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Assessment of Organic Chemistry Students Utilizing Molecular Modeling Images: Quiz Results of Multiple Choice and Explanation

Questions.

Julie B. Ealy and Jim Hermanson

Penn State University

Berks-Lehigh Valley

American Chemical Society

Anaheim, CA – March 2004

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Multiple Molecular Images in Organic Chemistry

• CD – 3D molecular images that can be manipulated

• Molecular modeling software

• Physical ball and stick models

• Textbook – ball and wire; space filling; line drawings; “wedge” images

• Online images that can be manipulated

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Cognitive Theory of Multimedia Learning

• Mayer, 2001 - material presented in both pictorial and verbal form

• Process pictures and words in sensory memory visually and auditorily – promotes active engagement in learning – contributes to transfer of knowledge

• Assessment through use of molecular images and questions not previously encountered in class

• Was there a transfer of knowledge?

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Cyclohexane Quiz

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Hydrogen 1 and 2

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Rank: most eq to least eq

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Ranking of structures C & D – preference for equatorial

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Explanation of ranking

Explanation scored as correct or incorrect

n Mean

15 1.286

12 1.182

35 1.471

Overall mean = 1.370

ANOVA = 1.798 p = .175

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Explanation: ranking, correct

• 59.68% (37) - Branch group larger: more hydrogens, more atoms

• 17.74% (11) - More room needed, larger groups cause more crowding

• 12.90% (8) – Stability: more stable if farther away from cyclohexane

• 12.90% (8) – Strain: the larger the molecule the more steric strain; more carbons and hydrogens on C – there is more steric hinderance

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Explanation: ranking, correct

• 6.45% (4) – Repulsion: larger groups exert more repulsive forces

• 4.84% (3) – Electron cloud: Since C has more electrons, it would prefer the equatorial position where it can be further away

• 1.61% (1) – Energy: Groups such as C and D have large electron clouds and molecules containing these groups are most energetically stable when the groups are far apart from other atoms

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Explanation: ranking, incorrect

• 29.03% (18) – Double bonded: harder for it to get where it wants to be; has no rotational ability; locked into place by pi bonds

• 8.06% (5) – Stability: D is more stable; C is more stable; C & D are more stable than A & B

• 6.45% (4) – Energy: more in C; more in C & D; D wants lower energy

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Explanation: ranking, incorrect

• 6.45% (4) – NC: D would want to be closer due to sp2 orbital of C more readily than C’s sp3 orbital of carbon

• 4.84% (3) – Strain: The steric hinderance is not as great with a double bond.

• 3.23% (2) – Branch group larger

• 1.61% (1) – Repulsive forces and Electron cloud

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Stereoisomer Quiz

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Representation of the structures

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If stereoisomers, then…

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Explanation – If stereoisomers, then why?

Explanation scored as correct or incorrect50.00% correct (7) 3, no responseMean = 1.500Correct responses50.00% (7) – different spatial arrangement42.86% (6) – same formula21.43 % (3) – same structure21.43% (3) – mirror images

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Explanation: stereoisomers, correct

• They are stereoisomers because they have the same formula and same structure except the OH groups on the 2nd and 3rd carbons could not possibly be manipulated to match each other without breaking any bonds

• Same molecular formula, same connectivity, different spatial arrangements

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Explanation: stereoisomers, incorrect

• Compounds are mirror images of each other (incomplete)

• These images are not a mirror reflection of each other, although they have the same molecular formula. The H’s off of C-2 in the first picture are in the axial position, one equatorial in picture 2.

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Equivalence Quiz

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Unique carbons?

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Equivalent sets of hydrogens?

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Explanation – structure A

• Scored as correct or incorrectMean = 1.500 n = 14Correct, 50 %, (7)

- equivalent sets of hydrogens were listed by number; one student circled the 3 equivalent sets- There are 3 equivalent sets of hydrogen. There are 3 different environments in which hydrogens occur. Because of the double bond this occurs.

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Explanation – structure A, incorrect

a. 29.57% (4) – 1, 2, 3, 4, grouped as one set and 5, 6 grouped as a second set

b. 7.14% (1) – unclear answer

Carbons 1, 2, 3, and 4 have sets of 2 H

c. 14.29% (2) – no response

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Reactivity Quiz

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Order of increasing reactivity

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Alkyl halide description

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Transfer of knowledge?

• Equatorial vs. axial* Yes – greater than 60% responded correctly on the three quiz questions

• Stereoisomers* Yes – identification of molecular images as stereoisomers - > 76%41% identification of molecules as enantiomers50% explanation of images as stereoisomers

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Transfer of knowledge?

• Equivalence quiz

* No – 0% - uniqueness of carbons – no axis of symmetry created difficulty

Yes - equivalent sets of hydrogens >57% - axis of symmetry

Explain hydrogen sets – 50%• Reactivity

* No – 37 % - perhaps attributed to reacting substances

Yes – 100% - identification of 1o, 2o, 3o

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Further Study

• Write new multiple choice questions• Rewrite some existing multiple choice questions

utilizing students’ conceptual errors• Write alternative fixed response questions

(Johnstone & Ambusaidi, 2001) utilizing students’ conceptual errors

• Rewrite multiple choice questions based on ambiguity

• Continue to increase sample size