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 ( ) More on Carbohydrates ( ) Monosaccharides Monosaccharides Cyclic Monosaccharides Cyclic Monosaccharides Reactions of carbohydrates Reactions of carbohydrates Disaccharides Disaccharides

2 acid hydrolysis acid hydrolysis O || || O CH 3 —C—OH + NH 4 + Cl – O CH 3 —C—OH + NH 4 + Cl – || HCl + H 2 O || HCl + H 2 O CH 3 —C—NH 2 NaOH O NaOH O || || CH 3 —C—O – Na + + NH 3 CH 3 —C—O – Na + + NH 3 base hydrolysis Last Time: Amide Hydrolysis

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

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

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

6 Aldoses monosaccharides with an aldehyde group…monosaccharides with an aldehyde group… …and many hydroxyl groups.…and many hydroxyl groups. triose (3C atoms) tetrose (4C atoms) pentose (5C atoms) hexose (6C atoms) O ║ C─H aldose C─H aldose │ H─ C─OH H─ C─OH │ │ CH 2 OH CH 2 OH Erythose Erythose

7 Ketoses monosaccharides with a ketone group…monosaccharides with a ketone group… …and many hydroxyl groups.…and many hydroxyl groups. CH 2 OH CH 2 OH │ C=O ketose C=O ketose │ H─ C─OH H─ C─OH │ │ │ CH 2 OH CH 2 OH Fructose, a ketohexose

8 Fischer Projections also used to represent carbohydrates.also used to represent carbohydrates. places the most oxidized group at the top.places the most oxidized group at the top. shows chiral carbons as the intersection of vertical and horizontal lines.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.chiral carbon farthest from the carbonyl group determines an L or D isomer. left = L for the L-form.left = L for the L-form. right = D for the D-form. (MOST COMMON IN NATURE!)right = D for the D-form. (MOST COMMON IN NATURE!)

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

11 D-Glucose found in fruits, corn syrup, and honeyfound in fruits, corn syrup, and honey an aldohexose with the formula C 6 H 12 O 6an aldohexose with the formula C 6 H 12 O 6 known as blood sugar in the bodyknown as blood sugar in the body the monosaccharide in polymers of starch, cellulose, and glycogenthe monosaccharide in polymers of starch, cellulose, and glycogen

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

13 D-Fructose is a ketohexose C 6 H 12 O 6is a ketohexose C 6 H 12 O 6 is the sweetest carbohydrateis the sweetest carbohydrate found in fruit juices and honeyfound in fruit juices and honey converts to glucose in the bodyconverts to glucose in the body

14 D-Galactose is an aldohexose C 6 H 12 O 6.is an aldohexose C 6 H 12 O 6. not found free in nature.not found free in nature. is obtained from lactose, a disaccharide.is obtained from lactose, a disaccharide. has a similar structure to glucose except for thehas a similar structure to glucose except for the –OH on C4 –OH on C4 Which C is C4???

15 Cyclic Structures (14.3) prevalent form of monosaccharides with 5 or 6 carbon atomsprevalent form of monosaccharides with 5 or 6 carbon atoms form when the hydroxyl group on C-5 reacts with the aldehyde group or ketone groupform 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 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

17 Cyclic Structure for Glucose STEP 2 Fold into a hexagon. Bond the C5 –O– to C1.Bond the C5 –O– to C1. Place the C6 group above the ring.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 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 the –OH group on C3 above the ring. Write a new –OH on C1.Write a new –OH on C

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

19 Summary of the Formation of Cyclic Glucose

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

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

22 Chemical Properties of Monosaccharides (14.4)

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

24 Oxidation of D-Glucose 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 Reduction of Monosaccharides involves the carbonyl group.involves the carbonyl group. produces sugar alcohols, or alditols.produces sugar alcohols, or alditols. such as D- glucose gives D-glucitol also called sorbitol.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 disaccharide consists of two monosaccharides. Monosaccharides Disaccharide glucose + glucose maltose + H 2 O glucose + glucose maltose + H 2 O glucose + galactoselactose + H 2 O glucose + fructosesucrose + H 2 O

31 Maltose Free α-OH A.K.A. “malt sugar” obtained from starch hydrolysis used in cereals, candies, and brewing linked by an  -1,4- glycosidic bond 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

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

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