Which method is commonly used for the qualitative analysis of organic compounds?

Thin-layer chromatography (TLC) is widely utilized for the qualitative analysis of organic compounds due to its efficiency in separating mixtures based on their polarity. In a typical TLC setup, a sample mixture is applied on a thin layer of stationary phase, commonly silica gel or alumina, coated on a glass or plastic plate. When a solvent is allowed to travel up the plate by capillary action, different compounds in the mixture move at varying rates, with more polar compounds adhering more strongly to the stationary phase, while less polar compounds travel further up the plate.

After development, the distinct spots corresponding to individual components can be observed either visibly or by using appropriate staining techniques. The position of the spots (measured as the Rf value) allows for identification of the components by comparing them against known standards. This qualitative data gives insights into the number of compounds present, their relative polarities, and in some cases, even their identity when matched with standard references.

While gas chromatography, mass spectrometry, and infrared spectroscopy are powerful instrumental techniques used in the analysis of organic compounds, they are often employed for quantitative analysis and structural determination rather than basic qualitative assessments of mixtures.