Announcements & Agenda (04/09/07)

1. Announcements& Agenda(04/09/07) • Extra Credit Assignment Due NOW! • Pick Up Graded Quizzes • Quiz Friday (13.4, 13.5, & Ch 14) • Today • More on Carbohydrates (14.1-14.3) • Monosaccharides • Cyclic Monosaccharides • Reactions of carbohydrates • Disaccharides

2. Last Time: Amide Hydrolysis acid hydrolysis O || O CH3—C—OH + NH4+Cl– ||HCl+ H2O CH3—C—NH2 NaOHO || CH3—C—O– Na+ + NH3 base hydrolysis

3. Last Time: Carbohydrates Intro • a major source of energy from our diet • composed of C, H, & O • also known as saccharides, which means “sugars.”

4. Last Time: Types of Carbohydrates • Monosaccharides: simplest carbohydrates. • Disaccharides: consist of two monosaccharides. • Polysaccharides: contain many monosaccharides.

5. Last Time: Monosaccharides • typically 3-6 carbon atoms • have a C=O group (aldehyde or ketone) • aldoses • ketoses • several hydroxyl groups

6. Aldoses O ║ C─H aldose │ H─ C─OH │ H─ C─OH │ CH2OH Erythose • monosaccharides with an aldehyde group… • …and many hydroxyl groups. triose (3C atoms) tetrose (4C atoms) pentose (5C atoms) hexose (6C atoms)

7. Ketoses CH2OH │ C=O ketose │ H─ C─OH │ H─ C─OH │ H─C─OH │ CH2OH • monosaccharides with a ketone group… • …and many hydroxyl groups. Fructose, a ketohexose

8. Fischer Projections • also used to represent carbohydrates. • places the most oxidized group at the top. • shows chiral carbons as the intersection of vertical and horizontal lines.

9. D & L Notations: Know This Now… In a Fischer projection, the −OH group on the • chiral carbon farthest from the carbonyl group determines an L or D isomer. • left = Lfor the L-form. • right = Dfor the D-form. (MOST COMMON IN NATURE!)

10. Learning Check Identify each as the D or L isomer. A. B. C. __-Ribose __- Threose __- Fructose L D L

11. D-Glucose • found in fruits, corn syrup, and honey • an aldohexose with the formula C6H12O6 • known as blood sugar in the body • the monosaccharide in polymers of starch, cellulose, and glycogen

12. Blood Glucose Level In the body, • normal blood: [glucose] = 70-90 mg/dL. • a glucose tolerance test measures blood glucose for several hours after ingesting glucose.

13. D-Fructose • is a ketohexose C6H12O6 • is the sweetest carbohydrate • found in fruit juices and honey • converts to glucose in the body

14. D-Galactose • is an aldohexose C6H12O6. • not found free in nature. • is obtained from lactose, a disaccharide. • has a similar structure to glucose except for the –OH on C4 Which C is C4???

15. Cyclic Structures (14.3) • prevalent form of monosaccharides with 5 or 6 carbon atoms • form when the hydroxyl group on C-5 reacts with the aldehyde group or ketone group • Orgo-Chem reaction not previously mentioned: “C=O” + ROH → hemiacetal

16. Drawing Cyclic Structures: Practice! Example: Glucose STEP 1 Number the carbon chain and turn clockwise to form a linear open chain. 1 2 3 4 5 6 6 5 4 3 2 1

17. Cyclic Structure for Glucose STEP 2 Fold into a hexagon. • Bond the C5 –O– to C1. • Place the C6 group above the ring. • Write the –OH groups on C2 & C4 below the ring (These are the C atoms that pointed down from Step 1). • Write the –OH group on C3 above the ring. • Write a new –OH on C1. 6 5 4 1 3 2

18. Cyclic Structure for Glucose • STEP 3 Write the new –OH on C1 • down for the  form. • up for the  form.   -D-Glucose-D-Glucose

19. Summary of the Formation of Cyclic Glucose

20. C H O H C H O H C H O H 2 2 2 H O O O O H O C O H O H O H H O H O H O H O H O H O H O H Mutarotation • cyclic structures open and close. • -D-glucose converts to β-D-glucose & vice versa. • at any time, only a small amount of open chain forms. -D-glucose D-glucose (open) β-D-glucose (36%) (trace) (64%)

21. C H O H 2 C H O H C H O H C H O H O H 2 2 O O C O 2 H O C H O H O H H C O H O H C H O H 2 H C O H O H O H C H O H 2 Cyclic Structure of Fructose • is a ketohexose. • reacts the -OH on C-5 with the C=O on C-2 α-D-fructose D-fructose -D-fructose

22. Chemical Properties of Monosaccharides (14.4)

23. Reducing Sugars • are monosaccharides that oxidize to give a carboxylic acid. • undergo reaction in the Benedict’s test. • include the monosaccharides glucose, galactose, and fructose.

24. Oxidation of D-Glucose [O] QUESTION: WHY CAN FRUCTOSE (A KETONE) BE OXIDIZED??? ANSWER: ISOMERIZATION TO AN ALDEHYDE…

25. One Test for Glucose in Urine: Benedict’s Test

26. Reduction of Monosaccharides • involves the carbonyl group. • produces sugar alcohols, or alditols. • such as D-glucose gives D-glucitol also called sorbitol. D-Glucitol

27. Learning Check Write the products of the oxidation and reduction of D-mannose. D-mannose

28. Solution D-mannitol D-mannose D-mannonic acid

29. Disaccharides (14.5)

30. Important Disaccharides: Know These 3 A disaccharideconsists of two monosaccharides. Monosaccharides Disaccharide glucose + glucose maltose + H2O glucose + galactose lactose + H2O glucose + fructose sucrose + H2O

31. Maltose • A.K.A. “malt sugar” • obtained from starch hydrolysis • used in cereals, candies, and brewing • linked by an -1,4-glycosidicbond formed from the  −OH on C1 of the 1st glucose and −OH on C4 of the 2nd glucose • found in both the - and β - forms Free α-OH

32. Lactose • a disaccharide of β-D-galactose and α- orβ-D-glucose. • contains a β -1,4-glycosidic bond. • is found in milk and milk products. α-form α-form

33. Sucrose Sucrose or table sugar • is obtained from sugar cane and sugar beets. • consists of α-D-glucose and β-D-fructose.. • has an α,β-1,2-glycosidic bond. α-D-glucose β-D-fructose

34. Learning Check Write the structures of the two monosaccharides that form when sucrose is hydrolyzed.

35. Solution