Analysis text on the canvas
Short answer: Right click the canvas and click Add analysis to canvas, or press Ctrl+K and type Add analysis. MolDraw places a text box under the structure with the formula, exact mass, molecular weight, m/z and elemental analysis. The box updates when you edit the structure.
The analysis box is normal canvas text. It exports with your drawing, so it suits figures, lab reports and supporting information. To read values without adding text, use the Info panel. See names, formula and properties.
Add an analysis box#
- Draw your structure in the editor.
- Optional: select one structure if the canvas has several.
- Right click the canvas and click Add analysis to canvas.
- The box appears centred under the structure. Drag it where you want it.
You can also run it from the command palette. Press Ctrl+K, type analysis, exact mass or elemental, and pick Add analysis to canvas.
What gets added#
- With a selection: one box for the structures you selected. A partial selection still analyses the whole connected structure.
- With nothing selected: one box under every separate structure on the canvas.
Each box has five lines. Here is the box for caffeine:
| Line | Example | Notes |
|---|---|---|
| Chemical Formula | C8H10N4O2 | Counts are subscripts. A charge is a superscript. |
| Exact Mass | 194.0804 | Monoisotopic mass, 4 decimals. |
| Molecular Weight | 194.19 | Average mass, 2 decimals. |
| m/z | 195.0877 ([M+H]+) | [M+H]+ for neutral structures. Charged structures show M divided by the charge. |
| Elemental Analysis | C, 49.48; H, 5.19; N, 28.85; O, 16.48 | Mass percent of each element. |
The text uses the canvas font from your settings. Its size follows your bond length.
Keep it live, or freeze it#
The box stays linked to its structure. Add a methyl group and the formula, masses and percentages change at once.
Warning
If you edit the text of the box yourself, the link breaks. The box keeps your text and stops updating. Undo with Ctrl+Z if you did not mean to.
If you delete the structure, the box stays with its last values. Delete the box too, or press Ctrl+Z.
Tips#
- Add the box after the structure is final, then use Clean up and align the text. See select, move and align.
- For a reaction, select each product and add a box under it. Reagents and arrows are not included.
- Compare the m/z value with a predicted spectrum in the mass spectrum predictor or the isotope pattern calculator.
- For combustion data, the combustion analysis calculator works the other way, from percentages to a formula.
Common problems#
| Symptom | Fix |
|---|---|
| A note says Draw or select a structure to analyse | The canvas has no atoms. Draw a structure first. |
| The menu item is missing from the right click menu | The item shows only when the canvas has atoms. |
| The values did not change after an edit | The box text was edited by hand, so it is no longer linked. Delete it and add a new one. |
Questions and answers
How do I show exact mass and molecular weight under a structure?
Right click the canvas and click Add analysis to canvas. A text box with formula, exact mass, molecular weight, m/z and elemental analysis appears under the structure.
Does the analysis text update when I change the molecule?
Yes. The box is linked to its structure and updates after every edit, unless you type into the box yourself.
What m/z value does MolDraw show?
For a neutral structure it shows [M+H]+. For a charged structure it shows the mass divided by the charge.
Is the analysis box included in exports?
Yes. It is ordinary canvas text, so PNG, SVG and PDF exports include it.
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