Table 2 SMARTS atomic and bond primitives

*: any atom

a: aromatic

A : aliphatic

D<n>: degree, <n> explicit connections

H<n>: total-H-count, <n> attached hydrogens

h<n>: implicit-H-count, <n> implicit  hydrogens

R<n>: ring membership, in <n> SSSR rings

r<n>            ring size, in smallest SSSR ring of size <n>

v<n>: valence, total bond order <n>

X<n>: connectivity, <n> total connections

x<n>: ring connectivity, <n> total ring connections

+<n>: positive charge, +<n> formal charge

-<n>: negative charge, +<n> formal charge

#n : atomic number

@: chirality

-: single bond (aliphatic)

/: directional bond "up"

\: directional bond "down"

/?: directional bond "up or unspecified"

\?: directional bond "down or unspecified"

= : double bond

#: triple bond

: : aromatic bond

~: any bond (wildcard)

@  : any ring bond