Answer
The $BF_3$ is an electrophile and the $CH_3CH_2CH_2$ is a nucleophile. The curved arrow mechanism is shown in the picture.
This reaction is Brønsted–Lowry acid–base reaction.
Work Step by Step
1) $BF_3$ is an electrophile because it accepts the lone pair of electrons and $CH_3CH_2CH_2$ is a nucleophile because it donates the pair of electron.
2) The curved arrow originated from the double bond between CH and $CH_2$ in $CH_3CH_2CH_2$ and goes towards the B in $BF_3$.
3) In this reaction there is no proton transfer.
Therefore, it is not a Brønsted–Lowry acid–base reaction.
