Chapter FourteenChapter Fourteen

Alcohols, Phenols, And Ethers

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Functional Groups

• Groups of atoms within a larger molecule that have characteristic chemical behavior.

• A functional group behaves almost the _____ way in every molecule it is in (electronic structure, reactivity, geometry all generally stay the ______).

• The chemistry of every organic molecule is determined by the functional groups it contains.

• It is very important for this course that you learn to recognize functional groups.

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Functional Groups

Name Structure Example Alkane

(Not a

functional Group)

Alkene

Alkyne

Arene

(aromatic ring)

C CH3C CH3

H2C CH2C C

C C

C

C

C

C

C

C

HC CH

HC

HC

CH

CH

CH

HC

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Functional Groups

Name Structure Example

Halide

Alcohol

Ether

H3C ClC X

C OH H3C OH

C O C H3C O CH3

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Fig. 14.1 Space-filling models for the three simplest unbranched chain alcohols: methyl alcohol, ethyl alcohol, and propyl alcohol.

Alcohols, Phenols, and Ethers cont’d

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The Bonding of Oxygen

• To understand the bonding patterns of oxygen, we must review what we know about oxygen– How many valence electrons does oxygen have?

– How many electrons does oxygen need to have an octet of electrons in its valence shell?

– Oxygen’s octet is filled when it forms ___ bonds to other atoms:

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→ Fig. 14.2 The similar shapes of water and methanol. Methyl alcohol may be viewed structurally as an alkyl derivative of water.

Alcohols, Phenols, and Ethers cont’d

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Classifying Alcohols

• Alcohols are classified by the number of carbon substituents bonded to the carbon. – primary (1o)– secondary (2o)– tertiary (3o)

CR

H

H

OH CR

H

R

OH CR

R

R

OH

Primary Tertiary Secondary

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Alcohols, Phenols, and Ethers cont’d

Which are primary?

Which are secondary?

Which are tertiary?

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← Fig. 14.3 Racing cars are fueled with methyl alcohol.

Alcohols Used As Fuels and Fuel Additives

Jonathan Ferrey/Getty Images

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Ethyl Alcohol In Beverages and Other Consumer Products

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← Fig. 14.5 Ethylene glycol is the major ingredient in de-icers for planes.

Commercial Uses of Alcohols

© Hank Morgan/Rainbow

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→ Fig. 14.6 For survival in northern winters, many fish and insects produce large amount of glycerol that dissolve in their blood, thereby lowering the freezing point.

Metabolic Alcohols

James Cotier/Getty Images

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A carbon compound that contain -OH (hydroxyl) group

In IUPAC name, the -e in alkane name is replaced with -ol.

CH4 methane

CH3OH methanol (methyl alcohol)

CH3CH3 ethane

CH3CH2OH ethanol (ethyl alcohol)

Naming Alcohols

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IUPAC names for longer chains number the chain from the end nearest the -OH group.

CH3CH2CH2OH 1-propanol

OH CH3CHCH3 2-propanol

CH3 OH CH3CHCH2CH2CHCH3 5-methyl-2-hexanol

Naming Alcohols, Part II

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OH

“rubbing alcohol” CH3CHCH3

2-propanol (isopropyl alcohol)

antifreeze HO-CH2-CH2-OH

1,2-ethanediol (ethylene glycol)

OH

glycerol HO-CH2-CH-CH2OH

Ant

i-fre

eze

Some Typical Alcohols

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Name these alcohols.

OH

HO OH

OHOHOH

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Fig. 14.7 (a) The polar hydroxyl functional group dominates the physical properties of methanol. (b) Conversely, the nonpolar portion of 1- octanol dominates its physical properties.

Alcohols, Phenols, and Ethers cont’d

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← Fig. 14.8 (a) Boiling points and (b) solubilities in water of selected 1- alcohols.

Alcohols, Phenols, and Ethers cont’d

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Table 14.3

Alcohols, Phenols, and Ethers cont’d

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← Fig. 14.10 Alcohol boiling points are higher than those of the corresponding alkanes because of the alcohol-alcohol hydrogen bonding.

Alcohols, Phenols, and Ethers cont’d

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→ Fig. 14.11 Because of hydrogen bonding between alcohol molecules and water molecules, small molecular mass alcohols have unlimited solubility in water.

Alcohols, Phenols, and Ethers cont’d

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Synthesis of Alcohols

• Alcohols can be prepared from many other kinds of compounds.– Alkenes

• Hydration!

– Alkyl halides– Ketones – Aldehydes– Esters

• They can also be transformed into a wide assortment of compounds.

alcohol

R-OH

R=R

R-X

R-C-R

R-O-R

R-C-H

=O

=O

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• Preparation by hydration of alkenes.

H2OH2SO4

H2OH2SO4

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• Aldehyde and ketone reduction (adding hydrogen across the double bond) reactions:

R

O

1. NaBH4, ethanol

2. H3O+

R

O

R

1. NaBH4, ethanol

2. H3O+

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Combustion

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

Dehydration

H OH H+, heat

H-C-C-H H-C=C-H + H2O

H H H H

alcohol alkene

Reactions of Alcohols

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← Fig. 14.12 In an intramolecular alcohol dehydration the components of water are removed from neighboring carbon atoms. This is an elimination reaction.

Alcohols, Phenols, and Ethers cont’d

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Reactions of Alcohols: Dehydration

• Dehydration of an alcohol produces an _________• Phenols __________ undergo dehydration• Zaitsev’s rule

– The major product in an intramolecular alcohol dehydration reaction is the ________ that has the greatest number of alkyl groups attached to the carbon atoms of the double bond

H2O, 50 oC

H2SO4

OH

H2O, 50 oC

H2SO4HO

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Reactions of Alcohols: Intermolecular Alcohol Dehydration

• Ethers form when two alcohols dehydrate at a ____ temperature (140oC)

– H3C-OH + HO-CH3 H3C-O-CH3 + H2O

– Two methanol dimethyl ether + water

– Note: Dehydration to an alkene at _____oC

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Reactions of Alcohols: Oxidation and Reduction

• In organic chemistry, an easy way to recognize oxidation:– An increase in the number of C-O bonds OR– A loss of hydrogen atoms

• In organic chemistry, an easy way to recognize reduction:– A decrease in the number of C-O bonds OR– A gain of hydrogen atoms

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R

OH Oxidizing agent

O

• Oxidation of alcohols. • Valuable reaction to yield carbonyl (C=O) compounds.

– Product depends on starting alcohol and amount of oxidizer.

O

OH

O

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• Oxidation of alcohols. – Primary alcohols

yield aldehydesand carboxylicacids.

– Secondary alcoholsyield ketones.

– Tertiary alcohols do not react.

From primaryalcohols

From primaryalcohols

From secondaryalcohols

O

O

OHO

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• Oxidation reactions:

R

OH

PCCCH2Cl2 R

O

R

O

OHR

OH

CrO3, H3O+

or Na2Cr2O7, H2O, CH3CO2H

R

OH

CrO3, H3O+

or Na2Cr2O7, H2O, CH3CO2HR R

O

R

R-OH R(CO)R or RCHO RCOOH* PCC = Pyridinium chlorochromate

*

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• Levels of oxidation of secondary alcohols:– Ketone (Most oxidized)– Alcohol (Least oxidized)

• Levels of oxidation of primary alcohols:– Carboxylic Acid (Most oxidized)– Aldehyde– Alcohol (Least oxidized)

OOH

OH O

OH

O

Most OxidizedLeast Oxidized

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Reactions of Alcohols: Halogenation

• Substitution reactions– Halogen replaces the hydroxyl group– Reactants: Phosphorus trihalides (with heat)

– 3R-OH + PX3 3R-X + H3PO3

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Chemistry at a Glance:Summary of Reactions Involving Alcohols

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→ Fig. 14.14Phenol molecule

Phenols

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• Phenols. – Phenols are named as seen in Chapter 13. – Use “phenol” as the parent name instead of

benzene.OH

H3C

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OH

OH

OH OH

OH

CH2CH2CH2CH2CH2CH3

Resorcinol 4-Hexylresorcinal(antiseptic) (antiseptic)

Phenol

Phenols in Medicine

Phenols are weak acids and are used as antiseptics

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→ Fig. 14.17 The similar shapes of water and dimethyl ether molecules.

Ethers

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← Fig. 14.18 Alcohols and ethers with the same number of carbon atoms and the same degree of saturation are structural isomers.

Ethers

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CC 14.3 Marijuana

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→ Fig. 14.21 Thiols are responsible for the strong odor of "essence of skunk.“

What is the chemical composition of a thiol, and how does it relate to alcohols?

Thiols contain sulfur, in particular a R–S-H group.

PHEW !

Jeff Lepore/Photo Researchers

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Alcohols, Phenols, and Ethers cont’d

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Thiols

Many thiols have disagreeable odorsUsed to detect gas leakFound in onions, oysters, garlic and oysters

Onions CH3CH2CH2-SH 1-propanethiol

Garlic CH2= CHCH2-SH 2-propene-1-thiol

Skunk spray

CH3 trans-2-butene-1-thiol

CH = CH

CH2SH

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← Fig. 14.22 A comparison involving dimethyl ether and demethyl sulfide.

Alcohols, Phenols, and Ethers cont’d

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Properties of Ethers

• Non-polar• Low boiling points• Anesthetic (diethylether)• Flammable• React slowly with oxygen to form unstable

hydroperoxides and perioxides• However, generally unreactive

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Ethers

• Contain an oxygen atom between ______ carbon atoms

• Simple ethers are named by listing the alkyl names in alphabetical order followed by “ether”– CH3-O-CH3

– CH3-O-CH2CH3

– CH3-CH2-O-CH2CH3

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• Ethers (naming). – Simple ethers that contain no other functional groups: name the

two organic groups and add the word “ether.”– Otherwise, use “alkoxy” as the substituent name.

OO O

O

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Ethers as Anesthetics

Anesthetics inhibit pain signals to the brainCH3CH2-O-CH2CH3 used for over a century (Morton, 1846)Causes nausea and is highly flammable1960s developed nonflammable anesthetics

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