Site hosted by Angelfire.com: Build your free website today!

Survey of Wedge Conventions used in Selected Organic Textbooks

(From: Those “Dash-ed!” Wedges: The Use of Nomenclature/Structure Software in the Teaching/Learning of Structural Organic Chemistry. April 7-11, Orlando, FL, USA, ACS Spring 2002

Bert Ramsay, Department of Chemistry, Eastern Michigan University, Ypsilanti, MI 48197, (734) 487-0426, Bert.Ramsay@emich.edu; and Antony Williams and Andrey Erin, Advanced Chemistry Development, 90 Adelaide Street West, Suite 600, Toronto, Canada, M5H 2L3, 416-368-3435 tony@acdlabs.com, erin@acdlabs.ru.)

 

Many students taking beginning organic chemistry have difficulty in determining and “seeing” the configuration about a stereogenic carbon presented in structures drawn with “dash-wedge” bonds. It is also not clear to the student whether it makes any difference if the wedges are drawn with any “shape”. Formula I shows a dashed wedge drawn with the “correct” perspective; II with an “incorrect” perspective.27 The graphical representation recommended by the IUPAC in 1996 is shown in formula IV.26 (There does not seem to be much sentiment to use such inverted solid wedges.28 ) Although IUPAC does not recommend the use of a broken line (III) or the tapered dashed wedge (I and II), the authors of many organic textbooks still use them (see below). The situation is further complicated by the lack of agreement among organic textbook authors as to the correct method of drawing the bond behind the plane of the paper. The conventions used in several textbooks for representing (2R)-2-bromobutane are shown below.

 

 

Dashed Wedge

Dashed Wedge

Dashed Line

Dashed Bar

Organic Chemistry textbooks

1, 2, 6a, 8, 10, 11,13, 15, 19

4, 5, 12, 16

7, 14, 17, 18

3, 4, 9, 6b

Stereochemistry texts

22

 

20, 21b, 22,23, 24, 25

21a

 

References:

  1. Adkins, R.C. and Carey, F.A., Organic Chemistry: A Brief Course (3rd Edn.), 2002 [McGraw-Hill]
  2. Bailey, Jr., P.S. and Bailey, C.A., Organic Chemistry: A Brief Survey of Concepts and Applications (6th Edn.) 2000 {Prentice-Hall]
  3. Boxer, R., Essentials of Organic Chemistry, 1997 [Wm. C. Brown]
  4. Brown, W.H. and Foote, C.S., Organic Chemistry (3rd Edn.) 2002 [Saunders]
  5. Bruice, P.Y., Organic Chemistry (3rd Edn.) 2001 [Prentice-Hall]
  6. a) Carey, F.A., Organic Chemistry (4th Edn.) 2000; b) Carey, F.A. and Sundberg, R.J., Advanced Organic Chemistry (3rd Edn.) 1990 [Plenum]
  7. Eğe, S.M., Organic Chemistry (4th) 1999  [Houghton-Mifflin]
  8. Fessenden, R.J. and J.S., Organic Chemistry (6th) 1998  [Brooks-Cole]
  9. Fox, M.A. and Whitesell, J.K., Organic Chemistry (2nd) 1997  [Jones and Bartlett]
  10. Hart, H., Craine, L., Hart, D.J., Organic Chemistry: A Short Course (10th) 1999 [Houghton-Mifflin]
  11. Johnson, A.W., Invitation to Organic Chemistry, 1999 [Jones and Bartlett]
  12. Jones, Jr., M., Organic Chemistry (2nd) 2000  [W.W. Norton]
  13. Louden, M.C., Organic Chemistry (3rd) 1995 [Brooks-Cole]
  14. McMurray, J., Organic Chemistry (5th) 2000 [Brooks-Cole]
  15. Morrison, R.T. and Boyd, R.N., Organic Chemistry (6th) 1992 [Prentice-Hall]
  16. Solomons, G. and Fryhle, C., Organic Chemistry (7th) 2000  [Wiley]
  17. Streitweiser, A., Heathcock, C.H., Kosower, E.M., Introduction to Organic Chemistry (4th) 1992  [MacMillan]
  18. Vollhardt, K.P.C. and Schore, N.E., Organic Chemistry: Structure and Function (3rd) 1999  [W.H. Freeman]
  19. Wade, Jr., L.G., Organic Chemistry (4th) 1999 [Prentice-Hall]
  20. Allinger, N.L. and Allinger, J., Structures of Organic Molecules, 1965  [Prentice-Hall]
  21. a) Eliel, E.L. and Wilen, S.H., Stereochemistry of Organic Compounds, 1994 [Wiley], b) Eliel, E.L., Stereochemistry of Carbon Compounds, 1962 [McGraw-Hill]
  22. Juaristi, E., Introduction to Stereochemistry and Conformational Analysis, 1991 [Wiley]
  23. Kagan, H., Organic Stereochemistry, 1979 [Wiley]
  24. Mislow, K., Introduction to Stereochemistry, 1965 [W.A. Benjamin]
  25. Natta, G. and Farina, M., Stereochemistry, 1968

 

Stereochemical Nomenclature and Automatic Naming Software

  1. IUPAC, Basic Terminology of Stereochemistry, (Recommendations 1996), Pure Appl. Chem., 68, 2193-2222 (1996)

 “…Bonds to atoms above the plane are shown with a bold wedge ◄ (starting from an atom in the plane of the drawing at the narrow end of the wedge). Bonds to atoms below the plane are shown with short parallel lines (׀׀׀׀). As an alternative, a bold bond ▬ may be used instead of bold wedge. A broken line --- has been used instead of parallel lines but this is better reserved for a partial bond, delocalization, or a hydrogen bond. The use of a wedge of parallel lines [insert] is not recommended as it is ambiguous.”

  1. Juaristi, E. and Welch, C.J., “Configurational Drawings: Responses from Readers”, Enantiomer, 4, pp. 483-484 (1999)
  2. Lin, S-K., Patiny, L., Yerin, A., Wisniewski, J.L., Testa, B., “One Wedge Convention for Stereochemical Representations”, Enantiomer, 5. Pp.571-583 (2000)
  3. Starkey, L., “The Use of Stick Figures to Visualize Fischer Projections”, Journal of Chemical Education, 78 (11), p. 1486 (2001)

“I always consider the skinny end to be the point of reference (i.e. the atom that is in the board)”. [personal communication] (Uses formula II dashed wedge]