Chemistry Department

 

University of Alberta

           

CHEM 261

 

Exam II

 

March 13, 2008

 

1. Using acceptable chemical nomenclature, provide an unambiguous name for the following compounds:

 

a.     

 

                       

                       

 

b.     

 

                       

 

                               

c.     

 

                       

 

                                           

2.  Complete the following partial structure of (R)-2-methyl-3-bromoheptane:

 

 

3. Complete the following partial Fischer structure of (2R,3S)-2,3-dibromopentane:

 

 

4. Consider the diastereoisomers of 1-bromo-4-chlorocyclohexane.

 

a.    Explain the term "diastereoisomer".

 

b.    Draw the most stable conformation of cis-1-bromo-4-chlorocyclohexane.

 

c.    Draw the most stable conformation of trans-1-bromo-4-chlorocyclohexane.

 

d.    Use the principles of conformational analysis to predict which isomer is the more stable. Explain your answer.

 

e.    Is the trans isomer chiral?

 

5. Propose a synthesis of 2,2-dimethylpentane starting from (CH₃)₃CH.  You can use any other organic compounds having a maximum of three carbons and any inorganic reagents that you wish!

 

6. Bromotrichloromethane will brominate alkanes in the presence of light. The relative reactivity of the hydrogens in this reaction (tertiary : secondary : primary) is 1600 : 82 :1. The overall reaction is shown below:

 

a.    Draw the structure of the major product of bromotrichloromethane monobromination of (CH₃)₃CH.

 

b.    Propose a mechanism for the formation of the product drawn in “a”. Do not worry about termination steps.

 

c.     Propose a mechanism to explain the light induced bromination of (CH₃)₃CH using Br₂. Do not worry about termination steps. 

 

d.    Calculate DH for the propagation steps in your mechanism from part “c”.

 

e.    Calculate DH for the analogous steps for the chlorination of (CH₃)₃CH.

 

f.     The bromination of (CH₃)₃CH using Br₂ is slowed down by the addition of fairly large amounts of HBr. Explain why this occurs.

 

g.    Why does HCl not react in this way?

 

7. What reagents would you use to effect the following conversions?

 

a.     

                       

                       

b.     

           

                       

 

8. Give the major product(s) of the following reaction:

 

           

 

               

       

 

Bond broken	DH (kJ/mol)	Bond broken	DH (kJ/mol)
H - H	436	(CH3)2CH - H	401
D - D	444	(CH3)2CH - F	439
F - F	159	(CH3)2CH - Cl	339
Cl - Cl	243	(CH3)2CH - Br	274
Br - Br	193	(CH3)2CH - I	222
I - I	151	(CH3)2CH - OH	385
H - F	570	(CH3)2CH - OCH3	337
H - Cl	432	(CH3)2CHCH2 - H	410
H - Br	366	(CH3)3C - H	390
H - I	298	(CH3)3C - Cl	330
H3C - H	438	(CH3)3C - Br	263
H3C - F	452	(CH3)3C - I	209
H3C - Cl	351	(CH3)3C - OH	379
H3C - Br	293	(CH3)3C - OCH3	326
H3C - I	234	C6H5CH2 - H	368
H3C - OH	380	CH2=CHCH2 - H	361
H3C - OCH3	335	CH2=CH - H	444
CH3CH2 - H	420	C6H5 - H	464
CH3CH2 - F	444	HCºC - H	552
CH3CH2 - Cl	338	H3C - CH3	376
CH3CH2 - Br	285	CH3CH2 - CH3	355
CH3CH2 - I	222	CH3CH2CH2 - CH3	355
CH3CH2 - OH	380	CH3CH2 - CH2CH3	343
CH3CH2 - OCH3	335	(CH3)2CH - CH3	351
CH3CH2CH2 - H	410	(CH3)3C - CH3	339
CH3CH2CH2 - F	444	HO - H	498
CH3CH2CH2 - Cl	338	HOO - H	377
CH3CH2CH2 - Br	285	HO - OH	213
CH3CH2CH2 - I	222	CH3CH2O - OCH3	184
CH3CH2CH2 - OH	380	CH3CH2O - H	436
CH3CH2CH2 - OCH3	335