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Ch. 17 - AromaticityWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins
Ch. 26 - Transition Metals
Huckel's Rule
Pi Electrons
Aromatic Hydrocarbons
Aromatic Heterocycles
Frost Circle
Naming Benzene Rings
Acidity of Aromatic Hydrocarbons
Basicity of Aromatic Heterocycles
Ionization of Aromatics

Concept #1: Inscribed Polygon Method

Example #1: Inscribed Polygon Method


Hey guys let's take a look at the following question so here apply the polygon circle method. Which we also call Frost circles to the following compound does it show any special stability? If yes why so basically we have to determine is this molecule aromatic not aromatic or anti aromatic, aromatic shows very high stability non aromatic just means your normal compound and anti aromatic means you're super unstable so if we take a look at the name we have tropyllium another name for tropyllium just means that we have cycloheptatriene, So the tropyllium just means cycloheptatriene, cyclo means ring hepta mean seven cabons, so we have seven carbons and tri means three double bonds.

Now I say the word cation which means this carbon up here which is not double bond like the others is positive, so that would be our molecule. Now here we're going to draw the frost circle. Now we're going to draw apex down the molecule so point part down. The larger these rings get the harder it becomes to draw them so it takes practice guys to make sure you draw it correctly, not the straightest but good enough. Now we're going to cut this in half so here this is your non bonding region. Down here is your bonding up here is your antibonding. Everywhere a carbon touches becomes a molecular orbital. Now we're going to say how many pi electrons we have we have 2,4, 6 pi electrons so one up one down up up down down. We're going to say this molecule shows special stability because all of the molecule orbitals in the body region are completely filled in which would indicate that we have an aromatic compound. so tropylium cation is aromatic here we know it from the old tools that we talked about but we also know it because we just did a frost circle and it approves it the molecular orbitals in the body region are all completely filled it.