Organic Chemistry - Alcohols, Phenols, and Ethers

Introduction

• Alcohols, phenols, and ethers are important compounds used in various industries and daily life.

• Substitution of hydrogen atoms in hydrocarbons with other atoms or groups of atoms results in the formation of new compounds with different properties and applications.

• Alcohols and phenols are formed when a hydrogen atom in a hydrocarbon is replaced by an -OH group.

• Ethers are formed by substituting the hydrogen atom of the hydroxyl group of an alcohol or phenol with an alkyl or aryl group.

Classification of Alcohols, Phenols, and Ethers

• Alcohols and phenols can be classified as mono-, di-, tri-, or polyhydric compounds based on the number of hydroxyl groups they contain.

• Alcohols can be further classified based on the hybridization of the carbon atom to which the hydroxyl group is attached.

• Allylic alcohols have the -OH group attached to a sp3 hybridized carbon adjacent to a carbon-carbon double bond.

• Benzylic alcohols have the -OH group attached to a sp3 hybridized carbon atom next to an aromatic ring.

• Ethers can be classified as simple or symmetrical if the alkyl or aryl groups attached to the oxygen atom are the same, and mixed or unsymmetrical if the two groups are different.

Nomenclature

• Alcohols are named by substituting the 'e' of the alkane name with the suffix 'ol' and indicating the position of substituents using numerals.

• Polyhydric alcohols retain the 'e' of the alkane name and add the multiplicative prefix (di, tri, etc.) before 'ol' to indicate the number of -OH groups.

• Phenols are named using common names or accepted IUPAC names, with the terms ortho, meta, and para used to indicate the positions of substituents in substituted compounds.

Examples of Alcohols and Phenols

• Methyl alcohol (methanol) - CH3OH

• n-Propyl alcohol (propan-1-ol) - CH3CH2CH2OH

• Isopropyl alcohol (propan-2-ol) - CH3CH(OH)CH3

• n-Butyl alcohol (butan-1-ol) - CH3CH2CH2CH2OH

• sec-Butyl alcohol (butan-2-ol) - CH3CH(OH)CH2CH3

• Isobutyl alcohol (2-methylpropan-1-ol) - (CH3)2CHCH2OH

• tert-Butyl alcohol (2-methylpropan-2-ol) - (CH3)3COH

• Ethylene glycol (ethane-1,2-diol) - HOCH2CH2OH

• Glycerol (propane-1,2,3-triol) - HOCH2CH(OH)CH2OH

• Cyclohexanol - OH

• 2-Methylcyclopentanol

Reactions and Preparation

• Alcohols can be prepared from alkenes, aldehydes, ketones, and carboxylic acids.

• Phenols can be prepared from haloarenes, benzene sulphonic acids, diazonium salts, and cumene.

• Ethers can be prepared from alcohols and alkyl halides, or from alcohols and sodium alkoxides/aryloxides.

Physical Properties and Functional Groups

• The physical properties of alcohols, phenols, and ethers can be correlated with their structures.

• Chemical reactions of these compounds can be explained based on their functional groups.

Note: This summary includes the main ideas and supporting details from the given transcript on pages 1-4.

Page 5:

• Alcohols, Phenols, and Ethers

• Common names and IUPAC names of alcohols, phenols, and ethers

  • Alcohols:

    • Common names: Phenol, o-Cresol, m-Cresol, p-Cresol

    • IUPAC names: Phenol, 2-Methylphenol, 3-Methylphenol, 4-Methylphenol

  • Dihydroxy derivatives of benzene:

    • Common names: Catechol, Benzene-diol, 1,2-Resorcinol, Benzene-diol 1,3-, Hydroquinone or quinol

    • IUPAC names: Benzene-diol 1,4-

  • Ethers:

    • Common names derived from alkyl/aryl groups

    • Example: CH3OC2H5 is ethylmethyl ether

  • Table 7.2: Common and IUPAC Names of Some Ethers

Page 6:

• Chemistry

• Naming ethers in the IUPAC system

• Ethers as hydrocarbon derivatives with -OR or -OAr groups

• Larger (R) group chosen as the parent hydrocarbon

• Example 7.1: Naming compounds according to IUPAC system

Page 7:

• Alcohols, Phenols, and Ethers

• Bond angles in alcohols, phenols, and ethers

• Oxygen of -OH group attached to carbon by sigma bond

• Structure of methanol, phenol, and methoxymethane

• IUPAC names of compounds

Page 8:

• Chemistry

• Preparation of alcohols

  • From alkenes: acid-catalyzed hydration and hydroboration-oxidation

  • From carbonyl compounds: reduction of aldehydes, ketones, carboxylic acids, and esters

• Hydroboration-oxidation reaction

• Reduction of aldehydes and ketones using catalysts

• Reduction of carboxylic acids and esters using lithium aluminium hydride

• Use of esters for commercial reduction of acids to alcohols

Page 9:

• Alcohols are produced by the reaction of Grignard reagents with aldehydes and ketones.

  • First step: nucleophilic addition of Grignard reagent to the carbonyl group to form an adduct.

  • Hydrolysis of the adduct yields an alcohol.

• Different aldehydes and ketones produce different types of alcohols.

  • Methanal produces a primary alcohol.

  • Other aldehydes produce secondary alcohols.

  • Ketones produce tertiary alcohols.

• Examples of reactions:

  • Catalytic reduction of butanal.

  • Hydration of propene in the presence of dilute sulphuric acid.

  • Reaction of propanone with methylmagnesium bromide followed by hydrolysis.

Page 10:

• Phenol can be prepared from various sources:

  • Chlorobenzene is fused with NaOH to obtain phenol.

  • Benzene is sulphonated with oleum to form benzene sulphonic acid, which is then converted to sodium phenoxide.

  • Aromatic primary amines are treated with nitrous acid to form diazonium salts, which can be hydrolyzed to phenols.

  • Cumene can be oxidized to cumene hydroperoxide, which is then converted to phenol and acetone.

Page 11:

• Alcohols and phenols consist of an alkyl/aryl group and a hydroxyl group.

• Boiling points of alcohols and phenols increase with the number of carbon atoms.

• Boiling points of alcohols decrease with branching in the carbon chain.

• Alcohols and phenols can form intermolecular hydrogen bonding.

• Boiling points of alcohols and phenols are higher compared to hydrocarbons, ethers, haloalkanes, and haloarenes of similar molecular masses.

Page 12:

• High boiling points of alcohols are due to intermolecular hydrogen bonding.

• Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with water molecules.

• Solubility decreases with the increase in size of alkyl/aryl groups.

• Examples of compounds arranged in order of increasing boiling points.

Page 13:

• Alcohols and phenols can react as nucleophiles and electrophiles.

• Reactions involving cleavage of O-H bond.

  • Alcohols and phenols react with active metals to yield alkoxides/phenoxides and hydrogen.

  • Phenols can react with aqueous sodium hydroxide to form sodium phenoxides.

• Acidity of alcohols and phenols.

  • Alcohols and phenols are Brönsted acids.

  • Acidity of alcohols is influenced by the polar nature of the O-H bond.

  • Electron-releasing groups decrease the acid strength of alcohols.

Organic Chemistry Notes

Page 14

• Alcohols are weaker acids than water

  • Water is a better proton donor (stronger acid) than alcohol

  • Alkoxide ion is a better proton acceptor than hydroxide ion, suggesting alkoxides are stronger bases

• Alcohols act as Bronsted bases

  • Presence of unshared electron pairs on oxygen makes them proton acceptors

• Phenols are stronger acids than alcohols and water

  • Phenol's resonance structures cause oxygen of -OH group to be positive

  • Phenol's higher electronegativity of sp2 hybridized carbon decreases electron density on oxygen, increasing polarity of O-H bond and ionization of phenols

Page 15

• Phenoxide ion is more stable than alkoxide ion due to charge delocalization

• Phenol is more acidic than ethanol

• pKa values of some phenols and ethanol:

  • o-Nitrophenol: 7.2

  • m-Nitrophenol: 8.3

  • p-Nitrophenol: 7.1

  • Phenol: 10.0

  • o-Cresol: 10.2

  • m-Cresol: 10.1

  • p-Cresol: 10.2

  • Ethanol: 15.9

• Increasing order of acid strength: Propan-1-ol, 2,4,6-trinitrophenol, 3-nitrophenol, 3,5-dinitrophenol, phenol, 4-methylphenol

Page 16

• Alcohols and phenols react with carboxylic acids, acid chlorides, and acid anhydrides to form esters

• Electron-withdrawing groups enhance the acidic strength of phenol, while electron-releasing groups decrease it

• Acetylation of salicylic acid produces aspirin

• Reactions involving cleavage of C-O bond in alcohols

  • Alcohols react with hydrogen halides to form alkyl halides

  • Alcohols react with phosphorus trihalides to form alkyl bromides

  • Alcohols undergo dehydration to form alkenes

• Tertiary alcohols are easiest to dehydrate, followed by secondary and primary alcohols

Page 17

• Mechanism of dehydration of ethanol involves formation of protonated alcohol, carbocation, and ethene

• Oxidation of alcohols involves formation of a carbon-oxygen double bond with cleavage of O-H and C-H bonds

• Primary alcohol is oxidized to aldehyde, which is further oxidized to carboxylic acid

• Tertiary carbocations are more stable and easier to form than secondary and primary carbocations

Page 18:

• Strong oxidizing agents used to obtain carboxylic acids from alcohols directly

  • Acidified potassium permanganate

• CrO3 used as oxidizing agent for isolation of aldehydes

• Pyridinium chlorochromate (PCC) is a better reagent for oxidation of primary alcohols to aldehydes

• Chromic anhydride (CrO3) used to oxidize secondary alcohols to ketones

• Tertiary alcohols do not undergo oxidation reaction

• Cleavage of C-C bonds occurs under strong reaction conditions, forming a mixture of carboxylic acids with fewer carbon atoms

• Dehydrogenation of primary or secondary alcohols over heated copper at 573 K forms aldehydes or ketones, while tertiary alcohols undergo dehydration

• Methanol and ethanol undergo biological oxidation in the body, producing corresponding aldehydes followed by acids

• Methanol poisoning can be treated by giving intravenous infusions of diluted ethanol

Page 19:

• Phenols undergo electrophilic substitution reactions on the aromatic ring

• The -OH group attached to the benzene ring activates it towards electrophilic substitution

• The -OH group directs incoming groups to ortho and para positions due to resonance effect

• Common electrophilic aromatic substitution reactions in phenol include nitration and halogenation

• Nitration of phenol yields a mixture of ortho and para nitrophenols

• Halogenation of phenol forms different reaction products under different experimental conditions

• Phenol can undergo Kolbe's reaction and Reimer-Tiemann reaction

• Phenol can be oxidized to produce benzoquinone

Page 20:

• Phenol reacts with bromine to form monobromophenols in solvents of low polarity and low temperature

• The presence of the -OH group in phenol polarizes the bromine molecule, allowing halogenation to occur even without a Lewis acid

• Phenol treated with bromine water forms 2,4,6-tribromophenol as a white precipitate

• Phenol can undergo Kolbe's reaction and Reimer-Tiemann reaction

• Phenol can be oxidized to produce benzoquinone

• Alcohol reactions with HCl-ZnCl2, HBr, and SOCl2 are discussed

• Acid-catalyzed dehydration of 1-methylcyclohexanol and butan-1-ol is discussed

• Ortho and para nitrophenols are more acidic than phenol

• Equations for Reimer-Tiemann reaction and Kolbe's reaction are provided

Page 22:

• Methanol and ethanol are commercially important alcohols.

  • Methanol is produced by catalytic hydrogenation of carbon monoxide.

    • Methanol is highly poisonous and used as a solvent in paints and varnishes.

  • Ethanol is obtained by fermentation of sugars.

    • Ethanol is used as a solvent in the paint industry and in the preparation of carbon compounds.

    • Ethanol is made unfit for drinking through denaturation.

Page 23:

• Alcohols can undergo dehydration to form alkenes or ethers.

  • Dehydration of ethanol can produce ethene or ethoxyethane depending on the reaction conditions.

• Ethers can be prepared through acidic dehydration of alcohols or through Williamson synthesis.

  • Williamson synthesis is suitable for preparing symmetrical and unsymmetrical ethers.

  • Diethyl ether has been used as an inhalation anaesthetic.

Page 24:

• Alkyl halides can react with sodium alkoxide to form ethers through Williamson synthesis.

  • Primary alkyl halides give better results than secondary and tertiary alkyl halides.

  • Tertiary alkyl halides only produce alkenes.

• The C-O bonds in ethers are polar, giving them a net dipole moment.

  • Ethers have lower boiling points than alcohols due to the absence of hydrogen bonding.

  • Ethers can form hydrogen bonds with water, similar to alcohols.

Page 25:

• Ethers are the least reactive of the functional groups.

  • Cleavage of C-O bond in ethers occurs under drastic conditions with excess hydrogen halides.

  • Alkyl aryl ethers are cleaved at the alkyl-oxygen bond, yielding phenol and alkyl halide.

• Ethers have similar miscibility with water as alcohols of the same molecular mass.

  • Ethoxyethane and butan-1-ol are miscible with water, while pentane is immiscible.

Page 26

• Reaction of ether with concentrated HI

  • Step 1: Protonation of ether molecule

  • Step 2: Attack by iodide ion displaces alcohol molecule by SN2 mechanism

    • Alkyl iodide formed depends on the nature of alkyl groups

      • Primary or secondary alkyl groups: lower alkyl group forms alkyl iodide (SN2 reaction)

      • Tertiary alkyl group: tertiary halide formed (SN1 mechanism)

  • Step 3: Mechanism for tertiary alkyl group formation

• Cleavage of mixed ethers with two different alkyl groups

  • Alcohol and alkyl iodide formed depend on alkyl groups

  • Tertiary alkyl group forms tertiary halide due to more stable carbocation formation

• Reaction of anisole (methylphenyl ether)

  • Formation of methylphenyl oxonium ion by protonation of ether

  • Weaker bond between O-CH3 compared to O-C6H5 due to partial double bond character

Page 27

• Phenols do not react further to give halides

  • sp2 hybridized carbon of phenol cannot undergo nucleophilic substitution reaction

• Electrophilic substitution of alkoxy group (-OR)

  • Ortho, para directing and activates aromatic ring

• Halogenation of phenylalkyl ethers

  • Anisole undergoes bromination in the benzene ring

  • Activation of benzene ring by methoxy group

  • Para isomer obtained in 90% yield

Page 28

• Williamson synthesis of 2-ethoxy-3-methylpentane

• Reactants for the preparation of 1-methoxy-4-nitrobenzene

• Friedel-Crafts reaction of anisole

  • Introduction of alkyl and acyl groups at ortho and para positions

• Nitration of anisole

  • Mixture of ortho and para nitroanisole formed

Page 29

• Classification of alcohols, phenols, and ethers

• Preparation of alcohols and phenols

• Solubility and boiling points of alcohols, phenols, and ethers

• Acidic nature of alcohols and phenols

• Nucleophilic substitution of alcohols with hydrogen halides

• Dehydration of alcohols to form alkenes

• Oxidation of alcohols

• Activation of aromatic ring in phenols

• Reimer-Tiemann reaction of phenol

• Kolbe's reaction of phenol in alkaline medium

• Preparation of ethers

• Cleavage of C-O bond in ethers by hydrogen halides

• Electrophilic substitution of alkoxy group in ethers

Page 30: Chemistry 222 Exercises

• Write IUPAC names of compounds

  • (i) C6H5–O–C2H5

  • (ii) C6H5–O–C7H15(n–)

  • (iii) 2-Methylbutan-2-ol

  • (iv) 1-Phenylpropan-2-ol

  • (v) 3,5-Dimethylhexane –1, 3, 5-triol

  • (vi) 2,3 – Diethylphenol

  • (vii) 1 – Ethoxypropane

  • (viii) 2-Ethoxy-3-methylpentane

  • (ix) Cyclohexylmethanol

  • (x) 3-Cyclohexylpentan-3-ol

  • (xi) Cyclopent-3-en-1-ol

  • (xii) 4-Chloro-3-ethylbutan-1-ol

• Draw structures of compounds with given IUPAC names

• Draw structures of isomeric alcohols with molecular formula C5H12O

• Classify isomers of alcohols as primary, secondary, and tertiary

• Explain why propanol has a higher boiling point than butane

• Explain why alcohols are more soluble in water than hydrocarbons

• Define hydroboration-oxidation reaction and provide an example

• Provide structures and IUPAC names of monohydric phenols with molecular formula C7H8O

• Identify the isomer of ortho and para nitrophenols that is steam volatile

• Provide equations for the preparation of phenol from cumene

• Provide the chemical reaction for the preparation of phenol from chlorobenzene

• Explain the mechanism of hydration of ethene to yield ethanol

• Provide equations for the preparation of phenol using benzene, conc. H2SO4, and NaOH

Page 31: Alcohols, Phenols and Ethers

• Synthesize 1-phenylethanol from a suitable alkene

• Synthesize cyclohexylmethanol using an alkyl halide by an SN2 reaction

• Synthesize pentan-1-ol using a suitable alkyl halide

• Provide two reactions that show the acidic nature of phenol and compare it with ethanol

• Explain why ortho nitrophenol is more acidic than ortho methoxyphenol

• Explain how the -OH group attached to a carbon of a benzene ring activates it towards electrophilic substitution

• Provide equations for various reactions involving alcohols and phenols

• Explain Kolbe's reaction, Reimer-Tiemann reaction, Williamson ether synthesis, and unsymmetrical ether

• Provide the mechanism of acid dehydration of ethanol to yield ethene

• Explain the conversions of propene to propan-2-ol, benzyl chloride to benzyl alcohol, ethyl magnesium chloride to propan-1-ol, and methyl magnesium bromide to 2-Methylpropan-2-ol

• Name the reagents used in various reactions involving alcohols and phenols

• Explain the higher boiling point of ethanol compared to methoxymethane

Page 32:

• Provide IUPAC names of various ethers

• Provide names of reagents and equations for the preparation of ethers by Williamson's synthesis

• Illustrate the limitations of Williamson synthesis for the preparation of certain types of ethers

• Synthesize 1-propoxypropane from propan-1-ol and provide the mechanism of this reaction

• Explain why the preparation of ethers by acid dehydration of secondary or tertiary alcohols is not suitable

• Provide the reaction equations of hydrogen iodide with various ethers

• Explain the activation and directing effects of alkoxy groups in aryl alkyl ethers

• Provide the mechanism of the reaction of HI with methoxymethane

• Provide equations for various reactions involving ethers

• Synthesize alcohols from appropriate alkenes

• Provide the mechanism for the reaction of 3-methylbutan-2-ol with HBr

Page 33: Answers to Some Intext Questions

• Identify primary, secondary, and tertiary alcohols

• Provide IUPAC names for primary, secondary, and tertiary alcohols

• Provide structures and IUPAC names for isomeric alcohols with molecular formula C5H12O

Organic Chemistry - Page 34

Chemistry 226 7.11 (ii) 7.12 (i)

• Reaction: CH CH CH OH + CH Br -> (CH C I C H OH)3

• Rationalized in 2023-24

Supporting Details

• The reaction involves the addition of CH Br to CH CH CH OH

• The resulting compound is (CH C I C H OH)3

• The reaction was rationalized in 2023-24

Chemistry 226 7.11 (ii) 7.12 (iii)

• Reaction: CH CH CH OH + CH Br -> (CH C I C H OH)5

Supporting Details

• The reaction involves the addition of CH Br to CH CH CH OH

• The resulting compound is (CH C I C H OH)5

Chemistry 226 7.11 (ii) 7.12 (iv)

• Reaction: CH CH CH OH + CH Br -> (CH C I C H OH)2

Supporting Details

• The reaction involves the addition of CH Br to CH CH CH OH

• The resulting compound is (CH