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Topic: Ranking organic chloride reactivity toward SN1  (Read 327 times)

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Offline yogurtspoon

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Ranking organic chloride reactivity toward SN1
« on: November 18, 2020, 12:38:00 PM »
This is what I have so far, in order of decreasing reactivity toward SN1:
1) (1-chloroethyl)benzene
2) tert-butyl chloride
3) 2-chlorobutane
4) Benzyl chloride
5) 1-chlorobutane

I'm unsure about my ranking for benzyl chloride. I don't know whether its carbocation would be more or less stable than 2-chlorobutane and/or 1-chorobutane.

I initially thought that tert-butyl chloride would be the most reactive toward SN1 since it forms a tertiary carbocation. But right now I have (1-chloroethyl)benzene first because the carbocation is stabilized by resonance. But now that I think about it, the resonance structure would disrupt the aromaticity of the ring right? So maybe tert-butyl chloride would be the most reactive after all?

I discussed it with a friend and she said she found a textbook source that said tert-butyl and (1-chloroethyl)benzene would have the same reaction rate. But Idk if our professor would accept that as an answer, so I thought I would ask for more opinions.

Thanks in advance to anyone who offers help.
« Last Edit: November 18, 2020, 01:52:47 PM by yogurtspoon »

Offline rolnor

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Re: Ranking organic chloride reactivity toward SN1
« Reply #1 on: November 19, 2020, 02:24:40 PM »
I would go 1, 2,4,3,5. Its a little tricky because benzylchloride I think is a good SN2-electrophile as well but t-butylchloride is really bad and will give only SN1. But I think a benzyl cation is more stable than a 2-butylcation. Maybe its a trick-question and, as you suggest, 1 and 2 are very similar.

Offline AWK

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AWK

Offline rolnor

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Re: Ranking organic chloride reactivity toward SN1
« Reply #3 on: November 19, 2020, 04:08:33 PM »
Thanks AWK. The question of the order of these componds is not so easy to answer then, I really dont know.

Offline AWK

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Re: Ranking organic chloride reactivity toward SN1
« Reply #4 on: November 19, 2020, 04:28:05 PM »
First of all, the question is too general and there are no specific reaction conditions.
You can even write a book about it.
A comparison of the reactivity of compounds 2,4,5 is included in every textbook, but not every textbook already states that comparisons should be made under identical conditions.
Moreover, the mixed nomenclature is offensive.
AWK

Offline rolnor

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Re: Ranking organic chloride reactivity toward SN1
« Reply #5 on: November 20, 2020, 11:01:04 AM »
I still think the question is interesting, is a benzylic position likely to react SN1 or SN2 and how does this vary depending on nucleophile, solvent etc. compared to a tertiary or secondary alkyl-position. I would be a interesting book.

Offline yogurtspoon

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Re: Ranking organic chloride reactivity toward SN1
« Reply #6 on: November 28, 2020, 10:06:05 AM »
Just to update since I got the assignment graded:

The accepted answer was 1, 2, 3, 5, 4. He also accepted 1=2, 3, 5, 4. And he gave partial credit for anyone who had either 1 or 2 first. He said that 4 should be last because it forms a vinylic carbonation, and that makes it less reactive / non-reactive? toward SN1.

First of all, the question is too general and there are no specific reaction conditions.
You can even write a book about it.
A comparison of the reactivity of compounds 2,4,5 is included in every textbook, but not every textbook already states that comparisons should be made under identical conditions.
Moreover, the mixed nomenclature is offensive.

Yeah, unfortunately this was the only information he gave us with the question. Apologies for the mixed nomenclature haha, he only gave us the structures of the compounds and I'm crap with naming. Thanks for the link to the article by the way.

Offline yogurtspoon

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Re: Ranking organic chloride reactivity toward SN1
« Reply #7 on: November 28, 2020, 10:10:12 AM »
Okay, so I just realized I proved how awful I am at naming. Should've been chlorobenzene instead of benzyl chloride. Now rolnor's answer makes more sense, haha...

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