Easy Orgo question

[rah08e]

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n-propyl chloride reacts with KOH (a strong, protic BASE). Is this reaction SN1? It can't be SN2 because KOH is protic, right?


I'm confused because the answer says that the product is Propene, but if this is SN1, won't you also get some of the substitution product?

 

[needzmoar]

n-propyl chloride reacts with KOH (a strong, protic BASE). Is this reaction SN1? It can't be SN2 because KOH is protic, right?


I'm confused because the answer says that the product is Propene, but if this is SN1, won't you also get some of the substitution product?

KOH isn't protic. The product should be mostly SN2 if it's a primary halide.

 

[rah08e]

KOH isn't protic. The product should be mostly SN2 if it's a primary halide.

Yeah thats what I thought. This is a kaplan question. My answer was n-propyl alcohol since a strong base will react with a primary halide via SN2.

 

[needzmoar]

Yeah thats what I thought. This is a kaplan question. My answer was n-propyl alcohol since a strong base will react with a primary halide via SN2.

yeah, I saw a few errors in the p.exam from the KBB

 

[LetsGo2DSchool]

n-propyl chloride reacts with KOH (a strong, protic BASE). Is this reaction SN1? It can't be SN2 because KOH is protic, right?


I'm confused because the answer says that the product is Propene, but if this is SN1, won't you also get some of the substitution product?

Also, you can run SN2 rxn in protic solvent. It just won't react as fast as it would in aprotic.

But with SN1, it needs protic for sure though.

 

[needzmoar]

also, you can run sn2 rxn in protic solvent. It just won't react as fast as it would in aprotic.

But with sn1, it needs protic for sure though.

+1

 

[rah08e]

+1

Okay so to clarify..... primary alkyl halide + KOH ---> primary alcohol via SN2?

 

[Demps]

Okay so to clarify..... primary alkyl halide + KOH ---> primary alcohol via SN2?

Correct

 

[impact2d]

I hate to revive a dead thread, but I was just searching for the answer to this very same problem and it was just explained correctly to me. I don't want someone searching for the answer to be steered in the wrong direction, and it doesn't seem to have been answered correctly anywhere on SDN> The key to this question is that the reaction is happening in protic solvent.

We already know a primary RX is not stable enough to undergo E1/Sn1; thus the competing reactions are E2/Sn2. The trick in this question is the following: Sn2 is severely inhibited by protic solvents, that is why when used with a secondary RX it favors Sn1. E2 is only marginally inhibited by protic solvents; thus, elimination is the favored mechanism.

In Summary, the key was the solvent, Substitution and Elimination are always competing, and a primary RX in a strong base usually let's substitution win out-but using an Sn2 inhibiting solvent allows elimination to win.

 

[TXpredent]

wait I'm confused, so the reaction mechanism is E2 here and not SN2 like they said earlier?

 

[Dotoday]

The substitution product is minor since the only across ion is in a strong base. If it was a good nucleophile like cn, it could have been Sn2. Hope this helps.

Sent from my MB855 using Tapatalk

 

[biomolecmed]

as a rule of thumb. Whenever you have a strong base, think elimination. Since this is a primrimary halide, think E2.

 

[ttpharm]

KOH is protic........