Question

locate any planes of symmetry in each. please explain how to do this.

Problem 4.3 Locate any planes of symmetry in each of the following compounds. Which of the compounds! are chiral? Which are achiral? CH3 CH3 -CH₃ CH3 CH3 (a) (b) (c) (d)

Answer 1

a) It is not easy to explain how to find a symmetry plane, since it is purely based in observation. For sure, you need to pay special attention to those carbon atoms that look chiral, since the plane of symmetry will go through them (if it exists). In these cases, the compounds are not chiral, dure to the presence of the symmetry plane. Knowing that, a little bit of imagination to survey the molecule is always helpful. For example, for molecule A, the potential chiral carbon is the one at the "tip" of the molecule, with the methyl group. If looked at carefully, you will see there is a symmetry plane going through this carbon, cutting the molecule in half. It goes through that C atom and through the C-C bonds at the right and left:

The dotted lines are behind the plane, which slices the molecule in two equal halves (the methyl group at the top is also sliced in half, transversally).

b) There is a symmetry plane, although in a different direction, "cutting" the methyl group in half (I hope this is understandable):

c) and d) don't have any symmetry planes, which means they are chiral. If you try, you will not fin a symmetry plane (remember that it always has to go through the "chiral" carbon).