Problem: Sodium cyanide reacts with 2-bromobutane in dimethylsulfoxide to form a substitution product. Identify the configuration of the 2-bromobutane structure shown below. Then draw the substitution product formed when this enantiomer reacts with NaCN in DMSO, and indicate the stereochemistry of the product.Use wedge-and-dash bonds to show stereochemistry, and show explicitly the hydrogen on any asymmetric carbon. a) (R)-2-bromobutaneb) (S)-2-bromobutaneThe substitution product is: a) R b) S c) racemic d) achiral 

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FREE Expert Solution

Recall that SN2 mechanism is favored: 

  • strong nucleophile → NaCN
  • aprotic solvent → DPSO 




When H is at the back (dash):

  • Higher atomic number → higher priority (1- highest, 4 - lowest)
  • S – counterclockwise
  • R – clockwise
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Problem Details

Sodium cyanide reacts with 2-bromobutane in dimethylsulfoxide to form a substitution product. Identify the configuration of the 2-bromobutane structure shown below. Then draw the substitution product formed when this enantiomer reacts with NaCN in DMSO, and indicate the stereochemistry of the product.

Use wedge-and-dash bonds to show stereochemistry, and show explicitly the hydrogen on any asymmetric carbon. 

a) (R)-2-bromobutane

b) (S)-2-bromobutane


The substitution product is: 

a) R 

b) S 

c) racemic 

d) achiral 



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Our tutors have indicated that to solve this problem you will need to apply the Substitution Comparison concept. You can view video lessons to learn Substitution Comparison. Or if you need more Substitution Comparison practice, you can also practice Substitution Comparison practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Rowland's class at OLE MISS.