Ether Question

[DrRoyal Pains]

If you have benzyl ethyl ether and treat it with excess HI, you get phenol and 1-iodoethane as your products. Why cant the I attack the benzene ring and give rise to iodobenzene? Is it because it wont be able to leave due to residing on an Sp2 carbon?

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[UCSD1984]

If you have benzyl ethyl ether and treat it with excess HI, you get phenol and 1-iodoethane as your products. Why cant the I attack the benzene ring and give rise to iodobenzene? Is it because it wont be able to leave due to residing on an Sp2 carbon?

Is this from Destroyer? Sounds awfully familiar. If so, reference the problem number for me.

 

[PhansterZ]

Look at where the nucleophile can attack and how stable the leaving group is.

Case 1:
It can attack either the sp3 carbon via the Sn2 reaction, releasing phenol (a very good leaving group, pka ~10). Rather simple process with better leaving group.

Case 2:
Or it can attack the sp2 carbon on the benzyl, which only via resonance can kick out the -OC2H5 (pka ~ 17). Complicated process with worst leaving group.

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Case 1 would be favored.

 

[DrRoyal Pains]

Gotcha, thanks man. Im around question 150 in Destroyer OC and have not seen a similar problem yet. It was on Chad's handout from the section on ethers and epoxides. AMAZING scores by the way PhansterZ. I saw the link to your breakdown and had to check it out lol.