Which of the following correctly depicts the bond line and condensed structure of the compounds? (i) \(2,2,4\)-Trimethylpentane, (ii) Hexanedial, O=CCCCCC=O \(.\) OHC \(-\left(\mathrm{CH}_{2}\right)_{4}=\mathrm{CHO}\) (iii) 2-Hydroxypropane- \(1,2,3\)-tricarboxylic acid, O=C(O)CC(O)(CC(=O)O)C(=O)O (a) (i) (b) (ii) (c) (i) and (ii) (d) (i), (ii) and (Hi)

When it comes to visualizing organic molecules, the bond line structure is a widely used and highly efficient method for representing chemical compounds. Instead of drawing out every single carbon and hydrogen atom, chemists use this shorthand, which allows for quicker and clearer understanding of large molecules.

In a bond line structure, the ends, and vertices of lines represent carbon atoms, and hydrogens attached to carbons are implied rather than explicitly drawn. This simplification assumes each carbon has enough hydrogens to complete its tetravalence. Bonds between carbon atoms are shown as lines – a single line for a single bond, double lines for a double bond, and so on. For instance, a zig-zag line depicts a carbon chain, where each angle indicates a carbon atom.

Other elements and functional groups are usually drawn out, especially if they are part of the molecule's active site. For example, in the bond line representation of 2,2,4-Trimethylpentane, the main carbon chain is depicted as a zig-zag line with additional lines indicating the three methyl groups.

The condensed chemical structure takes a more explicit approach than the bond line method. It provides a compact written form of a molecule, showing all atoms involved and how they are connected. In these structures, each carbon atom is followed by the hydrogen atoms attached to it, and bonds between atoms in functional groups may be omitted for simplicity.

Condensed structures are particularly useful for conveying molecular information in a text-based format without requiring elaborate graphical depictions. For instance, the condensed chemical structure of Hexanedial would be written as 'OHC-(CH2)4-CHO', which specifies the aldehyde groups ('OHC-') at both ends of a four-carbon ('(CH2)4') chain. While this approach lacks the spatial representation of molecules seen in bond line drawings, it is an efficient way to relay chemical information, particularly for smaller molecules or in contexts where spatial conformation is less relevant.

SMILES notation, or the Simplified Molecular Input Line Entry System, is a powerful tool that allows the description of the structure of a chemical compound using short ASCII strings. SMILES can uniquely represent a molecular structure in a way that is readable both by humans and by computers, which makes it invaluable in informatics applications such as database searches and computational chemistry.

The notation encodes molecular structures using series of letters and symbols that denote atoms and bonds. For example, 'O=CCCCCC=O' is the SMILES representation for Hexanedial, clearly illustrating the molecule as a chain of six carbon atoms with double-bonded oxygen atoms (aldehyde groups) at each end. SMILES strings provide a great deal of information in a very compact form, including the presence of rings, double and triple bonds, and stereochemistry.

The precise nature of SMILES notation allows for easy conversion to other forms of chemical structure representation, making it an essential tool for chemists, particularly in the areas of cheminformatics and molecular modeling.