- Learning Objectives
- Name alcohols, phenols, and ethers according to the IUPAC system of nomenclature.
- Discuss the reactions involved in the preparation of alcohols from alkenes, aldehydes, ketones, and carboxylic acids.
- Discuss the reactions involved in the preparation of phenols from haloarenes, benzene sulphonic acids, diazonium salts, and cumene.
- Discuss the reactions for the preparation of ethers from alcohols and alkyl halides.
- Correlate physical properties of alcohols, phenols, and ethers with their structures.
- Discuss chemical reactions of alcohols, phenols, and ethers on the basis of their functional groups.
Alcohols: Phenols and Ethers
CBSE Learning Objectives – Key Concepts & Skills You Must Know
CBSE Revision Notes & Quick Summary for Last-Minute Study
Notes on Alcohols, Phenols, and Ethers
Overview
Alcohols, phenols, and ethers are important organic compounds with various applications in industry and daily life. They are characterized by the presence of hydroxyl (-OH) groups.
IUPAC Nomenclature
- Ethers: Named by identifying the alkyl or aryl groups attached to the oxygen atom. For example:
- C₂H₅OCH₂−CH−CH₃: Ethyl isopropyl ether
- CH₃OCH₂CH₂Cl: Methoxyethyl chloride
Classification
Alcohols
- Monohydric: Contain one hydroxyl group (e.g., CH₃OH - Methanol)
- Dihydric: Contain two hydroxyl groups (e.g., C₂H₄(OH)₂ - Ethylene glycol)
- Trihydric: Contain three hydroxyl groups (e.g., C₃H₈O₃ - Glycerol)
Phenols
- Monohydric Phenols: Contain one hydroxyl group attached to a benzene ring (e.g., C₆H₅OH - Phenol)
- Dihydric and Trihydric Phenols: Contain two or three hydroxyl groups respectively.
Ethers
- Simple (Symmetrical): Same alkyl or aryl groups (e.g., C₂H₅OC₂H₅ - Diethyl ether)
- Mixed (Unsymmetrical): Different alkyl or aryl groups (e.g., C₂H₅OCH₃ - Ethyl methyl ether)
Reactions
Williamson Synthesis
- A method for preparing ethers by reacting an alkoxide with a primary alkyl halide.
- Example: 1-Propoxypropane can be synthesized from sodium propoxide and 1-bromopropane.
Acid Dehydration
- Not suitable for certain ethers due to the formation of carbocations that can rearrange.
Reactions with Hydrogen Iodide
- Ethers react with hydrogen iodide to yield alcohols and alkyl iodides.
- Example: CH₃OCH₃ + HI → CH₃I + CH₃OH
Physical Properties
- Boiling Points: Alcohols and phenols have higher boiling points than hydrocarbons due to hydrogen bonding.
- Solubility: Alcohols are generally more soluble in water than hydrocarbons of comparable molecular mass due to the presence of the hydroxyl group.
Limitations of Williamson Synthesis
- Not effective for secondary or tertiary alkyl halides due to steric hindrance.
Key Concepts
- Acidity of Phenols: Ortho and para nitrophenols are more acidic than phenol due to resonance stabilization of the phenoxide ion.
- Electrophilic Substitution: The -OH group in phenols activates the benzene ring towards electrophilic substitution, directing incoming substituents to ortho and para positions.
Summary of Key Reactions
| Reaction Type | Example | Products |
|---|---|---|
| Williamson Synthesis | Sodium propoxide + 1-bromopropane | 1-Propoxypropane |
| Acid Dehydration | Ethanol | Ethene |
| Reaction with HI | Methoxybenzene + HI | Methanol + Iodide |
Conclusion
Understanding the structure, classification, and reactions of alcohols, phenols, and ethers is crucial for their application in various chemical processes.
CBSE Exam Tips, Important Questions & Common Mistakes to Avoid
Common Mistakes and Exam Tips
Common Pitfalls
- Misnaming Compounds: Ensure correct IUPAC naming of alcohols, phenols, and ethers. For example, CH₃OH is methyl alcohol, not methanol.
- Confusing Alcohol Types: Remember to classify alcohols accurately as primary, secondary, or tertiary based on the carbon to which the -OH group is attached.
- Ignoring Isomerism: When asked to draw structures, consider all possible isomers for given molecular formulas.
- Overlooking Physical Properties: Be aware that alcohols have higher boiling points than hydrocarbons due to hydrogen bonding.
Tips for Success
- Practice Nomenclature: Regularly practice writing IUPAC names and structures to build familiarity.
- Understand Reactions: Focus on understanding the mechanisms of reactions, such as the hydration of alkenes and the Williamson synthesis for ethers.
- Use Diagrams: Draw diagrams to visualize reactions and mechanisms, especially for complex reactions like the Reimer-Tiemann reaction.
- Review Solubility Trends: Remember that alcohols are more soluble in water than hydrocarbons of similar molecular weights due to their ability to form hydrogen bonds.
- Clarify Acid-Base Properties: Know the acidic nature of phenols compared to alcohols and how substituents affect acidity.
CBSE Quiz & Practice Test – MCQs, True/False Questions with Solutions
Multiple Choice Questions
A.
Oxidation of cumene with oxygen followed by acid-catalyzed rearrangement
B.
Direct chlorination of cumene followed by hydrolysis
C.
Hydrogenation of cumene followed by oxidation
D.
Nitration of cumene followed by reduction
Correct Answer: A
Solution:
Phenol is industrially prepared from cumene by oxidation with oxygen to form cumene hydroperoxide, which is then rearranged in the presence of an acid catalyst to yield phenol and acetone.
A.
KMnO₄
B.
NaBH₄
C.
LiAlH₄
D.
H₂/Pd
Correct Answer: A
Solution:
KMnO₄ is a strong oxidizing agent used to oxidize primary alcohols to carboxylic acids.
A.
Methanol
B.
Ethanol
C.
2-Methylpropan-2-ol
D.
Propan-1-ol
Correct Answer: C
Solution:
2-Methylpropan-2-ol is a tertiary alcohol because the carbon atom holding the hydroxyl group is attached to three other carbon atoms.
A.
Salicylaldehyde
B.
2,4,6-Tribromophenol
C.
Phenyl acetate
D.
Anisole
Correct Answer: A
Solution:
The Reimer-Tiemann reaction involves the formation of salicylaldehyde when phenol reacts with chloroform in the presence of aqueous NaOH.
A.
Propan-2-ol
B.
Cyclohexanol
C.
Butan-1-ol
D.
2-Methylpropan-2-ol
Correct Answer: A
Solution:
Propan-2-ol can be synthesized by the hydration of propene in the presence of an acid catalyst.
A.
Ethanol has a larger molecular mass.
B.
Ethanol forms hydrogen bonds.
C.
Methoxymethane is a solid at room temperature.
D.
Methoxymethane has a higher molecular mass.
Correct Answer: B
Solution:
Ethanol has a higher boiling point because it forms hydrogen bonds, which are stronger than the van der Waals forces present in methoxymethane.
A.
Ethanol cation
B.
Ethyl cation
C.
Ethyl ether
D.
Ethyl radical
Correct Answer: B
Solution:
During the dehydration of ethanol to ethene, an ethyl cation is formed as an intermediate after the protonation of the hydroxyl group.
A.
Nitro group is electron-withdrawing
B.
Methoxy group is electron-withdrawing
C.
Nitro group is electron-donating
D.
Methoxy group is electron-donating
Correct Answer: A
Solution:
The nitro group is electron-withdrawing, which stabilizes the phenoxide ion, making ortho nitrophenol more acidic.
A.
Salicylaldehyde
B.
Benzoic acid
C.
Phenyl acetate
D.
Anisole
Correct Answer: A
Solution:
Phenol reacts with chloroform in the presence of aqueous NaOH to form salicylaldehyde, a process known as the Reimer-Tiemann reaction.
A.
Kolbe's reaction
B.
Reimer-Tiemann reaction
C.
Oxidation with alkaline KMnO₄
D.
Oxidation of cumene hydroperoxide
Correct Answer: D
Solution:
Phenol is prepared from cumene by oxidation to form cumene hydroperoxide, which is then converted to phenol.
A.
Methoxyethane
B.
Ethoxymethane
C.
Dimethyl ether
D.
Methyl ethyl ether
Correct Answer: A
Solution:
The IUPAC name for CH₃CH₂OCH₃ is methoxyethane, as it consists of a methoxy group (CH₃O-) attached to an ethane (CH₃CH₂-) group.
A.
Ethylene glycol
B.
Methanol
C.
Phenol
D.
Ethanol
Correct Answer: A
Solution:
Ethylene glycol is a dihydric alcohol as it contains two hydroxyl groups.
A.
Phenol is less acidic than ethanol due to resonance stabilization of the phenoxide ion.
B.
Phenol is more acidic than ethanol because the phenoxide ion is resonance stabilized.
C.
Phenol and ethanol have similar acidity because both form stable ions.
D.
Ethanol is more acidic than phenol due to the electron-withdrawing effect of the ethyl group.
Correct Answer: B
Solution:
Phenol is more acidic than ethanol because the phenoxide ion formed after losing a proton is resonance stabilized, which is not the case for the ethoxide ion.
A.
Kolbe's reaction
B.
Williamson ether synthesis
C.
Reimer-Tiemann reaction
D.
Friedel-Crafts acylation
Correct Answer: B
Solution:
Williamson ether synthesis is a method used to prepare ethers.
A.
Methanol
B.
Propan-1-ol
C.
Butan-1-ol
D.
Pentan-1-ol
Correct Answer: A
Solution:
Methanol is the most soluble in water due to its ability to form hydrogen bonds and its smaller alkyl group, which is less hydrophobic.
A.
2,4,6-tribromophenol
B.
2-bromophenol
C.
4-bromophenol
D.
3-bromophenol
Correct Answer: A
Solution:
When phenol is treated with bromine in carbon disulfide, the major product is 2,4,6-tribromophenol.
A.
Alcohols have stronger van der Waals forces.
B.
Alcohols can form hydrogen bonds.
C.
Ethers have higher molecular weights.
D.
Ethers have stronger dipole-dipole interactions.
Correct Answer: B
Solution:
Alcohols have higher boiling points because they can form intermolecular hydrogen bonds.
A.
Salicylic acid
B.
Salicylaldehyde
C.
2,4,6-Tribromophenol
D.
Phenyl acetate
Correct Answer: A
Solution:
Kolbe's reaction involves the conversion of phenol into salicylic acid through the reaction with sodium hydroxide and carbon dioxide.
A.
1-Propoxypropane
B.
Ethoxybenzene
C.
2-Methoxy-2-methylpropane
D.
1-Methoxyethane
Correct Answer: A
Solution:
Williamson's synthesis involves the reaction of an alkoxide ion with a primary alkyl halide. 1-Propoxypropane can be synthesized by reacting sodium propoxide with 1-bromopropane. This method is less suitable for secondary and tertiary alkyl halides due to elimination side reactions.
A.
2-Bromo-3-methylbutane
B.
3-Bromo-3-methylbutane
C.
2-Methyl-2-butanol
D.
3-Methylbut-2-ene
Correct Answer: B
Solution:
The reaction of 3-methylbutan-2-ol with HBr proceeds through the formation of a secondary carbocation, which rearranges to a more stable tertiary carbocation by a hydride shift. This rearranged carbocation then reacts with bromide ion to form 3-bromo-3-methylbutane.
A.
PCC
B.
KMnO₄
C.
LiAlH₄
D.
H₂/Pd-C
Correct Answer: B
Solution:
KMnO₄ is a strong oxidizing agent that can oxidize benzyl alcohol to benzoic acid.
A.
2-Chloroethyl methyl ether
B.
Chloroethyl methoxy
C.
Methoxyethyl chloride
D.
Ethyl chloro methoxy
Correct Answer: A
Solution:
The IUPAC name for CH₃OCH₂CH₂Cl is 2-Chloroethyl methyl ether, where the longest chain is ethyl with a chlorine substituent.
A.
Cumene hydroperoxide
B.
Benzene
C.
Acetone
D.
Toluene
Correct Answer: A
Solution:
Cumene is first converted to cumene hydroperoxide, which is then transformed into phenol and acetone.
A.
Reaction of an alkyl halide with sodium alkoxide
B.
Dehydration of alcohols
C.
Hydration of alkenes
D.
Oxidation of alcohols
Correct Answer: A
Solution:
Williamson ether synthesis involves the reaction of an alkyl halide with sodium alkoxide to form an ether.
A.
Hydration of benzene
B.
Oxidation of benzene
C.
Hydrolysis of diazonium salts
D.
Reduction of benzene
Correct Answer: C
Solution:
Phenol can be prepared by hydrolysis of diazonium salts.
A.
Phenol reacts with NaOH to form sodium phenoxide.
B.
Phenol reacts with HCl to form chlorophenol.
C.
Phenol reacts with ethanol to form ethyl phenyl ether.
D.
Phenol reacts with bromine to form bromophenol.
Correct Answer: A
Solution:
Phenol reacts with bases like NaOH to form sodium phenoxide, demonstrating its acidic nature.
A.
2-Nitrophenol
B.
4-Nitrophenol
C.
2,4-Dinitrophenol
D.
3-Nitrophenol
Correct Answer: A
Solution:
When phenol is treated with dilute nitric acid, the major product is 2-nitrophenol due to the ortho-directing effect of the hydroxyl group.
A.
2,4,6-Tribromophenol
B.
Bromobenzene
C.
Phenyl bromide
D.
2-Bromophenol
Correct Answer: A
Solution:
The reaction of phenol with bromine in CS₂ leads to the formation of 2,4,6-tribromophenol due to the activating effect of the -OH group on the benzene ring.
A.
Propanal
B.
Propanoic acid
C.
Propanone
D.
Methanol
Correct Answer: B
Solution:
Propan-1-ol is a primary alcohol and oxidizes to form propanoic acid when treated with a strong oxidizing agent like alkaline KMnO₄.
A.
Phenol reacts with sodium hydroxide to form sodium phenoxide and water.
B.
Phenol reacts with bromine in carbon disulfide to form 2,4,6-tribromophenol.
C.
Phenol undergoes nitration to form nitrophenol.
D.
Phenol reacts with chloroform in the presence of NaOH to form salicylaldehyde.
Correct Answer: A
Solution:
Phenol reacts with sodium hydroxide to form sodium phenoxide and water, demonstrating its acidic nature.
A.
Methanol
B.
Propan-2-ol
C.
Ethanol
D.
Butan-1-ol
Correct Answer: B
Solution:
A secondary alcohol has the -OH group attached to a carbon atom that is bonded to two other carbon atoms. Propan-2-ol fits this description.
A.
Methanol
B.
Ethanol
C.
Propan-1-ol
D.
Butan-1-ol
Correct Answer: D
Solution:
The boiling point of alcohols increases with the length of the carbon chain due to stronger van der Waals forces. Butan-1-ol has the longest carbon chain among the options.
A.
2-Bromophenol
B.
4-Bromophenol
C.
2,4,6-Tribromophenol
D.
3-Bromophenol
Correct Answer: C
Solution:
When phenol reacts with bromine in carbon disulfide, it undergoes electrophilic substitution to form 2,4,6-tribromophenol. The hydroxyl group activates the benzene ring, making it more susceptible to bromination at the ortho and para positions.
A.
2,4-Dinitrophenol
B.
2-Nitrophenol
C.
3-Nitrophenol
D.
4-Nitrophenol
Correct Answer: B
Solution:
Phenol reacts with dilute HNO₃ to form 2-nitrophenol due to the activating effect of the hydroxyl group.
A.
Pyridinium chlorochromate (PCC)
B.
Alkaline KMnO₄
C.
Dilute HNO₃
D.
Concentrated H₂SO₄
Correct Answer: A
Solution:
Pyridinium chlorochromate (PCC) is a mild oxidizing agent used to oxidize primary alcohols to aldehydes without further oxidation to carboxylic acids.
A.
It involves the reaction of an alkyl halide with a sodium alkoxide.
B.
It requires an acid catalyst to proceed.
C.
It is used to prepare symmetrical ethers only.
D.
It is a method for the dehydration of alcohols.
Correct Answer: A
Solution:
The Williamson ether synthesis involves the reaction of an alkyl halide with a sodium alkoxide to produce an ether.
A.
Phenol
B.
Ethanol
C.
Cyclohexanol
D.
Methanol
Correct Answer: D
Solution:
Methanol is a primary alcohol, which is more likely to undergo an SN2 reaction with an alkyl halide to form an ether due to less steric hindrance compared to secondary or tertiary alcohols.
A.
CH₃CH₂OH
B.
CH₃CHOHCH₃
C.
CH₃C(CH₃)₂OH
D.
C₆H₅OH
Correct Answer: A
Solution:
CH₃CH₂OH is ethanol, a primary alcohol, because the hydroxyl group is attached to a carbon atom that is only bonded to one other carbon atom.
A.
Reaction of sodium ethoxide with ethyl bromide
B.
Reaction of ethanol with sulfuric acid
C.
Reaction of phenol with bromine in CS
D.
Reaction of methanol with hydrochloric acid
Correct Answer: A
Solution:
Williamson synthesis involves the reaction of an alkoxide ion with a primary alkyl halide to form an ether. In this case, sodium ethoxide reacting with ethyl bromide will form diethyl ether.
A.
Propene and propanol
B.
Iodopropane and propanol
C.
Propane and propene
D.
Iodopropane and propane
Correct Answer: B
Solution:
The reaction of 1-propoxypropane with HI results in the cleavage of the ether linkage, producing iodopropane and propanol.
A.
Phenol reacting with chloroform in the presence of NaOH to form salicylaldehyde.
B.
Phenol reacting with bromine in CS₂ to form 2,4,6-tribromophenol.
C.
Phenol reacting with dilute HNO₃ to form nitrophenols.
D.
Phenol reacting with acetic anhydride to form phenyl acetate.
Correct Answer: A
Solution:
The Reimer-Tiemann reaction involves the formation of salicylaldehyde from phenol using chloroform and NaOH.
A.
The nitro group is an electron-withdrawing group, increasing the acidity.
B.
The methoxy group donates electrons, decreasing acidity.
C.
The nitro group forms hydrogen bonds with water.
D.
The methoxy group forms a stable resonance structure.
Correct Answer: A
Solution:
Ortho nitrophenol is more acidic because the nitro group is an electron-withdrawing group, which stabilizes the phenoxide ion formed after deprotonation.
A.
SN1 reaction
B.
SN2 reaction
C.
E1 reaction
D.
E2 reaction
Correct Answer: B
Solution:
Cyclohexylmethanol can be prepared using an alkyl halide by an SN2 reaction, which involves a nucleophilic substitution mechanism.
A.
2-Methylpropan-2-ol
B.
Ethanol
C.
Propan-1-ol
D.
Butan-2-ol
Correct Answer: A
Solution:
A tertiary alcohol has the -OH group attached to a carbon atom that is bonded to three other carbon atoms. 2-Methylpropan-2-ol fits this description.
A.
Methanol
B.
Ethanol
C.
Propan-1-ol
D.
Butan-1-ol
Correct Answer: D
Solution:
Butan-1-ol has the highest boiling point due to the increased number of carbon atoms, which leads to stronger van der Waals forces.
A.
Potassium permanganate
B.
Pyridinium chlorochromate (PCC)
C.
Chromic acid
D.
Sodium dichromate
Correct Answer: B
Solution:
Pyridinium chlorochromate (PCC) is a reagent that oxidizes primary alcohols to aldehydes without further oxidation to carboxylic acids.
A.
CH₃CH₂OH + CH₃Br
B.
CH₃ONa + CH₃CH₂Br
C.
C₆H₅OH + NaOH
D.
CH₃CH₂OH + H₂SO₄
Correct Answer: B
Solution:
Williamson ether synthesis involves the reaction of an alkoxide ion with a primary alkyl halide to form an ether.
A.
Ethanol
B.
Propan-1-ol
C.
Butan-1-ol
D.
Pentan-1-ol
Correct Answer: A
Solution:
The reaction of a Grignard reagent with methanal (formaldehyde) produces a primary alcohol, specifically ethanol.
A.
Propanol
B.
Propan-1-ol
C.
Isopropanol
D.
Methoxyethane
Correct Answer: B
Solution:
The IUPAC name for CH₃-CH₂-CH₂-OH is Propan-1-ol, as it is a primary alcohol with the hydroxyl group on the first carbon.
A.
Phenol forms stronger hydrogen bonds with water.
B.
Phenoxide ion is resonance stabilized.
C.
Phenol has a higher molecular weight.
D.
Phenol is more soluble in water.
Correct Answer: B
Solution:
Phenol is more acidic than ethanol because the phenoxide ion, formed after losing a proton, is resonance stabilized. This stabilization disperses the negative charge over the aromatic ring, making the loss of a proton more favorable.
A.
Williamson ether synthesis
B.
Kolbe's reaction
C.
Reimer-Tiemann reaction
D.
Friedel-Crafts alkylation
Correct Answer: A
Solution:
Williamson ether synthesis is used to prepare ethers from alcohols.
A.
Hydration of styrene in the presence of an acid catalyst
B.
Hydroboration-oxidation of ethylene
C.
Ozonolysis of propene
D.
Dehydration of ethanol
Correct Answer: A
Solution:
1-phenylethanol can be prepared by the hydration of styrene (phenylethene) in the presence of an acid catalyst, where water adds across the double bond.
A.
2-Nitrophenol
B.
4-Nitrophenol
C.
2,4-Dinitrophenol
D.
3-Nitrophenol
Correct Answer: B
Solution:
When phenol is treated with dilute HNO₃, it predominantly forms 4-nitrophenol due to the activating effect of the hydroxyl group directing substitution to the para position.
A.
2,4,6-tribromophenol
B.
Bromobenzene
C.
Phenyl bromide
D.
Benzyl bromide
Correct Answer: A
Solution:
Phenol reacts with bromine in CS₂ to form 2,4,6-tribromophenol.
A.
Diethyl ether
B.
Ethoxybenzene
C.
1-Methoxyethane
D.
2-Methoxy-2-methylpropane
Correct Answer: B
Solution:
Ethoxybenzene can be synthesized using the Williamson ether synthesis, which involves the reaction of an alkoxide ion with a primary alkyl halide.
A.
Sodium phenoxide and ethyl bromide
B.
Phenol and ethyl bromide
C.
Sodium ethoxide and bromobenzene
D.
Phenol and sodium ethoxide
Correct Answer: A
Solution:
In Williamson ether synthesis, sodium phenoxide reacts with ethyl bromide to form ethoxybenzene.
A.
Ethanol has a larger molecular weight than methoxymethane.
B.
Ethanol can form hydrogen bonds, while methoxymethane cannot.
C.
Ethanol has a more complex molecular structure than methoxymethane.
D.
Ethanol is a polar molecule, whereas methoxymethane is non-polar.
Correct Answer: B
Solution:
Ethanol has a higher boiling point than methoxymethane because ethanol molecules can form intermolecular hydrogen bonds, which require more energy to break.
A.
Cyclohexyl bromide with sodium methoxide
B.
Cyclohexyl chloride with sodium hydroxide
C.
Cyclohexyl iodide with sodium acetate
D.
Cyclohexyl chloride with sodium methoxide
Correct Answer: B
Solution:
Cyclohexyl chloride can undergo an SN2 reaction with sodium hydroxide to form cyclohexylmethanol. The SN2 mechanism involves the nucleophilic attack of hydroxide ion on the carbon atom bearing the chloride, resulting in the substitution of the chloride ion with a hydroxyl group.
A.
Butan-1-ol
B.
Butan-2-ol
C.
2-Methylpropan-2-ol
D.
2,3-Dimethylbutan-2-ol
Correct Answer: A
Solution:
Hydroboration-oxidation of 1-butene results in the anti-Markovnikov addition of water, leading to the formation of butan-1-ol.
A.
CH₃OH
B.
C₆H₅OH
C.
CH₃OCH₃
D.
CH₃CH₂OH
Correct Answer: C
Solution:
CH₃OCH₃ is dimethyl ether, which is an example of an ether where an alkoxy group is attached to a carbon atom.
A.
Salicylaldehyde
B.
Catechol
C.
Hydroquinone
D.
Anisole
Correct Answer: A
Solution:
The Reimer-Tiemann reaction involves the conversion of phenol to salicylaldehyde using chloroform and sodium hydroxide.
A.
Ethanol has a larger molecular weight than methoxymethane.
B.
Ethanol forms stronger van der Waals forces than methoxymethane.
C.
Ethanol can form intermolecular hydrogen bonds, while methoxymethane cannot.
D.
Ethanol is more polar than methoxymethane.
Correct Answer: C
Solution:
Ethanol can form intermolecular hydrogen bonds due to the presence of the hydroxyl group, which significantly increases its boiling point compared to methoxymethane, which cannot form such bonds.
A.
CH₃CH₂OH
B.
CH₃CH(OH)CH₃
C.
CH₃C(CH₃)(OH)CH₃
D.
C₆H₅OH
Correct Answer: A
Solution:
CH₃CH₂OH is ethanol, which is a primary alcohol because the hydroxyl group is attached to a primary carbon atom.
A.
H₂SO₄
B.
KMnO₄
C.
NaOH
D.
HCl
Correct Answer: A
Solution:
Concentrated sulfuric acid (H₂SO₄) is commonly used to dehydrate alcohols to alkenes.
A.
Primary alkyl halide
B.
Secondary alkyl halide
C.
Tertiary alkyl halide
D.
Aryl halide
Correct Answer: A
Solution:
In Williamson ether synthesis, primary alkyl halides are preferred because they are less likely to undergo elimination reactions compared to secondary and tertiary alkyl halides.
A.
Alkaline KMnO₄
B.
PCC
C.
LiAlH₄
D.
NaBH₄
Correct Answer: A
Solution:
Alkaline KMnO₄ is a strong oxidizing agent that can oxidize primary alcohols to carboxylic acids.
A.
Salicylaldehyde
B.
Phenyl acetate
C.
Benzaldehyde
D.
Benzoic acid
Correct Answer: A
Solution:
The Reimer-Tiemann reaction involves treating phenol with chloroform in the presence of aqueous NaOH to form salicylaldehyde.
True or False
Correct Answer: True
Solution:
In alcohols, the boiling points decrease with an increase in branching of the carbon chain due to a decrease in van der Waals forces with a decrease in surface area.
Correct Answer: False
Solution:
Phenoxide ion is more reactive than phenol due to increased electron density from the negative charge, making it more susceptible to electrophilic substitution.
Correct Answer: False
Solution:
The excerpt states that the -OH group in phenols activates the aromatic ring towards electrophilic substitution due to the resonance effect.
Correct Answer: True
Solution:
The alkoxy group in ethers is an electron-donating group that activates the aromatic ring towards electrophilic substitution.
Correct Answer: True
Solution:
Ethers can be prepared by the dehydration of alcohols, which involves the removal of a water molecule.
Correct Answer: False
Solution:
Ethers generally have lower boiling points than alcohols of comparable molecular mass because alcohols can form intermolecular hydrogen bonds, which are stronger than the dipole-dipole interactions in ethers.
Correct Answer: True
Solution:
The presence of intermolecular hydrogen bonding in alcohols and phenols results in higher boiling points compared to hydrocarbons, which lack such bonding.
Correct Answer: True
Solution:
The excerpt states that alcohols, phenols, and ethers are the basic compounds for the formation of detergents, antiseptics, and fragrances, respectively.
Correct Answer: True
Solution:
Ethers can be prepared by the dehydration of alcohols and by Williamson synthesis.
Correct Answer: False
Solution:
The excerpt provides data showing that ethanol has a higher boiling point than methoxymethane due to the presence of intermolecular hydrogen bonding in alcohols.
Correct Answer: True
Solution:
Alcohols may be prepared by hydration of alkenes in the presence of an acid.
Correct Answer: True
Solution:
Phenols are more acidic than alcohols because the phenoxide ion formed after losing a hydrogen ion is resonance stabilized, making it more stable than the alkoxide ion formed from alcohols.
Correct Answer: False
Solution:
Tertiary alcohols dehydrate more readily than secondary or primary alcohols due to the stability of the carbocation intermediate formed during the reaction.
Correct Answer: False
Solution:
Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method due to potential side reactions and instability.
Correct Answer: True
Solution:
Ethanol can form hydrogen bonds due to its hydroxyl group, which significantly increases its boiling point compared to methoxymethane, which lacks this capability.
Correct Answer: True
Solution:
Alcohols, phenols, and ethers are indeed fundamental compounds used in the production of detergents, antiseptics, and fragrances, respectively.
Correct Answer: True
Solution:
Williamson ether synthesis involves the reaction of an alkyl halide with sodium alkoxide to form an ether.
Correct Answer: False
Solution:
The boiling points of alcohols increase with an increase in the number of carbon atoms due to increased van der Waals forces.
Correct Answer: True
Solution:
The C-O bond in ethers can indeed be cleaved by hydrogen halides, as mentioned in the excerpts.
Correct Answer: False
Solution:
In electrophilic substitution reactions, the alkoxy group in aryl alkyl ethers activates the benzene ring and directs the incoming substituents to ortho and para positions.
Correct Answer: True
Solution:
Ethers can be synthesized by the dehydration of alcohols, although this method is not suitable for secondary or tertiary alcohols.
Correct Answer: True
Solution:
Phenol is industrially synthesized from cumene via the formation of cumene hydroperoxide, which is then converted to phenol and acetone.
Correct Answer: True
Solution:
Phenols can be prepared by the substitution of a halogen atom in haloarenes with an -OH group.
Correct Answer: True
Solution:
Phenol is more acidic than ethanol because the negative charge on the phenoxide ion can be delocalized over the aromatic ring, providing resonance stabilization.
Correct Answer: True
Solution:
The presence of intermolecular hydrogen bonding in alcohols and phenols leads to higher boiling points compared to hydrocarbons, which lack such bonding.
Correct Answer: True
Solution:
The -OH group in phenols donates electron density to the benzene ring through resonance, making it more reactive towards electrophilic substitution.
Correct Answer: False
Solution:
Ethanol has a higher boiling point than methoxymethane due to the presence of hydrogen bonding in ethanol, which is absent in methoxymethane.
Correct Answer: True
Solution:
Alcohols and phenols are classified based on the number of hydroxyl groups and the hybridization of the carbon atom (sp³ or sp²) to which the -OH group is attached.
Correct Answer: False
Solution:
Phenol is more acidic than ethanol. The resonance stabilization of the phenoxide ion makes phenol more acidic.
Correct Answer: False
Solution:
The boiling points of alcohols increase with an increase in the number of carbon atoms due to stronger van der Waals forces.
Correct Answer: False
Solution:
Tertiary alcohols are resistant to oxidation and do not easily form carboxylic acids.
Correct Answer: True
Solution:
Alcohols and phenols are indeed classified by the number of hydroxyl groups they contain and the hybridization state of the carbon atom bonded to the hydroxyl group.
Correct Answer: True
Solution:
The high boiling points of alcohols are mainly due to the presence of intermolecular hydrogen bonding in them, which is lacking in ethers.
Correct Answer: True
Solution:
The -OH group in phenols activates the benzene ring towards electrophilic substitution due to resonance, directing incoming groups to ortho and para positions.
Correct Answer: False
Solution:
The substitution of a hydrogen atom in a hydrocarbon by an alkoxy or aryloxy group yields ethers, not alcohols.
Correct Answer: False
Solution:
Phenols are formed when a hydrogen atom in an aromatic hydrocarbon is replaced by an -OH group, not in an aliphatic hydrocarbon.
Correct Answer: True
Solution:
Ethers can be cleaved by hydrogen halides, which is a common reaction involving the breaking of the C-O bond in ethers.
Correct Answer: True
Solution:
Alcohols, phenols, and ethers are indeed used in the formation of detergents, antiseptics, and fragrances, respectively, as mentioned in the provided excerpts.
Correct Answer: True
Solution:
Ethers can be prepared by the dehydration of alcohols, although this method is not suitable for secondary or tertiary alcohols.
Correct Answer: True
Solution:
Tertiary alcohols do not have a hydrogen atom attached to the carbon with the -OH group, making them resistant to oxidation compared to primary and secondary alcohols.
Correct Answer: True
Solution:
Alcohols can form intermolecular hydrogen bonds due to the presence of the -OH group, which increases their boiling points compared to ethers that lack such hydrogen bonding.
Correct Answer: False
Solution:
Phenols are more acidic than alcohols because the phenoxide ion formed after losing a hydrogen ion is resonance stabilized, which is not the case for alkoxide ions from alcohols.
Correct Answer: True
Solution:
Alcohols and phenols can form hydrogen bonds due to the presence of the hydroxyl group (-OH), while ethers can form hydrogen bonds due to the presence of the oxygen atom. This ability contributes to their solubility in water.
Correct Answer: False
Solution:
Electron-withdrawing groups in phenol increase its acidic strength by stabilizing the phenoxide ion.
Correct Answer: True
Solution:
The ability of alcohols, phenols, and ethers to form intermolecular hydrogen bonding with water makes them soluble in it.
Correct Answer: False
Solution:
The -OH group in phenols activates the aromatic ring towards electrophilic substitution due to the resonance effect.
Correct Answer: True
Solution:
Phenols can be prepared by substituting the halogen atom in haloarenes with a hydroxyl group.
Correct Answer: True
Solution:
Alcohols can form hydrogen bonds with water molecules, increasing their solubility compared to hydrocarbons, which cannot form such bonds.
Correct Answer: True
Solution:
Ethers have boiling points that resemble those of alkanes because they lack the hydrogen bonding that significantly raises the boiling points of alcohols.
Correct Answer: True
Solution:
Tertiary alcohols do not have a hydrogen atom attached to the carbon with the -OH group, making them resistant to oxidation.
Correct Answer: True
Solution:
Alcohols can indeed be prepared by the hydration of alkenes in the presence of an acid, as this is a common method for synthesizing alcohols.
Correct Answer: False
Solution:
The presence of an -OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect.
Correct Answer: True
Solution:
The -OH group in phenols donates electrons to the benzene ring through resonance, increasing the electron density on the ring and activating it towards electrophilic substitution reactions.
Correct Answer: True
Solution:
The solubility of alcohols in water is due to their ability to form hydrogen bonds, making them more soluble than hydrocarbons of comparable molecular masses.
Correct Answer: True
Solution:
Ethers may be prepared by Williamson synthesis.
Correct Answer: True
Solution:
Williamson ether synthesis involves the reaction of an alkoxide ion with a primary alkyl halide, which can be used to prepare both symmetrical and unsymmetrical ethers.
Correct Answer: False
Solution:
The substitution of a hydrogen atom in a hydrocarbon by an alkoxy group results in the formation of ethers, not alcohols.
Correct Answer: True
Solution:
Ethers are indeed formed by replacing a hydrogen atom in a hydrocarbon with an alkoxy or aryloxy group, as described in the excerpts.
Correct Answer: True
Solution:
The solubility of alcohols in water decreases as the size of the hydrophobic alkyl group increases, reducing the ability to form hydrogen bonds with water.