Carbocation Rearrangements
The protonation reaction shown below generates a carbocation. Using the drawing
pallet on the right, draw the structures of the initially formed carbocation on the left side of the arrow, and the structure of the most stable carbocation, following rearrangement, on the right side of the arrow.
The initially formed secondary carbocation undergoes a 1,2-hydride shift to give the more stable tertiary carbocation, as shown below.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The initially formed secondary carbocation undergoes a 1,2-methyl shift to give the more stable tertiary carbocation, as shown below. If the carbocation forms on carbon #1 of the alkene, a hydride- and a methyl-shift are necessary.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The initially formed secondary carbocation undergoes a 1,2-hydride shift to give the more stable tertiary carbocation, as shown below.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The initially formed secondary carbocation undergoes a 1,2-methyl shift to give the more stable tertiary carbocation, as shown below.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The initially formed secondary carbocation undergoes a 1,2-hydride shift to give the more stable tertiary carbocation, as shown below.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The parent hydrocarbon is a cyclohexadiene with double bonds in positions 1 and 3. A methyl group is bonded to carbon #5. Remember that the ring is numbered through the double bond in the direction to give the lowest number to the diene carbons.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The parent hydrocarbon is a cyclohexene. Two bromines are bonded to carbons #3 and 6 and the the stereochemistry of these groups is trans-, that is, on opposite sides of the ring plane. Be sure to show stereochemistry using the "wedge bond".
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The parent hydrocarbon is a cycloheptatriene with double bonds in positions 1, 3 and 5. A methyl group is bonded to carbon #7. Remember that the ring is numbered through the double bond in the direction to give the lowest number to the diene carbons.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
The parent hydrocarbon is a cyclopropene. A methyl group and an ethyl group are bonded to carbon #3 and the ring is numbered through the double bond in the direction to give the lowest number at the first point of difference.
Using the drawing
pallet on the right, draw the structure of the major organic product for the reaction shown below:
When a carbocation intermediate is generated in a reaction, and that intermediate has a sufficient lifetime in the reaction mixture, a skeletal rearrangement can occur. Rearrangements are most favorable if the initially formed carbocation is adjacent to a carbon in the molecule that can transfer a hydride or alkyl anion to the positive center and, in doing so, generate a more stable carbocation. Rearrangements from non-adjacent centers also occur, but product mixtures are more common in multiple step rearrangements. Recall that, in general, carbocations adjacent to heteroatoms with unshared pairs of electrons are the most stable, followed by carbocations which are stabilized on other carbons by resonance, followed by alkyl carbocations in the order, tertiary, secondary and primary.
That is correct!
Sorry, that is
not correct. You should modify your structures and try again. Remember to draw only the carbocations in the window. The positive charge in the initially formed carbocation should be on the carbon of the alkene which is closest to the more stable carbocation center. Please make sure the structures are on the proper sides of the arrow and that the "X" atom window has the text string [C+].
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Note: Use NEW to begin drawing a second molecule. To enter a positive carbon, use the "X" atom and enter [C+] in the window.
Be sure to completely clear the window before typing (Right Arrow, Delete, Delete).
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