E2 from organic chemistry question

[joonkimdds]

according to the solution,
a) solvolysis , so it is Sn1 or E1, not E2
b) primary carbon substrate
c) CH3CH2Cl , substrate , free-radical
d) acid, base
e) tertiary carbon, strong base, heated.

answer is E and I don't understand any of the tips that are given above.

the second question is asking
"which alcohol undergoes acid-catalyzed dehydration at the fastest rate?"
and the answer is d) because it is tertiary carbon.

the tip says this is unimoleculre so C+ formed and teritiary > secondary > primary. but I don't understand this tip either.

this third question is asking which alkyl halide below will undergo most readily the loss of HCL by KOH in H2O at 100 celcius.

the tip says it is E2 and d) is the answer because it is tertiary and SN2 hinderence is the reason. but again, I don't understand this tip 🙁

Could you guys please help me?

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[Streetwolf]

I can't see the entire question in the first one so I won't even bother with it. As far as the second one goes, it will be an SN1 reaction (acid catalyzed) and that means bulkier is better. So tertiary is the best. The rate limiting step is the formation of the carbocation which is what happens when acid is added. It's all about stability. Tertiary carbons are far more stable than secondary which are far more stable than primary. Look up hyperconjugation.

And I didn't see the third one until I started replying so I'll leave that for someone else. I'm tired.

 

[joonkimdds]

I can't see the entire question in the first one so I won't even bother with it. As far as the second one goes, it will be an SN1 reaction (acid catalyzed) and that means bulkier is better. So tertiary is the best. The rate limiting step is the formation of the carbocation which is what happens when acid is added. It's all about stability. Tertiary carbons are far more stable than secondary which are far more stable than primary. Look up hyperconjugation.

And I didn't see the third one until I started replying so I'll leave that for someone else. I'm tired.

Thank you very much, I just fixed the pictures so you can see them now.
Does acid catalyze always mean Sn1 reaction?

Could someone answer the other problems please?

 

[Streetwolf]

Thank you very much, I just fixed the pictures so you can see them now.
Does acid catalyze always mean Sn1 reaction?

Could someone answer the other problems please?

Okay, for #1 they are all just properties of reactions, that's all. It's stuff you'll see in your orgo book. Just memorize it. Each answer explains why it isn't E2 by saying what's going on. So E2 likes the tertiary carbon + strong base, it also likes hinderedness if that's a word.

For #3 you want the loss of HCl which sounds like an elimination mechanism. You also have a strong base at a high temperature which really sounds like E2. So you're looking for the tertiary carbon which is in D.

If you ever had to just guess, you should immediately eliminate B and C because they are both the same type of carbon (secondary in this case). That would leave you guessing between A and D.

 

[joonkimdds]

For #3 you want the loss of HCl which sounds like an elimination mechanism. You also have a strong base at a high temperature which really sounds like E2. So you're looking for the tertiary carbon which is in D.

If you ever had to just guess, you should immediately eliminate B and C because they are both the same type of carbon (secondary in this case). That would leave you guessing between A and D.

does E2 always require strong base at a high temperature to eliminate?
what about E1? does it require weak base at a low temperature to eliminate?

 

[Streetwolf]

I'm sure somewhere online or at least in a text book there is a nice chart describing all the possible conditions, ie primary/secondary/tertiary substrate, nucleophile, basicity of nucleophile, etc and what mechanism takes place with each set of conditions. Find a table like that and study it.