The discussion clarifies the roles of $C{H}_{3}Cl$ in organic chemistry, establishing it as an electrophile due to the polarization of the chlorine atom when bonded to the methyl group. The chlorine atom, while negatively polarized near the carbon, exhibits a positive charge on the exterior, making the entire molecule an electrophile. The chlorine can only act as a nucleophile when it exists as a $\ce{Cl-}$ ion, which occurs when it loses an electron. The conversation emphasizes that chlorine typically does not act as an electrophilic site in standard organic reactions.
PREREQUISITESChemistry students, organic chemists, and anyone interested in understanding the behavior of electrophiles and nucleophiles in chemical reactions.
MermaidWonders said:Stupid question here, but why wouldn't it be possible for $C{H}_{3}Cl$ to act as a nucleophile also since it has a nucleophilic site at the chlorine due to it being negatively-polarized when attached to methyl group?
I like Serena said:With the chlorine bound to the methyl group, it's single valence electron is near the methyl group.
Consequently, on the outside of the molecule, the chlorine is slightly positive charged, and attracts an electron.
It makes the molecule as a whole an electrophile.
If the chlorine atom would actually bind a lose electron, it would detach itself and form a $\ce Cl^-$ ion, which is a nucleophile.
MermaidWonders said:Wait... doesn't the polar bond between C and Cl result in Cl being negatively-polarized?
I like Serena said:A $\ce Cl$ atom on its own is neutrally charged.
When it bonds to $\ce C$, the electron in its outer shell moves to the $\ce C$ atom.
So it's indeed negatively polarized near the $\ce C$-atom, but at the same time it is positively polarized on the other side, which is the outside of the molecule.
Attractions to other particles happen on the outside of the molecule.
MermaidWonders said:Ah, I see now. :) So if the whole molecule is an electrophile overall, is there a case where the Cl atom serves as the electrophilic site? It's just that with the problems I've encountered so far, I'm used to seeing the C atom acting as the electrophilic site and Cl the nucleophilic site but never the Cl atom yet...
I like Serena said:A $\ce{Cl}$ atom doesn't (normally) occur on its own. If it does we call it a radical meaning it will immediately react with anything that comes nearby.
Instead we'll either have a $\ce{Cl2}$ molecule, which is electrophilic.
Or we'll have a $\ce{Cl-}$ ion, which is nucleophilic.