SN2 of Cyanide with Alkyl Halides to give Nitriles
Description: Alkyl halides (or tosylates) will react with cyanide ion to give alkyl cyanides (nitriles) in an SN2 reaction. [private_ReactionGuide]
Notes: X here is a halide (Cl, Br, I) or sulfonate (OTs, OMs, OTf). Any alkali metal can be used (Li, Na, K…) as the counter-ion for the CN. For our purposes the exact identity is unimportant.
Notes: Note that since this is an SN2 reaction and proceeds via backside attack, there will be inversion of configuration at the carbon (note the last two examples).
Mechanism: In the SN2 reaction the nucleophile CN(-) attacks the carbon with the good leaving group (C-1 in this case), displacing chloride ion int this example (Step 1, arrows A and B). The reaction is concerted, meaning both steps occur at the same time.
Notes: As with all SN2 reactions, the reaction is facilitated by a polar aprotic solvent such as DMSO, acetone, or acetonitrile.