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1. How many pi electrons are there in ?10 The hybridization of the oxygen atom will remain sp³. If it were to change to sp², there would be 12 pi electrons in this cyclic system, which would be anti-aromatic. In other words, the molecule will be more stable if a lone pair of electrons on the oxygen does not conjugate to the rest of the pi system than if it does.

2. Draw the structure of the simplest aromatic cation there is.c1c[cH+]1

3. Draw the structure of the simplest aromatic anion there is.c1cc[cH-]c1

4. Draw the structure of the complex that is formed in the following reaction: CC[Cl+][Al-](Cl)(Cl)Cl

5. Consider the following reaction: From the perspective of the benzene, this is an example of an electrophilic aromatic substitution. What type of reaction is it from the perspective of the acetyl chloride? Nucleophilic acyl substitution

6. Which of the following compounds would react fastest with HNO₃/H₂SO₄?Both the O and the CH₂ groups are activating groups.

7. Which of the compounds shown in Question 6 would react slowest with HNO₃/H₂SO₄?This is the only choice with an electron withdrawing carbonyl group attached directly to the aromatic ring.

8. Which of the following compounds would not be suitable as a catalyst for a Friedel-Crafts acylation reaction?

A. MgCl₂ The Mg has a filled shell. The metal atoms in all the other salts do not.

9. Before the structure of benzene was known, one approach to establishing its structure involved the determination of the number of isomers that it formed upon substitution of a bromine atom for a hydrogen.. For example, the reaction C₆H₆ + Br₂ always yielded a single compound with the formula C₆H₅Br, while the reaction C₆ H₅Br + Br₂ produced three compounds with the formula C₆H₄Br₂ . How many isomers of C₆H₃Br₃ were produced by the reaction C₆ H₄Br₂ + Br₂?

10. is an isomer of benzene. How many isomers with the formula C₆H₃Br₃ would produced by a series of reactions analogous to those described in Question 9? Do not include enantiomers. 9 The pairs enclosed in boxes are enantiomers.

11. Draw the resonance structure that makes the most important contribution to the arenium ion that is formed in the following reaction:

C[O+]=C1C=CC=CC1Cl

12. and 13.

12) ClC(=O)c1ccccc1

13) O=C(c1ccccc1)c2ccccc2

14. Select the compound that is most acidic:The 10 pi electrons present in the conjugate base are delocalized over 9 carbon nuclei. In compounds A and B, the conjugate bases each have 8 pi electrons, i.e. they are anti-aromatic.

15. Consider the following hypothetical transformation:. Select the X/Y pair that would produce the desired outcome:

A. X = OCH₃/Y =Cl B. X = OCH₃/Y = CO₂CH₃ C. X = CO₂CH₃ / OCH₃ D. X = CO₂CH₃ /Y = CO₂CH₃

16. Consider the chemical shifts of the methyl signal in a family of molecules represented by the formula GCH₂CH₃:

What does this data allow you to say about the electronic effect of a phenyl group?

B. Its inductive effect is electron withdrawing. The phenyl group is separated from the methyl group by an intervening sp² hybridized carbon. Therefore there is no resonance interaction between the phenyl and the methyl groups. The only effect is inductive.

17.CC(Br)C(Br)c1ccccc1

18. In principle, the reaction should go fastest when X is

A. OH B. NH₂ C. OAc D. Cl From the perspective of the reagent, this reaction is a nucleophilic acyl substitution. Acid chlorides are the most reactive members of the carboxylic acid family toward nucleophiles.

19. Would you expect to display aromatic properties? No. If the oxygen were sp² hybridized, then there would by 4 pi electrons in the ring. This is anti-aromatic. If the oxygen is sp³ hybridized, ten you don't have a cyclic pi system.

20. is the MO digaram ofSince the MO diagram contains 7 orbitals, it must represent a structure that contains sp² hybridized atoms.

21. Using the principles of MO theory, would you predict whether the pK of would be

A. greater than 19. If your postulate this typical resonance interaction, then you have to say that the structure on the right is anti-aromatic. If you don't postulate such an interaction, then the pK should be greater than 19 also.

22. Polly Ester thought that the pK ofmight be unusually low for an ester. She felt that the conjugate base of this compound might have aromatic character. So she decided to make the compound in order to measure its acidity. She considered the four routes shown below. Which route is most likely to succeed?

23. Is Polly justified in thinking that this ion should be more acidic than a simple ester? Enter yes or no into the text field. (To answer this question Polly considered ideas from MO theory, resonance theory, and hybridization theory.)

Yes, Polly's thinking is reasonable. Consider this resonance picture:Deprotonation of the alpha carbon generates an enolate ion which has an aromatic pi system: it contains 2 electrons from the double bond, two from the lone pair on the carbon, and two from a lone pair on the oxygen. The oxygen should be sp² hydridized so that each atom within the ring has a p orbital available for pi overlap with its two neighbors.

24. The H-MNR spectrum of the product of the following reaction is shown below. Draw the structure of the product.

O=C1CCc2ccccc12

25. How many 1,3-diaxial interactions are there in? 2

26. Select the compound for which there are three stereoisomers:

27. The reaction shown below would proceed fastest when G = A. 3-OCH₃ B. 4-OCH₃ C. 3-CHO D. 4-CHO (Enter the letter corresponding to your choice, not the formula for the substituent.)

The structure of the starting material and the reaction conditions both are consistent with an Sn1 mechanism. The carbocation intermediate is stabilized by conjugation with the aromatic ring. When there is a methoxy group in the 4 position of that ring, the oxygen can contribute electron density to the electron deficient center as well.

28. Enter the letter of the statement that best describes the outcome of the following reaction:

C. The product is a mixture of diastereomers. The pre-existing chiral center makes the top and botom faces of the carbonyl pi system non-equivalent. Delivery of hydride ion to these two faces is therefore not equally probable.

29. Chlorobenzene is less reactive than benzene in electrophilic aromatic substitution reactions. This is because

A. the inductive effect of the chlorine reduces the electron density in the ring.

30. Select the strongest base: