tb30 - Chaoter 30 - Orbitals and OrJ!anic Chemistrv:...

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a. "'I b. "'2 c. "'3* d. "'4* Answer: c Chaoter 30 - Orbitals and OrJ!anic Chemistrv: Pericvclic Reactions 1. There are three major classes of pericyclic reactions. Which of the following types of reactions is not an example of a pericyclic process? a. b. c. d. sigmatropic rearrangements cycloaddition reactions annulation reactions electrocyclic reactions Answer: c 2. The mneumonic phrase "The Electrons Circle Around", TECA, assists in predicting stereochemistry of pericyclic reactions. Describe application of this mneumonic. The mneumonic TECA assists us in remembering that "Thermal pericyc1ic reactions with Even numbers of electrons will occur with Conrotatory or Antarafacial stereochemistry". As a result, the following statements also apply: Photochemical pericyclic reactions with even numbers of electrons will occur with disrotatory or suprafacial stereochemistry. Thermal pericyclic reactions with odd numbers of electrons will occur with disrotatory or suprafacial stereochemistry. Photochemical pericyclic reactions with odd numbers of electrons will occur with comotatory or antarafacial stereochemistry. Answer: 3. To answer the following questions, consider the 1tmolecular orbitals of a conjugated diene shown below: Which molecular orbital of a conjugated diene contains two nodes between nuclei? Four 2p atomic orbitals Energy 336 0/* ~ 0/* m ~ ~ Chapter 30: Orbitals and Organic Chemistry: Pericyclic Reactions
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a. 'VI b. 'V2 c. 'V3 * d. 'V4* Answer: b a. 'VI b. 'Vz c. 'V3* d. 'V4 * Answer: d .,. 4. Which molecular orbital of a ground-state conjugated diene is the highest occupied molecular orbital (HOMO)? 5. Which molecular orbital of an excited-state conjugated diene is the lowest unoccupied molecular orbital (LUMO)? 6. Draw the product(s) you would expect to obtain from photochemical cyclization of (2Z,4E)-hexadiene. -1J Answer: hv - H3~ H CH3 II H3C - OCH3 , , CH3 Test Items for McMurry's Organic Chemistry, Seventh Edition 337
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Consider the reaction below to answer the following questions: H ~ H . 7.
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This note was uploaded on 10/10/2011 for the course CHEMISTRY CHM2046 taught by Professor Johnston during the Spring '11 term at University of South Florida - Tampa.

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tb30 - Chaoter 30 - Orbitals and OrJ!anic Chemistrv:...

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