Curly arrow mechanism boxing the structure of the

This preview shows page 2 - 4 out of 6 pages.

curly-arrow mechanism, boxing the structure of the intermediate 1c in your answer. [16] b) Explain why the isomerization proceeds from 1a to 1b but not in the reverse direction, i.e. from 1b to 1a . [3] These retro-aldol and aldol reactions are reversible and under thermodynamic control. The ______________ thermodynamically most stable product will predominate. 1b is more stable than 1a because it is __________ more extensively conjugated. ________________________________________________________________ O O O O O OH O O OH H–OH O O O H OH O O O 1 2 3 4 5 6 O O O = (draw reactive conformation for intramolecular aldol) 1 6 2 3 4 5 O O O O O O H–OH OH O O H OH OH O O O O conjugate addition retro-aldol aldol dehydration H HO H OH 1 2 3 4 5 6 O O O 1c Initials: Chem 30C, Winter 2012, Second Midterm Examination (Practice Paper) Page 2 of 6
Image of page 2

Subscribe to view the full document.

Question 2: Mechanisms 2 [Total: 17] O H N Br OMe OMe 2 equiv. N Li O N 1. 2. H 3 O + (workup) 2a 2b 2c MeO OMe H H a) Name compound 2c . Answer: _______ lithium diisopropylamide _______ [2] b) Addition of one equivalent of 2c to 2a results in an acid–base reaction. What is the structure of the conjugate base of 2a ? [3] O N Br OMe OMe or covalent form with N–Li bond c) Addition of a second equivalent of 2c results in the formation of 2b after aqueous workup. The reaction proceeds through a non-brominated reactive intermediate. Draw the structure of this intermediate. [4] O N OMe OMe or covalent form with N–Li bond d) Complete the mechanism for the conversion of the intermediate you draw in part (c) to the final product, 2b .
Image of page 3
Image of page 4
You've reached the end of this preview.
  • Spring '10
  • lamd
  • Chemistry, Amine, buffer solution, practice paper

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern