Organic chemistry How do you locate a stereocentre on a compound?

Question

How do you locate a stereocentre on a compound?

Answer 1

A stereocenter lacks an inversion point, mirror planes, and improper axes of symmetry. It cannot be superposed upon its mirror image by any sequence of rotations and translations. It may or may not be coincident with an atom location (e.g., helicenes). Start by looking for an sp3, tetrahedral carbon bearing four different groups.

Physical chirality of a mass distribution (anonymous points in space) can be explicitly calculated,

J. Math. Phys. 40(9) 4587 (1999)

Would you like to see a PERFECTLY chiral molecule?

http://www.mazepath.com/uncleal/chiral2.gif
http://www.mazepath.com/uncleal/chiral3.gif

Note that many of the chiral carbon atoms - the center one, for instance - have four *identical* substituents! Each substituent is homochiral. CRRRR and CSSS are nonsuperposable mirror images. Every six-membered ring is a homochiral twist-boat cyclohexane. Overall point group is T (not Th or Td).

Answer 2

I know the formula/drawing for Chlorobenzoic Acid, but I'm not to sure about how the prefix "ortho-" modifies it. "Ortho-" means "straight" or "correct," but I don't see how it would change anything here. Anyway, here's a rough ASCII sketch of the compound. ........O - H .........| ..O = C. Cl ........ | .. | ........C - C .......// .. ..\\ .. - C ....... C - .... ..\ ..... / .......C = C ........| ... | Note: Bonds attached to nothing imply a hydrogen on the other end. Ignore the periods used to space the image. One line = 1 bond, two lines = two bonds, if that wasn't clear. It's just a Benzene ring with a COOH (Carboxyl) group on one carbon, and a Halogen group (containing Cl) on the next.

Answer 3

The stereocenter is the one with 4 different groups bonded to it.

Answer 4

Look for a C atom with 4 different groups on it - not 4 different atoms.