Letter pubs.acs.org/jchemeduc
A Supplement to the “Historical Origins of Stereochemical Line and Wedge Symbolism” Andrew P. Dicks* Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6 Canada ABSTRACT: Clarification is provided regarding IUPAC recommendations on representing molecules in three dimensions, specifically with reference to drawing chemical bonds as “hatched” wedges. KEYWORDS: First-Year Undergraduate/General, Second-Year Undergraduate, Textbooks/Reference Books, Stereochemistry
■ ■
I
ACKNOWLEDGMENTS The author wishes to thank Randall J. Wildman for assistance in preparation of this letter.
read with interest the communication by William B. Jensen entitled “The Historical Origins of Stereochemical Line and Wedge Symbolism” in a recent issue of this Journal.1 The use of horizontally “hatched” or “broken” wedges to represent receding bonds is discouraged, particularly when drawn with the “thin end of the wedge” closest to the viewer. A previous letter proposed that an “inverted broken wedge” (1) or a “simple dotted line representation” (2) should be used to indicate a substituent lying below the plane of the paper.2
REFERENCES
(1) Jensen, W. B. The Historical Origins of Stereochemical Line and Wedge Symbolism. J. Chem. Educ. 2013, 90, 676−677. (2) Kapoor, V. K. Use Correct Projection. J. Chem. Educ. 2005, 82, 838. (3) Brecher, J. Graphical Representation of Stereochemical Configuration. Pure Appl. Chem. 2006, 78, 1897−1970. (4) Moss, G. P. Basic Terminology of Stereochemistry. Pure Appl. Chem. 1996, 68, 2193−2222. http://www.chem.qmul.ac.uk/iupac/ stereo/intro.html (accessed July 2013). (5) Cram, D. J.; Hammond, G. S. Organic Chemistry; McGraw-Hill: New York, 1959.
It is significant for the chemistry community to note that the International Union of Pure and Applied Chemistry actually recommends orienting both solid and hatched wedges with the narrow ends at a stereogenic center (3).3 This supersedes the 1996 preference that was stated as follows: “bonds to atoms below the plane are (to be) shown with short parallel lines” (4).4 Moreover, use of a dotted or dashed line (as in Cram and Hammond’s 1959 textbook5 and several others of more recent vintage) is considered unacceptable, as this “should be reserved for the indication of partial bonding of various types, including hydrogen bonding. It should not be used to represent configuration.”3
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest. © XXXX American Chemical Society and Division of Chemical Education, Inc.
A
dx.doi.org/10.1021/ed400249y | J. Chem. Educ. XXXX, XXX, XXX−XXX
