Organic Chemistry I Exam 2 - CHEM 233 by Davis - Prof. Jeffery T. Davis, Exams of Organic Chemistry

Download Organic Chemistry I Exam 2 - CHEM 233 by Davis - Prof. Jeffery T. Davis and more Exams Organic Chemistry in PDF only on Docsity! 'CHEM 233 Davis Hour Exam 2 Friday Nov. 5,, 1999 ORGANIC CHEMISTRY I Name TA There are 10 questions and 6 pages. Each question is worth 10 points. Write all answers legibly on pages 1-6. There is a blank page for scratch work at the end of the exam. Nothing on this page will be graded. 1. _________ 6. 2. ____.____ 7. 3. ____.____ 8. 4. ____.____ 9. 5. 10. TOTAL PAGE \ Electrophilic Addition HCI B 1,3-Butadiene reacts with HCI to give 3-chloro-l-butene (B) and 1-chloro-trans-2- butene (C). The reaction to give B and C involves a common intermediate, carbonium ion A. Answer the following questions based on the energy diagram below: Energy Cl B Reaction Pathway a) Intermediate A is a resonance hybrid. Propose a structure for its other resonance form. Show proper electron motion in drawing this other resonance form. (5 pts) b) Which product, B orC, is formed faster from A? (3 pts c) Which species, A,B orC. is most stable? (2 pts) 1 PAGE 4 6. a) Hydroboration-oxidation of cis-CH3CH = CHCF3 could yield 2 different addition products, regioisomers A and B. Draw the structures of both possible products. (5 pts) 1)BH 3 , THF 2) HoOo, NaOH H 3C CF3 B b) But, only one product is actually formed in this hydroboration. Identify the product (either regioisomer A or B) and justify your reasoning. (5 pts) 7. Using detailed structures, illustrate why the following acid-catalyzed hydration reaction is not a C 3od method for preparing 3,3-dimethyl-2-butanol? (10 pts) OH ,CH3 H 3C CH 3 H2S04 + H 3C CH3 H 3C CH3 PAGE 5 8. a) Use drawings, with p orbitals, to illustrate why there is not free rotation about the C=C double bond in cis-2-butene. (5 pts) b) Show a step-wise mechanism for the following isomerization. (5 pts; HoC /=\ ChU HoO+ CH, 9. Suggest a reasonable mechanism for the following reaction. Show all intermediates and indicate proper electron movement. (10 pts) O, Brc Br H-Br PAGE 6 10. Indicate the expected major product from each of the following reactions. Indicate the proper cis or trans stereochemistry when necessary. (10 pts) HCH,-Znl 1) OsO4 2) NaHSO3 , H 2O Br0 H 2 , Pd/C 1)03 2) Zn, H 2O