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Chapter 23: Problem 581

Write structural formulas for substances (one for each part) that fit the following descriptions: (a) a phenol that would be a stronger acid than phenol itself (b) that isomer of dichlorophenol that is the strongest acid (c) the Claisen rearrangement product from a \(\alpha\) -methylally1 2,6 -dimethylpheny 1 ether (d) a quinone which does not undergo Diels-Alder addition (e) a quinone that would be a better charge-transfer agent than quinone itself.

Short Answer

Expert verified
(a) The structural formula of the stronger acid is: \( \begin{array}{c} \ce{O-Ph-NO2}\\ \ce{NO2}\\ \end{array} \) (b) The structural formula of the strongest acid among the dichlorophenol isomers is: \( \ce{O-Ph(Cl2)}\\ \ce{2,4-(Cl2)}\\ \) (c) The structural formula of the Claisen rearrangement product is: \( \ce{OC6H3(CH3)2CH=CHCH2CH3} \) (d) The structural formula of the quinone that does not undergo Diels-Alder addition is: \( \ce{O=C\C=C\CO} \) (e) The structural formula of the quinone that acts as a better charge-transfer agent is: \( \ce{O=C\C=C(\ce{OCH3})\CO} \)

Step by step solution

01

(a) Stronger Acidic Phenol than Phenol Itself

To make a phenol stronger than phenol itself, we should add electron-withdrawing groups to the phenol ring, which will stabilize the conjugate base after deprotonation. Here, we can add a nitro group (-NO2) to the phenol ring as it is an electron withdrawing group that will increase the acidity of the phenol. The structural formula of the stronger acid is as follows: \( \begin{array}{c} \ce{O-Ph-NO2}\\ \ce{NO2}\\ \end{array} \) Here, "\(-\)Ph" represents the phenol group and "\(-\)NO2" is the nitro group connected to the phenol ring. This form of phenol, with the nitro group added, is a stronger acid than phenol itself.
02

(b) Strongest Acidic Isomer of Dichlorophenol

The strongest acidic isomer of dichlorophenol will have chlorine atoms as substituents in positions that maximally enhance the acidity of the phenolic group by stabilizing its conjugate base. This can be achieved by placing the chlorine atoms at positions 2 and 4 (ortho and para to the phenolic group). These positions will have the strongest inductive and resonance effects on the compound. The structural formula of this isomer is: \( \ce{O-Ph(Cl2)}\\ \ce{2,4-(Cl2)}\\ \) Here, the "\(-\)Ph(Cl2)" represents the phenol group with chlorine atoms at positions 2 and 4, and this is the strongest acid among the dichlorophenol isomers.
03

(c) Claisen rearrangement product from α-methylally1 2,6-dimethylphenyl 1 ether

The Claisen rearrangement involves a [3,3] sigmatropic rearrangement of allyl vinyl ethers. In this case, the starting compound is α-methylallyl 2,6-dimethylphenyl 1 ether, and we need to find the rearrangement product. The structural formula of the starting compound is as follows: \( \ce{O(C6H3(CH3)2)C=C(CH3)CH2} \) The rearrangement will involve the migration of the aryl group to the terminal carbon of the allyl group and the formation of a new carbon-carbon bond. The structural formula of the Claisen rearrangement product is: \( \ce{OC6H3(CH3)2CH=CHCH2CH3} \)
04

(d) A Quinone that does not undergo Diels-Alder addition

Diels-Alder reactions involve the cycloaddition of a diene with a dienophile. To make a quinone that cannot undergo Diels-Alder reactions, we need to remove the diene or dienophile characteristics of the molecule. We can achieve this by putting a double bond between the carbonyl groups in the quinone ring. This will prevent the structure from acting as a dienophile. The structural formula of this quinone is: \( \ce{O=C\C=C\CO} \)
05

(e) A Quinone that acts as a better charge-transfer agent than quinone itself

To enhance the charge-transfer ability of a quinone, we can introduce electron-donating groups that will stabilize the radical cation formed upon charge-transfer. We can achieve this by attaching a methoxy group (-OCH3) to one of the ring carbons. The structural formula of this quinone is: \( \ce{O=C\C=C(\ce{OCH3})\CO} \)

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Most popular questions from this chapter

How much difference in physical properties would you expect for o-and \(p\) -cyanophenol isomers? Explain.

Write structures for each of the following names: (a) m-cresol (b) 3 -hydroxybenzenesulfonamide (c) 3 -chloro-1, 2 -benzoquinone (d) o-methoxyphenol (e) \(\mathrm{p}(\mathrm{t}-\) tolyl \()\) azophenol (f) benzyl pheny 1 ether (g) \(3-\) (o-hydroxy phenyl pentanoic acid) (h) 2 -methoxy-1, 4 -naphthoquinone

Phenol samples that have been allowed to stand in air always possess a pink or red color because of oxidation. Write a mechanism for the oxidation of phenol by oxygen that could lead to one or more products that might be expected to be colored.

Show by means of equations how each of the following substances might be synthesized, starting from the indicated materials. Specify reagents and approximate reaction conditions. (a) methy1 2-methoxybenzoate from phenol. (b) \(2,6-\) dibromo-4-t-butylanisole from phenol. (c) 4-cyanophenoxyacetic acid from phenol. (d) cyanoquinone from hydroquinone.

A student attempted the following synthesis of - methoxy- benzyl alcohol from o-cresol, but got essentially no yield. What went wrong?
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