A cubic micron of water contains about 90 billion atoms

Chapter 19 & 20
Esters, Amides and Carbohydrates
Chemistry B11
Esters
Formation of Esters
RC O H
O
A carboxylic acid
=
Fischer Esterification
RCO R
'
O
RC-OH
O
H
-
O R
'
=
=
An alcohol
A carboxylic acid
An ester
H
2
SO
4
+ H
2

O
•
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
CH
3
—

C—O —CH
3
ethanoate IUPAC: methyl ethanoate
(acetate) common: methyl acetate
Naming of Esters
O

propyl
CH
3
—

C—O —CH
2
—CH
2
—CH
3

Propyl ethanoate (IUPAC)
Propyl acetate (common)


CH
3
—CH
2
—C—O—CH
2
—CH
3
Ethyl propanoate
Naming of Esters
O
O

CH
3
—

C—OH + HO—CH
2
—CH
3

CH
3
—

C—O—CH
2
—CH
3
+

H
2
O
Fischer Esterification
H
2
SO
4
Ethanoic acid
(Acetic acid)
Ethanol
(Ethyl alcohol)
Ethyl ethanoate
(Ethyl acetate)
O
Esters give flowers and fruits their pleasant fragrances and
flavors.
Properties of Esters
Hydrolysis: reaction with water.
(breaking a bond and adding the elements of water)
RCO R '
O
RC-OH
O

H
-
O R
'
=
=
An alcohol
A carboxylic acid
An ester
+ H
2
O
+
Heat
Acid
Properties of Esters
Saponification (Hydrolysis): an ester reacts with a hot aqueous base.
RCO R
'
O
RCO-Na
O
H
- O R
'
=
=
An alcohol
A sodium salt
An ester

+ NaOH
+
H
2
O
Heat
-
+
CH
3
CO
CH
2
CH
3
O
CO-Na
O
CH
3
CH
2
OH
=
=
Ethanol
Sodium acetate
Ethyl Ethanoate
+ NaOH
+

-
+
CH
3
Amides
In an amide, the -OH group in the carboxyl group of a
carboxylic acid is replaced by an Amino group (-NH
2
).



CH
3
—

C—OH CH
3
—

C — NH
2

Amides
=
O
=
O
Formation of Amides
RC O H

O
A carboxylic acid
=
RCNHR
'
O
RC-OH
O
H
-
N HR
=
=
An Amine
A carboxylic acid
An amide
Heat
+ H
2
O
'
H
2
OCH
3
C-NHCH
2
CH
3
O

H HN CH
2
CH
3
CH
3
C-OH
O
+
+
Acetic acid
Ethanamine
N-ethylethanamide
Change the end of the name of the carboxylic acids from
“-oic acid” to “-amide”.
methanoic acid

H–C–NH
2
methanamide (IUPAC)

propanoic acid
CH
3
–CH
2
–C–NH
2
propanamide (IUPAC)
Naming of Amides

O
=
=
O
CH
3
–C–NH–CH
3
N-methylethanamide
CH
3
–CH
2
–C–N(CH
3
)
2
N,N-dimethylpropanamide

CH
3
–C–N(CH
2
CH
3
)
2
N,N-diethylethanamide
Naming of Amides
=

O
=
O
=
O
Properties of Amides
Such as esters:
Hydrolysis in hot aqueous acid or base
Carbohydrates
6CO
2
+ 6H
2
O + energy C
6
H
12
O
6
+ 6O
2
Photosynthesis
Respiration
•
Produced by photosynthesis
in plants.
•
The major source of energy
from our diet.
•

Composed of the elements
C, H, and O.
glucose
C
n
(H
2
O)
n
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.
Carbohydrates
1. Monosaccharide + H
2
O no hydrolysis
H
+
or enzyme
2. Disaccharide + H
2
O two monosaccharide units
+
3. Polysaccharide + many H

2
O many monosaccharide units
H
+
or enzyme
H
+
or enzyme
Monosaccharides
Monosaccharides are carbohydrates with:
•
3-9 carbon atoms
•
A carbonyl group (aldehyde or ketone)
•
Several hydroxyl groups
C
n
H
2n
O
n
A carbohydrate that cannot be split or hydrolyzed into smaller carbohydrates.

║
C ─ H
│
H─ C ─ OH
│
H─ C ─ OH

│
CH
2
OH
O
C
n
(H
2
O)
n
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
O
║
C ─ H aldose
│
H─ C ─ OH

│
H─ C ─ OH
│
CH
2
OH
an aldotetrose
(Erythose)
Monosaccharides - Aldose
Monosaccharides - Ketose
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
CH
2
OH
│
C = O ketose
│
H─ C ─ OH

│
H─ C ─ OH
│
H─ C ─ OH
│
CH
2
OH
a ketohexose
(Fructose)
Some important Monosaccharides
Glucose
(C
6
H
12
O
6
, 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.
HHO
H

CH
2
OH
OHC
H
H
OH
OH
C
C
C
OH
C
Some important Monosaccharides
Fructose
(C
6
H
12
O
6
, 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).
O
HHO
H
CH
2
OH
OHC
H OHC
C
C
CH
2
OH
Some important Monosaccharides
Galactose
(C
6
H
12
O
6
, 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).
HHO
HHO
H
CH
2
OH
OHC
H OH
C
C
C
OH
C
Galactosemia
missing the enzyme that convert galactose to glucose.
Accumulation of galactose in the blood and tissues.
Disease - Galactosemia
Mental retardation and cataract
Solution: removing the galactose from food: no milk.