Orgo question about leaving groups

[Dandpez337]

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I'm studying with 2010 Destroyer. I'm doing pretty good but I have a question about the leaving groups.

For #50, one reaction is 3-chloropentane reacted with Sodium Iodide in Acetone. Why does this go forward considering Iodine is a better leaving group than chlorine? Is it because the acetone protonates the Cl as it leaves?

 

[Demps]

Better leaving group = more stable anion when it leaves the carbon

bigger the atom, more stable for anions

I is bigger than Cl in size so I- is more stable than Cl-... so I is the better leaving group.

 

[Vaheb]

I'm studying with 2010 Destroyer. I'm doing pretty good but I have a question about the leaving groups.

For #50, one reaction is 3-chloropentane reacted with Sodium Iodide in Acetone. Why does this go forward considering Iodine is a better leaving group than chlorine? Is it because the acetone protonates the Cl as it leaves?

Iodine is a good nucleophile and it attacks the Carbon which is occupying the Chlorine because it has electrophilic properties. Iodine does a backside attack on the Carbon, forcing the Chlorine to leave.

Remember NaI is really Na+ and I-, Na is just a spectator ion, while the I- is the one doing all the work.