- A2-Ethoxy-3, 3-dimethyl butane
- B1-Ethoxy-3, 3-dimethyl butane
- C2-Ethoxy-2, 3-dimethyl butane
- D2-Hydroxy-3, 3-dimethyl butane
View written solutionFree
Correct answer: C
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Write the structure of the substrate
The compound is 3-bromo-2,2-dimethylbutane.
Start from butane:
Put two methyl groups at C-2 and bromine at C-3:
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Nature of reagent/solvent
The reaction is carried out in ethanol .
In alcoholic medium, alkyl halides can undergo solvolysis/substitution. Here, since the carbon bearing Br is adjacent to a quaternary-like crowded center, ionization can be followed by rearrangement to form a more stable carbocation.
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Formation of carbocation
Loss of from
gives a secondary carbocation at C-3:
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Rearrangement of carbocation
The adjacent carbon (C-2) is highly substituted. A 1,2-methyl shift from C-2 to the carbocation center (C-3) occurs, generating a more stable tertiary carbocation.
After methyl shift, the positive charge moves to C-2:
This is a tertiary carbocation.
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Attack by ethanol
Ethanol attacks the tertiary carbocation at C-2, followed by deprotonation, giving the ether:
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IUPAC name of the product
Longest chain = butane.
Substituents:
- at C-2: ethoxy and methyl
- at C-3: methyl
Hence the product is:
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Check options
- A: 2-Ethoxy-3,3-dimethyl butane incorrect structure
- B: 1-Ethoxy-3,3-dimethyl butane incorrect
- C: 2-Ethoxy-2,3-dimethyl butane correct
- D: 2-Hydroxy-3,3-dimethyl butane alcohol not expected with ethanol as nucleophile
Therefore, the major product is Option C.
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