CHAPTER 4: Question 4

 

2D explanations

There are two stereoisomers of the starting material, these are the two enantiomers shown below, and their existence is due to the stereocentre at the carbon atom shown in red in the following diagrams. The nitrogen atom can also be considered as a stereocentre. However, as discussed in the text, amines undergo rapid 'umbrella' inversion which results in interconversion of stereoisomers formed as a result of the stereocentre at the nitrogen atom. Hence, no separate stereoisomers due to the arrangement of the groups around the nitrogen atom can be isolated or detected in this type of compound.

There are however, four stereoisomers of the product. This is because the nitrogen atom is now an ammonium salt and, as discussed in the text, ammonium salts do not undergo 'umbrella' inversion. Thus, there are two stereocentres present in this compound giving a total of four stereoisomers as shown below.

back to simple answer to question 4          back to CHAPTER 4 answers

back to answers to problems          back to STEREOCHEMISTRY home page