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One of the following compounds is much more stable than the other two. Classify each as aromatic, antiaromatic, or nonaromatic

(a)Methyl heptalene

(b) Methyl azulene


(c) Methyl pentalene


Short Answer

Expert verified

(a) Methyl heptalene


(b) Methyl azulene


(c) Methyl pentalene


Step by step solution

01

Aromaticity

Enrich Huckel demonstrated a rule which predicts that the given annulene or related compounds are aromatic or antiaromatic. If the number of electrons in a pi-electron system is (4n+2), the system is aromatic and if it is 4n then the system is antiaromatic where n is an integer.

02

Classification of the aromatic and nonaromatic molecule

Heptalene is antiaromatic, azulene is aromatic because it follows pi electrons and it is planar. Pentalene is antiaromatic. Azulene is aromatic, hence it is most stable than the other two which are antiaromatic.

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Most popular questions from this chapter

(a) Use the polygon rule to draw an energy diagram for the MOs of a planar cyclooctatetraenyl system.

(b) Fill in the eight pi electrons for cyclooctatetraene. Is this electronic configuration aromatic or antiaromatic? Could the cyclooctatetraene system be aromatic if it gained or lost electrons?

(c) Draw pictorial representations for the three bonding MOs and the two nonbonding MOs of cyclooctatetraene. The antibonding MOs are difficult to draw, except for the all-antibonding MO

Question: The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

a. Use resonance forms to show the delocalization (over four carbon atoms) of the positive charge, unpaired electron, and negative charge of the benzyl cation, radical, and anion.

b. Toulene reacts with bromine in the presence of light to give benzyl bromide. Propose a mechanism for this reaction.

c. Which of the following reactions will have the faster rate and give the better yield? Use a drawing of the transition state to explain your answer.

Show which of the nitrogen atoms in purine are basic, and which one is not basic. For the nonbasic nitrogen, explain why its nonbonding electrons are not easily available to become protonated

Question: For each NMR spectrum, propose a structure consistent with the spectrum and the additional information provided.

a. Elemental analysis shows the molecular formula to be C8H7OCl . The IR spectrum shows a moderate absorption at 1602 cm-1 and a strong absorption at 1690 cm-1 .

b.The mass spectrum shows a double molecular ion of ratio 1:1 at m/z 184 and 186.

When 3-chlorocyclopropene is treated with AgBF4, AgCl precipitates. The organic product can be obtained as a crystalline material, soluble in polar solvents such as nitromethane but insoluble in hexane. When the crystalline material is dissolved in nitromethane containing KCl, the original 3-chlorocyclopropene is regenerated. Determine the structure of the crystalline material, and write equations for its formation and its reaction with chloride ion

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