An inquiry-based activity is described in which organic-chemistry students explore how IR radiation impacts functional-group-bond movements. Through the iSpartan and Spartan apps, students calculate ...the IR spectra for select organic compounds and manipulate the resulting 3D models and IR spectra to visualize bond vibrations. After developing an IR-frequency chart on the basis of these observations, the students analyze spectral data for the presence of functional groups. The results showed that students successfully prepared the chart and analyzed IR-spectral data without previous experience with IR spectroscopy or instructor intervention. Student responses to the inquiry-based learning activity were favorable. This activity was implemented at three academic institutions over a 4 year period and is an attractive approach for students to explore IR spectroscopy in a nonthreatening environment.
A 2-week hands-on activity is described in which introductory organic chemistry students prepare, obtain, and analyze 1H NMR spectra of known organic compounds to draw conclusions on multiplicity, ...integration, and chemical shift. Students performed well on instructor-designed worksheets to develop chemical shift correlation graphs based on their findings. While exam scores remain an assessment, this activity includes student-generated videos about 1H NMR spectroscopy as an equitable evaluation of student learning. The videos contained accurate information and allowed students to utilize a familiar approach, the recording devices on their cell phones and computers, to present information. Student responses to this activity were favorable. This is an attractive approach for students that augments knowledge of 1H NMR spectroscopy with traditional lecture and laboratory experiments.
Persons excluded due to ethnicity or race (PEERs) leave STEM at disproportionate rates; therefore, efforts to engage undergraduate PEERs are critical to creating a diverse STEM workforce. Through a ...Howard Hughes Medical Institute funded Inclusive Excellence grant (HHMI-IE), the REALISE (REALizing Inclusive Science Excellence) program was developed with the goal to increase student retention and success. As part of this project, an extensive faculty development program, including a backward course design module, workshops on microaggressions and implicit bias, and teamwork training, was created to help faculty implement inclusive pedagogy strategies. There were 33 faculty members who participated in the trainings within faculty learning communities (FLCs) and were further supported with STEM-Education (STEM-Ed) reading groups, faculty mixers, minigrants, and engagement from the Center for Innovative Teaching and Learning (CITL). Evaluation of 10 faculty members’ change narratives and reflective prompts revealed that low-stakes opportunities such as STEM-Ed reading groups had the most influence for instituting learner-centered classroom practices, and the workshops on microaggressions and implicit biases prompted faculty to create opportunities to build respectful relationships with students. Here, we share lessons learned from our program evaluation so that others can successfully implement inclusive pedagogy in chemistry.
Background
Current methods of removing organic pollutants from water are becoming ineffective as the world population increases. In this study, a series of biorenewable triblock copolymers with ...hydrophobic poly(ε-caprolactone) block and hydrophilic poly(
l
-lactide) blocks were synthesized and tested as agents to remove environmental pollutants from an aqueous solution. The percent of pollutant removed and equilibrium inclusion constants were calculated for the polymers. These values were compared to previously known removal agents for their effectiveness.
Results
Triblock copolymer samples removed over 70% of the polycyclic aromatic hydrocarbon (PAH) phenanthrene from an aqueous solution, with selectivity for the adsorption of phenanthrene over other PAHs tested. The inclusion constant was 7.4 × 10
5
M
−1
and adsorption capacity was 5.8 × 10
−7
mol phenanthrene/g polymer. Rose Bengal was used to further probe the nature of interactions between the copolymers and a small molecule guest. Solid samples of the
block
-poly(
l
-lactide)–
block
-poly(ε-caprolactone)–
block
-poly(
l
-lactide) (PLLA–PCL–PLLA) systems were found to rapidly remove over 90% of Rose Bengal from aqueous solution, resulting in a complete disappearance of the characteristic pink color. Solutions of the copolymers in dichloromethane also removed Rose Bengal from water with a similar level of efficiency. Large inclusion constant values were obtained, ranging from 1.0 × 10
5
to 7.9 × 10
5
M
−1
, and the average adsorption capacity value of 6.2 × 10
−7
mol/g polymer was determined. Aged polymer samples exhibited different adsorption characteristics and mechanistic theories for the removal of Rose Bengal were determined.
Conclusion
The triblock copolymer consisting of
l
-lactide and ε-caprolactone was effective in removing various organic pollutants in aqueous environments. It is a biorenewable material which leads to minimal waste production during its lifecycle. These polymers were in general more effective in removing organic pollutants than commercially available pollution removal systems.
Expanding the use of modern characterization methods and discovery-based experiments is a goal for many second-year undergraduate introductory organic chemistry laboratory instructors. Large ...enrollments for this course limit the number and range of experiments that can be performed due to constraints on instruments and resources. The experiment described employs a discovery-based approach to enhance a previously published mixed-aldol condensation experiment by incorporating modern structure analysis methods.
Basic groups from acid hydrolysis: 1,3,5‐Triazaadamantanes (TAAs) are shown to degrade in acidic conditions to produce basic byproducts (see scheme). The rate of hydrolysis can be tuned by changing ...the substituents present on the aromatic rings. TAA‐containing dendrimers can be synthesized readily as a result of the branched architecture of the TAA building blocks.
Several closely related branched structures related to the well-established benzyl ether dendrimers were tested as hosts for the removal of pyrene from water. Fluorescence spectroscopy based ...complexation studies showed that the first generation benzyl ether dendrimers removed on average 94 % of pyrene from a saturated aqueous solution after 30 min. By contrast, branched systems containing modified benzyl ether or cyclohexane functional groups removed between 0 and 75 % of pyrene at the same time point while systems with benzyl amine resulted in a 77 % decrease in pyrene. This selectivity eroded over two days after which time all dendrimeric types removed pyrene to approximately the same extent. Inclusion constants of 10
9
–10
11
M
−1
were calculated for the branched systems studied.
Bisimine and bisamine AB2 monomers have been synthesized from 3,5-diaminobenzoic acid and benzaldehyde derivatives without the need for protective groups or purification. This monomer preparation is ...universal for various electron-donating and electron-withdrawing benzaldehyde substrates. To demonstrate the versatility of these previously unreported AB2 monomers in the formation of high molecular weight structures, novel first-generation dendrimers and hybrid second-generation dendrimers have been synthesized. Using fluorescence spectroscopy, pyrene was shown to be removed from an aqueous environment upon exposure to thin dendrimer films, with the first-generation dendrimer removing 70% of the pyrene within 30 min and the hybrid second-generation dendrimers removing 38-52%. Inclusion formation constants were calculated to be on the order of 10(9)-10(11) M(-1) and are comparable to the values of previously reported macromolecules. These results illustrate that size may not influence pyrene removal as effectively as composition.
Benzene-1,3,5-triyl tribenzoate Corfield, Peter W R; Balija, Amy M
Acta crystallographica. Section E, Structure reports online,
12/2013, Letnik:
69, Številka:
Pt 12
Journal Article
Recenzirano
Odprti dostop
The title compound, C27H18O6, commonly known as phloroglucinol tribenzoate, is a standard unit for the family of benzyl ether dendrimers. The central phloroglucinol residue is close to planar, with ...out-of-plane distances for the three oxygen atoms of up to 0.095 (3) Å, while the three attached benzoate groups are approximately planar. One benzoate group is twisted C-C-O-C torsion angle = 98.2 (3)° from the central plane, with its carbonyl O atom 2.226 (4) Å above that plane, while the other two benzoate groups are twisted in the opposite direction C-C-O-C torsion angles = 24.7 (2) and 54.8 (2)°, so that their carbonyl O atoms are on the other side of, and closer to the central plane, with distances from the plane of 1.743 (4) and 1.206 (4) Å. One benzoate group is disordered between two conformers, with occupancies of 86.9 (3) and 13.1 (3)%, related by a 143 (1)° rotation about the bond to the central benzene ring. The phenyl groups of the two conformers occupy the same space. The mol-ecule packs in the crystal with two of the three benzoate phenyl rings stacked parallel to symmetry-related counterparts, with perpendicular distances of 3.715 (5) and 3.791 (5) Å. The parallel rings are slipped away from each other, however, with centroid-centroid distances of 4.122 (2) and 4.363 (2) Å, respectively.
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