General formulas in organic chemistry provide a simplified representation of a series of compounds, indicating the overall ratio of elements. However, they have significant limitations. Firstly, general formulas do not convey structural information about how atoms are connected within a molecule. For example, the general formula ( CnH{2n+2} ) for alkanes doesn’t differentiate between straight-chain and branched alkanes. Secondly, they cannot represent the complexity of functional groups or the presence of multiple functional groups in a molecule. This limitation is particularly evident in complex organic molecules where the arrangement and type of functional groups significantly impact the molecule's chemical properties and reactivity. Lastly, general formulas are inadequate for depicting stereochemistry or geometric isomerism, which are crucial in understanding many biological and chemical processes. Therefore, while general formulas are useful for summarising a class of compounds, they are insufficient for detailed structural and functional analysis in organic chemistry.

Displayed formulas are instrumental in understanding chemical reactions involving organic compounds because they provide a detailed and accurate representation of the molecular structure, including the specific arrangement of all atoms and the type of bonds between them. By showing the precise location of each atom and bond, displayed formulas allow chemists to visualise how a molecule might interact with other molecules or reagents in a chemical reaction. This is particularly important in organic chemistry, where the reactivity of a molecule can be highly dependent on its structure. For example, in a substitution reaction, a displayed formula can help identify the specific site of reactivity, such as a functional group or a particular bond. Additionally, displayed formulas can show the geometry of a molecule, which is crucial in understanding stereoselective and regioselective reactions. Thus, displayed formulas provide a comprehensive view of a molecule's structure, which is essential for predicting and understanding its behaviour in chemical reactions.

Skeletal formulas are a convenient and effective way to represent many types of organic molecules, particularly large or complex ones, but they do have limitations. One of the main limitations is that they do not explicitly show hydrogen atoms attached to carbon, which can sometimes lead to ambiguity in understanding the molecule's exact structure. This is especially true for molecules where the position or number of hydrogen atoms is critical for understanding the molecule's reactivity or properties. Additionally, skeletal formulas may not effectively represent stereochemistry, which is crucial in many organic compounds, such as drugs and biomolecules. The 3D arrangement of atoms, critical in stereochemistry, is not conveyed in the 2D representation of skeletal formulas. Furthermore, they are not well-suited for representing small or simple molecules, where the detailed representation of every atom and bond, as in displayed formulas, is more informative. In summary, while skeletal formulas are invaluable for simplifying and visualising complex organic structures, they have limitations in conveying certain types of structural information.

Skeletal formulas are preferred for representing large organic molecules due to their simplicity and clarity. In skeletal formulas, the carbon atoms at the ends of lines and at junctions are implied, and hydrogen atoms attached to these carbons are also omitted. This leads to a less cluttered and more readable representation, especially for complex molecules with many atoms. In contrast, displayed formulas, which show all atoms and bonds explicitly, can become overly intricate and difficult to interpret for large molecules. For instance, in a large hydrocarbon chain, a skeletal formula can succinctly represent the molecule with a few lines, whereas the displayed formula would require the depiction of every carbon and hydrogen atom, leading to a crowded and potentially confusing diagram. The skeletal formula's ability to simplify without losing essential structural information makes it highly effective for visualising and understanding the structure of large organic compounds.

Isomers are compounds with the same molecular formula but different structures, and their representation in structural and skeletal formulas highlights this difference. In structural formulas, isomers are distinguished by the specific arrangement of atoms and bonds. For instance, the structural formulas for butanol isomers vary by the position of the OH group and the carbon chain's structure. Skeletal formulas, on the other hand, provide a more streamlined representation, focusing on the carbon skeleton. This makes it easier to distinguish isomers, particularly in complex molecules. For example, the skeletal formula for butanol isomers would show the branching and positioning of the hydroxyl group differently for each isomer. However, skeletal formulas may sometimes be less clear in distinguishing certain types of isomers, such as cis-trans isomers, compared to structural formulas. Thus, both types of formulas offer unique perspectives in representing isomers, with structural formulas giving detailed atom-by-atom representation and skeletal formulas offering a clearer view of the overall carbon framework.