Draw the skeletal (bond-line, zig-zag) formula of but-1-yne
1. clears the editing area (or the current molecule, if structure contains several parts)
2. delete mode (click on atom or bond to delete it)
3. switches between allowed charged states on clicked atom
4. undo
5. redo
6. opens functional group popup menu
7. Carbon chains
8. Frequent atoms
9. Other atoms
To change an atom, select the location and type the symbol (useful for H we want to represent explicitly eg on an asymmetrical C atom)
