Substitutionsmuster

Substitutionsmuster, literally "substitution pattern" in English, is a concept in organic chemistry used to describe the arrangement of substituent groups on a molecular framework after a substitution reaction. It is commonly applied to aromatic systems to describe regioselectivity and the distribution of new substituents across the available positions. In benzene derivatives, the key patterns are ortho, meta, and para substitutions. For polycyclic and heterocyclic systems, patterns are denoted by ring position numbers (for example 1,2- or 1,4-substitution) relative to a defined reference substituent or functional group.

Substitutionsmuster is determined by directing effects of existing substituents, the reaction mechanism, and reaction conditions. Electron-donating groups typically direct electrophilic aromatic substitution to ortho and para positions, while electron-withdrawing groups direct to meta positions. Steric hindrance, solvent, catalysts, and temperature can modify the observed pattern, sometimes yielding mixtures whose composition is quantified as regioisomeric ratios.

Applications include planning and analyzing synthetic routes, characterizing products, and predicting outcomes in pharmaceutical, agrochemical, and materials chemistry. Experimental determination uses techniques such as nuclear magnetic resonance, mass spectrometry, and X-ray crystallography, sometimes complemented by computational methods that estimate directing effects (for example Hammett constants) and predict the most favorable substitution pattern.

Limitations exist in predicting exact distributions for complex substrates or multi-step sequences, where competing pathways can lead to unexpected isomer mixtures. See also: regioselectivity, directing effect, electrophilic aromatic substitution, substitution reaction.