SMILE ALWAYS, IT IS SMILES NOTATION!!

SMILES is an acronym for Simplified Molecular Input Line Entry System. It is a chemical notation system used to represent a molecular structure by a linear string of symbols. The SMILES notation system was specifically designed for computer use by chemists. 

Atoms

Atoms are represented by their atomic symbols.

C is carbon N is nitrogen S is sulfur F is fluorine I is iodine P is phosphorus O is oxygen Cl is chlorine 

The hydrogen atom are not include in smiles notation. Hydrogen attachments are determined by the program. This greatly simplifies a SMILES notation.

Compound    Molecular Formula    SMILES Notation




Ethylene            CH2=CH2                    C=C


Propylene        CH2=CH-CH3                C=CC

2-Butene       CH3-CH=CH-CH3            CC=CC

Bond

Single bonds do not need to be shown

Compound    Molecular Formula    SMILES Notation



Propane          CH3-CH2-CH3              CCC

Butane         CH3-CH2-CH2-CH3        CCCC




Branches

Branches in molecular structures are designated by enclosures in parentheses. The examples of SMILES given in the lists above represent straight, linear compounds. When a structure contains a branch, the SMILES Notation of the structure requires that the branch be designated in enclosed parentheses. The figure below illustrates branching.






A single structure can have more than one valid SMILES notation. As an example, valid SMILES notations for the isobutyric acid structure include the following:









CC(C)C(=O)O
C(C)(C)C(=O)O
OC(=O)C(C)C
O=C(O)C(C)C




Cyclic structure






(1) Cyclic structures require numbers to indicate where the ring starts and stops. The numbers 1 through 9 are used to indicate the starting and terminating atoms.




(2) The same number is used to indicate the starting and terminating atom for each ring. The starting and terminating atom must be connected to each other!




(3) Each number that is used (1, 2, 3, etc.) must appear twice and only twice in the entire smiles notation.




(4) Numbers are entered immediately following the atoms used to indicate the starting and terminating positions.




(5) A starting or terminating atom can be associated with two consecutive numbers. For example, naphthalene can be coded as: c12ccccc1cccc2. 








Here is some example about the structures and the notation to make you more understand. 

Unbranches chain	Propane CH3-CH2-CH3 CCC Ethylene CH2=CH2 C=C 2-Butene CH3-CH=CH-CH3 CC=CC
Branches chain
Cyclic structure

If you want to further your knowledge about this SMILES Notation. You can learn from here

 That's all from us. May what have we shown to you give u a better understanding. :)

Assalammualaikum w.b.t.