13-1

Principles and Applications ofInorganic, Organic, and

Biological ChemistryDenniston, Topping, and Caret

4th edChapter 13

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Power Point to Accompany

13-2

FormulasAlcohols have the general formula R-OHEthers have the formula R-O-R

R can be aliphatic or aromaticPhenols have the formula Ar-OH

Ar must be an aromatic ring (eg. Benzene)

Thiols have the formula R-SHDisulfides have the formula R-S-S-R

R may be aliphatic or aromatic

13-3

13.1 Alcohol: Structure and Properties

Low molecular weight alcohols (up to 5-6 carbons) are soluble in water because they are polar and hydrogen bond (through the OH) with the water molecule.

Eg. CH3CH2OH solube but CH3OCH3 barely

soluble.

CH3CH2CH2CH2OH, 7 g per 100 mL but

HOCH2CH2CH2CH2OH is very soluble!

(two OH groups)

13-4

Alcohol Boiling PtsAlcohols have abnormally high bp

relative to their molecular weights due to their ability to hydrogen bond.

CH3CH2OH

CH3CH2O

H

CH3CH2OH

13-5

Alcohol Boiling Pts-2

Trends in boiling points (Similar MW)

CH3CH2OH

CH3O CH3

CH3CH2CH3 bp -42 oC

bp -23 oC

bp +78.5 oC

13-6

13.2 Alcohols: Nomenclature

IUPAC: based on the longest chain containing the OH carbon.

The e of the alkane name is replaced with ol. The chain is numbered from the end giving the OH carbon the lower number. The name is prefixed with the number indicating the position of the OH group.

For cyclic alcohols, the OH is at C-1.

13-7

Alcohols: names-2

Name the alcohols.

CH3CHCHCH3OH

CH3

OH

CH3

3-methyl-2-butanol3-methylcyclohexanolOH must be at C-1

13-8

Alcohols: names-3The common names for alcohols consist

of the alkyl group name, a space, and the word alcohol. Name:

CH3 C CH3

CH3

OHCH3CH CH3

OHt-butyl alcohol isopropyl alcohol

13-9

13.3 Alcohol Examples of Interest

CH3CH2OHethyl alcohol(drinking alcohol)

OH CH2CH2OHethylene glycol(antifreeze)

OH CH2CH CH2OHOH

glycerol(in fats,a moisturizer)

13-10

13.4 Classes of Alcohols

CH3CH2OH

CH3CH CH3OH

CH3 C CH3

CH3

OH

Primary: one R group on alcohol C

Secondary:Two R groups on alcohol C

Tertiary:Three R groups on alcohol C

13-11

13.5 Reactions Involving Alcohols: prep

1. Form alkenes by adding water (hydration)

CH3 CH CH2

CH3 CH CH3

OH

H2O, H+

CH3 CH2 CH2

OH

Major Product

13-12

Alcohols Rxns: prep2. Form aldehydes/ketones by reduction

hydrogenation with H2.

CH3 C CH3

OCH3 CH3

OHCH

H2, Pt/Pd/Ni

CH3 C HO

CH3

OHCH2

H2, Pt/Pd/Ni

2o

1o

13-13

Alcohols: reactions1. Alcohols dehydrate with heat and strong

acid to give alkenes. Zaitsev’s rule (most substituted alkene) applies to determine the major product.

CH3CHCH CH3

OH

CH3warmH2SO4 or

H3PO4

CH3C CH CH3

CH3

CH3CHCH CH2

CH3

Major product

Minor product

13-14

Alcohols: reactionsZaitsev’s rule applied again

CH3

OH

CH3

major product:more substitutedalkene

warmH2SO4 orH3PO4

H may leave from

13-15

Alcohols: reactions

2. Oxidation

Secondary alcohols oxidize to ketones. (The reaction is also an elimination of 2H.)

The usual oxidizing agent is a Cr(VI) species.

Tertiary alcohols do not oxidize as there is no H on the carbonyl carbon to remove!

OH CrO3, py orK2Cr2O7

O

2H eliminated

13-16

Alcohols: reactionsPrimary alcohols usually oxidize to

acids. With some care (Usually CrO3)

an aldehyde may be obtained.

CH3CH2CH2OH

CH3CH2CHO

CrO3, py

KMnO4CH3CH2C

OOH

[O]

[O]

Easily oxidizedto acid

13-17

13.6 Redox in Living SystemsOxidation-gain of oxygen

loss of hydrogen (usually 2)

Reduction-loss of oxygen

gain of hydrogen (usually 2)

R CH

HH

R CH

OHH

R CH

O R COH

O

More oxidized form

More reduced form

13-18

Biological Redox-2Oxidoreductases catalyze biological

redox reactions. Coenzymes (organic molecules) are required to donate or accept hydrogen.

NAD+ is a common coenzyme.

O CCOO

-

HCH2COO

-

H OCCOO

-

CH2COO

-

+ NAD+

Malatedehydrogenase

+ NADH + H+

13-19

13.7 PhenolsWidely used as health care germicides andas flavors and preservatives.

Thymol

(mint)

CH3

OHCHCH3CH3

OH

CH3

p-cresolin Lysol

OH

CH2

OHCH35

hexyl resorcinolin throat lozenges

13-20

13.7 Phenols-2

Phenols are acidic but not as acidic as carboxylic acids. They react with NaOH to give salts and water. (Acid/base chapter.)

Note: alcohols are not acidic in the context of our class.

OH+NaOH

ONa

+H2O

13-21

13.8 Ethers

Ethers are slightly polar but do not hydrogen bond to one another.

Trends in boiling points (Similar MW)

CH3CH2OH

CH3O CH3

CH3CH2CH3 bp -42 oC

bp -23 oC

bp +78.5 oC

13-22

Ethers: namesCommon names for ethers consist of the

names of the two groups attached to the O listed in alphabetical order (or size) and followed by ‘ether’. Each part is a separate word. Name:

CH3 CH O

CH3

CH3

CH3CH2O

Isopropyl methyl etherethyl phenyl ether

13-23

Ethers: names-2

The IUPAC names for ethers are based on the alkane name of the longest chain attached to the O. The shorter chain is named as an alkoxy substituent. (alkane with the ane replaced by oxy, eg. CH3CH2O=ethoxy)

Thus CH3CH2CH2CH2CH2-O-CH3

1-methoxypentane

13-24

Ethers: reactions

• Chemically ethers are moderately inert

• Symmetrical ethers may be prepared by dehydrating two alcohol molecules

CH3 CH2O CH2 CH3

CH3 CH2OH CH3CH2OH

H+ (H3PO4) warm

13-25

Ethers: uses

Ethers are often used as anesthetics.

CH3 CH2O CH2 CH3Diethyl etherFirst successfulgeneral anesthetic

CH3O C C HF

F

Cl

Clpenthrane

13-26

13.9 Thiols: names

Named based on longest alkane chain with the suffix thiol position indicated by number. E. g.

CH2 CH2CH3 CHSH

CH3

3-methy-1-butanethiol

13-27

Thiols/Disulfides: reactions

The thiol-disulfide redox pair is responsible for a critical factor in protein structure called a disulfide bridge.

H C

NH2

COOH

SH H C

NH2

CH2 S

COOH

HC

NH2

CH2S

COOH

cysteine, anamino acid

cystine, importantin proteins

I2 (very mild)

H2, PtLiAlH4

NaBH4

2

+ 2H

13-28

The End

Alcohols, etc.