Later, a solid wedge was used to indicate a substituent oriented above the plane. It was an improvement over the earlier representation because the wedge starts as a thin wedge and gradually gets thicker as it moves up towards the viewer. This gives a three-dimensional impression of the substituent as being projected above the plane towards the viewer.

However, to indicate the orientation of the substituent lying below the plane of the paper, a broken wedge is typically used, originating as a thin broken wedge and becoming thicker as it goes away from the viewer.

This kind of representation is commonly seen in many popular chemistry books (1) and prestigious journals (2–5) too (probably for the sake of convenience in its drawing). From a purist’s point of view this seems like a misrepresentation. If a substituent is to be shown as lying below the plane of the paper it should be more appropriately indicated by an “inverted broken wedge”.

In this case, the substituent originates with thicker side of broken wedge and gets thinner as it goes away from the viewer as has been described by Morrison and Boyd (6). Alternatively, a simple dotted line representation should be used.

Literature Cited

1. Solomons, T. W. G.; Fryhle, C. B. Organic Chemistry, 7th ed.; John Wiley & Sons, Inc.: New York, 2002, p 45.
2. Clark, T. P.; Landis, C. R. J. Am. Chem. Soc. 2003, 125, 11792.
3. Stabile, R. G.; Dicks, A. P. J. Chem. Educ. 2003, 80, 1439.
4. Zhu, S.; Hudson, T. H.; Kyle, D. E.; Lin, A. J. J. Med. Chem. 2002, 45, 3491.
5. Han, J.; Lee, J.-G., Min, S.-S.; Park, S.-H.; Angerhofer, C. K.; Cordell, G. A.; Kim, S.-U. J. Nat. Prod. 2001, 64, 1201.
6. Morrison, R. T.; Boyd, R. N. Organic Chemistry, 6th ed., Prentice-Hall, Inc.: New Jersey, 1992, p 40.