Carbohydrates

II optically active? yes

*

*

how many possible stereoisomers? 4how many actual stereoisomers? 4Is this D- or L-? Is this (+) or (-)? ?

II optically active? how many possible stereoisomers?how many actual stereoisomers?Is this D- or L-? Is this (+) or (-)?

yes

***

23 = 88

?

II

CnH2nOn

1 degree of unsaturation

COH

C O

C OHH

C OHH

CH2OH

C OH

COH

COH

CH2OH

H

H

H

CH2OH

C (H2O)

I IICarbohydrates can be:

simple monosaccharidescan’t be hydrolyzed

complex disaccharideshydrolyzed to 2 monosaccharidespolysaccharideshydrolyzed to 3 - 1000’s

I IIClassifying monosaccharides

1. carbonyl group “aldo” or “keto”2. number of carbon atoms“tri”, “tetr”, “pent”, “hex”3. suffix “ose”I aldotetrose II ketohexose

22 isomers 23 isomers

C=O

Physical properties

2-deoxyriboseDNA

Classify: aldopentose

What are IMF ?

H-bond donors and acceptorshigh b.p.solids at room Tsoluble in H2O

chiral 2-deoxyribose has ______ isomers 4Is this L- or D- isomer

**

CHO

aldo

CH2OH

hexose

OH

OHOH

HOH

HHH

____stereocenters

****

4

______stereoisomers24=16

glucoseD-

CHO

CH2OH

H

HH

HHO

OHHOHO

L-glucose

natural monosaccharides = D

monosaccharides to know:

D-glucose D-galactose

aldohexose diastereomers

D-fructose

ketohexose

+ R’-OHH+

.. .. H+

..

..+ H+

aldehyde alcohol

hemi-acetalcyclic

R CO

H

R CO

H

RO

HOR’

H

OH

hemi-acetal formation

O=C_HOH

COHC

OHCHO C

CH2OH

6

OHHO

OHOH

O=C_H

12345

CH2OH

6HOH2C

OH

5

right = down

aldehyde +left = up

alcohol

O=C_H

OHC

OHCCH2OH

OHC

OHC

H+

+

+

..

..

Fischer Haworth

H+

2 1

3

4

5

6

OHHO

OHOH

CH2OH

O=C_H

123456

1

23

4

56

*

**

*

**

*

*

*

created a new C* at C1

25 isomers

differ only at C1

OH up =

OH down = racemic mixture

-D-glucose

-D-glucose

anomers

C1 = anomeric C

CC

C

C OCH2OH

OH

OHH

OHC

HO

CC

C

C OCH2OH

OH

OH

H

OH

C

HO

hemi-acetal unstable

3OH

12

4

56

OH

OH

OCH2OH

OH

H

3OH

12

4

56

OH

OH

OCH2OH

OH

H

-D-glucose

-D-glucose

anomers diastereomersdifferent physical properties

b.p. = 150o

b.p. = 146o

OH

HO

OH

CH2OH

OH

HO

OH

CH2OH

OH

OH

more stable

123

4 56

OHHO

OHOH

CH2OH

O=C_H

OH

HO

OH

CH2OH

OH64% 36%

0.01% hemi-acetals

alcohol + aldehyde hemi-acetal

aldehyde carboxylic acidFehling’s reagent - reducing sugars

hemi-acetals

OHHO

OH

OH

CH2OH

-D-glucose -D-glucose

unstable

[O]+ Cu2+ + Cu+Ag+ Ag

cyclic hemi-ketals123

4

5

6OHHOH2C

23

4

5

OOHHO

CH2OH

C2 is anomeric C

OH

CH2OH

D-fructose

OH

CH2OH

5 sided ring

--D-fructose

oxidation of ketoses

ketone no reaction[O]

ketose carboxylic acid[O]

ketose “enol” aldose

all monosaccharides are reducing sugars