Quiz7A - 1 CHM 2123, Quiz #7: Preparation of a Cyclic Ketal...

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1 CHM 2123, Quiz #7: Preparation of a Cyclic Ketal Assigned: November 2, 2006 Due: November 6, 2006, before 5pm MARKING SCHEME 1. The experimental procedure at the end of experiment #6 was modified after experiment #7 failed for the majority of students last year. Only one section, having covered their vials with filter paper rather than with vial caps, obtained good results (because their diol was able to dry). Therefore, it seems that the diol obtained by most students contained an excess of water and that this excess prevented the ketalization reaction. Briefly explain with the help of an equation. (2 points) The ketalization reaction also achieves the following equilibrium : H + R 1 R 2 O + HO Ph Ph OH R 1 R 2 O O Ph Ph + H 2 O The ketal product formed from the diol and the 2,2-dimethoxypropane can revert to acetone and the diol in the presence of water. An excess of water will therefore disfavor ketal formation, in accordance with Le Châtelier’s principle. 2.
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This note was uploaded on 01/25/2011 for the course MAT 1330 taught by Professor Dumitriscu during the Spring '08 term at University of Ottawa.

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Quiz7A - 1 CHM 2123, Quiz #7: Preparation of a Cyclic Ketal...

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