According to this video, a curly arrow representing a reaction mechanism can only have its tail starting from a double bond or a lone pair.

I am wondering if the tail of a curly arrow could also start from an atom (involved in a covalent bond) having a partial negative charge ?

I ask this question because this possibility seems quite natural to me, since the head of a curly arrow can very well "attack" a partially positive charged atom.

  • 3
    $\begingroup$ I'm not sure what "curly arrow representing a reaction mechanism" means, and frankly I'm not inclined to watch a 8-minute long video. If possible, please add a screenshot. I suspect you might mean an arrow representing electron(s) flow. I'd also use a decent textbook on writing reaction mechanisms (look up OC section) (or Wikipedia) rather than YouTube. $\endgroup$
    – andselisk
    Commented Apr 23 at 10:55

1 Answer 1


This is not true in a carbocation rearrangement. Draw the electron movement for, let us say, an iso-butyl cation rearranging to a tert-butyl one. The electron pair that moves starts and ends as a carbon-hydrogen bond.


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