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I have got a very clear idea about Swarts reaction for monohalo compound. But I found the following reaction in Chrome Swarts reaction

Now, my question is why are 2 products formed? Secondly why is there no trifluoro compound? What is the possible mechanism for this reaction?

Source: https://protonstalk.com/wp-content/uploads/2021/02/image1-e1612596758363.png Source of the image

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  • $\begingroup$ Do you have a reference for just mono-fluorination of multi-chlorinated compounds? I'm finding otherwise. Just see here. $\endgroup$ Jun 21, 2023 at 20:08

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Since $\ce{SbCl5}$ is a Lewis acid, we can consider a carbocation mechanism.

In the first stage, a chlorine atom is preferentially taken off the $\ce{CCl2}$ carbon because then the carbocation is stabilized by pi back-donation from the other chlorine. The antimony in $\ce{SbF3}$, being in a lower oxidation state and less acidic than its counterpart in $\ce{SbCl5}$, gives off a fluoride ion to restore neutrality to the organic compound.

In the second stage, the carbocation is stabilized by pi back-donaation from the fluorine, which is very electronegative but has available electrons and good overlap with the carbon. The $\ce{R}$ group lacks lone pairs and is less effective at stabilizing the carbocation, so difluorination at what was originally the $\ce{CCl2}$ carbon is a likely end point.

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