Malcolm E. Kenney
Case Institute of Technology Cleveland, Ohio
Lecture-Size Molecular Models
with Magnetic Couplings
T h e molecular models made by Lamhertl are among the many useful types that have built.2. m e ones pictured here are based on Lambert's ideas and' others but are designed specifically for use with ,lirge classes. They have been built to a scale of two Angstroms to the inch, a scale that makes even the smallest models (the hydrogens) approximately 4 in. in diameter. The bond angles and the relative sizes ' of the covalent and van der Waals radii used in the design of the models are similar to those of the common sets.4 Most ,of. the models were made from polystyrene foam',.hut several of the spherical models were made of flexible polyurethane foam and of polyethylene foam.5 ' The rigid foam was s h a ~ e dwith a knife and sandoa~ered . by haid. The flexible foams were shaped with the aid of a sandmg drum and a special jig. The foam was first roughly preshaped and a disk (temporary or permanent) was glued on the bond face. The disk was then mounlted on the shaft of a horizontal crank perpendicular to the axis of the shaft. The whole assembly was next fitted in a holder constructed so that it could he rotated through more than 180° about a vertical axis intersecting the crankshaft axis at the center of the model. The model was formed by
rotating the foam about both axes while gradually decreasing the distance between the center of the model and a sanding drum rotating about a fixed vertical axis a t a position horizontally displaced from the center of the model (the distance was varied by moving the whole jig). The polyethylene foam, although somewhat di5cult t o fabricate, proved to be superior
.
A
Presented at the 135th American Chemical Society Meeting, Boston, Mass., April 1959. ' LAMBEET,F. L., J. &EM. EDUC.,30,503 (1953). Since this paper was given, a. lecture set of molecular models (2 in. = 1 A) with pin type connectors has been advertised. Descriptions of some other sets -of models are given in: J. C., J. CHEM.EDUC.,36, 140 (1959); BRIEGLEB, G., GODFAEY, "Methoden der Organisehen Chemie (Houben-Weyl)," 4th ed., Georg Thieme Verlag, Stuttgart, 1955, Vol. III/l, p. 550; and C., Trans.Fa~adaySac., 48,847 HARTLET, G. S., AND ROBINSON, (10.57> \-"*-,. ' Detailed dimensions for a research set of wooden molecular R. B., AND PAULING, L., models ( I in. = 1 A) are given in COREY, Reu. Sci. Insbuments, 24, 621 (1953). 'Low density polyethylene foam manufactured by the Dow Chemical Co. was used. It is available in Pin. and 6-in. rods from plastics fabricatore.
b w a u s ~of its rcsiitance to mechanical and chemical damage. White glue ("Elmer's") was used with all three kindsof foam. The bond faces of the models made of polystyrene and polyurethane were covered with '/a in. of plywood or Masonite. The magnets and steel plates used in the couplings were screwed to wooden blocks attached t o the hacks of the bond faces. For the polyethylene models it was found unnecessary to protect the bond faces with plywood and accordingly the magnets were imbedded in blocks of high density foam and these units were glued directly in the faces of the models. Alnico magnets6 weighing one ounce for the hydrogens and two ounces for the larger units were found to be best (although one-ounce magnets did work satisfactorily for some of the larger units). In order to 'General Hardware Manufacturing Co., New York 13, N . Y. (purchased in hardware stores).
Volume 39, Number 3, Morch 1962
1 129
A selection of individual atoms and permanently built,-up groups useful for lecturing is shown in the table. With this assortmer~t,models of a wide variety of common organic molecules can be made including saturated and unsat,urated hydrocarbons, aromatic hydrocarbons, alcohols, ethers, amines, ketones, aldehydes, acids, esters, and halides. In addition, chain isomers, position isomers, fnnct,ional group isomers, cis-trans isomers and optical isomers can he shown as well as ccrtaiu inorganic molecules (NH?OH, etc.). Assortment o f Molecular Models for Lecturing
. .
2 OH
get maximum visibility the models wcre painted with daylight fluorescent pigments.'
1 -NH2
2 -CHs
1 >G=cP "'Day-glo" printing pastes (thinned with paint thinner), Switner Brothers he., Cleveland, Ohid (obtained in locd stares).
130
1 Javrnd of Chemical Education
Steel plate in one of the faces.
1 -C=CH
