Organic Chemistry

Organic Chemistry is fundamentally the study of hydrocarbons (compounds of carbon and hydrogen) and their derivatives. Carbon is unique due to its tetravalency (valency of four) and the property of catenation—the ability of carbon atoms to form long chains and rings by bonding with each other. In Pakistani BISE board exams, you must remember that organic compounds are generally non-polar, have lower melting and boiling points, and exhibit isomerism (compounds having the same molecular formula but different structural formulas). They are the primary components of fossil fuels, and their sources include petroleum, coal, and natural gas.

Hydrocarbons are broadly classified into saturated and unsaturated types. Saturated hydrocarbons are called alkanes (or paraffins), containing only single covalent bonds with the general formula $\text{C}n\text{H}{2n+2}$. Unsaturated hydrocarbons contain double bonds (alkenes, $\text{C}n\text{H}{2n}$) or triple bonds (alkynes, $\text{C}n\text{H}{2n-2}$). Board questions frequently test the naming of these compounds using IUPAC nomenclature rules, as well as their characteristic chemical reactions. Alkanes typically undergo substitution reactions (such as halogenation in the presence of sunlight), while alkenes and alkynes undergo addition reactions (such as hydrogenation, halogenation, and hydration) due to the presence of reactive $\pi$ (pi) bonds.

The chapter also introduces important functional groups, which are specific atoms or groups of atoms that determine the chemical properties of an organic family. You must memorize the functional groups, general formulas, and suffixes for alcohols ($-\text{OH}$), aldehydes ($-\text{CHO}$), ketones ($-\text{CO}-$), carboxylic acids ($-\text{COOH}$), and esters ($-\text{COOR}$). Finally, pay special attention to the sources and uses of organic compounds, particularly coal (destructive distillation producing coke, coal tar, and coal gas) and petroleum (fractional distillation yielding various useful fuels). Practicing the preparation methods of methane and ethene, along with structural formulas of simple isomers, is essential for securing high marks in both objective and subjective portions of the exam.