2-bromobutane reacts with cyanide

[Coco Hailey 2E]

In the equation

CH3CHBRCH2CH3 + CN(-) ---> CH3CNCHCH2CH3 + Br(-),

which I'm guessing the naming would be 2-bromobutane + cyanide yields 2-cyanobutane + bromide,

specifically which atom in the cyanide ion is the nucleophile? Is it the carbon or the nitrogen and why?

[Chem_Mod]

If you draw the lewis structure of cyanide, you'll find that carbon has a lone pair and is making a triple bond. Therefore the C atom is negatively charged so it is the more nucleophilic end of cyanide. Note that there is also a lone pair on the nitrogen atom so in some cases, the N atom is making that bond. You can tell the difference because the molecule will be written as ---CN (attached by the C) or as ---NC (attached by the N).