Скачать или смотреть How to Convert a Wedge-Dash into a Fischer Projection

Wedge-dash (also called flying wedge) projections represent tetrahedral stereochemistry in 3D, with solid wedges indicating bonds coming out of the page (toward the viewer) and dashed lines showing bonds receding behind the page (away from the viewer). Fischer projections simplify this into a 2D cross format for chiral molecules, especially sugars and amino acids, where the horizontal bonds project forward (toward the viewer) and vertical bonds project backward (away from the viewer), with the intersection as the chiral carbon.
Conversion Steps
Identify the chiral carbon in the wedge-dash structure and orient the molecule so the main chain (e.g., carbon backbone) runs vertically, with the lowest-numbered carbon at the top. Rotate the molecule mentally or on paper by 180° around bonds if needed to eclipse substituents, ensuring vertical bonds point away and horizontal ones point toward you—wedges become left or right horizontal lines, dashes become the opposite.
For a single chiral center, draw a vertical line for the carbon chain, placing wedge groups on one horizontal side and dash groups on the other; swap if necessary to match the eclipsed Fischer conformation without changing stereochemistry.
Example: (R)-2-Bromobutane
Start with wedge-dash: CH3-CH(Br)-CH2CH3, where Br is a wedge (forward), H is a dash (back), CH3 top, CH2CH3 bottom. Rotate to eclipse: vertical becomes CH3 (top, back) and CH2CH3 (bottom, back); horizontal becomes Br (left, forward) and H (right, back, but swap to maintain config). Fischer result: CH3 at top, Br left, H right, CH2CH3 bottom.
Multiple Chiral Centers
For chains like glucose, position C1 (aldehyde) at top, align all chiral carbons vertically, and convert each center independently— wedges forward to horizontal left/right, dashes back to vertical or swap pairs. Verify by ensuring no odd-number swaps (which invert configuration); use 180° rotations to align without crossing bonds.
Common Rules and Tips
Maintain stereochemistry: even swaps (2, 4) preserve configuration; odd swaps invert it, requiring a correction. For verification, convert back to wedge-dash by making horizontals wedges/dashes. Practice with models helps visualize rotations.
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