Chapter 5.6, Problem 22CC

Molecules with a plane of symmetry between the chiral centers are achiral and meso. Determine if this molecule has a plane of symmetry and if it is meso. *****||||| A) There is a plane of symmetry in this molecule and it is achiral, but it is not meso. B) There is a plane of symmetry in this molecule and it is achiral. This molecule is meso. C) There is no plane of symmetry in this molecule and it is achiral. This molecule is not meso. D) There is no plane of symmetry in this molecule and it is chiral. It is not meso. E) There is no plane of symmetry in this molecule and it is chiral. It is meso. +

Which of these do not contain a plane of symmetry?

Inversion is not a symmetry operation of methane.Explain.

If a molecule is chiral, is it guaranteed to have a stereocentre (or multiple stereocentres)?

2. We can form a group of symmetry operations, with our operation being do one operation and do another. For a molecule with an isosceles triangle molecule like water, we talked about the 4 symmetry operations as E (do nothing), C2 (rotation by 180°), σv (the reflection of one hydrogen to the other), and σv’ (the reflection from front to back). By putting coordinates on each of the three atoms (z points along the C2 rotation axis, x points from one hydrogen to the other, and y points out of the plane of the molecule) find the “multiplication” table for this group.

Compounds with several chiral centres may have configurations referred to as meso. Meso configurations arise when the molecule can adopt a configuration with an internal mirror plane. When this occurs, the mirror image of a molecule with an internal mirror plane is an identical configuration. Thus, even though the molecule may possess several chiral centres, they are reflection of each other (within the molecule) thus resulting in an achiral meso form. This occurs for example for tartaric acid (Figure 3.1). Because of this, tartaric acid only has three stereoisomers instead of four. It has the two chiral (R,R) and (S,S) enantiomers, and the meso form. Figure 3.1. Stereoisomers of tartaric acid. Given the information above on meso forms, how many different stereoisomers do compounds A to D (Figure 3.2) have? Figure 3.2. Structure of compounds A, B, C and D.

N2O4 is planar. Show that it possesses three planes of symmetry.

Which of the following statements regarding optical rotation is not true?

Q.2Identify the symmetry elements belonging to the following molecules for the appropriate operation; and write it above the arrow (one step). B₁ B₂ B3 B3- B₂ -B₁ -B3