Video Solution: Select the compound in each of the following pairs that will...

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Select the compound in each of the following pairs that will be converted to the corresponding alkyl bromide more rapidly on being treated with hydrogen bromide. Explain the reason for your choice.

 (g) 1-Cyclopentylethanol or 1-ethylcyclopentanol 

Video Transcript

Hey everyone. So, in this question we;re going to be looking at these two compounds and figure out which one's going to be more reactive towards hydrogen bromide to get the corresponding alkyl bromide, so that means, just think of both of these compounds reacting with HBr and note that you may have been confused on how to draw them because their names almost look like they were incorrect but what they were trying to indicate is that for the first one it says, 1-cyclo penta ethanol, so the route is ethanol, which is this group right here and then coming off our position number one we have a cyclo penta group. Now, for the next one we have cyclopentanol as our group, so that's going to be this right here, and then coming off position one, which is this one, we have an ethyl group, okay? So I hope that cleared things up. Now, if we were able to draw them correctly you would see that we're comparing 2 different alcohol groups, we have one right here coming off of this carbon and we have one right here coming off of this carbon. Now, the alcohol reactivity has a trend that we should definitely commit to memory, we know that tertiary alcohols are going to react the fastest, secondary alcohols will come next and then we have our primary. So, really we're actually comparing 2 different types of alcohols, one of them secondary and the other ones tertiary, which one is which? well this one's secondary, right? Because the two carbons are at this one in this one and the one on the right is actually tertiary because the carbons we're looking at is this one, this one and the ethyl group carbon, okay? So you'd see that our 1-ethyl cyclopentanol group is actually going to be the compound that's going to be more reactive towards our hydrogen bromine, okay? Because its tertiary. Alright, so I hope that makes sense and now let's take a look at our next question.

Rank the substrates below in terms of relative SN1 reaction rate. (1 = fastest, 4 = slowest)

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For the following carbocations, rank them from 1-3 according to overall carbocation stability, with a 1 under the LEAST STABLE CARBOCATION and a 3 under the MOST STABLE CARBOCATION.

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When 2-methylbutene is reacted with hydrochloric acid, where does the carbocation form and why?

1. The carbocation forms at the tertiary position because of steric hindrance.

2. The carbocation forms at the secondary position because of hyperconjugation from neighboring carbons.

3. The carbocation forms at the primary position because nature says so.

4. The carbocation forms at the tertiary position because of hyperconjugation from neighboring carbons.

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Rank the following molecules in order of increasing relative rate of SN1 solvolysis with methanol and heat (slowest to fastest reacting).

A) 5 < 4 < 3 < 2 < 1

B) 1 < 2 < 5 < 4 < 3

C) 2 < 3 < 4 < 1 < 5

D) 3 < 2 < 4 < 5 < 1

E) 2 < 3 < 4 < 5 < 1

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Circle the correct answer

 

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The following statements are true. Choose from among the following three possibilities and in the space provided, write the letter of the one or more phenomena that best explain the true statement.

A. The inductive effect     B. Hyperconjugation     C. Resonance delocalization of a charged species

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The driving force for carbocation rearrangements is that the less stable 2° carbocation is converted into a more stable 3° carbocation ( True or False )

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Identify which of the following substrates will undergo an SN1 reaction more rapidly. Explain your choice

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Which two compounds ionize with loss of bromide ion to form the same carbocation?

a. 1 and 2

b. 2 and 3

c. 1 and 4

d. 3 and 4

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Which alcohol is dehydrated fastest in concentrated H2SO4?

 

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Which carbocation is the most stable?

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Rank the following carbocations in order of stability: 

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