Transcript What is Organic Chemistry

Introduction to Organic
Chemistry
(What are Things Made of?)
IJSO Training (Phase 2)
Dr. Kendrew K. W. Mak
Department of Chemistry
The Chinese University of Hong Kong
1
Roles of Organic Chemistry in
Daily Life
Organic compounds (有機化合物) can be found in:
Detergents (清潔劑)
Pesticides (農藥 / 殺蟲劑)
Gasoline (汽油) / Fuels (燃料)
Paints
Dyes (染料)
Medicines
Computers / Communication
products
Living organisms
Food
Plastics / polymers (塑膠 / 聚合物)
and a lot more ……
2
What is Organic Chemistry (有機化學)
Classical Definition
Compounds obtained or derived from living organisms
Modern Definition
Compounds that are made up of carbon atoms.
About 13 million organic compounds are known today.
About 100,000 new ones discovered every year.
There are only 200,000 to 300,000 known inorganic compounds
(those are made up of elements other than carbon)
3
Interesting Organic Compounds –
Compounds having favorable aromas
O
H
O
CH 3
OH
Vanillin (香草醛)
N
N
Tetramethylpyrazine
(川芎嗪)
4
Organic Compounds
Natural Organic Compounds
Proteins (蛋白質), enzyme (酵), vitamins (維生素), lipids (脂質) ,
carbohydrates (碳水化合物), nucleic acid (核酸) ……
Synthetic (Man-made Compounds)
Synthetic fabrics (合成織品), plastics (塑膠), synthetic rubber (合成
橡膠), medicine (藥物) , adhesives (黏合劑), photographic film (攝影
菲林) ……
5
Diversified Structures
O
H 3C
CH 3
H H H
H C C O
H H
O
O
O
NH
O
O
OH
O
(CH 3 CH 2OH)
OH
HO
O
OO
OH
HO
HO
O
OH
O
O
O
OH
O
OH
OH
OH
Complex
Simple
6
Hydrocarbons – Contain only Carbon
and Hydrogen Atoms
Organic compounds that contain only carbon and hydrogen are
called hydrocarbons (碳氫化合物).
Hydrocarbons differ from one another in the number of carbon
atoms present in one molecule, and the ways that they are
bonded together.
Methane (甲烷) has one carbon atom, and octane (辛烷) has eight.
Polyethylene (聚乙烯) contains hundreds to thousands of carbon
and hydrogen atoms in each molecules.
Methane (CH4)
Octane (C8H18)
Polyethene
7
Molecular Sizes and Properties
Physical Properties of Some Alkanes (烷烴)
Name
Molecular
Formula
Methane
CH4
-182
-164
Gas
Ethane
C2H6
-183
-89
Gas
Propane
C3H8
-190
-42
Gas
Butane
C4H10
-138
-1
Gas
Pentane
C5H12
-130
36
Liquid
Hexane
C6H14
-95
69
Liquid
Heptane
C7H16
-91
98
Liquid
Octane
C8H18
-57
125
Liquid
Nonane
C9H20
-51
151
Liquid
Decane
C10H22
-30
174
Liquid
Melting Point (°C) Boiling Point (°C)
Physical State
(At 20°C)
8
Structural Isomers of Hydrocarbons
Hydrocarbons also differ from one another in the way the
carbon atoms bonded to each other.
HH
H
C
HH
C
H
H
C
C
C
HH
H
H
H
H
n-Pentane, C5H12
Straight chain (直鏈)
H
C
C
H
H
C
C
H
HH
H
H
H
H H
C
H
H
H
C
H
iso-Pentane, C5H12
C
H
H
H
C
C
H
H
C
HH
H
neo-Pentane, C5H12
Branched chains (支鏈)
9
Structural Isomers of Hydrocarbons
Boiling Point.
36°C
n-Pentane, C5H12
iso-Pentane, C5H12
30°C
The number of possible structural
isomers (異構體) of a chemical
formula increases rapidly as the
number of carbon atoms increases.
C5H12
C8H18
C20H42
3 isomers
75 isomers
366,316 isomers
10°C
neo-Pentane, C5H12
10
Conformers – Same Molecule with
Different Spatial Orientations
11
Petroleum (石油) –
Major Source of Hydrocarbon
Petroleum (also known as
crude oil) is a complex
mixture consisting mainly of
alkanes.
It corresponds to the fossil
(化石) remains of
microscopic animals that
lived in the seas in ancient
times.
Fractional distillation (分餾)
12
Alkane –
The Simplest Form of Hydrocarbon
Methane (CH4)
Natural Gas
Biogas (marsh gas)
H3C
H2
C
C
H2
CH3
H
H
C
H
H
Butane (丁烷) (C4H10)
Liquefied petroleum gas (液化石油氣)(LPG)
Lighter gas
13
Alkane –
The Simplest Form of Hydrocarbon
H3C
H2
C
C
H2
H2
C
C
H2
H2
C
Octane Number
(辛烷值)
CH3
0
Heptane
H3C
H3C
CH3 CH3
C
C
H2
CH
CH3
100
2,2,4-Trimethylpentane
14
Boosting Up the Octane Number
Anti-Knocking Agent
(抗震劑)
Tetramethyl lead (四甲基鉛), Pb(CH3)4
Tetraethyl lead (四乙基鉛), Pb(C2H5)4
Benzene
C6 H 6
Toluene
C7 H 8
p-Xylene
C 8H 10
Octane No. = 106
Octane No. = 118
Octane No. = 116
Toxic – leukemia (白血病)
Cause air pollution Produce smog (煙霧)
15
Saturated and Unsaturated
Hydrocarbons
Saturated Hydrocarbons – contain single bonds only
Unsaturated Hydrocarbons – contain multiple bonds
Saturated hydrocarbon
(飽和碳氫化合物)
H
H H
C
H
C
H
H
H
H
H
C
H
n-Butane, C4H10
(丁烷)
H
C
C
H H
Unsaturated hydrocarbon
(不飽和碳氫化合物)
H
C
C
H
H
C
H
H
But-2-ene, C4H8
(丁-2-烯)
16
Alkenes –
Hydrocarbons with C=C Double Bonds
Ethene/Ethylene (乙烯) (C2H4) – The simplest alkene (烯)
H
H
C C
H
H
Use:
Making polymer (polythene)
A plant hormone (triggers fruit ripening)
beta-carotene
(胡蘿蔔素)
Beta-carotene is the precursor molecule to vitamin A
17
Alkenes –
Hydrocarbons with C=C Double Bonds
H
H
H
C
C
C
H
H
C
H
H
H
H
C
H
C
H
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
Polymerization
(聚合作用)
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
18
Sigma (s) Bond and Pi (p) Bond
Compounds with double covalent bond
Pi (p) – side-to-side overlap
Ethene (CH2=CH2)
Double covalent bond = 1 s bond + 1 p bond
H
1.08Å
121.7°
C
H
C
116.6°
H 1.33Å H
A double bond consists of
one σ bond and one p bond
19
Geometrical Isomers (幾何異構體)
of Alkene
H3C
H
CH3
H
H3C
H
H
CH3
cis-2-butene
trans-2-butene
(順-丁-2-烯)
(反-丁-2-烯)
20
C=C Double Bonds:
Absorption of Light
Compound
H2C
CH2
UV-C:
UV-B:
UV-A:
Visible light:
below 280 nm
280 nm – 320 nm
320 nm – 400 nm
400 nm – 700 nm
max (nm)
 (M-1cm-1)
165
15,000
217
21,000
256
50,000
290
85,000
334
125,000
364
138,000
1 nm = 10-9 m
21
Sunscreens (防曬霜)
not very soluble
in oily skin lotions
O
OH
(CH 3 )2N
H2 N
O
CH 2CH3
COCH2 CHCH2 CH2 CH 2CH 3
para-aminobenzoic acid
PABA
2-ethylhexyl 4-(dimethylamino)benzoate
Padimate O
absorb UV-B
absorb UV-B
O
CH2 CH3
OCH2 CHCH2 CH 2CH 2CH3
CH 3O
2-ethylhexyl (E)-2-(4-methoxyphenyl)-2-propenoate
Giv Tan F
absorb UV-A & UV-B
22
C=C Double Bonds:
Absorption of Light
-carotene (胡蘿蔔素)
max = 455nm
carrots, apricots, sweet potatoes
(orange)
lycopene (番茄紅素)
max = 474nm
tomatoes, watermelon, pink grapefruit
(red)
1 nm = 10-9 m
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Benzene and Aromatic Compounds
The electrons of the double
bonds in benzene (苯) are not
confined between any two
carbon atoms. These
electrons are able to move
freely around the ring.
some common aromatic compounds (芳香族化合物):
Cl
Cl
Toluene
Naphthalene
1,4-Dichlorobenzene
24
The Delocalization of Electrons in
Benzene
H
6
C
5
H
C
4
H
1
C
C
H
C2
C
3
H
H
H
H
H
1
C
6
C
5
C
4
C
C2
C
3
H
H
H
I
II
Resonance structures (共振結構) of benzene
H
C
C
H
C
154 nm
H
C
H
H
C133 nm
C
H
H
H
C
C
H
C
C
H
H
C 140 nm
C
H
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The Delocalization of Electrons in
Benzene
• A compound with delocalized electrons is more stable than it
would be if all of its electrons were localized.
• The extra stability a compound gains from having delocalized
electrons is called delocalization energy (離域能) or
resonance energy (共振能) .
Potential energy
“cyclohexatriene” + 3H2
benzene + 3H2
H° = -85.8 kcal/mol
(-359kJ/mol)
36 kcal/mol
(151kJ/mol)
H° = -49.8 kcal/mol
(-208kJ/mol)
cyclohexane
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Delocalization (離域作用)
– Two More Examples
Delocalization in the carbonate ion
OO C
O-
OO- C
O
O
O- C
O-
2/3 -
O
O C
2/3 O
2/3 -
Resonance Hybrid
Resonance Structures
Bonding in ethanoic acid and the ethanoate ion
127 pm
124 pm
O
H3C C
OH
143 pm
Only one structure
for the acid
O
H3C C
O-
OH3C C
O
Two equivalent resonance
structures for the anion
1/2 -
O
H3C C
O1/2 127 pm
Resonance Hybrid
27
Organic Molecules are Classified
by Functional Groups
Ethane
(C2H6)
Boiling point = - 88°C
A gas at room temperature
Insoluble in water.
H H H
H C C O
H H
Ethanol
(C2H5OH)
Boiling point = + 78°C
A liquid at room temperature
Soluble in water
For making alcoholic beverages
H H H
H C C N
H H H
Ethylamine
(C2H5NH2)
A corrosive (腐蝕性), pungent (刺激性),
highly toxic gas
H H
H C C H
H H
28
Organic Molecules
General
are Classified
Structure
by Functional
C OH
Groups
C C
C
Name
Class
Hydroxyl group
Alcohols
Phenolic group
Phenols
Ether group
Ethers
Amine group
Amines
Ketone group
Ketones
Aldehyde
group
Aldehydes
Amide group
Amides
Carboxyl group
Carboxylic acids
Ester group
Esters
C OH
C C
C O C
Function group (官能基) is
defined as a combination of
atoms that behave as a unit.
C N
O
C
C
O
C
O
C
O
C
O
C
C
H
N
OH
O C
29
Alcohols Contain the Hydroxyl Group
Alcohols are organic molecules in which a hydroxyl group is
bonded to a saturated carbon.
H
H
H
C O
H
Methanol
(甲醇)
• Making methylated spirit
• Fuel for racing car
OH
H 3C C CH 3
H
Isopropanol
(異丙醇)
• Rubbing alcohol
30
Alcohols Contain the Hydroxyl Group
H H
H C C OH
H H
Ethanol
Fermentation (發酵作用)
(C6H10O5)x
Starch
enzymes
C6H12O6
Glucose
enzymes
2 CH3CH2OH + 2 CO 2
Ethanol
31
Transformation of Function Groups
Conversion of alkenes to alcohols (hydration水合作用)
H+
+
CH3CH CH2
H2O
heat
propene
CH3CH CH2
OH H
2-propanol
An acid-catalyzed reaction
without H +
CH3CH CH2
+
H 2O
No reaction
propene
32
Interconversion of Alcohols and
Alkyl Halides
CH3OH +
HBr
heat
CH3Br +
H2O
bromomethane
CH3Br +
OH-
CH3OH +
Br-
33
Some Common Halogenated
Hydrocarbons
Some Halogenated Hydrocarbons
Formula
Common name
CH3Cl
Methyl chloride
CH2Cl2
IUPAC name
Derived from methane
Some important uses
Chloromethane
Refrigerant; manufacture of
silicones, methyl cellulose,
and synthetic rubber
Methylene chloride
Dichloromethane
Laboratory and industrial
solvent
CHCl3
Chloroform
Trichloromethane
Industrial solvent
CCl4
Carbon tetrachloride
Tetrachloromethane
(see text)
CBrF3
Halon-1301
Bromotrifluoromethane
Fire extinguisher systems
CCl2F2
CFC-12
Dichlorodifluoromethane
Refrigerant
CH3CH2Cl
Ethyl chloride
ClCH2CH2Cl
CCl3CH3
Derived form ethane
Chloroethane
Local anesthetic
Ethylene dichloride
1,2-dichloroethane
Solvent for rubber
Methylchloroform
1,1,1-trichloroethane
Solvent for cleaning
computer chips and molds
for shaping plastics
34
Reactions of Alcohols and
Halogenated Hydrocarbons
CH3CH2OH
+
CH3CH2Cl
CH3CH2OCH2CH3
Diethyl ether
Diethyl ether was used as an anesthetic (麻醉劑) starting from
mid-19th century.
A commonly used laboratory solvent.
MTBE as fuel additive (燃料添加劑)
O
Methyl tert-butyl ether (MTBE)
•
It burns very completely and
reduces the emission of carbon
monoxide.
•
Very high octane rating (116),
replace aromatic hydrocarbons
•
Very strong odor, sickening to
some people.
•
Decompose very slowly in nature,
polluting the environment.
35
Different Types of Isomers
Isomers
Structural Isomers
(結構異構體)
(Different bonding)
Stereoisomers
(立體異構體)
(Different shapes)
Positional
Isomers
Hydrocarbon
Chain Isomers
Functional Group
Isomers
Geometric
Isomers
Enantiomers
(Optical Isomers)
位置異構體
碳氫鏈異構體
官能基異構體
幾何異構體
對映異構體
(旋光異構體)
36
Different Types of Isomers
Positional
Isomers
Hydrocarbon
Chain Isomers
Functional Group
Isomers
Br
Br
Br
OH
OH
OH
O
OH
C5H11Br
C4H9OH
C4H10O
37
Different Types of Isomers
Geometric
Isomers
Enantiomers
(Optical Isomers)
H3C
CH3
H3C
CH3
C4H8
(See next page……)
38
Optical Isomers and
Chiral Compounds
Asymmetric Carbon (不對稱碳原子) – is a carbon atom that
bonded to four different groups
An asymmetric carbon can be known as a chiral (手性) center
*
CH3CHCH2CH3
Br
2-bromobutane
Br
H3CH2C
C
Br
H
H3C
H
CH3
C
CH2CH3
mirror
the two isomers of 2-bromobutane
enantiomers (對映異構體)
39
Conversion of Alcohols to
Aldehydes (醛)
liver enzymes
CH3OH
H
H
Formaldehyde
LD50 = 0.070 g
Methanol
CH3CH2OH
Ethanol
Very toxic
O
C
liver enzymes
CH3
O
C
The aldehyde
group
H
Acetaldehyde
Less toxic
LD50 = 1.9 g
Oxidation Reaction (氧化反應)
40
Some Common Aldehydes
O
• Large amounts of formaldehyde are
used for producing adhesives for
making plywood (夾板).
• Embalming (防腐)
H
C
H
Formaldehyde
(甲醛)
41
Some Common Aldehydes
Aldehydes
Structure
Vanillin
O
C
(香草醛)
Food that contain the
aldehydes
Vanilla Ice-cream
H
HO
O
Benzaldehyde
(苯醛)
Cinnamaldehyde
(肉桂醛)
CH 3
O
C
Almond
H
O
H
C H
C C
H
Cinnamon
42
From Wine to Vinegar
CH3CH2OH
oxidation
CH3COOH
Ethanol
Acetic acid
an alcohol
a carboxylic acid
White vinegar – 5% acetic acid solution
O
OH
Carboxyl group
43
Carboxylic Acids Found in Foods
AHAs
Alpha-hydroxy acids
AHAs contain a hydroxyl
group (-OH) bonded to the
first carbon atom attached
to the –COOH group.
HO
O
OH
OH
O
C
CH
CH
C
HO
OH
Tartaric acid
O
OH
O
C
CH
CH2 C
Malic acid
O
HO
C
CH CH 3
O
OH
HO
C
OH
CH 2 C
O
O
CH 2 C
OH
C
OH
Lactic acid
OH
Citric acid
44
Reactions of Carboxylic Acids
with Alcohols
CH3CH2CH2
O
C
butyric acid
CH3
O
C
OH
+
H+
CH3CH2OH
CH3CH2CH2
ethanol
OH
acetic acid
pentanol
OCH2CH3
+ H2O
ethyl butyrate
(pineapple favour)
+
+ CH3CH2CH2CH2CH2OH
O
C
H
CH3
O
C
OCH2CH2CH2CH2CH3
+ H2O
pentyl acetate
(banana favour)
O
C
O
ester linkage (酯鍵合)
45
Some Esters (酯) and Their Odors
Name
Structure
Odor
Ethyl formate
HCOO—CH2CH3
Rum
Isobutyl formate
HCOO—CH2CH(CH3)2
raspberry
Ethyl acetate
CH3COO—CH2CH3
Floral
Propy acetate
CH3COO—CH2CH2CH3
Pear
Pentyl acetate
CH3COO—CH2CH2CH2CH2CH3
Banana
Isopentyl acetate
CH3COO—CH2CH2CH(CH3)2
Banana
Octyl acetate
CH3COO—
CH2CH2CH2CH2CH2CH2CH2CH3
Orange
Benzyl acetate
CH3COO—CH2C6H5
Jasmine
Isobutyl propionate
CH3CH2COO—CH2CH(CH3)2
Apple
Methyl butyrate
CH3CH2CH2COO—CH3
Rum
Ethyl butyrate
CH3CH2CH2COO—CH2CH3
Pineapple
Butyl butyrate
CH3CH2CH2COO—CH2CH2CH2CH3
Pineapple
Amyl butyrate
CH3CH2CH2COO—CH2CH2CH2CH2CH3
Apricot
Isoamyl pentanoate
CH3CH2CH2CH2COO—CH2CH2CH(CH3)2
Apple
46
More About Oxidation and
Reduction Reactions
H
H
H C O
H
Methanol
- "2 H"
oxidation
H
O
C
+ "O"
H
oxidation
Formaldehyde
H
O
C
O
H
Formic acid
Oxidation (in organic chemistry) – often refers to:
• gaining oxygen atoms (+ O)
• losing hydrogen atoms (- H)
oxidation – 氧化作用; reduction – 還原作用
47
More About Oxidation and
Reduction Reactions
H
O
C
+ "2 H"
H
reduction
Formaldehyde
H
O
C
O
H
Formic acid
H
H
H C O
H
Methanol
+ "2 H", - "O"
reduction
H
H
H C O
H
Methanol
Reduction (in organic chemistry) – often refers to:
• losing oxygen atoms (- O)
• gaining hydrogen atoms (+ H)
48
More About Oxidation and
Reduction Reactions
H H H
H
H C C C O
H H H
oxidation
H H O
H C C C
H H H
1o alcohol
H
H O H
H C C C H
H H H
2o alcohol
CH3 H
H3C C O
CH3
3o alcohol
aldehyde
oxidation
H
C
H
H
O
C
oxidation
H H O
H C C C
H H O H
carboxylic acid
H
C
H
H
ketone
Not easily oxidized
No H attached to the "C" atom
49
Amines (胺) and Amides (酰胺)
Amines – substances with “fishy” smell.
CH3 NH 2
CH 3CH 2 NH 2
primary (1o ) amine
H3 C
N CH 3
H3 C
H3 C
N H
H3 C
secondary (2o ) amine
tertiary (3 o) amine
Amides – linking the amino acids in proteins
O
H
N
S
H2N
O
O
N
H
H
N
O
N
H
OH
O
H
N
O
N
H
O
HO
H
N
O
O
N
H
NH
H
N
N
N
O
OH
NH2
50
Organic Chemistry in Daily Life
• Polymers & Plastics (聚合物及塑膠)
• Detergents (清潔劑)
51
What is Polymer?
Polymer – substances that contain very long molecular chains and have the
same structural unit repeating over and over again.
Examples of natural polymers – cotton, silk and rubber.
cotton
clothes made from silk
tire made of rubber
52
Natural polymers
Cotton – mainly composed of cellulose (纖維素).
OH
OH
OH
O
HO
HO
HO
OH
OH
HO
O
OH
OH
H
O
O
O
H OH
HO
HO
OH
H
n-2
O
OH
H
cellulose
H
-D-glucose
Silk – natural protein fiber
H3C
CH C OH
NH2
alanine
O
O
O
H
CH C OH
NH2
glycine
H2C
CH C
OH
OH NH 2
serine
Rubber – formed from the polymerization of isoprene (異戊二烯)
......
......
n
isoprene
polyisoprene
53
Addition Polymerization
(加成聚合作用)
The two major ways of making polymers: addition polymerization and condensation
polymerization.
Addition polymerization – joining the monomers together without losing any small
molecule or atom. Examples are
Polythene (PE) n
(聚乙烯)
Polystyrene (PS)
H
H
C C
H
n
H
addition
polymerization
H
H
C C
H
addition
polymerization
H H
C C
H H
n
H H
C C
H
n
(聚苯乙烯)
Monomer (單體) –
low molecular weight compound that can be connected together to give
a polymer
54
Condensation Polymerization
(縮合聚合作用)
Condensation polymers are formed by condensation (縮合作用) reactions, in which
small molecules such as water or hydrogen chloride are eliminated in the polymerization
process. Examples are
O
Nylon
n
OH
HO
+ n H2N
NH2
O
O
H
N
N
H n
O
Polyethylene
terephthalate
(PET)
HO
+ 2n H2O
OH
n
O
OH
n HO
+
O
(聚對苯二甲酸乙二酯)
O
“ A polyester – 聚酯”
O
O
O
n
+ 2n H2O
55
Thermoplastics (熱塑性塑膠)
Thermoplastics
The polymer molecules are held together by the weak
intermolecular van Der Waals forces (范德華力). At elevated
temperature, it is easy to "melt" these bonds and the molecular
chains can slide past one another easily. These polymers can be
soften or melted by heating, and can be remolded into different
forms.
polymer strands
original form
have little tendency to
return to its original form
The chain can be stretched, which cause them to
flow pass each other, When released, the polymer
will not return to its original form.
56
Thermosetting Plastics (熱固性塑膠)
Thermosetting Plastics
These are three-dimensional polymers which are highly cross-linked by
strong chemical bonds such as covalent bonds. Thermosetting polymers are
“set” or “polymerized” through chemical reactions to form the cross-links (交
鍵). Once the chemical reaction or polymerization is complete, the polymer
becomes a hard, infusible, insoluble material which cannot be softened,
melted or molded.
57
Soaps and Detergents
(肥皂及清潔劑)
Water is a poor cleaning agent:
• Water has high surface tension (表面張力). It tends to form
beads and droplets, and does not wet substances very well.
• It cannot dissolve greasy dirt effectively.
Soap cleans by:
• Decreasing water’s surface tension, making it a better
wetting agent;
• Converting greasy and oily dirt into small particles that
become dispersed in the soapy water;
• Keeping the grease particles in suspension (懸浮狀態),
preventing them getting together and stick back to the clean
surface.
58
The Soap Molecule
Na+
or
K+
Hydrophobic (疏水性) tail is attracted to oily,
greasy, hydrocarbon-like substances.
CH3 (CH2)n CO2- Na+
Hydrophilic (親水性) head is
attracted to water molecules.
n: even number, ranging from 8 - 16
a soap molecule
59
Breaking the Surface Tension
60
Removing the Greasy Dirt
The soap molecules embed
the hydrophobic tails into
the greasy dirt and leave it
off the surface.
The particles (micelles)
repel each other, forming
many tiny suspended
droplets.
61
Making of Soap :
Saponification of Triglyceride
Triglycerides are the principal constituents of animal fats and vegetable
oils.
O
O
CH2
O
C
CH2
R
O
CH
O
C
R'
+
3NaOH
H2O
Heat
R
OH
O
C
O- Na+
O
CH
OH
+
R'
C
O-Na+
O
O
CH2
C
R"
CH2
A triglyceride
OH
Glycerol
R"
C
O-Na+
Soaps
The saponification of a triglyceride.
R, R’ and R”: Straight (unbranched) hydrocarbon chains.
saponification – 皂化作用; triglyceride – 甘油三酸酯
62
Soap and Hard Water (硬水)
Hard water:
•
•
high mineral content
rich in calcium ions (Ca2+) and magnesium ions (Mg2+)
Soap forms insoluble precipitates (soap curd) with hard water. It
reduces the cleaning power of soap.
2 CH3 (CH 2) nCO2 - Na +
+ Ca2+
aqueous solut ion
2 CH 3 (CH2 )n CO 2- Na+
aqueous solution
precipitate – 沉澱物
(CH 3(CH 2) nCO2 -) 2 Ca 2+
insoluble pr ecipitat es
+ Mg2+
(CH3 (CH2 )n CO2- )2 Mg 2+
insoluble precipitates
63
Soapless Detergent (非皂性清潔劑)
Replace the anionic carboxylate group with a sulfonate group. Alkyl
sulfonates do not form insoluble salts in hard water.
O O
S - +
O O Na
Sodium lauryl sulfate (SLS) or sodium dodecyl sulfate (SDS)
R
SO3- Na+
R = alkyl group
Sodium alkylbenzenesulfonate
64