Enter substituent priorities into Priority 1–4 Positions, specify the Priority 4 Stereochemistry and Configuration Type, and the R/S & E/Z Configuration Calculator determines the correct Stereochemical Configuration — along with the Rule Applied and Priority Path Direction so you can see how the assignment was made.
Stereochemical Configuration
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Rule Applied
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Priority Path Direction
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R/S configuration refers to the absolute stereochemistry at chiral centers (tetrahedral carbons), while E/Z configuration describes the stereochemistry of alkenes (double bonds). R/S uses priority rules around a central atom, while E/Z compares priority groups on each carbon of a double bond.
CIP (Cahn-Ingold-Prelog) priorities are assigned based on atomic number. Higher atomic number gets higher priority (1 > 2 > 3 > 4). For identical atoms, look at the next atoms in the chain. Double and triple bonds are treated as multiple single bonds to the same atom.
If the lowest priority group (4) is pointing toward you (solid wedge), you must invert the result. If the 1→2→3 path appears clockwise, the actual configuration is S. If it appears counterclockwise, the actual configuration is R.
First, identify the higher priority group on each carbon of the double bond using CIP rules. If the two higher priority groups are on the same side of the double bond, it's Z (zusammen = together). If they're on opposite sides, it's E (entgegen = opposite).
Yes, complex molecules can have multiple stereocenters and double bonds, each with their own configuration. Each chiral center gets an R or S designation, and each double bond gets an E or Z designation independently.
Fischer projections show molecules as crosses where vertical lines represent bonds going away from you and horizontal lines represent bonds coming toward you. This affects how you visualize the stereochemistry and may require adjusting your analysis accordingly.
Stereochemistry is crucial because molecules with the same connectivity but different spatial arrangements (stereoisomers) can have vastly different biological activities, physical properties, and chemical reactivities. This is especially important in drug design and biochemistry.