Predicting order of nucleophilic substitution reactivity What order of reactivity do you predict will be observed when each alkyl halide is mixed with sodium iodide in acetone?
  
  
  1-Chlorobutane
  1-Bromobutane
  2-Chloro-2-methylpropane
  Bromobenzene
  2-Chlorobutane
  1-Chloro-2-butene
  
  


I know that $\ce{I-}$ is the best leaving group, followed by $\ce{Br-}$ and $\ce{Cl-}$.
For the $\ce{NaI}$ reaction, tertiary halides should react fastest and primary halides should react slowest.


  
  What order of reactivity do you predict will b observed when each alkyl halide is mixed with silver nitrate in ethanol?
  
  
  1-Chlorobutane
  1-Bromobutane
  2-Chloro-2-methylpropane
  Bromobenzene
  2-Chlorobutane
  1-Chloro-2-butene
  
  


For the $\ce{AgNO3}$ reaction, primary halides should react fastest and tertiary halides should react slowest.

Which takes preference, leaving group or rank? Also, how do I rank 1-chlorobutane vs. 1-chloro-2-butene? They are both primary and the halide is $\ce{Cl-}$ for both.
Acetone a is aprotic polar solvent which is often used as solvent for $\ce{S_{N}2}$ reactions (notably in conjunction with $\ce{NaI}$ as in the Finkelstein reaction). For $\ce{S_{N}2}$ reactions steric hindrance and leaving group capability is of great importance, so primary halides will be usually easier replaced by iodine then tertiary.
$\ce{AgNO3}$ will probably react as a base forming nitric acid. Even though nitric acid is a rather strong acid this is more likely than $\ce{NO_3-}$ acting as nucleophile. Besides that, $\ce{Ag+}$ is known to have a unique selectivity for halogens and will attack them readily, forming $\ce{AgX}$ and a carbocation, hence promoting $\ce{E 1}$/$\ce{S_{N}1}$.