The Altona equations were not implimented since only guesses were desired. Please see: C. A. G. Haasnoot, F. A. A. M. DeLeeuw and C. Altona, "The Relationship Between Proton-Proton Coupling Constants and Substituent Electronegativities-I," Tetrahedron, 1981, 36(19), 2783-2792.

The ³J vinyl and ⁴J allylic coupling constants are based on the modified Karplus Equation:

3J = 6.6 cos2(phi) + 2.6 sin2(phi)	(0o<= phi <= 90o)
3J = 11.6 cos2(phi) + 2.6 sin2(phi)	(90o<= phi <= 180o)
4J = 1.3 cos2(phi) - 2.6 sin2(phi)	(0o<= phi <= 90o)
3J = - 2.6 sin2(phi)	(90o<= phi <= 180o)

Please see: E. W. Garbisch, Jr., "Conformations. VI. Vinyl-Allylic Proton Spin Couplings," J. Amer. Chem. Soc, 1964, 86, 5561-5564.

For the other coupling types, typical values were selected from Table 3.26i, 3.27, and 3.29 in D. H. Williams, I. Fleming, "Spectroscopic Methods in Organic Chemistry,4th ed.," McGraw-Hill, London, 1987. pp 143-146. For more exact calculations, including second order effects please see JD: Spin-Spin Splitting Simulation

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