[lrw1793]

http://imgur.com/4C5K7eQ
For this reaction, does the OEt attach, and then the fluorine leave in the next step?

The question is how would the rate change if the fluoride was replaced by chloride B. If I'm right about the mechanism then I don't understand how replacing fluorine with chlorine would change the rate. Unless it has something to do with sterics?

The last question is why couldn't the reaction go ahead with D. I've put that the intermediate would not be very stable as there are no double bonds and therefore no mesomeric effects. The negative charge could therefore not be shared and in order to attach OEt would have to love a hydrogen.
Am I along the right lines?

[Archer]

http://imgur.com/4C5K7eQ
For this reaction, does the OEt attach, and then the fluorine leave in the next step?

The question is how would the rate change if the fluoride was replaced by chloride B. If I'm right about the mechanism then I don't understand how replacing fluorine with chlorine would change the rate. Unless it has something to do with sterics?

The last question is why couldn't the reaction go ahead with D. I've put that the intermediate would not be very stable as there are no double bonds and therefore no mesomeric effects. The negative charge could therefore not be shared and in order to attach OEt would have to love a hydrogen.
Am I along the right lines?

Could you please upload your proposed mechanism. Including any resonance stabilisation mechanisms.