strong correlation between students' automaticity MUST skills and their QL/QR ability (r = 0.60) and indicate that when taking both diagnostic assessments into consideration, convincing signals appear allowing for the identification of almost 50% of the Chem I students and about 45% of the Chem II students who will not succeed. With the addition of the QL/QR to the first-week assessments, about 9% more students who enter the courses underprepared were identified than when only the MUST was administered. Outcomes indicate that students with at least average arithmetic and QL/QR automaticity abilities are those who are better prepared for these courses. For on-sequence students with at least one average or above diagnostic score, 88.3% Chem I and 90.5% Chem II were successful.
This investigation sought to elucidate the influence of students' academic legacy on their prior knowledge and course outcomes providing crucial insights for educators who teach general chemistry. This six-semester analysis involved 6,914 students enrolled in classes across nine Texas universities. Explored were personal circumstances associated with students' successes and failures that influenced performance in on- and off-sequence, first- and second-semester general chemistry (Chem 1 and Chem 2). Students' academic legacy based on their categorization as first generation (neither grandparent nor parent/guardian with a 4-year bachelor's degree), second generation (at least one grandparent or parent/guardian with a bachelor's degree), or third generation (at least one grandparent and at least one parent/guardian hold a bachelor's degree) was investigated. Of the students in the dataset 33.8% (<i>n</i> = 2,340) self-identified as Hispanic. Results for Hispanic and non-Hispanic students indicated that first-generation students struggled more with Chem 1 and Chem 2 than students in the other two legacy groups. As students' academic legacy extended, they were more apt to succeed in general chemistry. Second- and third-generation students demonstrated stronger prior high-school chemistry backgrounds and were enrolled in more advanced mathematics courses. As expected, students with stronger academic backgrounds in chemistry and mathematics scored higher on the diagnostic MUST (Math-Up Skills Test), had greater self-efficacy relative to their preparation to succeed, and reported fewer paid work hours. First-generation students on the average entered with lower diagnostic MUST scores, felt less prepared to succeed, and disclosed a greater need to be employed.
To identify the reasons for the very low barrier that has been measured for ring inversion of 1,4,5,5-tetrafluorobicyclo[2.1.0]pentane (deltaG(double dagger) = 6.8 +/- 0.2 kcal/mol), CASSCF and CASPT2 calculations have been performed on ring inversion in this and other bicyclo[2.1.0]pentanes. The results of the calculations show that a cooperative interaction between the geminal fluorines at C2 and the fluorines at C1 and C3 in the singlet cyclopentane-1,3-diyl transition structure (TS) contributes 3.7 kcal/mol to lowering the barrier to ring inversion in the tetrafluoro compound. In contrast, a competitive substituent effect in the TS for ring inversion of 1,4-dicyano-5,5-difluorobicyclo[2.1.0]pentane is predicted to raise the barrier height by 6.1 kcal/mol. The origin of these cooperative and competitive substituent effects is discussed.
In the presence of an excess of pyridine ligand L, osmium tetroxide oxidizes tertiary silanes (Et(3)SiH, (i)Pr(3)SiH, Ph(3)SiH, or PhMe(2)SiH) to the corresponding silanols. With L = 4-tert-butylpyridine ((t)Bupy), OsO(4)((t)Bupy) oxidizes Et(3)SiH and PhMe(2)SiH to yield 100 +/- 2% of silanol and the structurally characterized osmium(VI) mu-oxo dimer [OsO(2)((t)Bupy)(2)](2)(mu-O)(2) (1a). With L = pyridine (py), only 40-60% yields of R(3)SiOH are obtained, apparently because of coprecipitation of osmium(VIII) with [Os(O)(2)py(2)](2)(mu-O)(2) (1b). Excess silane in these reactions causes further reduction of the OsVI products, and similar osmium "over-reduction" is observed with PhSiH(3), Bu(3)SnH, and boranes. The pathway for OsO(4)(L) + R(3)SiH involves an intermediate, which forms rapidly at 200 K and decays more slowly to products. NMR and IR spectra indicate that the intermediate is a monomeric Os(VI)-hydroxo-siloxo complex, trans-cis-cis-Os(O)(2)L(2)(OH)(OSiR(3)). Mechanistic studies and density functional theory calculations indicate that the intermediate is formed by the [3 + 2] addition of an Si-H bond across an O=Os=O fragment. This is the first direct observation of a [3 + 2] intermediate in a sigma-bond oxidation, though such species have previously been implicated in reactions of H-H and C-H bonds with OsO(4)(L) and RuO(4).
The Networking for Science Advancement (NSA) team's institutions consist of nine universities located in one large southwestern US state. This study evaluated students enrolled from Spring 2017 to Fall 2019 in firstand second-semester general chemistry. Over 90% of the students (n = 6,694) have been exposed to a secondary school isomorphic curriculum. The population studied, Chem I (n = 4,619) and Chem II (n = 2,075), met entry-level criteria and are therefore expected to succeed (i.e., earn grades of A, B or C). This study's focus is to disaggregate data based on binary gender (M/F) in hopes of revealing patterns that might remain hidden when studying an undivided population. In Chem I, the female population was 59.6% and increased to 64.5% for Chem II. The 15- min., diagnostic Math-Up Skills Test's (MUST) scores identified about half of all students who were unsuccessful (grades of D and F). Results from the study support that males enter Chem I and II with better automaticity skills (what can be done without using a calculator) than females. However, females outperformed males on course averages in Chem I but not Chem II. Our data provide supporting evidence that the gender gap may be closing.
AbstractThis article looks at the effects of environmental factors such as classification, residence location, and employment status of Hispanic students who unsuccessfully completed first-semester general chemistry (Chem I) at a Hispanic-Serving or emerging Hispanic-Serving Institution. Students ’ automaticity skills in arithmetic and quantitative reasoning (QR) were evaluated as a way to identify at-risk students. Arithmetic skills, measured by the Math-Up Skills Test (MUST), had a higher effect size than the QR assessment. Using both diagnostics identified more than 90% of at-risk Hispanic students. Results indicate positive correlations with course performance at both types of institutions; thus the diagnostics were considered appropriate for early identification of at-risk students. Evaluation of environmental factors revealed few differences between at-risk Hispanic students who attended either type of institution. The most marked result identified a group of typical students who worked at least 31 hours per week and entered with QR scores within the average range but completed Chem I with class averages of less than 50%. Correcting for this observation is possible when students have additional financial support. Additional informationNotes on contributorsBlain MamiyaBlain Mamiya (bmm172@txstate.edu) is a lecturer in the Department of Chemistry at Texas State University in San Marcos, Texas.Cynthia B. PowellCynthia B. Powell is a professor in the Department of Chemistry and Biochemistry and executive director for the Center for Pre-Health Professions at Abilene Christian University in Abilene, Texas.G. Robert SheltonG. Robert Shelton is an instructional assistant professor in the Department of Physical, Mathematical, and Engineering Sciences at Texas A&M University San Antonio in San Antonio, Texas.Anton DubrovskiyAnton Dubrovskiy is an associate professor in the Department of Physical & Applied Sciences at University of Houston-Clear Lake in Houston, Texas.Adrian Villalta-CerdasAdrian Villalta-Cerdas is an assistant professor in the Department of Chemistry at Sam Houston State University in Huntsville, Texas.Susan BroadwaySusan Broadway is a lecturer and inventory supervisor, Department of Chemistry at University of North Texas in Denton, Texas.Rebecca WeberRebecca Weber is a senior lecturer and undergraduate advisor, Department of Chemistry at University of North Texas in Denton, Texas.Diana MasonDiana Mason is a professor emeritus, Department of Chemistry at University of North Texas in Denton, Texas.
This report summarizes one of the invited papers to the ConfChem online conference on Mathematics in Undergraduate Chemistry Instruction, held from October 23 to November 27, 2017, and hosted by the ACS DivCHED Committee on Computers in Chemical Education (CCCE). Combining data collected by a team of nine instructors from six Texas institutions for an IRB-approved investigation, this research correlated the arithmetic skills of first-year general chemistry students (n = 2127) to final course grades. The validated, highly reliable (KR-21 = 0.821) instrument, named the Math-Up Skills Test (MUST), evaluated the following topics using 16 questions: multiplication, division, fractions, scientific notation, exponential notation, logarithms, square roots, and balancing chemical equations. The MUST was given twice to each student: first without the use of a calculator followed by a similar, modified version with the use of a calculator. Outcomes suggest that general chemistry students' arithmetic skills are more correlated with course grades when calculators are not used than when calculators are used. Perhaps more emphasis should be placed on improving students' mathematics automaticity.
