MolDraw Docs

Inductive arrows and partial charges

Short answer: Open the bond menu in the left rail and pick Inductive. Click a single bond to put an arrow on it that points at the atom that pulls harder. For partial charges, open the charge menu, pick δ+ or δ− and click an atom. Click again for δδ+ and δδδ+.

Last updated · By the MolDraw team at LabCanvas

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Inductive arrows and partial charges show bond polarity. The Inductive tool puts an arrowhead on a σ bond. The δ+ and δ− tools put partial charge labels on atoms. Both are display only. They do not change the formula, the charge or the SMILES.

Inductive arrows#

  1. Open the bond menu in the left tool rail. Its name is Bond type.
  2. Under Query / stereo, pick Inductive.
  3. Click a bond. The arrow points at the atom that pulls the electrons harder.
  4. Click the same bond again to reverse the arrow.
  5. Click a third time to remove it.

You can also draw new bonds with the tool. Click an atom to add a bond with an arrow, or drag from atom to atom. You can pick the tool from the command palette too: press Ctrl+K and type Inductive.

Which way the arrow points#

MolDraw compares the Pauling electronegativity of the two atoms. On C-Cl the arrow points at Cl. On a bond between two atoms of the same element, like C-C, it looks at the neighbours. The carbon that carries Cl, O or another electronegative group pulls harder. If both sides pull the same, the second click removes the arrow.

When you draw a new inductive bond, arrows on nearby C-C bonds can turn around. MolDraw checks them again because the new bond changes the balance. Draw a chain like Cl-C-C-C with the tool, and the arrows point toward Cl.

Rules#

  • Inductive arrows sit only on single bonds. Clicking a double bond with the tool makes it a single bond with an arrow.
  • To clear an arrow, click the bond until the arrow goes, or click it with the Single bond tool.

Partial charges: δ+ and δ−#

Note

The δ tools live in the charge menu of the left rail, Charge and symbol tools, in the Charge group.

  1. Open the charge menu and pick δ+ or δ−.
  2. Click an atom. It shows δ+ or δ−.
  3. Click it again for δδ+, then δδδ+. The next click clears it.
  4. To place the label, press on the atom and drag. The label follows the pointer.

Use δδ+ and δδδ+ to show the effect fading along a chain. A δ+ click on an atom with δ− replaces it with δ+.

Partial charges are separate from formal charges. The plus and minus tools set real charges. See Lone pairs, radicals and charges.

Tips#

  • Draw the arrows first, then add δ labels at each end of the polar bond.
  • Use Clean up to tidy the structure before a polarity figure.
  • Arrows and labels show in PNG, SVG and PDF downloads.

Common problems#

Problem Fix
The arrow points the wrong way Click the bond again to reverse it.
The arrow disappeared You clicked a third time, or both atoms pull equally. Click once more.
The δ label sits on a bond Press on the atom and drag the label to a free spot.
A δ+ became δδ+ Each click steps up. Keep clicking to clear it, then click once.

For the theory, read the bond polarity and dipole guide. To check a bond quickly, try the bond polarity checker.

Questions and answers

How do I draw an inductive effect arrow in MolDraw?

Open the Bond type menu in the left rail and pick Inductive under Query / stereo. Click a single bond and the arrow points at the more electronegative side.

How do I add delta plus and delta minus to atoms?

Open the charge menu in the left rail, pick δ+ or δ−, and click the atom. Press and drag on the atom to move the label.

How do I draw δδ+ in MolDraw?

Pick the δ+ tool and click the same atom twice. A third click gives δδδ+ and a fourth click clears it.

Do partial charges change the molecular formula or charge?

No. δ+ and δ− labels and inductive arrows are display only. The formula, net charge and SMILES stay the same.

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