Exam1_2009_Answers

Exam1_2009_Answers - Name_ SISD_ Chemistry 350 Exam 1 -...

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Name____________________________ SISD________________________ 1 Chemistry 350 Exam 1 - February 23, 2009 Answer Key Problem 1. (15 points) Provide structures of all isomers that have the formula C 3 H 7 N . For each isomer, all atoms must have complete octets and zero formal charge. There may be more or fewer boxes than isomers. 1 pt for each correct structure. 15 pts maximum. Do not take off points for duplicate structures. H 2 N NH 2 NH 2 NH 2 N N N H N H N H N NH NH N HN NH 2 HN
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Name____________________________ SISD________________________ 2 Problem 2 . (15 points) For each trimethylcyclohexane in parts A-C you are provided with five drawings; one flat cyclohexane, two Newman projections, and two chair conformations. For each molecule, only one out of the five drawings is completed. Your job is to: (i) Fill in the methyl groups on the four drawings that are not complete. The carbon atoms in each drawing are numbered. Make sure to fill in the incomplete drawings using the numbering scheme that is provided. When you fill in the chair templates you must draw, unambiguously, the methyl groups in the proper equatorial or axial positions. (ii) For each of the three molecules, estimate the energy difference between the two chair conformations. Then put an X in the appropriate space to complete the sentence below each set of structures. A) (5 points) Me 1 2 3 4 5 Me H H Me H H H Me H Me Me H H H Me H 1 2 3 4 5 6 1 2 3 4 5 6 Me 1 2 3 4 1 2 3 4 5 5 Me largest middle smallest This molecule has the energy difference between the two chair conformations. X 1 pt for each structure that is completely correct. 0 pts if any structure has one or more mistakes. 1 pt for the correct X in the sentence. Do not take off points for missing H’s on the Newman diagrams. Positioning of axial and equatorial methyl
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Name____________________________ SISD________________________ 3 B) (5 points) 1 2 3 4 5 Me H Me H H Me H H H Me H Me Me H H H 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 1 2 3 4 5 5 largest middle smallest This molecule has the energy difference between the two chair conformations. X
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This note was uploaded on 02/23/2011 for the course CHEM 350 taught by Professor Zimmt during the Spring '09 term at Brown.

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Exam1_2009_Answers - Name_ SISD_ Chemistry 350 Exam 1 -...

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