Esters, Amides and Carbohydrates

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Chemistry B11
Chapter 19 20 Esters, Amides and Carbohydrates
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Esters
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(No Transcript)
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Formation of Esters
O

A carboxylic acid
Fischer Esterification
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Naming of Esters

• Name the alkyl group from the alcohol OR.
• Followed by name of the acid in which the suffix
  -ic acid is replaced by suffix -ate.
• acid alcohol
• ?? methyl
• CH3 CO CH3
• ethanoate IUPAC methyl ethanoate
• (acetate) common methyl acetate

O
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Naming of Esters
propyl CH3 CO
CH2CH2CH3 Propyl ethanoate (IUPAC) Propyl
acetate (common)
O

• CH3CH2 COCH2CH3
• Ethyl propanoate

O
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Fischer Esterification

• CH3 COH HOCH2CH3
• CH3 COCH2CH3 H2O

O
H2SO4
Ethanoic acid (Acetic acid)
Ethanol (Ethyl alcohol)
Ethyl ethanoate (Ethyl acetate)
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Properties of Esters
Esters give flowers and fruits their pleasant
fragrances and flavors.
Hydrolysis reaction with water. (breaking a
bond and adding the elements of water)
Heat
Acid
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Properties of Esters
Saponification (Hydrolysis) an ester reacts with
a hot aqueous base.
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Amides
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Amides
In an amide, the -OH group in the carboxyl group
of a carboxylic acid is replaced by an Amino
group (-NH2).

CH3 COH
CH3 C NH2
O
O


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Formation of Amides
O

A carboxylic acid
O
O
H
HN
C
H
C
H
C
H
C
-
O
H

C
H
C
-
N
H
C
H
C
H

3
3
2
3
2
3
Ethanamine
N-ethylethanamide
Acetic acid
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Naming of Amides
Change the end of the name of the carboxylic
acids from -oic acid to -amide.
methanoic acid HCNH2
methanamide (IUPAC)
propanoic acid CH3CH2CNH2 propanamide
(IUPAC)
O

O

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Naming of Amides

• CH3CNHCH3 N-methylethanamide
• CH3CH2CN(CH3)2 N,N-dimethylpropanamide
• CH3CN(CH2CH3)2 N,N-diethylethanamide

O

O

O

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Properties of Amides
Such as esters Hydrolysis in hot aqueous acid
or base
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Carbohydrates

• Produced by photosynthesis in plants.
• The major source of energy from our diet.
• Composed of the elements C, H, and O.

Cn(H2O)n
Photosynthesis
6CO2 6H2O energy C6H12O6 6O2
Respiration
glucose
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Carbohydrates

• The most abundant organic compounds in the plant
  world.
• 3/4 of the weight of plants.
• 1 of the weight of animals and humans (they do
  not store).
• 65 of the foods in our diet.

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Carbohydrates
H or enzyme
1. Monosaccharide H2O no hydrolysis
H or enzyme
2. Disaccharide H2O two monosaccharide units

H or enzyme
3. Polysaccharide many H2O many
monosaccharide units
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Monosaccharides
A carbohydrate that cannot be split or hydrolyzed
into smaller carbohydrates.

• Monosaccharides are carbohydrates with
• 3-9 carbon atoms
• A carbonyl group (aldehyde or ketone)
• Several hydroxyl groups

Cn(H2O)n
CnH2nOn
C - H
H- C - OH H- C -
OH CH2OH
O
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Monosaccharides - Aldose
O C - H aldose
H- C - OH
H- C - OH CH2OH an
aldotetrose (Erythose)

• Aldose is monosaccharide
• With an aldehyde group and many hydroxyl (-OH)
  groups.
• triose (3C atoms)
• tetrose (4C atoms)
• pentose (5 C atoms)
• hexose (6 C atoms)
• Aldo- suffix

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Monosaccharides - Ketose
CH2OH C
O ketose H- C - OH
H- C - OH H- C - OH
CH2OH a ketohexose
(Fructose)

• Ketose is monosaccharide
• With a ketone group and many hydroxyl (-OH)
  groups.
• triose (3C atoms)
• tetrose (4C atoms)
• pentose (5 C atoms)
• hexose (6 C atoms)
• Keto- suffix

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Some important Monosaccharides

• Glucose
• (C6H12O6, aldohexose) blood sugar
• Is found in fruits, vegetables,
• corn syrup, and honey.
• Is found in disaccharides such as sucrose,
  lactose, and maltose.
• Makes up polysaccharides such as starch,
  cellulose, and glycogen.

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Some important Monosaccharides

• Fructose
• (C6H12O6, ketohexose),
• Is the sweetest of the carbohydrates.
• Is found in fruit juices and honey (fruit sugar).
  
• In bloodstream, it is converted to its isomer,
  glucose.
• Is bonded to glucose in sucrose (a disaccharide
  known as table sugar).

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Some important Monosaccharides

• Galactose
• (C6H12O6, aldohexose),
• Has a similar structure to glucose except for the
  OH on Carbon 4.
• Cannot find in the free form in nature.
• Exist in the cellular membranes of the brain and
  nervous system.
• Combines with glucose in lactose (a disaccharide
  and a sugar in milk).

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Disease - Galactosemia
Galactosemia missing the enzyme that convert
galactose to glucose. Accumulation of
galactose in the blood and tissues.
Mental retardation and cataract
Solution removing the galactose from food no
milk.
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Fischer Projections
- Horizontal lines represent bonds projecting
forward from the stereocenter. - Vertical lines
represent bonds projecting to the rear. - Only
the stereocenter is in the plane.
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Fischer Projections
1. Carbon with four different groups bonded to
it. 2. The chiral carbon furthest from the
carbonyl group (-CHO).
HO
H
D - glucose
L - glucose
More common in the nature
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Cyclic Structure Haworth Structure
1
1
Anomeric carbon
1
1
1
Alpha (a)
Beta (?)
More stable form
Anomers
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Cyclic Structure Haworth Structure
?
1
1
?
?-Glucose ?-Glucose
1
1
?-Galactose ?-Galactose
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Cyclic Structure Haworth Structure
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Cyclic Structure Haworth Structure
?
1
1
?
?-Glucose ?-Glucose
Humans have ?-amylase (an enzyme) and they can
digest starch products such as pasta (contain
?-glucose) Humans do not have ß-amylase (an
enzyme) and they cannot digest cellulose such as
wood or paper (contain ß-glucose)
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Mutarotation
Change in specific rotation that accompanies the
equilibration of a and ? anomers in aqueous
solution.
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64
lt 0.02
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Physical properties of Monosaccharides

• Colorless
• Crystalline solids
• Soluble in water (H-bond because of OH groups)
• Insoluble in nonpolar solvents

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Oxidation of Monosaccharides
Aldonic acids
Reducing sugars reduce another substance.
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Oxidation of Monosaccharides
O
H
CH2OH
C
Rearrangement (Tautomerism)
C O
C OH
H
D-fructose (ketose)
D-glucose (aldose)
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Reduction of Monosaccharides
Alditols
Sugars alcohols sweetners in many sugar-free
(diet drinks sugarless gum).
Problem diarrhea and cataract
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Disaccharides

• A disaccharide
• Consists of two monosaccharides linked by a
  glycosidic bond (when one OH group reacts with
  another OH group).
• Glucose glucose maltose H2O
• Glucose galactose lactose H2O
• Glucose fructose sucrose H2O

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Disaccharides

• Maltose
• Is a disaccharide of two glucose molecules.
• Has a a -1,4-glycosidic bond (between two
  a-glucoses).
• Is obtained from the breakdown of starches.
• Is used in cereals and candies.
• Is a reducing sugar (carbon 1 can open to give a
  free aldehyde to oxidize).

? -1,4-glycosidic bond
?

1
1
4
4
a-glucose
a-glucose
?- maltose
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Disaccharides

• Lactose
• Is a disaccharide of galactose and glucose.
• Has a ß -1,4-glycosidic bond (between ß-galactose
  and a-gulcose).
• Is found in milk and milk products (almost no
  sweet).
• Is a reducing sugar (carbon 1 can open to give a
  free aldehyde to oxidize).

?
?-lactose
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Disaccharides

• Sucrose
• Is found in table sugar.
• Consists of glucose and fructose.
• Has an a,ß-1,2-glycosidic bond (between a-glucose
  and ?-fructose).
• Is not a reducing sugar (carbon 1 cannot open to
  give a free aldehyde
• to oxidize).

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Polysaccharides

• Polymers of many monosaccharides units.
• Amylose (20)
• Starch
• Amylopectin (80)
• Glycogen (animal starch in muscle and liver. It
  is
• hydrolyzed in our cells and provides energy
  ).
• Cellulose (plant and wood structures).

(starch that stores glucose in plants such as
rice, potatoes, beans, and wheat).
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Polysaccharides

• Amylose
• Is a polysaccharide of a-glucose in a
• continuous (unbranched) chain (helical or
  coil
• form).
• Has a-1,4-glycosidic bonds between the
• a-glucose units (250 to 4000 units).

a-1,4-glycosidic bond
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Polysaccharides

• Amylopectin
• Is a polysaccharide of glucose units in branched
  chains.
• Has a-1,4-glycosidic bonds between the a-glucose
  units.
• Has a-1,6 bonds to branches of glucose units.
• (at about every 25 glucose units, there is a
  branch).
• Glycogen has same structure (more highly
  branched-every 10-15 units).

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Polysaccharides
Amlose, Amylopectin (starch)
H or amylase (enzyme in saliva)
Digestion process
Dextrins (6-8 glucose units)
H or amylase (enzyme in saliva)
Maltose (2 glucose units)
H or maltase (enzyme)
Many a-D-glucose units
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Respiration
C6H12O6 6O2 6CO2 6H2O energy
glucose
Fermentation
Yeast
C6H12O6 2C2H5OH CO2 energy
Ethanol
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Polysaccharides

• Cellulose
• Is a polysaccharide of glucose units in
  unbranched chains with ß-1,4-glycosidic bonds.
• Has rigid structure (H-bond) and insoluble in
  water.
• Is the major structural material of wood plants
  (cotton 100).
• Cannot be digested by humans because of the
• ß-1,4-glycosidic bonds (needs a special
  enzyme).