Stereochemistry and stereoisomers
Morrison and Boyd § 4.17.
The 3D models used in this page show the compounds in a particular
conformation, that differs from the drawings in Morrison & Boyd.
The latter are based on drawing convention, with all horizontal
bonds pointing in the direction of the reader. Such a structure
corresponds to an eclipsed orientation of bonds.
In this web page more realistic 3D models are used, showing e.g. the
pentane skeleton in a more stable all-trans conformation. Of course,
this choice should not affect the conclusions about the stereochemistry!
In 2,3-dichloropentane we have two carbons with each four different
substitituents: C2 and C3. Therefore,
four different structures can be made of 2,3-dichloropentane:
Arrange the structures in each pair A,B and C,D such a way that they form left and right
mirror images. Then try to rotate one structure to make it identical
('superimposable') with the three others. Which structures are mirror images, which
are diastereoisomers (=different, neither identical, nor mirror images)?
Assign R/S labels to the chiral centers.
What is the correct label for the yellow