In this section, we explore the methods used to estimate the percentage composition of oxygen in organic compounds, which is typically determined by calculating the difference between the total percentage (100%) and the sum of the percentages of all other elements present in the compound. The estimation is often conducted through combustion analysis, where the organic compound's carbon and hydrogen are oxidized to carbon dioxide and water, respectively. For semi-direct methods, complete combustion in a controlled environment and subsequent measurement of the gaseous products help in deriving accurate quantifications. Understanding the role and presence of oxygen is crucial, as it significantly impacts the chemical behavior and reactivity of various organic compounds.