Chem 1152: Ch. 13 Alcohols, Phenols and Ethers. Introduction Alcohol: Any cmpd with a hydroxy (-OH) functional group attached on aliphatic carbon. Phenol:

Chem 1152: Ch. 13

Alcohols, Phenols and Ethers

IntroductionIntroduction

• Alcohol: Any cmpd with a hydroxy (-OH) functional group attached on aliphatic carbon.

• Phenol: Hydroxy functional group attached to benzene ring, where the parent is a combination of the benzene ring and the (-OH) group.

• Ether: Oxygen with carbon attached on either side.

R OH

OH

R

O R

H OH R OH

R

O R

H

O H

Water structure analogs to alcohol and ether

alcohol

ether

Classification of AlcoholsClassification of Alcohols

Primary (1°)R O

H H

H

OH

H HH

Secondary (2°)

Tertiary (3°)

R O

R H

H

R O

R R

H

Hydroxy bearing C is attached to either 0 or 1 other C

Hydroxy bearing C is attached to 2 other C


Examples of AlcoholsExamples of Alcohols

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Examples of AlcoholsExamples of Alcohols• Antifreezes

1,2-ethanediol (ethylene glycol)

• 1,2-propanediol (propylene glycol)


Rules for naming alcoholsRules for naming alcohols

For single hydroxy (-OH) group•Step 1: Identify longest chain that includes (-OH) group. Drop –e from hydrocarbon name, and replace with ending –ol.•Step 2: Number this parent chain to give lowest number to carbon with attached (-OH) group.•Step 3: Locate position of (-OH) group.•Step 4: Locate and name all branches attached to parent chain.•Step 5: Include names of all branches (still in alphabetical order) in prefix of compound name. Include location of (-OH) group.•Note: Multiple (-OH) groups are named by addiing diol, triol, etc, to end of alkane without removing -e.

CH3

CH3

OH1

253

4

2-ethyl-1-pentanol

OHOH

CH3

12 3

4

2-methyl-1,4-butanediol

Naming AlcoholsNaming Alcohols

CH3

CH3

CH3

CH3

OHCH3

OH

CH3

CH3 OH

CH3

OH

OH

CH3 CH3

CH3

OH

OH

Br

CH3

CH3CH3

CH3

OH

OH

CH3CH3

OH

OHOH

CH3

OH

Naming AlcoholsNaming Alcohols

CH3

CH3

CH3

CH3

OHCH3

2,2,4-trimethyl-3-hexanol

OH

CH3

CH3 OH

CH3

3-butyl-2,4-hexanediol

OH

OH

1,2-cyclohexanediol

CH3 CH3

CH3

OH

3-methyl-3-pentanol

OH

Br

CH3

5-bromo-3-ethyl-1-pentanol

CH3CH3

CH3

OH

2-isopropyl-1-methylcyclopropanol

OH

CH3CH3

2,2-dimethylcyclopentanol

OH

OHOH

CH3

1,2,4-hexanetriol

OH

3-phenyl-1-propanol

Physical Properties of alcohols- SolubilityPhysical Properties of alcohols- Solubility

• Low MW alcohols (methanol, ethanol, propanol) are miscible with water.

• As alkane chain gets longer, alcohol behaves more like an alkane:

– More soluble in nonpolar organic solvents (benzene, CCl4, ether)

CH3

OH

CH3 OH

HOH

CH3

OH

CH3 CH3

Alcohols that look like water, behave like water. Alcohols that look more like alkanes behave like alkanes.Due to hydrogen bonding.


Hydrogen bondingHydrogen bonding

• Hydrogen bond: Attractive interaction of a hydrogen atom with an electronegative atom (e.g. N, O, F) from another molecule or chemical group.

• The H must be covalently bonded to another electronegative atom.

– This is why H on hydrocarbon chain does not participate in H-bonding.

• H-bond relatively weak.• Bond energy for C-H 413 kJ/mol• H-bond energy 2 kJ/mol


Effects of hydrogen bondingEffects of hydrogen bonding

• H-bonding between alcohol molecules increases BP for alcohol compared to similar MW alkane

CH3

OH

CH3

OH

CH3 CH3


CH3

OCH3

Alcohol ReactionsAlcohol Reactions

1. Alcohol Dehydration (Elimination Rxn):

H-OHH2SO4

R

OH

RR

HR 180 C

+

R

RR

R

• Alcohol Hydration (Addition Rxn)R

RR

R

H-OH+H2SO4

R

OH

RR

HR

Alcohol Dehydration to produce alkeneAlcohol Dehydration to produce alkene• Alcohol Dehydration (Elimination Rxn):

OH

CC

CC

H

HH

HH

HH

HH

H2SO4

180 oC

CC

C

CH

HH

H

H

H

HH

CC

CC

H

HH

HH

H

H

H

H-OH+

H-OH+

2-butene

1-butene

This rxn (at 180 °C) generates 2 products: 2-butene and 1-butene. The major product is 2-butene (90%) because both C=C bond carbons are

attached to at least one other carbon. The minor product is 1-butene (10%) because only one of the C=C bond

carbons is attached to at least one other carbon. The major product in these rxns will always be the one resulting in the

highest number of carbon groups bonded to the C=C carbons.

Alcohol dehydration in biochemistryAlcohol dehydration in biochemistry

Enzyme H-OH+O-OC

H

OH

C C CH2 COO-

COO-

H

O-OC

H

C C

CH2 COO-

COO-

This rxn is catalyzed by an enzyme rather than an acid in the human body. Alcohol dehydration rxns in general are involved in the formation of:

Carbohydrates Fats Proteins

citrate cis-aconitrate

Examples: Alcohol Dehydration to Produce AlkeneExamples: Alcohol Dehydration to Produce Alkene

CH3

CH3

CH3

CH3

OH

H2SO4

180 oC

CH3 CH3

CH3

OH

H2SO4

180 oC

CH3 CH3

CH3

OH

CH3

H2SO4

180 oC

H2SO4

180 oC

H2SO4

180 oC

CH3

CH3

CH3 CH3

CH3CH3

OH

CH3

CH3

OH

Alcohol Dehydration to produce etherAlcohol Dehydration to produce ether• Alcohol Dehydration (Elimination Rxn):

This rxn (at 140 °C) generates an ether and water. This rxn works mainly with primary alcohols.

H2SO4

140 oCR

OH H

R

O+ R

R

O

H

OH+

etheralcohol alcohol

Primary (1°)R O

H H

H

OH

H HH


H2SO4

140 oCOHCH3 +

H

OH+CH3H

O OCH3

CH3

H2SO4

140 oCOHCH3

H

OH+CH3OCH3

Alcohol OxidationAlcohol Oxidation Oxidation: Loss of hydrogen or gain of oxygen. Oxidizing Agent: Compound that oxidizes another compound.

KMnO4 (potassium permanganate) K2Cr2O7 (potassium dichromate)

This rxn works different depending on whether alcohol is 1°, 2° or 3°. H-OH lost in oxidation rxns comes from the same carbon, rather than

adjacent carbons as seen in dehydration rxns to form alkenes.

Primary (1 � )R O

H H

H

OH

H HH

Secondary (2 � )

Tertiary (3 � )

R O

R H

H

R O

R R

H




H-OH+RC

O

HH

H

(O)+ R C

O

H

(O)R C

O

OH

Alcohol Oxidation for Primary AlcoholAlcohol Oxidation for Primary Alcohol

Carboxylic acid

Primary alcoholaldehyde

Immediate product of oxidation of primary alcohol is aldehyde, which is then readily further oxidized to a carboxylic acid.

The aldehyde product may be isolated before further oxidation by maintaining high temp. and boiling aldehyde out of rxn mixture.

This is possible because aldehydes do not H-bond like alcohols and carboxylic acids.

H-OH+RC

O

HR

H

(O)+ R C

O

R

Alcohol Oxidation for Secondary and Tertiary AlcoholsAlcohol Oxidation for Secondary and Tertiary Alcohols

Secondary alcohol ketone

Product of oxidation of secondary alcohol is a ketone, which resists further oxidation.

NO RXNR

CO

RR

H

(O)+

Tertiary alcohol

Examples: Identify Rxn and draw productExamples: Identify Rxn and draw product

CH3 CH3

CH3

OH

H2SO4

180 oC

CH3

CH3

OH

H2SO4

140 oC

CH3 CH3

CH3

OH

(O)+

CH3

CH3

OH

(O)+

Examples: Identify Rxn and Draw ProductExamples: Identify Rxn and Draw Product

CH3 CH3

CH3

OH

H2SO4

180 oCCH3 CH3

CH3

H

CH3

CH3

OH

H2SO4

140 oC

CH3

CH3

O

CH3 CH3

CH3 CH3

CH3

OH

(O)+ CH3 CH3

CH3

O

CH3

CH3

OH

(O)+H

CH3

CH3

O

OH

CH3

CH3

O

(O)

Summary of Alcohol ReactionsSummary of Alcohol Reactions


PhenolsPhenols

• Phenol: Hydroxy functional group attached to benzene ring, where the parent is a combination of the benzene ring and the (-OH) group.

• Low MP solid that liquefies at room temp. with small amount of water.• Weakly acidic in water (due to conjugated pi bonds on benzene ring).

– Can damage proteins in skin.

• In dilute solutions, can be used as antiseptics and disinfectants.– Phenol first used by Joseph Lister in hospitals in 1800’s.– Phenol derivatives used today in Lysol, mouthwashes and throat lozenges.

• Other phenol derivatives used as antioxidants.

OH

OH2+

O-

OH3+

+

Naming PhenolsNaming Phenols

• Substituted phenols are usually named as derivatives of the parent compound phenol.

• Examples:


EthersEthers• Ether: Oxygen with carbon attached on either side.• Naming ethers• Common Names

1. Name the two groups attached to the oxygen then add the word ether2. If both groups the same, can be named with prefix di-.

• IUPAC Names– O-R group is alkoxy.– The –yl ending of smaller R group is replaced by –oxy.

CH3

O CH3

CH3 OCH3

CH3

OCH3

butyl methyl ether

ethyl propyl ether

dipropyl ether

CH3

CH3 OCH3

isopropyl propyl ether 1-methoxybutane

1-ethoxypropane

1-propoxypropane

1-isopropoxypropaneCl

CH3

CH3 OCH3

2-chloro-1-isopropoxypropane

OCH3

CH3

p-methoxytoluene

CH3

CH3

CH3 O

CH3

CH3

2-ethoxy-3,4-dimethylhexane

Properties of EthersProperties of Ethers• Oxygen atom of ether can H-bond with water

– Ethers more soluble in water than hydrocarbons, less soluble than alcohols of comparable MW.

• Ethers cannot H-bond with other ethers in pure state– Results in low BP close to those of hydrocarbons of comparable MW.

• Ethers mostly inert and unreactive– Why diethyl ether is useful solvent– Diethyl ether is also highly-flammable and was historically an important anesthetic– History Note: First physician to use diethyl ether as anesthesia was Crawford Long in

1842


ThiolsThiols• Thiols: Sulfur analogs of alcohols (-SH instead of –OH)• Chemically- similar (i.e., form similar compounds)• More volatile (lower BP) than alcohols but less water-soluble• Thiols stink!

– This is how skunks defend themselves– Chopped onions emit propanethiol– Thiols found in garlic– Ethanethiol added to natural gas (methane) so you can smell a leak

• IUPAC Names for simple thiols– The –SH group is a sulfhydryl group.– Follow the same steps for naming as you do for alcohols, but do not modify alkane

ending; instead add –thiol to end of parent.

SH

CH3

SH

CH3CH3

SH

CH3

CH3

CH3

butanethiol 2-butanethiol 2-methyl-3-hexanethiol

Thiol/Sulfide RxnsThiol/Sulfide Rxns

HRS

RHS+ O O+ R

SRS OH2+

Oxidation (Formation of disulfide bond)

RSR

SH H+ HR

SRH

S+

Reduction (breaking disulfide bond)

Polyfunctional CompoundsPolyfunctional Compounds Substances that can contain more than 1 functional group.

http://www.daviddarling.info/encyclopedia/R/ribose.htmlhttp://en.wikipedia.org/wiki/RNA

Ribose forms backbone of RNA (genetic transcription). Phosphorylated ribose becomes subunits of ATP, NADH, and several other

compounds that are critical to metabolism.

http://www.daviddarling.info/encyclopedia/R/ribose.html

http://en.wikipedia.org/wiki/RNA

Multistep RxnsMultistep Rxns The synthesis of most alcohols may require multiple steps (i.e., to get

product X from reactant A, a product (B, C …X) must be created). To solve these problems, work backwards from the final product.

O

OOH (O)+ H-OH+

Oxidize 2° alcohol to form ketone.

+ OHH-OHH2SO4

Use acid-catalyzed hydration (addition) to form alcohol.

+ OHH-OHH2SO4

(O)+ O H-OH+

The completed series of rxns.

Chem 1152: Ch. 13 Alcohols, Phenols and Ethers. Introduction Alcohol: Any cmpd with a hydroxy (-OH) functional group attached on aliphatic carbon. Phenol:

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