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SMILE - Simplified molecular input line entry specification

The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings
+ SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules
+ SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules

Graph-based definition
+ In terms of a graph-based computational procedure, SMILES is a string obtained by printing the
symbol nodes encountered in a depth-first tree traversal of a chemical graph
+ The chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree
+ Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes
+ Parentheses are used to indicate points of branching on the tree

SMILES Bonds
+ SINGLE
+ DOUBLE
+ TRIPLE
+ AROMATIC

SMILES Branches
+ Represented by enclosure in parentheses
+ Can be nested or stacked
Examples:
CC(O)CC is 2-Butanol
OCC(C)C is iso-Butanol
OC(C)(C)C is tert-Butanol

Another Application
SMILESCAS Database
Over 103,000 SMILES notations
Input CAS Registry Number
Leads to SMILES and thence to a structure search