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Chapter 23: Problem 610

Give for each of the following pairs of compounds a chemical test, preferably a test-tube reaction, that will distinguish between the two compounds. Write a structural formula for each compound and equations for the reactions involved. (a) phenol and cyclohexanol. (b) methy1 \(p\) -hydroxybenzoate and \(p\) -methoxybenzoic acid. (c) 9,10 -anthraquinone and 1,4 -anthraquinone.

Short Answer

Expert verified
a) Phenol and Cyclohexanol Structural formulas: Phenol: \(\text{C}_6\text{H}_5\text{OH}\), Cyclohexanol: \(\text{C}_6\text{H}_{11}\text{OH}\) Test: Reaction with bromine water. Phenol gives a white precipitate, while cyclohexanol doesn't react. Equations: Phenol: \(\text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2 \rightarrow \text{C}_6\text{H}_2\text{OBr}_3 + 3\text{HBr}\). Cyclohexanol: No reaction. b) Methyl \(p\)-hydroxybenzoate and \(p\)-methoxybenzoic acid Structural formulas: Methyl \(p\)-hydroxybenzoate: \(\text{CH}_3\text{O}\text{C(O)}\text{C}_6\text{H}_4\text{OH}\), \(p\)-methoxybenzoic acid: \(\text{C(O)OH}\text{C}_6\text{H}_4\text{OCH}_3\) Test: Hydrolysis with dilute NaOH. Methyl \(p\)-hydroxybenzoate reacts, while \(p\)-methoxybenzoic acid doesn't react. Equations: Methyl \(p\)-hydroxybenzoate: \(\text{CH}_3\text{O}\text{C(O)}\text{C}_6\text{H}_4\text{OH} + \text{NaOH} \rightarrow \text{C(O)ONa}\text{C}_6\text{H}_4\text{OH} + \text{CH}_3\text{OH}\). \(p\)-methoxybenzoic acid: No reaction. c) 9,10-Anthraquinone and 1,4-Anthraquinone Structural formulas: Both: \(\text{C}_{14}\text{H}_8\text{O}_2\) Test: Reaction with sodium bisulfite. Only 1,4-Anthraquinone forms an adduct. Equations: 9,10-Anthraquinone: No reaction. 1,4-Anthraquinone: \(\text{C}_{14}\text{H}_8\text{O}_2 + 2\text{NaHSO}_3 \rightarrow \text{C}_{14}\text{H}_8\text{O}_2(\text{HSO}_3)_2 + 2\text{Na}^+\).

Step by step solution

01

a) Phenol and Cyclohexanol

1. Write structural formula: Phenol has a hydroxyl group attached to a benzene ring, whereas cyclohexanol has a hydroxyl group attached to a cyclohexane ring. Their structural formulas are: Phenol: \(\text{C}_6\text{H}_5\text{OH}\) Cyclohexanol: \(\text{C}_6\text{H}_{11}\text{OH}\) 2. Find distinguishing tests: A test that can distinguish phenol and cyclohexanol is the reaction with bromine water. Phenol undergoes electrophilic aromatic substitution, giving a white precipitate, while cyclohexanol doesn't react. 3. Write equations for the reactions: Phenol + Bromine water: \(\text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2 \rightarrow \text{C}_6\text{H}_2\text{OBr}_3 + 3\text{HBr}\) (white precipitate) Cyclohexanol + Bromine water: No reaction
02

b) Methyl \(p\)-hydroxybenzoate and \(p\)-methoxybenzoic acid

1. Write structural formula: Methyl \(p\)-hydroxybenzoate and \(p\)-methoxybenzoic acid both have a benzene ring with substituents at para positions. Their structural formulas are: Methyl \(p\)-hydroxybenzoate: \(\text{CH}_3\text{O}\text{C(O)}\text{C}_6\text{H}_4\text{OH}\) \(p\)-methoxybenzoic acid: \(\text{C(O)OH}\text{C}_6\text{H}_4\text{OCH}_3\) 2. Find distinguishing tests: A test that can distinguish between these two compounds is the hydrolysis with a dilute base, such as sodium hydroxide. Methyl \(p\)-hydroxybenzoate will react with the base, forming sodium \(p\)-hydroxybenzoate and methanol, while \(p\)-methoxybenzoic acid will not react. 3. Write equations for the reactions: Methyl \(p\)-hydroxybenzoate + NaOH: \(\text{CH}_3\text{O}\text{C(O)}\text{C}_6\text{H}_4\text{OH} + \text{NaOH} \rightarrow \text{C(O)ONa}\text{C}_6\text{H}_4\text{OH} + \text{CH}_3\text{OH}\) \(p\)-methoxybenzoic acid + NaOH: No reaction
03

c) 9,10-Anthraquinone and 1,4-Anthraquinone

1. Write structural formula: 9,10 and 1,4-Anthraquinone have quinone structures with different positions of the carbonyl groups. Their structural formulas are: 9,10-Anthraquinone: \(\text{C}_{14}\text{H}_8\text{O}_2\) 1,4-Anthraquinone: \(\text{C}_{14}\text{H}_8\text{O}_2\) 2. Find distinguishing tests: A test that can differentiate between these two compounds is the reaction with sodium bisulfite. 1,4-Anthraquinone will react with sodium bisulfite to form an adduct, whereas 9,10-Anthraquinone will not react. 3. Write equations for the reactions: 9,10-Anthraquinone + Sodium bisulfite: No reaction 1,4-Anthraquinone + Sodium bisulfite: \(\text{C}_{14}\text{H}_8\text{O}_2 + 2\text{NaHSO}_3 \rightarrow \text{C}_{14}\text{H}_8\text{O}_2(\text{HSO}_3)_2 + 2\text{Na}^+\) (adduct formation)

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Most popular questions from this chapter

Outline all steps in the synthesis from toluene of: (a) p-cresol via diazotizatiori; (b) p-cresol via thallation; (c) m-cresol via diazotizatiori; (d) m-cresol via thallation.

Tropolone \(\left(\mathrm{I}, \mathrm{C}_{7} \mathrm{H}_{7} \mathrm{O}_{2}\right)\) has a flat molecule with all carbon-carbon bonds of the same length (1.40 A). The measured heat of combustion is \(20 \mathrm{kcal}\) lower than that calculated by the method of summing bond energies. Its dipole moment is \(3.71 \mathrm{D}\); that of 5-bromotropolone is \(2.07 \mathrm{D}\). Tropolone undergoes the Reimer-Tiemann reaction, couples with diazonium ions, and is nitrated by dilute nitric acid. It gives a green color with ferric chloride, and does not react with 2,4 -dinitrophenylhydrazine. Tropolone is both acidic \(\left(\mathrm{K}_{\mathrm{a}}=10^{-7}\right)\) and weakly basic, forming a hydrochloride in ether. (a) What class of compounds does tropolone resemble? Is it adequately represented by formula I? (b) Using both valence-bond and orbital structures, account for the properties of tropolone. (c) In what direction is the dipole moment of tropolone? Is this consistent with the structure you have proposed? (d) The infrared spectrum of tropolone shows a broad band at about \(3150 \mathrm{~cm}^{-1}\) that changes only slightly upon dilution. What does this tell you about the structure of tropolone?

Outline a synthesis of cumene from cheap, readily available hydrocarbons. Then synthesize phenol from cumene.

Give structures of all compounds below: (a) \(p\) -nitrophenol \(+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Br}+\mathrm{NaOH}(\mathrm{aq}) \rightarrow \mathrm{A}\left(\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{O}_{3} \mathrm{~N}\right)\) \(\mathrm{A}+\mathrm{Sn}+\mathrm{HCL} \rightarrow \mathrm{B}\left(\mathrm{C}_{8} \mathrm{~B}_{11} \mathrm{ON}\right)\) \(\mathrm{B}+\mathrm{NaNO}_{2}+\mathrm{HCL}\), then phenol \(\rightarrow \mathrm{C}\left(\mathrm{C}_{14} \mathrm{H}_{14} \mathrm{O}_{2} \mathrm{~N}_{2}\right)\) \(\mathrm{C}+\) ethyl sulfate \(+\mathrm{NaOH}\) (aq) \(\rightarrow \mathrm{D}\left(\mathrm{C}_{16} \mathrm{H}_{18} \mathrm{O}_{2} \mathrm{~N}_{2}\right)\) \(\mathrm{D}+\mathrm{SnCL}_{2} \rightarrow \mathrm{E}\left(\mathrm{C}_{8} \mathrm{H}_{11} \mathrm{ON}\right)\) \(E+\) acetyl chloride phenacetin \(\left(\mathrm{C}_{10} \mathrm{H}_{13} 2 \mathrm{~N}\right)\), an analgesic ("pain-killer") and antypyretic ("fever- killer") (b) \(\beta-(-0-\) hy droxyphenyl \()\) ethyl alcohol \(+\mathrm{HBr} \rightarrow \mathrm{F}\left(\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{OBr}\right)\) \(\mathrm{F}+\mathrm{KOH} \rightarrow\) coumarane \(\left(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}\right)\), insoluble in \(\mathrm{NaOH}\).

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.
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