Friedel craft alkylation halo-carbon bond cleavage

[![enter image description here](https://i.stack.imgur.com/bDUdj.png)](https://i.stack.imgur.com/bDUdj.png)


In this reaction, why is the $\ce{C-F}$ bond broken instead of the $\ce{C-Cl}$ 
bond, even though $\ce{C-F}$ bond is stronger than the $\ce{C-Cl}$ bond?




In Friedel-Crafts alkylation, the halogen-carbon bond breaking depends on the strength of bond between halogen atom and the Lewis acid used. The more stronger is the bond, the easier it is to generate a carbocation for the reaction.( In all cases, the carbocation exoplicitly needn't have to generate, a strong $\delta$+ charge on the electrophilic carbon is sufficient enough to have a $\ce{S\_E2}$ or $\ce{S\_E1}$ type reaction.   
Here, the Lewis acid used is $\ce{BCl\_3}$ where there is a vacant $\ce{2p\_z}$ orbital on the $\ce{B}$ atom,(Assuming, the molecule is oriented in a triangle in the $\ce{xy}$-plane.)and the Lewis base is the given reagent **1-chloro-3-fluoropropane**., which has two Basic centre. But donation through $\ce{F}$ will correspond to a stronger $\ce{2p$\pi$ -2p$\pi$}$ overlap with Lewis acid,rather than weaker $\ce{3p$\pi$ -2p$\pi$}$ overlap in the case of donation through $\ce{Cl }$ atom. Thus bonding with $\ce{F}$ will correspond to a very huge amount of $\ce{-I}$ effect of the adjacent carbon atom which will weaken the bond between them by pulling the electron pair towards $\ce{F}$ and easily favour the attack by the $\pi$-electron cloud of Benzene ring.Also, the repulsion between $\pi$-electron cloud and the large sized $\ce{Cl}$ atom is very less during the formation of the above compound. But, if it would have bonded through $\ce{Cl}$, there won't be a great electrophilic nature of the adjacent carbon due to less effective bonding in the case of $\ce{Cl}$(corresponding to even lesser $\ce{-I }$ effect),so attacking will correspond to a highly energetic transition state, and also, there will be a slight electrostatic repulsion with the $\ce{F}$ atom of the $\ce{$\pi$ }$-electron cloud.   

Due to such above mentioned phenomena and energetically favoured conditions, bonding through cleavage of $\ce{C-F}$ bond is more preffered over cleavage of $\ce{C-Cl}$ bond.


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