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Chapter 4: Alkenes*

Re: Q22 Alkenes

Postby skogias6733 » Fri Nov 26, 2021 9:29 am

Question 22 D

Hi,

I am still confused why the answer is D after reading the explanation.

This was the explanation given in the answers:
Three alkenes among the answer choices form a singular product consistent with Markovnikov's rule: 1-bromo-1,3,3-trimethylcyclohexane. The easiest way to notice the odd alkene is that 3 alkenes (answer choices A, B and D) have double bonds that include the carbon that ended up with Br. Notice that only answer choice D does not have a double bond to the carbon with the single methyl group

i understand the first part that (A, B and D all have double bonds that include the carbon that ended up with Br, which is what i got... but i dont understand the second part "Notice that only answer choice D does not have a double bond to the carbon with the single methyl group"
Isnt this the case for both C and D that they dont have double bond to the carbon with a single methyl group? What am i missing? Thank you
skogias6733
 
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Re: Chapter 4: Alkenes*

Postby goldstanda3269 » Sun Nov 28, 2021 1:44 pm

skogias6733 wrote:Question 22 D

Hi,

I am still confused why the answer is D after reading the explanation.

This was the explanation given in the answers:
Three alkenes among the answer choices form a singular product consistent with Markovnikov's rule: 1-bromo-1,3,3-trimethylcyclohexane. The easiest way to notice the odd alkene is that 3 alkenes (answer choices A, B and D) have double bonds that include the carbon that ended up with Br. Notice that only answer choice D does not have a double bond to the carbon with the single methyl group

i understand the first part that (A, B and D all have double bonds that include the carbon that ended up with Br, which is what i got... but i dont understand the second part "Notice that only answer choice D does not have a double bond to the carbon with the single methyl group"
Isnt this the case for both C and D that they dont have double bond to the carbon with a single methyl group? What am i missing? Thank you


You are not missing anything. The wording was, let's say, inelegant!

On Monday, we will change "the carbon with the single methyl group" to: carbon-1. For answer choice C, carbon-1 will have a single methyl group after the reaction with HBr but, as drawn, it does not as you correctly suggest.
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