---
title: Chains and group abbreviations
url: https://www.moldraw.com/docs/drawing/how-to-draw-carbon-chains-and-functional-group-abbreviations/
section: Draw structures
updated: 2026-10-20
publisher: LabCanvas
---

# Chains and group abbreviations

> Pick the Chain tool in the left rail and drag to draw a zigzag carbon chain. Numbers on each atom show the length. To grow a chain from an atom, point at it and press a number from 1 to 9. Type groups such as OMe, CO2Et or Boc on an atom. To expand one, right click it and pick Show as Full Structure.

1. Click the **Chain** tool in the left rail. It sits next to the bond button.
2. Press on an atom to grow the chain from it, or press on empty canvas for a free chain.
3. Drag. Each new atom shows a number, so you can count the carbons.
4. Release when the count is right.

## How the Chain tool works

- The chain is a zigzag with 120° angles, the usual skeletal style.
- Each bond has the document bond length. The direction follows **Bond angle snap** in **Settings**, **Bonds** (30° by default).
- When you start on an atom, the first bond points into the open space next to it.
- Drag back to make the chain shorter before you release.
- With the Chain tool active, hold `Ctrl` and drag on empty canvas to select instead of drawing.

On a phone, the Chain tool is in the **Bond** strip of the bottom bar.

## Add a chain with a number key

You do not need the Chain tool for short chains. Point the mouse at an atom and press a number key.

- `1` to `9` add a carbon chain of that many atoms.
- The chain leaves the atom on the side away from its other bonds.
- This works with any tool. See [Draw faster with hover keys](https://www.moldraw.com/docs/drawing/how-to-draw-faster-with-hover-shortcuts/) for the other keys.

## Group abbreviations

An abbreviation is a short label that stands for a whole group, such as `CO2Me` for a methyl ester. The basics of typing a label are on the [Atom labels and R-groups](https://www.moldraw.com/docs/drawing/how-to-add-atom-labels-and-r-groups/) page. This page lists the groups that MolDraw understands.

To type one fast, select one atom and start typing. Or point at an atom with a bond or ring tool active and type. A list of suggestions opens. Press `Tab` or `Enter` to accept one.

### Groups that expand

These labels expand into full atoms. Letter case does not matter.

| Type | Labels |
| --- | --- |
| Alkyl | Me, Et, nPr, iPr, nBu, iBu, sBu, tBu, vinyl, allyl, propargyl |
| Aryl and benzyl | Ph, Bn, OPh, SPh |
| Oxygen groups | OH, OMe, OEt, OPr, OtBu, CHO, Ac, COOH, CO2H, COONa |
| Esters and amides | COOMe, CO2Me, COOEt, CO2Et, CONH2 |
| Nitrogen and others | NH2, NO2, NO, CN, CF3, CCl3, SH, SO3H, SO2Me |
| Protecting groups | Boc, Cbz, Fmoc, Ts, Tos, Ms, TFA, PMB, Trt, MOM, THP, MEM, SEM, BOM |
| Silyl groups | TMS, TES, TBS, TBDMS, TIPS, TBDPS |

Condensed formulas also expand. For example `CH2CH2OH` or `C(CH3)3` become the right atoms and bonds.

### Expand a label

Right click the labelled atom and pick **Show as Full Structure**. The anchor atom and its bonds stay in place, so wedges next to the group keep their meaning. Press `Ctrl+Z` to go back.

A label MolDraw does not know stays as text. It still prints on your figure.

### Show short labels on drawn groups

**Settings**, **General**, **Condensed group labels** shows end groups as compact text such as CH₃ or NH₂. It is off by default.

## Common problems

| Problem | Fix |
| --- | --- |
| The chain goes the wrong way | Undo, then start the drag on the other side of the atom. Or use a number key on the atom. |
| A number key changed a bond instead | The pointer was over a bond. Move it onto the atom. |
| Typing a letter switched tools | Some letters are tool keys, such as `V` and `L`. Select the atom first, or double click it, then type. |
| Show as Full Structure is missing | The atom has no label, or the label is plain text that MolDraw does not know. |

For ready-made groups you can click instead of type, open the [Library](https://www.moldraw.com/docs/library/how-to-use-the-structure-library-and-templates/). To name the groups in a molecule, try the [functional group identifier](https://www.moldraw.com/tools/free-chem-tools/functional-group-identifier.html).

## Questions and answers

**How do I draw a long carbon chain in MolDraw?**
Pick the Chain tool in the left rail and drag. The numbers on each atom count the carbons, so release when the count is right.

**How do I add a butyl group to an atom quickly?**
Point the mouse at the atom and press 4. A four carbon chain grows from it.

**Which abbreviations can MolDraw expand?**
Common alkyl, aryl, ester, nitrogen, protecting and silyl groups such as Et, Ph, CO2Me, NO2, Boc and TBS. Condensed formulas like CH2CH2OH expand too.

**How do I expand an abbreviation into atoms?**
Right click the labelled atom and pick Show as Full Structure.

## Practice it

- Interactive lesson: [How to use R groups and labels like Ph and COOH](https://www.moldraw.com/learn/how-to-use-r-groups-and-atom-labels-like-ph-and-cooh/)

## Related pages

- [Atom labels and R-groups](https://www.moldraw.com/docs/drawing/how-to-add-atom-labels-and-r-groups/)
- [Draw faster with hover keys](https://www.moldraw.com/docs/drawing/how-to-draw-faster-with-hover-shortcuts/)
- [Draw bonds](https://www.moldraw.com/docs/drawing/how-to-draw-single-double-triple-and-wedge-bonds/)
- [Library and templates](https://www.moldraw.com/docs/library/how-to-use-the-structure-library-and-templates/)