Communication pubs.acs.org/jchemeduc
Improving a Lecture-Size Molecular Model Set by Repurposing Used Whiteboard Markers Veljko Dragojlovic* Wilkes Honors College of Florida Atlantic University, 5353 Parkside Drive, Jupiter, Florida 33458, United States S Supporting Information *
ABSTRACT: Preparation of an inexpensive model set from whiteboard markers and either HGS molecular model set or atoms made of wood is described. The model set is relatively easy to prepare and is sufficiently large to be suitable as an instructor set for use in lectures.
KEYWORDS: High School/Introductory Chemistry, First-Year Undergraduate/General, Second-Year Undergraduate, Inorganic Chemistry, Organic Chemistry, Molecular Properties/Structure, Hands-On Learning/Manipulatives, Conformational Analysis, Stereochemistry
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PREPARING THE MARKERS TO SERVE AS AN INSTRUCTIONAL MOLECULAR MODEL The model is made by attaching whiteboard marker end-caps to each of the four faces of a tetrahedron. The most challenging part of making any molecular model set is getting the bonds to accurately point to the corners of a tetrahedron. Numerous articles in this journal address the difficulty of producing accurate tetrahedral centers.9−15 Precise production is not trivial, and a small error will result in an obvious deviation from a tetrahedral angle. For example, a small, barely noticeable error in the drilling angle or position of a hole will become obvious once a long bond is inserted. Making tetrahedra can be avoided by using an old HGS model set.16 Its atoms are of adequate size for this project, and the faces and bonds are already positioned at the correct angles. End-caps are centered and secured with HGS bonds to each face of a tetrahedron and then either glued (Figure 1) or attached with screws (Supporting Information). An alternative is to make the atoms out of wood and attach the end-caps to them (Figure 2). This preparation requires more skill and takes more time but results in better quality models.
n instructor molecular model set should be of a size suitable for classroom demonstrations. It should also have other features of a good molecular model set, such as an appropriate representation of bonds and bond angles, and be suitable for the construction of cyclic molecules. Models should also be easy to assemble and manipulate. An example is a lecture-size molecular model set made of plastic soft drink bottles and caps.1 Although the model set is particularly useful for the representation of orbitals during lecture, it is unfortunately quite bulky, even when disassembled. A number of other approaches to make student model sets have also been reported.2−7 Of the commercially available sets, Darling models are the best on the market, particularly in terms of quality/price ratio.8 However, they are too flexible and do not hold their shape very well. In some cases, even holding them with two hands is not sufficient to illustrate the conformation of a more complex molecule, although using various supports such as rubber bands may help. A more suitable model would hold its shape so that an instructor can hold it with one hand and use the other to point to various aspects of the model or to rotate certain parts. As an alternative, a model set may be prepared from used whiteboard markers. Whiteboard markers are used extensively at most universities and, after the ink runs out, discarded. Thus, there is ample supply of used markers and by placing bins for used markers in classrooms, a substantial number of them may be collected over the course of a single semester. The markers are designed so that the cap can be firmly inserted into the end-cap of the tube. This method can be applied to make molecular models from any pens or markers that have such a feature. © XXXX American Chemical Society and Division of Chemical Education, Inc.
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USING THE PREPARED MARKERS WITH MODEL KITS The set is similar to commercially available sets and can be used to represent most common molecules. Two examples shown below are the anti conformation of butane (Figure 3) and the diequatorial conformation of 1,3-dimethylcyclohexane (Figure 4).
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DOI: 10.1021/ed500964n J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
Communication
Figure 1. (A) The end-cap is removed from a marker. (B) An HGS bond is fitted through the end-cap. (C) The assembly is glued to an HGS tetrahedral atom. (D) A completed tetrahedral atom. Detailed instructions for making the model set are provided in the Supporting Information.
Figure 2. (A) A tetrahedral atom made of wood. (B) End-caps are secured to the faces of the tetrahedron by means of short screws. (C) A marker model of methane.
Figure 3. Model of the anti conformation of butane. Views correspond to (A) perspective, (B) Newman, and (C) sawhorse formulas.
This model set is suitable for representation of cyclohexane with differently colored markers used to indicate axial and equatorial bonds. In a model of the diequatorial conformation of 1,3-dimethylcyclohexane, blue markers represent axial bonds, and black markers represent equatorial bonds. The two methyl groups are represented by green and blue markers (Figure 4). Photographs of additional models are provided in the Supporting Information. The described model set is an alternative to commercially available instructor kits. It is relatively easy to make and at a low cost. All of the materials are readily available and only simple inexpensive tools are needed. Preparations of the described model set may be suitable as a class project or take-home assignment as some students are skilled in using tools and have excellent technical skills.
Figure 4. Model of a diequatorial conformation of 1,3-dimethylcyclohexane.
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ASSOCIATED CONTENT
S Supporting Information *
Black markers are used to represent carbon−carbon bonds. Green markers represent hydrogens that lie in the same plane as carbon− carbon bonds. Red and blue markers represent hydrogens that project toward and away from the viewer, respectively (Figure 3A).
Detailed instructions for making a model set and photographs of models of some common molecules. This material is available via the Internet at http://pubs.acs.org. B
DOI: 10.1021/ed500964n J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
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DOI: 10.1021/ed500964n J. Chem. Educ. XXXX, XXX, XXX−XXX
