Alcohols, Phenols, Thiols, and Ethers

Alcohols, Phenols, Thiols, and Ethers

Chapter 13

Introduction

• Alcohol – organic compound that contains a hydroxyl (-OH) group attached to an alkyl group

• Phenol – organic compound that contains a hydroxyl (-OH) group attached to an aryl group

• Ether – organic compound that has two alkyl or aryl groups attached to the oxygen atom; can be thought of as a substituted alcohol.

Examples

Alcohols -OH hydroxyl CH3-OH

CH3CH2-OH

Phenols

Ethers -O- CH3-O-CH3

OHOH

Practice Problem 1

Classify each as an alcohol (1), phenol (2), or an ether (3):

A. _____ CH3CH2-O-CH3 C. _____ CH3CH2OH

B. _____

OH

CH3

Solution 1

Classify each as an alcohol (1), phenol (2), or an ether (3):

A. ____ CH3CH2-O-CH3 C. ____ CH3CH2OH

B. _ __

OH

CH3

Structure and Properties

• R-O-H portion of alcohol is similar to the structure of water.– The oxygen and two atoms bonded to it lie in

the same plane.– The bond angle is 104°

• Hydroxyl groups are very polar because of significantly different electronegativities.– Hydrogen bonding can form between alcohol

molecules.

Hydrogen Bonding

R O

H

O

H

H

O

R

H

O

HH

Results of Hydrogen Bonding

• Alcohols boil at much higher temperatures than hydrocarbons of similar molecular weight.

• Alcohols with fewer than five carbons are very soluble in water.

• Alcohols with five to eight carbons are moderately soluble in water.

• As the nonpolar (R) portion of the alcohol gets larger, the water solubility decreases.

• Very large alcohols are not soluble in water.

• Hydrophobic – “water fearing”; used to describe nonpolar region of molecule

• Hydrophilic – “water loving”; used to describe polar region of molecule

CH3CH2CH2CH2CH2CH2CH2CH2CH2OH

Hydrophobic Hydrophilic

Solubility of Alcohols

Solubility of Alcohols

• An increase in the number of hydroxyl groups will increase the influence of the polar hydroxyl group.

– Diols and triols are more water soluble than alcohols with only a single hydroxyl group.

Practice Problem 2

• Circle the more soluble alcohol in each pair.

H3C CH2

OHA. OR

H3C

H2C

CH2

H2C

OH

B.OH

OH

OR OH

C. OROH

Solution 2

• Circle the more soluble alcohol in each pair.

H3C CH2

OHA. OR

H3C

H2C

CH2

H2C

OH

B.OH

OH

OR OH

C. OROH

Nomenclature of Alcohols

• 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)

More Names of Alcohols

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

CH3CH2CH2OH

OH CH3CHCH3

CH3 OH CH3CHCH2CH2CHCH3

Alcohols that contain more than one hydroxyl group

• Alcohols containing two hydroxyl groups are named –diols.

• Alcohols containing three hydroxyl groups are named –triols.

• A number giving the position of each of the hydroxyl groups is needed in these cases.

Practice Problem 3

Name the following alcohols:

A. OH

CH3CHCHCH2CH3

CH3

OH

B.

Solution 3

Name the following alcohols:A. OH

CH3CHCHCH2CH3

CH3

OHB.

HomeworkPages 379-380 13.11-13.14

Page 360 13.1 – 13.2

Due Tomorrow!!!!

Section 13.3• It is your responsibility to read

over section 13.3 – Medically Important Alcohols (pgs. 360-361) and take notes on the material covered!

• It will be on the weekly quiz and the test!

Classification of Alcohols

• Alcohols can be classified as primary (1°), secondary (2°), or tertiary (3°) depending on the number of alkyl groups attached to the carbon bearing the –OH group.

C

H

HH

OH

H3C C

H

OH

H

H3C C

CH3

OH

H H3C C

CH3

CH3

OH

Methanol 1° alcohol 2° alcohol 3° alcohol

ethanol 2-propanol 2-methyl-2-propanol

Practice Problem 4

Classify each of the following alcohols as primary, secondary, tertiary, or aromatic.

1. 1-butanol

2. 3-pentanol

3. 1-methylcyclopentanol

4. 2-methyl-2-pentanol

Solution 4

1. 1-butanol

2. 3-pentanol

3. 1-methylcyclopentanol

4. 2-methyl-2-pentanol

Homework

• Pages 380-381: 13.15, 13.16, 13.18, 13.19, 13.20, 13.21, 13.22, 13.27, and 13.28

Due Tomorrow!

Preparation of Alcohols

• REVIEW: Hydration – an addition reaction in which a water molecule is added to an alkene; requires acid as catalyst

RR

R R

+

H

O H

H+ HR

R

R OH

R

Alkene Water Alcohol Markovnikov’s rule applies!!Markovnikov’s rule applies!!

Hydration Examples

• Ethene

• 1-butene

Preparation of Alcohols

• Hydrogenation of aldehydes and ketones

O

R1 R2

+H

HH

R2R1

OH

Catalyst

In an aldehyde, R1 and R2 may be either alkyl groups or H. In a ketone, R1 and R2 are both alkyl groups.

We will discuss this in more detail in section 14.4.

Hydrogenation Examples

• Ethanal

• 2-propanone

Preparation of Alcohols YOU TRY THESE!

Dehydration of Alcohols

• Alcohols undergo dehydration (lose water) when heating with concentrated sulfuric or phosphoric acid.

• Dehydration is an example of an elimination reaction.

• Elimination reaction – a reaction in which a molecule loses atoms or ions from its structure.

• Dehydration is opposite of hydration!

Dehydration of Alcohols• General Reaction

• Ethanol

• 2-butanol

RCH2CH2OHH +

RCH=CH2 + H2O

CH3CH2OHH +

C C C CH

H

H H

H H

OH

H

H

HH +

H e a t

Heat

Heat

Dehydration of Alcohols

• Zaitsev’s rule – in an elimination reaction, the alkene with the greatest number of alkyl groups on the double bonded carbon (more highly substituted alkene) is the major product of the reaction

• Another example:

Oxidation Reactions

• Oxidation – loss of electrons; add O and/or lose H

• Reduction – gain of electrons; add H and/or lose O

• Common oxidizing agents:– Basic potassium permanganate (KMnO4/OH-)

– Chromic Acid (H2CrO4)

• [O] Any general oxidizing agent

Oxidation of Primary Alcohols

• General equation:– Primary alcohol aldehyde

RCH2CH=O

EXAMPLE:

1-propanol

Oxidation of Secondary Alcohols

• General equation:– Secondary alcohol ketone

O

R-C-R

EXAMPLE:

2-propanol

Oxidation of Tertiary Alcohols

• General equation:– Tertiary alcohol NO REACTION!!!

YOU TRY THESE!C C C CH

H

H H

H H

OH

H

H

H[O ]

OH

[O ]

OH

[O ]

CH3CH2OH[O ]

Phenols

• Phenols – compounds in which the hydroxyl group is attached to a benzene ring

• They are polar compounds because of the polar hydroxyl group.

• Smaller phenols are somewhat soluble in water.

• They are found in fragrances and flavorings and are also used as preservatives and germicides.

Common Phenols and their Uses

CH3

OH

(CH3)2HC Thymol (mint)

CH3

OH

(CH3)2HCCarvacrol (savory)

Common Phenols and their Uses

OH

(CH3)3C

CH3

C(CH3)3

Butylated hydroxytoluene, BHT(Food preservative)

OH

Phenol(Carbolic acid when dissolved in water)

Antiseptic and disinfectant used by Joseph Lister to bathe wounds and sterlize

instruments

Ethers

Structure of Ethers

• Similar structure to alcohols

Alcohols: R-OH–OH is “hydroxy” group

Ethers: R-OR –OR is “alkoxy” group

Alkoxy group

• “R” groups can be the same:

CH3-O-CH3

• Both “R” groups have one carbon

• “R” groups can be different:

CH3CH2CH2-O-CH3

• One “R” group has three carbons

while the other has one

Alkoxy group

• The root names are used with –oxy to name that portion of the ether:– meth- + -oxy

– eth- + -oxy

– prop- + -oxy

= methoxy

= ethoxy

= propoxy

Naming ethers – IUPAC Way

1. Find the root name of the smaller “R” group Ex: meth-, eth-, prop-

2. Add –oxy

Ex: methoxy, ethoxy, propoxy

3. Add the full name of the larger “R” group

EXAMPLE:

Omethoxypropane

Naming ethers – IUPAC Way

• Alkyl groups don’t always bond to the oxygen at the end carbon.

• In these cases, name the ether using the largest alkyl group as the parent chain and the “alkoxy group” as a branch, using a number to identify which carbon is bonded to the oxygen

Naming ethers – IUPAC Way

• Example:

CH3CH2 parent: butane

O branch: ethoxy

CH3CH2CH2CH3 at carbon #2

2-ethoxybutane

Name that ether

O O

O

Draw the structure of:

1. methoxypropane

2. methoxyoctane

3. propoxypropane

4. ethoxypentane

Naming Ethers – Common Name

• Name by placing the names of the two alkyl groups attached to the ether oxygen as words in front of the word “ether.” Typically this is done in alphabetical order.

O O

O

Diethyl Ether Ethyl methyl ether

Butyl propyl ether

Properties of ethers

• The C-O bond in ethers is polar, making the molecule polar

• Ethers have very low boiling points

• Ethers are relatively inert, but flammable in air

Let’s compare…

Ether

CH3 –O-CH2CH3

Molecular Formula:

C3H8OMolecular Weight:

60.09g/molBoiling Point:

7.9°C

Alcohol

CH3CH2CH2-OH

Molecular Formula:

C3H8OMolecular Weight:

60.09g/molBoiling Point:

97.2°C

Preparing ethers

• Ethers are formed from alcohols

R-OH + R’-OH R-O-R’ +H2O

– R and R’ can be the same or different

– Called a dehydration reaction

H+

Predict the products

CH3OH + CH3CH2OH H+

CH3CH2CH2OH + CH3CHCH3H+

OH

Common uses

• Ethers as anesthetics:– Penthrane– Enthrane

• Ethers as additives in gasoline– MTBE – methyl tert-butyl ether

Thiols

• Compounds that contain the sulfhydryl group (-SH)

• Similar to alcohols in structure, but the sulfur atom replaces the oxygen atom

• Have nauseating aromas – defense spray of North American striped skunk

H2C

CH3H

H

SH

Trans-2-butene-1-thiol

Naming Thiols

• Use the same rules as for alcohols except that the full name of the alkane is retained.

• Add the suffix –thiol.

CH3CH2SH

CH3CHCH2CH2

CH3

SH

HSCH2CH2SH

ethanethiol

3-methyl-1-butanethiol

1,2-ethanedithiol

Uses of Thiols

• Thiols are involved in protein structure and conformation.

• Cysteine is an amino acid that contains a sulfhydryl group.

• BAL (British Anti-Lewisite) is used as an antidote for mercury poisoning.

• Coenzyme A serves as a carrier of acetyl groups in biochemical reactions.

Homework

•Pg. 381-382: 13.43, 13.44, 13.45, 13.48, 13.49, 13.51, 13.52, 13.53, 13.59, 13.60