Reaction scheme

I am supposed to explain why treatment of 2-methyltetrahydrofuran with hydrogen iodide leads to the formation of 5-iodopentan-2-ol. However, I am getting stuck as it seems that the less stable primary carbocation is being preferentially formed, leading to the product. Is my mechanism incorrect?

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    $\begingroup$ The reaction proceeds as either an $\ce {S_{N}1}$ or an $\ce {S_{N}2}$ mechanism. You need to review those mechanisms and determine which mechanism $\ce {I^-}$ would use. $\endgroup$
    – LDC3
    Commented Jul 26, 2015 at 5:34

1 Answer 1


Initially, the oxygen in the ring gets protonated. However, there is no formation of a carbocation. The ring opening proceeds by an SN2 pathway, where iodide ion attacks at the less hindered carbon:

Mechanism of reaction


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