be made selectively from an alkyne? If so, which alkyne?1038.This question would be appropriate for use after a unit on oxymercuration and hydroboration-oxidation. The instructor can use the hints that follow, soliciting suggestions from students at each step. The suggestions that follow each hint below were made by students during the lecture. The bolded suggestions are the suggestions that will lead to the selective synthesis of the alkyne.
Can this ketone
be made selectively from an alkyne? If so, which alkyne?
Possible hints with which the instructor can lead the class include:
What are possible alkynes that might be considered for this synthesis?
A. 
B.
What are possible reagents?
HgSO4, H2O
H2SO4, H2O
BH3 followed by H2O2 and NaOH (This suggestion would not give the correct product.)
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1039. The instructor can
use the hints that follow, soliciting suggestions from students at each
step. The suggestions that follow each hint below were made by students
during the lecture. The bolded suggestions are the suggestions that will
lead to the structure of allene and what the 
-bonds look like.
What is the structure of allene,
,
and what do its - bonds look like?
Possible hints with which the instructor can lead the class include:
Ethylene,
is planar and its - bonds are:
Possible structures of allene include:
A. 
or B. 
Possible - bonds include:
A.
or B. 
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Cortisone
contains how many alcohols? 2
How many ketones? 3
How many ethers? 0
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The selective synthesis of specific stereoisomers of epoxides can be
performed using enantiomers of Jacobsen's catalyst and subtle changes in
reaction conditions. Stereoisomers of phenylpropylene oxide,
, can be made this way.
What are the structures and names of the phenylpropylene oxide stereoisomers?
Possible hints with which the instructor can lead the class include:
How many stereo centers are there? 1, 2, 3
How many stereoisomers are there? 1, 2, 4, 6
What are their structures?
Ph=
Me= CH3
Which are mirror images of each other?
and
What are the configurations at each stereo center?
So, the names are:
R, R-PPO; S,S-PPO; R,S-PPO; S,R-PPO
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Would the products of this reaction retain the optical activity?
Hints with which the instructor can lead the class include:
Which hydrogens can be abstracted?
1,2,3,4,5,6,7,8
What are the structures (including resonance stabilization) for these radicals?
when hydrogen 3 or 4 is abstracted and
when hydrogen 8 is abstracted.
What are the products from the bromination of each radical?
The products from the abstraction of hydrogens 3 and 4 are:
The products from the abstraction of hydrogen 8 are:
Do the products have any optical activity?
Because the radical that is formed from the abstraction of hydrogen 8 is achiral, there is no preference for any of the enantiomeric forms of the products to form. The mixture of products, then, is not optically active. The radical that is formed when hydrogens 3 and 4 are abstracted retains its chirality, and there will be some preference for certain enantiomeric forms. Therefore, this mixture will be optically active.
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