EXAM 3

CHEMISTRY 220a

Friday, November 4, 2005

 

NAME (print): _______________________________________________________________

 

TA:_____________________    Section Day:_________________ Section Time:__________

 

 

No Calculators!  Take a few moments to look over the exam.  Answer each question on the exam paper.

 

Important clues and structures are in bold.

 

 Do all preliminary drawing or computations on the work sheets at the end of the exam. The work sheets will not be graded. 

 

The exam is 55 minutes.

 

STOP writing and hand in your exam when you are asked to do so.

 

Remember: Neatness is to your advantage.

 

 

1. (20 pts) Structure                                        ______

 

 

2.  (30 pts) Reactions (5 of 6)                        ______

 

 

3.  (25 pts) Potpourri                                       ______

 

 

4.  (25 pts) Mechanisms  (do 1 of 4)               ______

 

___________________________________________

 

Total (100 pts) 


 

1. Structure:  (20 pts) Treatment of compound A, C10H20, with O3 and then dimethyl sulfide provides a single, branched-chain ketone B. Exposure of A to bromine water affords (±)-C, which, when treated with aqueous NaOH, produces meso-epoxide D. What are the structures A-D?  Explain and illustrate.

2.   Reactions: (30 pts)  Complete 5 of 6 of the following questions.  Specify the structures in each one with a brief rationale for your choice.  Pay attention to stereochemistry, optical activity, etc. where they apply. .  If you do six questions, cross out the one that you do not want graded.

 

 

 

 

Écontinued next page

 

 

2. continued.

 

 

 

 

 

 

 

 

3.  Potpourri: (25 pts) Complete the following questions.

 

a)  Circle the hexene(s) with the greatest heat of hydrogenation.

 

 

 

b)  Circle the terms that apply to the addition of bromine to the 2-pentenes.

 

 

stereospecific               regiospecific                meso                anti                  bromonium ion

 

 

 

c)  Circle the terms that apply to the conversion of (E)- or (Z)-3-methyl-2-pentene to the alcohol 3-methyl-2-pentanol by hydroboration/NaOOH.

           

 

presence of diastereomers                   optically active                 stereospecific

 

 

common intermediate              anti addition

 

 

d)  Of the following additions to alkenes, circle the operations that we do not know how to accomplish.

 

 

form a 1,2-diol anti                  add Br2 syn                 form a chlorohydrin syn

 

 

form a 1,2-diol syn             add chlorine anti

 

 

e)  Circle the reactions that form meso compounds with (E)-3-hexene.

 

Br2/CCl4                                                   OsO4/H2O2                                            1) peracid; 2) H3O+

 

alkaline, aq. permanganate                               ozone/(CH3) 2S

   4.  Mechanisms: (25 pts) Provide a mechanism for one of the following reactions.  Use the curved arrow formalism.  Be as explicit as possible. If the mechanism of some particular step is not known, just write the reagent.  Briefly address issues of stereospecificity, regiochemistry, stereochemistry and stoichiometry as they may apply.  If you work on more than one solution, cross out the one that you do not want graded.  Two pages are provided.

 

a)  The ozonolysis of (E)-2-hexene.

b)  The reaction of (Z)-2-hexene with m-chloroperbenzoic acid and the subsequent reaction of the product with aqueous mineral acid.

c)  Epoxidation of (E)-2-hexene via the halohydrin route.

d)  Formation of an alcohol from  (Z)-3-methyl-3-hexene by the borane method.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Continued work space on the next pageÉ

 

4.  ContinuedÉ.

 

Work Sheets

Work Sheets

Work Sheets