Structure searching in CAS Online using STN Express:
An introductory workshop

Building structures: Overriding system defaults

What you draw is what you get …
If you want Do this
Block ring fusion
  1. Highlight one node in the ring
  2. Go to Query Definition in menu bar
  3. Click on Ring Isolation
  4. Select Isolated
Atoms drawn in a chain to also be part of a ring

Atoms drawn in a ring to also be part of a chain
  1. Highight the atom(s)
  2. Go to Query Definition in menu bar
  3. Click on Node Characteristics
  4. Select Ring/Chain
Bonds drawn in a chain to also be part of a ring

Bonds drawn in a ring to also be part of a chain
  1. Highight the atom(s)
  2. Go to Query Definition in menu bar
  3. Click on Bond Characteristics
  4. Select Ring/Chain
Bonds with any value
  1. Highlight the bond(s)
  2. Go to Draw in menu bar
  3. Select Unspecified
Bonds to be either present or absent
  1. Leave bond(s) out of structure
  2. Add node characteristics of ring/chain
  3. Go to Query Definition in menu bar
  4. Click on Node Characteristics
  5. Select Ring/Chain
Block substitution at all positions in your structure Run an Exact or Family structure search if non-carbon atoms are elements or shortcuts and a CSS search if non-carbon atoms include system-defined variables
Block substitution at some positions in your structure Add hydrogens at appropriate positions
Force substitution at a position in your structure Go to Draw in menu bar
  • To use system-defined variables, choose Variables
  • To create user-defined variables, choose G-groups