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I'm a beginner at ChemDraw.

I'd like to draw a molecule from SMILES and the ring bond should be drawn like the left image:

enter image description here

In my case, my image is drawn like the right image.

Is there any method to change the default style setting?

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  • $\begingroup$ One circle counts 6 electrons if I remember that correctly; if that is the case, the rightmost image would even be wrong. $\endgroup$
    – Martin - マーチン ♦
    Commented Jan 24, 2021 at 19:21
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    $\begingroup$ @Martin-マーチン I am not sure if there is a rule. I don't think so. Both representation requires underlying chemical knowledge, and in principle for new and exotic structures that isn't even available, strictly speaking. In other words left structures can be taken as having double bonds, one has to know what happens even in benzene. What is sure is that inner rings do not always represent 6 electrons. If there is a rule, it does not make other "localized" structures right, at least at first glance. $\endgroup$
    – Alchimista
    Commented Jan 25, 2021 at 9:44
  • $\begingroup$ It's worth noting that there is generally an "equivalence" between SMILES and resonance forms in most chemical drawing software, including ChemDraw. Specifically, c1ccccc1 which I view as a better SMILES representation of benzene, will be rendered with the circle, as you've shown on the right, and I think this is a worse visual representation of benzene. Conversely, if you want most drawing programs to show explicit double bonds (which I think is generally better), if you were pasting from SMILES you'd have to do C1=CC=CC=C1 (which is a worse SMILES representation). $\endgroup$
    – Curt F.
    Commented Jan 25, 2021 at 18:29
  • $\begingroup$ According to the Graphical Representation Standards for Chemical Structure Diagrams (IUPAC Recommendations 2008), the rightmost image is wrong. "It is generally not acceptable to use curves in two adjacent fused rings, since such diagrams are at best ambiguous in terms of the character of the shared fusion bond between the two rings." $\endgroup$
    – Loong
    Commented Mar 26, 2021 at 18:36

1 Answer 1

Reset to default
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From pp. 91–92 ChemDraw 20.0 User Guide, PDF version shipped with the ChemOffice suite:

Toggle Aromatic Display

An aromatic structure can be displayed either as an alternating double and single bond or as an aromatic circle. Toggle Aromatic Display option lets you change an aromatic structure from Alternating double/single bond to Aromatic circle and vice versa. To do so:

  1. Select the structure.
  2. Go to Structure → Toggle Aromatic Display.

enter image description here

When opening a file of non native chemical format or pasting as SMILES, you can now define the way aromatic structures are displayed.

To do so:

  1. Go to File → Preferences. The Preferences Dialog appears.

enter image description here

  1. Click Open/Save tab.
  2. Click the Normalize Aromatic Display checkbox and select either Alternating Double/Single Bond or Aromatic Cirlces as desired.
  3. Click Apply and then click OK. All aromatic structures in the file loaded or the SMILES string pasted will be of the defined representation.
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