+ All Categories
Home > Documents > 1 14.5 Physical Properties of Alcohols, Phenols, and Ethers 14.6 Reactions of Alcohols Chapter 14...

1 14.5 Physical Properties of Alcohols, Phenols, and Ethers 14.6 Reactions of Alcohols Chapter 14...

Date post: 19-Dec-2015
Category:
View: 247 times
Download: 5 times
Share this document with a friend
Popular Tags:
24
1 14.5 Physical Properties of Alcohols, Phenols, and Ethers 14.6 Reactions of Alcohols Chapter 14 Alcohols, Phenols, Ethers, and Thiols
Transcript

1

14.5 Physical Properties of Alcohols, Phenols, and Ethers

14.6 Reactions of Alcohols

Chapter 14 Alcohols, Phenols, Ethers, and Thiols

2

Boiling Points of Alcohols

Alcohols contain a strongly electronegative O in the OH groups.

Thus, hydrogen bonds form between alcohol molecules.

Hydrogen bonds contribute to higher boiling points for alcohols compared to alkanes and ethers of similar mass.

3

Boiling Points of Ethers

Ethers have an O atom, but there is no H attached.

Thus, hydrogen bonds cannot form between ether molecules.

4

Solubility of Alcohols and Ethers in Water

Alcohols and ethers are more soluble in water than alkanes because the oxygen atom can hydrogen bond with water.

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

5

Alcohols undergo combustion with O2 to produce CO2 and H2O.

2CH3OH + 3O2 2CO2 + 4H2O + Heat Dehydration removes H- and -OH from adjacent

carbon atoms by heating with an acid catalyst. H OH

| | H+, heatH—C—C—H H—C=C—H + H2O

| | | | H H H H

alcohol alkene

Reactions of Alcohols

6

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

7

Oxidation and Reduction In organic chemistry, oxidation is a loss of

hydrogen atoms or a gain of oxygen. In an oxidation, there is an increase in the

number of C-O bonds. Reduction is a gain of hydrogen or a loss of

oxygen. The number of C-O bonds decreases.

8

In the oxidation [O] of a primary alcohol, one H is lost from the –OH and another H from the carbon bonded to the OH.

[O] Primary alcohol Aldehyde

OH O | [O] ||

CH3—C—H CH3—C—H + H2O |

H Ethanol Ethanal (ethyl alcohol) (acetaldehyde)

Oxidation of Primary Alcohols

9

The oxidation of a secondary alcohol removes one H from –OH and another H from the carbon bonded to the –OH.

[O] Secondary alcohol Ketone OH O

| [O] || CH3—C—CH3 CH3—C—CH3 + H2O |

H 2-Propanol Propanone (Isopropyl alcohol) (Dimethylketone; Acetone)

Oxidation of Secondary Alcohols

10

Tertiary alcohols are resistant to oxidation.[O]

Tertiary alcohols no reaction OH | [O] CH3—C—CH3 no product | CH3 no H on the C-OH to oxidize 2-Methyl-2-propanol

Oxidation of Tertiary Alcohols

11

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 CH3CH2OH

12

Enzymes in the liver oxidize ethanol. The aldehyde produced impairs coordination. A blood alcohol level over 0.4% can be fatal.

O ||

CH3CH2OH CH3CH 2CO2 + H2OEthyl alcohol acetaldehyde

Oxidation of Alcohol in the Body

13

Oxidation of alcohols in liver

CH3CH2OH CH3C

O

HCH3C

O

OH

CO2 + H2O

ethyl alcoholethanol

acetaldehydeethanal

acetic acidethanoic acid

alcoholdehydrogenase

CH3OH HCO

H

alcoholdehydrogenase

metyl alcoholmethanol

formaldehydemethanal

reacts with proteins causing denaturationgreat toxicity to humansnot toxic to horses and rats

HCO

OH

formic acidmethanoic acid

acetaldehydedehydrogenase

14

Effect of Alcohol on the Body

15

Breathalyzer test

K2Cr2O7 (potassium dichromate) This orange colored solution is used in the

Breathalyzer test (test for blood alcohol level) Potassium dichromate changes color when it is

reduced by alcohol K2Cr2O7 oxidizes the alcohol

16

Breathalyzer reaction orange-red green

8H++Cr2O72-+3C2H5OH→2Cr3++3C2H4O+7H2O

dichromate ethyl chromium (III) acetaldehyde

ion alcohol ion

(from K2Cr2O7)

H3C C H

H

OH[O]

H3C C

O

H

+ H2O

ethylalcohol

acetaldehyde

17

% Ethanol Product

50% Whiskey, rum, brandy

40% Flavoring extracts

15-25% Listerine, Nyquil, Scope

12% Wine, Dristan, Cepacol

3-9% Beer, Lavoris

Alcohol Contents in Common Products

18

The proof of an alcohol The proof of an alcoholic beverage is merely twice the

percentage of alcohol by volume. The term has its origin in an old seventeenth-century

English method for testing whiskey. Dealers were often tempted to increase profits by adding

water to booze. A qualitative method for testing the whiskey was to pour

some of it on gunpowder and ignite it. If the gunpowder ignited after the alcohol had burned

away, this was considered “proof” that the whiskey did not contain too much water.

19

Production of ethanol from grain by fermentation Grain seeds are grounded and cooked → mash Malt (the dried sprouts of barley) or special mold is added

→ source of the enzyme diastase that catalyzes the conversion of starch to malt sugar, maltose

diastase

(C6H10O5)2x + H2O → x C12H22O11

starch maltose Pure yeast culture is addedC12H22O11 + H2O → 2 C6H12O6

maltose glucose

C6H12O6 → 2 CH3CH2OH + 2 CO2

glucose ethanol carbon dioxide

20

Preparation of alcohols Ethanol is made by hydration of ethylene (ethene)

in the presence of acid catalyst

C C

H

H

H

H

+ HOH[H+]

C C H

OH

HH

H

H

21

Isopropyl is produced by addition of water to propylene (1-

propene)

H3CHC CH2 + HOH

[H+]H3C

HC CH3

OH

(Markovnikov's rule)

CH3CH2CH2OHpropyl alcohol is never formed

22

Methanol is made commercially from carbon

monoxide and hydrogen

CO + 2H2 → CH3OH

23

Oxidation of Thiols. Mild oxidizing agens remove two hydrogen

atoms from two thiol molecules. The remaining pieces of thiols combine to

form a new molecule, disulfide, with a covalent bond between two sulfur atoms.

R – S – H H – S – R+I2 → RS – SR+2HI

2 RSH + H2O2 → RS – SR + 2 H2O

24

The chemistry of the “permanent” waving of hair. Hair is protein, and it is held in shape by disulfide linkages between adjacent

protein chains. The first step involves the use of lotion containing a reducing agent such as

thioglycolic acid, HS – CH2 – COOH. The wave lotion ruptures the disulfide linkages of the hair protein. The hair is then set on curles or rollers and is treated with a mild oxidizing

agent such as hydrogen peroxide (H2O2). Disulfide linkages are formed in new positions to give new shape to the hair. Exactly the same chemical process can be used to straighten naturally curly

hair. The change in hair style depends only on how one arranges the hair after the

disulfide bonds have been reduced and before the reoxidation takes place. Permanent Hair Wave (http://www.elmhurst.edu/~chm/vchembook/

568hairwave.html)


Recommended