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TOTAL-COORD-NO

TOTAL-COORD-NO is used to specify that an atom has a total coordination number n,

where

n = nca + nh

nca = number of connected atoms, excuding terminal hydrogen atoms

nh = number of attached terminal hydrogen atoms

Ex. 1 Suppose we have built the fragment (i) - see below.

(i)

Suppose we require that atom 1 is sp2- hybridised.

• Select TOTAL-COORD-NO

• Type the TOTAL COORDINATION NUMBER.
  (Press <RETURN> to mean "Unspecified")

• Type 3 <R>

  3 appears in the TOTAL-COORD-NO box.

• Select atom for TOTAL COORDINATION specification.
  (Select another command to end TOTAL-COORD-NO)

• Select atom 1

(ii)

A search conducted with this fragment would register hits for (iii) and (iv), but not (v) since atom 1 in (v) is sp3-hybridised.

(iii)

(iv)

(v)

If we wished to restrict the hits to structures of type (iii) then in addition to specifying T3 we would assign zero HYDROGENS to atom 1.

Ex. 2 This simply illustrates how to change or remove a total coordination number specification.

Suppose we have the fragment

(a) If we wish to change T3 to T4

• Select TOTAL-COORD-NO

• Type the TOTAL COORDINATION NUMBER
  (Press <RETURN> to mean "Unspecified")

• Type 4 <R>

  4 appears in the TOTAL-COORD-NO box.

• Select atom for TOTAL COORDINATION specification.
  (Select another command to end TOTAL-COORD-NO)

• Select C atom

(b) If we now wish to remove the T4 specification

• Select TOTAL-COORD-NO

• Type the TOTAL COORDINATION NUMBER
  (Press <RETURN> to mean "Unspecified")

• Press <R>

  Unsp. appears in the TOTAL-COORD-NO box.

• Select atom for TOTAL COORDINATION specification.
  (Select another command to end TOTAL-COORD-NO)

• Select C atom