5081

Draw an energy profile diagram for the chlorination of nitrobenzene, showing the Wheland intermediate, and comparing the potential energy profiles for the meta and para substitution pattern.

5082

Write the structure for the main organic product(s) in the space provided.

5083

If toluene is treated with isopropyl chloride in the presence of aluminum chloride at room temperature, a mixture of cymenes (isopropyltoluenes) is formed consisting of ortho (42%), meta (21%), and para (37%). Upon heating this mixture in the presence of fresh aluminum chloride, the mixture is converted to 100% meta isomer. Explain both the original isomer distribution and the product after heating.

5084

Write the structure of the major product of the following reaction:

5088

When acetyl chloride is treated with isotopically labeled aluminum chloride, Cl^*, the labeled chlorine atoms slowly appear in the acetyl chloride molecule.

What is the significance of this observation, and what relevance does this result have to the mechanism of the Friedel-Crafts acylation reaction?

5119

The starting point for a large number of steroid syntheses has been 6-methoxytetralone (see below). Show how this compound can be prepared from phenol and any necessary aliphatic or inorganic reagents. Be specific.

6-methoxytetralone

5167

Propose a reasonable mechanism for the following reaction:

5169

The nitroso group, –N=O, is an ortho-para director in electrophilic aromatic substitution. However, it also serves to activate the nucleophilic displacement of a halogen atom on an aromatic ring when the nitroso group is ortho or para to the halogen. Using mechanisms to support your argument, explain these effects.

(a) electrophilic aromatic substitution:

(b) nucleophilic aromatic substitution:

5185

Pyridine and pyrrole behave very differently toward aromatic substitution reactions. One is reactive toward nucleophilic aromatic substitution reagents, and the other is reactive towards electrophilic substitution reagents. Deduce from theoretical considerations which behaves in which manner, and indicate the positions on ring which are most reactive.

5252

State whether the following statements or equations are true or false. If any part of a statement is not true or any part of an equation is incorrect, then the item is false.

(a)

(b) When acetyl chloride is treated with isotopically labelled aluminum chloride, the labelled chlorine atoms slowly appear in the acetyl chloride molecules.

This result indicates that an addition/elimination mechanism is operating.

(c) The structure below is one of two valid, important, equivalent, resonance structures.

5261

Write the structure of the major organic product(s) and state whether the reaction will be faster or slower than the equivalent reaction with benzene as the aromatic substrate.

(a)

(b)

(c)

5354

Discuss the process for determining whether a specific functional group will be ortho/para or meta directing and activating or deactivating with respect to benzene in electrophilic aromatic substitution. Illustrate your main points using the nitration of methyl benzoate as a specific example