1. Esters, Amides and Carbohydrates
Chemistry B11
Chapter 13
Esters, Amides and Carbohydrates

2. Esters

4. Formation of Esters O R C O H R C O ' - H = Fischer Esterification =
A carboxylic acid
Fischer Esterification R C O ' - H =
An alcohol
A carboxylic acid
An ester
H2SO4
+ H2O

5. 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 — C—O —CH3
ethanoate IUPAC: methyl ethanoate
(acetate) common: methyl acetate O

6. Naming of Esters propyl CH3 — C—O —CH2—CH2—CH3 O
Propyl ethanoate (IUPAC)
Propyl acetate (common) O
CH3—CH2 —C—O—CH2—CH3
Ethyl propanoate O

7. Fischer Esterification
CH3 — C—OH + HO—CH2—CH3
CH3 — C—O—CH2—CH H2O O
H2SO4
Ethanoic acid
(Acetic acid)
Ethanol
(Ethyl alcohol)
Ethyl ethanoate
(Ethyl acetate)

8. (breaking a bond and adding the elements of water)
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) R C O ' - H =
An alcohol
A carboxylic acid
An ester
+ H2O +
Heat
Acid

9. Properties of Esters R C O ' O- N a H - CH3 C O CH2CH3 O- N a CH3CH2OH
Saponification (Hydrolysis): an ester reacts with a hot aqueous base. R C O ' O- N a H - =
An alcohol
A sodium salt
An ester
+ NaOH +
H2O
Heat
CH3 C O
CH2CH3 O- N a
CH3CH2OH =
Ethanol
Sodium acetate
Ethyl Ethanoate
+ NaOH + -

10. Amides

11. Amides In an amide, the -OH group in the carboxyl group of a
carboxylic acid is replaced by an Amino group (-NH2).
CH3 — C—OH CH3 — C — NH2 O O = =

12. Formation of Amides O R C O H R C NH ' O - H HR = = + H2O O O C H C -
A carboxylic acid R C NH ' O - H N HR =
An Amine
A carboxylic acid
An amide
Heat
+ H2O O O C H C - O H + H HN C H C H C H C - N H C H C H + H 2 O 3 2 3 3 2 3
Acetic acid
Ethanamine
N-ethylethanamide

13. Naming of Amides
Change the end of the name of the carboxylic acids from
“-oic acid” to “-amide”.
methanoic acid
H–C–NH2 methanamide (IUPAC)
propanoic acid
CH3–CH2–C–NH2
propanamide (IUPAC) O = O =

14. Naming of Amides O CH3–C–NH–CH3 N-methylethanamide =
CH3–CH2–C–N(CH3)2 N,N-dimethylpropanamide
CH3–C–N(CH2CH3)2 N,N-diethylethanamide O = O = O =

15. Hydrolysis in hot aqueous acid or base
Properties of Amides
Same as esters:
Hydrolysis in hot aqueous acid or base

16. Carbohydrates Cn(H2O)n 6CO2 + 6H2O + energy C6H12O6 + 6O2
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

17. 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.

18. Carbohydrates 1. Monosaccharide + H2O no hydrolysis
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

19. Monosaccharides Monosaccharides are carbohydrates with:
A carbohydrate that cannot be split or hydrolyzed into smaller carbohydrates.
Monosaccharides are carbohydrates with:
3-9 carbon atoms (typically 5-6)
A carbonyl group (aldehyde or ketone)
Several hydroxyl groups
Cn(H2O)n
CnH2nOn ║
C ─ H │
H─ C ─ OH
CH2OH O

20. O Monosaccharides - Aldose ║ C ─ H aldose │ H─ C ─ OH CH2OH
an aldotetrose
Aldose is a 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

21. Monosaccharides - Ketose
CH2OH │
C = O ketose
H─ C ─ OH
a ketohexose
(Fructose)
Ketose is a 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

22. Some important Monosaccharides
Glucose (Dextrose)
(C6H12O6, aldohexose) – Blood sugar
The most abundant monosaccharide
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.

23. Some important Monosaccharides
Glucose (Dextrose)
- Normal blood glucose levels are mg/dL.
- Excess glucose is stored as the polysaccharide glycogen or as fat.
- Insulin (a protein produced in the pancreas) regulates blood glucose levels by stimulating the uptake of glucose into tissues or the formation of glycogen.
- Patients with diabetes produce insufficient insulin to adequately regulate blood sugar levels, so they must monitor their diet and/or inject insulin daily.

24. 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).

25. 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).

26. Disease - Galactosemia
missing the enzyme that converts galactose to glucose.
Accumulation of galactose in the blood and tissues.
Mental retardation and cataracts
Solution: removing the galactose from food: no milk.

27. Fischer Projections 3D 2D C H O
- Horizontal lines represent bonds projecting forward from the stereocenter.
- Vertical lines represent bonds projecting to the rear.
- Only the stereocenter (tetrahedral carbon) is in the plane. C H O 2
Convert to Fischer
Projection 3D 2D

28. 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

29. Cyclic Structure – Haworth Structure1 1
Anomeric carbon 1 1 1
Alpha (α)
Beta ()
More stable form
Anomers

30. Cyclic Structure – Haworth Structure 1 1 
-Glucose -Glucose 1 1
-Galactose -Galactose

31. Cyclic Structure – Haworth Structure1
Anomeric carbon OH
C=O 5 2
CH2OH OH H HO
HOCH2
-D-fructose (opposite side) -D-fructose(same side) 2

32.   Cyclic Structure – Haworth Structure1 1 
-Glucose (opposite side) -Glucose (same side)
Humans have -amylase (an enzyme) and they can digest starch
products such as pasta (contain -glucose)
Humans do not have β-amylase (an enzyme) and they cannot digest
cellulose such as wood or paper (contain β-glucose)

33. Mutarotation
Change in specific rotation that accompanies the equilibration
of α and  anomers in aqueous solution.
-D-glucose
Open-chain form
(acyclic)
α-D-glucose
64%
< 0.02%
36%

34. Physical properties of Monosaccharides
Colorless
Sweet Tasting
Crystalline solids
Polar with high melting points (because of OH groups)
Soluble in water and insoluble in nonpolar solvents
(H-bond because of OH groups)

35. Oxidation of Monosaccharides
+ 2Cu2+
Oxidation
+ 2Cu+ OH
D - glucose
D – gluconic acid
Benedict’s
Reagent (blue)
(Brike red)
Aldonic acids
Reducing sugars: reduce another substance.

36. Oxidation of Monosaccharides
Rearrangement
(Tautomerism)
D-fructose
(ketose)
D-glucose
(aldose)

37. Reduction of Monosaccharides
Alditols
Sugars alcohols: sweetners in many sugar-free (diet drinks & sugarless gum).

38. 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

39. Disaccharides
The glycosidic bond joining the two rings can be alpha (a) or beta (b).

40. Is a disaccharide of two glucose molecules.
Disaccharides
Maltose:
Is a disaccharide of two glucose molecules.
Has a α -1,4-glycosidic bond (between two α-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 + 4 1 4
+ H2O
α-glucose
α-glucose
- maltose

41. Disaccharides Lactose: Is a disaccharide of galactose and glucose.
Has a β -1,4-glycosidic bond (between β-galactose and α-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

42. Is found in table sugar (obtained from sugar cane and sugar beets).
Disaccharides
Sucrose:
Is found in table sugar (obtained from sugar cane and sugar beets).
Consists of glucose and fructose.
Has a β-1,2-glycosidic bond (between α-glucose and -fructose).
Is not a reducing sugar (carbon 1 cannot open to give a free aldehyde
to oxidize).
β-1,2-glycosidic
bond

43. Disaccharides Sucrose: Aspartame, Saccharin, Sucralose
Sucrose is very sweet, but contains many calories.
To reduce caloric intake, many artificial sweeteners have been developed.
Aspartame, Saccharin, Sucralose
These artificial sweeteners were discovered accidentally.

44. Artificial sweeteners
Aspartame:
It (sold as Equal) is hydrolyzed into
phenylalanine, which cannot be processed by
those individuals with the condition phenylketonuria.

45. Artificial sweeteners
Saccharine:
It (sold at Sweet’n Low) was used extensively during World War I.
There were concerns in the 1970s that saccharin causes cancer.

46. Artificial sweeteners
Sucralose:
It (sold as Splenda) has a very similar structure to sucrose.

47. 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).

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

49. Polysaccharides
Amylopectin:
Is a polysaccharide of glucose units in branched chains.
Has α-1,4-glycosidic bonds between the α-glucose units.
Has α-1,6 bonds to branches of glucose units.
(at about every 25 glucose units, there is a branch).
Both forms of starch are water soluble.

50. Polysaccharides Glycogen:
- It is similar to amylopectin (more highly branched-every units).
- It is an energy storage molecule found in animals/humans.
- It is stored mainly in the liver and in muscle cells.
- When glucose is needed for energy, glucose units are hydrolyzed from the ends of the glycogen polymer.
- Because glycogen is highly branched, there are many ends available for hydrolysis.

51. Polysaccharides Digestion process Amylose, Amylopectin (starch)
H+ or α-amylase (enzyme in saliva)
Digestion process
Dextrins (6-8 glucose units)
H+ or α-amylase (enzyme in pancreas)
Maltose (2 glucose units)
H+ or α-maltase (enzyme)
Many α-D-glucose units

52. Respiration C6H12O6 + 6O2 6CO2 + 6H2O + energy Fermentation
glucose
Fermentation
Yeast
C6H12O C2H5OH + CO2 + energy
Ethanol

53. Polysaccharides Cellulose:
Is a polysaccharide of glucose units in unbranched chains with b-1,4-glycosidic bonds (2200 glucose units).
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
b-1,4-glycosidic bonds (needs an enzyme: b-glycosidase).