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Chapter 13 Alcohols, Phenols, and Thiols

13.1

Alcohols, Phenols, and Thiols

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Alcohols and Phenols

An alcohol contains A hydroxyl group

(—OH) attached to a carbon chain.

A phenol contains A hydroxyl group

(—OH) attached to a benzene ring.

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Alcohols are classified By the number of alkyl groups attached to the carbon

bonded to the hydroxyl. As primary (1°), secondary (2°), or tertiary (3°).

Primary (1º) Secondary (2º) Tertiary (3º)1 group 2 groups 3 groups H CH3 CH3

| | | CH3—C—OH CH3—C—OH CH3—C—OH

| | | H H CH3

Classification of Alcohols

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Classify each alcohol as (P) primary, (S) secondary, or (T) tertiary.

OH |

1. CH3—CH—CH2—CH3

2. CH3—CH2—CH2—OH

OH |

3. CH3—CH2—C—CH2—CH3 |

CH3

Learning Check

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OH |

1. CH3—CH—CH2—CH3 (S) secondary

2. CH3—CH2—CH2—OH (P) primary

OH |

3. CH3—CH2—C—CH2—CH3 (T) tertiary |

CH3

Solution

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Naming Alcohols

The names of alcohols In the IUPAC system replace -e of alkane name with -ol. that are common names use the name of the alkyl group

followed by alcohol. Formula IUPACCommon Name

CH4 methane

CH3─OH methanol methyl alcohol

CH3─CH3 ethane

CH3─CH2─OH ethanol ethyl alcohol

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More Names of Alcohols

In IUPAC names for longer carbon chains, the chain is

numbered from the end nearest the ─OH group.

CH3─CH2─CH2─OH 1-propanol

OH │CH3─CH─CH2─CH3 2-butanol

CH3 OH │ │CH3─CH─CH2─CH2─CH─CH3 5-methyl-2-

hexanol6 5 4 3 2 1

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Some Typical Alcohols

OH |“rubbing alcohol” CH3—CH—CH3

2-propanol (isopropyl alcohol)

antifreeze HO—CH2—CH2—OH

1,2-ethanediol (ethylene glycol) OH

| glycerolHO—CH2—CH—CH2—OH

1,2,3-propanetriol

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Learning Check

Give the IUPAC name for each of the following:

1. CH3—CH2—CH2—CH2—OH

OH CH3 | |2. CH3—CH—CH—CH2—CH3

3.

OH

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Solution

1. CH3—CH2—CH2—CH2—OH 1-butanol

OH CH3 | |2. CH3—CH—CH—CH2—CH3 3-methyl-2-pentanol

3. cyclopentanol OH

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Write the structure of the following:

A. 3-pentanol

B. ethyl alcohol

C. 3-methylcyclohexanol

Learning Check

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Solution

Write the structure of the following:A. 3-pentanol OH

|CH3—CH2—CH—CH2—CH3

B. ethyl alcohol CH3 —CH2 —OH

C. 3-methylcyclohexanol

CH3

OH

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Naming Phenols

To name a phenol with two substituents, Assign C-1 to the carbon attached to the –OH. Number the ring to give the lowest numbers. Use prefixes o, m, and p for common names.

OH

Cl

OHOH

Br

Phenol 3-chlorophenol 4-bromophenol (m-chlorophenol) (p-bromophenol)

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Phenols in Medicine

Phenol Is the IUPAC name for benzene with a hydroxyl

group. Is used in antiseptics and disinfectants.

phenol resorcinol 4-hexylresorcinol

OH

OH

CH2CH2CH2CH2CH2CH3

OH OH

OH

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Derivatives of Phenol

Compounds of phenol are the active ingredients in the essential oils of cloves, vanilla, nutmeg, and mint.

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Write the structure of each of the following:

A. 3-pentanol

B. ethyl alcohol

C. p-methylphenol

Learning Check

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Solution

Write the structure of each of the following:A. 3-pentanol OH

|CH3—CH2—CH—CH2—CH3

B. ethyl alcohol CH3—CH2—OH

C. p-methylphenol OH

CH3

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Thiols

Thiols Are carbon compounds

that contain a –SH group.

Are named in the IUPAC system by adding thiol to the alkane name of the longest carbon chain.

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In thiols with long carbon chains, the chain is numbered to locate the –SH group.

CH3—CH2—CH2—SH 1-propanethiol

SH |

CH3—CH—CH3 2-propanethiol

Naming Thiols

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Thiols

Thiols Often have

strong odors. Are used to

detect gas leaks. Are found in

onions, oysters, and garlic.

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Learning Check

Draw the structure of each compound.

A. 2-butanethiol

B. 2-methyl-1-butanol

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Solution

Draw the structure of each compound.A. 2-butanethiol

SH|

CH3—CH—CH2—CH3

B. 2-methyl-1-butanol

CH3

| HO—CH2—CH—CH2—CH3

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Learning Check

Name each of the following compounds: OH | A. CH3—CH2 —CH—CH3

CH3

| B. CH3—CH2—CH—CH2—CH2—OH

C. CH3—CH2—CH2—SH

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Solution

Name each of the following compounds:

OH | A. CH3—CH2 —CH—CH3 2-butanol

CH3

| B. CH3—CH2—CH—CH2—CH2—OH

3-methyl-1-pentanol

C. CH3—CH2—CH2—SH

1-propanethiol

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Chapter 13 Alcohols, Phenols, Ethers, and Thiols

13.2

Ethers

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Ethers

Ethers Contain an ─O─ between two carbon groups. That are simple are named by listing the alkyl names in alphabetical

order followed by ether

CH3─O─CH3 CH3─CH2─O─CH3

dimethyl ether ethyl methyl ether

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IUPAC Names for Ethers

In the IUPAC system, the shorter alkyl group and the oxygen are named as an alkoxy group attached to the longer alkane.

methoxy propane

CH3—O—CH2—CH2—CH3

1 2 3

Numbering the longer alkane gives

1-methoxypropane

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Ethers as Anesthetics

Anesthetics Inhibit pain signals to the brain. Such as ethyl ether CH3─CH2─O─CH2─CH3 were used

for over a century, but caused nausea and were flammable.

Developed by 1960s were nonflammable. Cl F F Cl F H │ │ │ │ │ │ H─C─C─O─C─H H─C─C─O─C─H │ │ │ │ │ │ F F F H F H

Ethane(enflurane) Penthrane

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MTBE

Methyl tert-butyl ether CH3

│

CH3─O─C─CH3

│ CH3

Is one of the most produced organic chemicals.

Is a fuel additive

Is used to improve gasoline combustion.

Use is questioned since the discovery that MTBE has contaminated water supplies.

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Learning Check

Draw the structure of each compound.

A. diethyl ether

B. ethyl methyl ether

C. 2-methoxybutane

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Solution

Draw the structure of each compound.A. diethyl ether

CH3—CH2—O—CH2—CH3

B. ethyl methyl ether CH3—CH2—O—CH3

C. 2-methoxybutane

O—CH3

| CH3—CH—CH2—CH3

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Cyclic Ethers

A cyclic ether Contains an O atom in a carbon ring. Is called a heterocyclic compound. Typically has 5 (furan) or 6 atoms (pyran) in the

ring.

O O O

furan tetrahydrofuran pyran 1,4-dioxane

O

O

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Dioxins

Dioxins are A group of ethers that are highly toxic. Formed during forest fires and as industrial by-

products. Often carcinogenic.

Cl

Cl Cl

OCH2 OHC

O

Cl

Cl

O

O

Cl

Cl

2,4,5-trichlorophenoxyacetic acid 2,3,7,8-tetrachlorodibenzodioxin(2,4,5-T; agent orange) (TTCC, “dioxin”)

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Learning Check

Name each of the following:

1.

2. O

O

OCH3

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Solution

1. methoxy cyclopentane

(cyclopentyl methyl ether)

2. 1,4-dioxaneO

O

OCH3

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Chapter 13 Alcohols, Phenols, Ethers, and Thiols

13.3

Physical Properties of Alcohols,

Phenols, and Ethers

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Boiling Points of Alcohols

Alcohols Contain a strongly

electronegative O in the OH groups.

Form hydrogen bonds between alcohol molecules.

Have higher boiling points than alkanes and ethers of similar mass.

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Boiling Points of Ethers

Ethers Have an O atom, but

no H is attached. Cannot form hydrogen

bonds between ether molecules.

Have boiling points similar to alkanes of similar mass.

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Solubility of Alcohols and Ethers in Water Alcohols and ethers are more soluble in water than

alkanes because the oxygen atom hydrogen bonds with water.

Alcohols with 1-4 C atoms are soluble, but alcohols with 5 or more C atoms are not.

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Comparing Solubility and Boiling Points

Compound Molar Boiling Soluble

Mass Point (°C) in Water?

Alkane CH3─CH2─CH3 44 -42 No

Ether CH3─O─CH3 46 -23 Yes

Alcohol CH3─CH2─OH 46 78 Yes

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Solubility of Phenol

Phenol Is soluble in water. Has a hydroxyl group that ionizes slightly (weak

acid). Is corrosive and irritating to the skin.

OH O-

+ H2O + H3O+

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Learning Check

Which compound would have the higher boiling

point? Explain.

ethyl methyl ether or 1-propanol

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Solution

1-propanol would have the higher boiling point because

an alcohol can form hydrogen bonds, but the ether

cannot.

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Learning Check

Which compound would be more soluble in water?

Explain.

ethanol or 2-pentanol

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Solution

Ethanol. An alcohol with two carbons in its carbon chain

is more soluble than one with 5 carbons. The longer

alkyl chain diminishes the effect of the –OH group.

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Chapter 13 Alcohols, Phenols, Ethers, and Thiols

13.4

Reactions of Alcohols and Thiols

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Combustion of Alcohols

Combustion is the reaction of an alcohol

with O2 to produce CO2 and H2O.

2CH3OH + 3O2 2CO2 + 4H2O + Heat

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Dehydration of an alcohol occurs When heated with an acid catalyst. With the loss of —H and —OH from adjacent carbon

atoms. H OH

| | H+, heatH—C—C—H H—C=C—H + H2O

| | | | H H H H

alcohol alkene

Dehydration of Alcohols

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Learning Check

Write the equations for the reactions when

2-propanol undergoes:

1. combustion

2. dehydration

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Solution

OH │CH3─CH─CH3

= 2-propanol = C3H8O

1. combustion

2C3H8O + 9O2 6CO2 + 8H2O

2. dehydration OH │ H+

CH3─CH─CH3 CH3─CH=CH2 + H2O

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Formation of Ethers

Ethers form when dehydration takes place at low temperature.

H+

CH3—OH + HO—CH3 CH3—O—CH3 + H2O

two methanol dimethyl ether

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Oxidation and Reduction

In the oxidation of an organic compound There is an increase in the number of C—O

bonds. There is a loss of H.

In the reduction of an organic compound There is an decrease in the number of C—O

bonds. There is a gain of H.

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Oxidation and Reduction

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When a primary alcohol is oxidized [O], One H is removed from the –OH. Another H is removed from the carbon bonded to the OH. An aldehyde is produced.

[O] Primary alcohol Aldehyde

OH O | [O] ||

CH3—C—H CH3—C—H + H2O |

H Ethanol Ethanal (ethyl alcohol) (acetaldehyde)

Oxidation of Primary (1) Alcohols

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Oxidation of Secondary (2) AlcoholsWhen a secondary alcohol is oxidized [O], One H is removed from the –OH. Another H is removed from the carbon bonded to the OH. A ketone is produced. [O] secondary alcohol ketone OH O

│ [O] ║ CH3—C—CH3 CH3—C—CH3 + H2O

│ H

2-propanol (isopropyl alcohol) 2-propanone(dimethyl ketone, “acetone”)

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Oxidation of Tertiary (3)Alcohols

Tertiary alcohols do not readily oxidize. [O]

Tertiary alcohol no reaction OH │ [O]

CH3─C─CH3 no product │ CH3 no H on the C-OH to oxidize

2-methyl-2-propanol

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Select the compound that would result for each reaction

of CH3—CH2—CH2—OH.

O

||1) CH3—CH=CH2 2) CO2 + H2O 3) CH3—CH2—C—H

A. H+, heat

B. [O]

C. O2, heat

Learning Check

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CH3—CH2—CH2—OH

A. H+, heat 1) CH3—CH=CH2

O ||

B. [O] 3) CH3—CH2—C—H

C. O2, heat 2) CO2 + H2O

Solution

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Oxidation of Ethanol in the Body

In the body, Ethanol is oxidized by enzymes in the liver. Aldehyde product impairs coordination. O O ║ ║

CH3─CH2─OH CH3─C─H CH3─C─OH ethyl alcohol acetaldehyde acetic acid

2CO2 + H2O

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Ethanol Acts as a depressant. Kills or disables more

people than any other drug. Is metabolized at a rate of

12-15 mg/dL per hour by a social drinker.

Is metabolized at a rate of 30 mg/dL per hour by an alcoholic.

Ethanol CH3─CH2─OH

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Effect of Alcohol on the Body

TABLE 13.2

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Learning Check

Select the product for the oxidation of OH │ [O]

CH3—CH—CH2—CH3

O ║

1) CH3—CH=CH—CH3 2) CH3—C—CH2 —CH3

OH │

3) CO2 + H2O 4) CH3—CH—CH2—CH3

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Solution

Select the product for the oxidation of OH │ [O]

CH3—CH—CH2—CH3

O ║

2) CH3—C—CH2—CH3

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Oxidation of Thiols

When thiols undergo oxidation, An H atom is lost from each of two –SH groups. The product is a disulfide.

[O]

CH3—SH + HS—CH3 CH3—S—S—CH3 + H2O