Conjugated Dienes and Ultraviolet Spectroscop

Conjugated Dienes and Ultraviolet Spectroscopy

Consider the reaction below to answer the following questions:

The nucleophile in this reaction is ____:

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The electrophile in this reaction is ____:

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The kinetically controlled product in this reaction is            .

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The product that results from 1,4-addition is            .

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Write a stepwise mechanism that accounts for both of the products shown. Show all intermediate structures and all electron flow with arrows.

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This reaction shows the prefered electrophilic addition of HBr to this unsymmetrical alkene. Draw the products of electrophilic addition to the opposite end of the conjugated diene.

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Electrophilic addition reaction of conjugated dienes that occur at high temperature and/or long reaction times (reversible conditions) are said to be under:

a.  1,2- control

b.  kinetic control

c.  1,4-control

d.  thermodynamic control

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The following molecules may be prepared using the Diels-Alder reactions. Write the structures of the starting diene and dienophile necessary to prepare each molecule and label them.

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For a diene to undergo a Diels-Alder reaction it must:

a.  be substituted with electron-withdrawing groups

b.  be able to adopt and s-trans conformation

c.  be substituted with electron-donating groups

d.  be able to adopt an s-cis conformation

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For Diels-Alder cycloaddition reactions to take place most rapidly and in highest yield the dienophile must:

a.  be substituted with electron-withdrawing groups

b.  be able to adopt and s-trans conformation

c.  be substituted with electron-donating groups

d.  be able to adopt an s-cis conformation

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Which of the following compounds will react as a diene in a Diels-Alder reaction?

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Write the structure(s) of the product(s) for each of the reactions below. Be sure to indicate any relevant stereochemistry.

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Chapter 17 - Alcohols and Phenols

Rank the following groups of compounds from most acidic (1) to least acidic (4). Place the number corresponding to the compound's relative rank in the blank below the structure.

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Explain why nonafluoro-2-methyl-2-propoxide is a much weaker base than tert-butoxide.

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Refer to the data below to answer the following questions.

The weakest acid in the table is:

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Which of the acids in the Table has the weakest conjugate base?

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How do you account for the difference in acidity between meta and para-nitrophenol?

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Consider the Grignard reaction below to answer the following questions.

The electrophile in this reaction is:

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The nucleophile in this reaction is:

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The alcohol product can be classified as a:

a.  1 alcohol

b.  2 alcohol

c.  3 alcohol

d.  4 alcohol

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A highly useful and general method for the synthesis of alcohols is the addition of Grignard reagents to carbonyl compounds. Show what Grignard reagent and what carbonyl compound you would start with to prepare each alcohol below. List all possibilities.

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Choose the best reagent(s) for carrying out the following conversions from the list provided below. Place the letter of the best choice in the blank to the left of the conversion. Reagents may be used more than once.

a.  1. CH₃MgBr, ether

2.

b.  1.

2. NaOH

c.  1. (CH₃)₃SiCl, (CH₃CH₂)₃N

2. , ether

3.

d.  1. , ether

2.

e.  1. p-TosCl, pyridine

2. NaOH

f. 

g.  1. , ethanol

2. H₃O⁺

h.  PCC,

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Propose structures for alcohols that have the following NMR spectra.

6H

1H

1H

  Spectrum obtained from: SBDSWeb: https://www.aist.go.jp/RIODB/SDBS/

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59. (neat solution; no solvent)

Spectrum obtained from: SBDSWeb: https://www.aist.go.jp/RIODB/SDBS/

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