Carbohydrates its Classification, Isomerism, Characteristic and Chemical properties

Explanation on Carbohydrates

1. Carbohydrates Classification of carbohydrate I somerism Characteristic of carbohydrate Chemical reactions

2. Introduction • Most Abundant Bio Molecules • Aldehyde or Ketone Compounds • Multiple Hydroxyl Groups • Heterogeneous Compounds • Found in all animals and plants • Forms 1% of total body mass in humans

3. Meaning The word “Carbohydrate” means hydrate of carbon. First compound of this group is glucose Polyhydroxylated compounds with three carbons

4. Classification

5. Monosaccharide • Simple sugars • Consists of single polyhydroxy aldehyde or ketone unit • Cannot be further hydrolyzed to simple carbohydrates • Either an aldose or ketose • White crystalline solids • Very soluble in water • Mostly have a sweet taste

6. Aldose and Ketose Forms of Monosaccharides

7. Oligosaccharides Short chained condensation products • Two to ten monosaccharide units • Joined covalently through glycosidic bonds • On hydrolysis yields two to ten monosaccharaides • Disaccharides physiologically very important e.g. maltose and sucrose • Other oligosaccharides are α dextrins , maltotriose , isomaltose

8. Polysaccharides • Sugar polymers • Contain large number of monosaccharide units • Serve as stores of fuels, structural elements of cell Types Homopolysaccharide Heteropolysaccharide

9. . Homopolysaccharide On hydrolysis yields one type of monomer Maybe a pure monosaccharide or complexed one Starch, cellulose, dextran, glycogen are glucose polymer Heteropolysaccharide Large group having two or more types of monosaccharide derivatives • Glycose – Amino – Glycans (GAGs) • Glycoconjugates • Mucilages

10. . Glycose – Amino – Glycans (GAGs) Also called mucopolysaccharides Includes hyaluronic acid, chondroitin Sulfates, Heparin, Serum Mucoide Glycoconjugates Includes proteoglycans, glycoproteins, glycolipids Mucilages Includes agar, vegetable gums and pectins

11. Isomerism in Monosaccrides : What is Isomerism ? Compound that posses the same chemical formula but different structural formula are called isomers. Example: Glucose,fructose and glactose have same chemical formula C6H6OH but different structural formula.

12. Types of Isomerism in Monosaccrides : Stereoisomerism Enantiomers Anomers Epimers Optical isomers

13. Stereoisomerism : Two or more monosaccrides having the same structural formula but differ in configuration i.e the arrangement of their atoms in space (three dimensional structure) from each other. Example: Naproxen have two isomers having the same structural formula but different arrangement of molecules.

14. Enantiomers: Each pair of molecule that are mirror image of each other. Example :

15. Anomers : The isomers that differ in configuration around the anomeric carbon atom i.e carbon atom of carbonyl group. Example:

16. Epimers : These are two isomers which differ in configuration around one specific carbon atom other than carbon atom of carbonyl group. Example: Glucose and glactose differ from each other only on position of -OH at carbon number 4. T hey are called carbon number 4 epimers .

17. Optical Isomerism in Monosaccharides

18. Optical isomerism: The two compounds which contain the same number and kinds of atoms, and bonds (i.e., the connectivity between atoms is the same), but different spatial arrangements of the atoms called Optical isomers.

19. Plane-polarized Light: When light is made to pass through certain media, then the light leaving through these media possesses only one plane of occilation , thus the light polarized in one plane only such a light is called plane-polarized light.

20. Polarimeter : The instrument used to measure the rotation of the plan- polarized light is called polarimeter or polariscope .

21. Principles of polarimeter : A beam of known wavelength is passed through a nicol prism. This beam is then passes through a solution of chemical substances in a glass tube of known length A second Nicol prism acts as an analyzer It can b rotated to find out the degree of rotation of the light to right or left.

22. Formula of specific rotation:

23. Specific rotaion of substance: The rotation in degree of one gram of substance/mL of the solvent in a tube of one decimeter (10cm) in length is called the Specific rotation of substance .

24. Optical activity of monosaccharide: Presence of asymmetric carbon atoms in the molecules of monosaccharide, the plane-polarized light when passed through their solutions , will b rotated to the left or to the right. The monosaccharides which rotate the light to the left side are called Levorotatory . Indicated by (-) sign. Themonosaccharides which rotate the light to the Right side are called dextrorotatory . Indicated by (+) sign.

25. Formula of specific rotation

26. Optical activity of monosaccharide: Presence of asymmetric carbon atoms in the molecules of monosaccharide, the plane-polarized light when passed through their solutions , will b rotated to the left or to the right. The monosaccharides which rotate the light to the left side are called Levorotatory . Indicated by (-) sign. Themonosaccharides which rotate the light to the Right side are called dextrorotatory . Indicated by (+) sign.

27. Glycerose and Glucose: The specific rotation of D- glycerose is +140° and L- glycerose is -140°, they are mirror image of each other. They have same physical and chemical properties except of specific rotation of plane-polarized light. The D- glucose have +52.7° and L-glucose have -52.7° of specific rotation , they are mirror image of each other. Their structurs shows that shows that configration of H and OH around all asymmetric carbon atoms (No.2 to No.5 ) is mirror image of each other.

28. D- GLUCOSE AND L- GLUCOSE:

29. Limitations to plane-polarized light: When a compound does not possess an asymmetric corbon atom. When equal amount of levo and dextro - rotatory isomers are present in the solution. Meso Compounds have asymmetric carbon atoms, but do not rotate the light. Due to internal compensations: The rotation of light to the right is exactly equal rotation to the rotation to the left, therefore no net rotation of light takes place. Example: meso -tartaric acid.

30. Chemical properties of monosaccharide with special reference to glucose

31. Properties Depend on different groups attached to it Osazones formation Reduction to form sugar alcohol Oxidation to form sugar acids Reducing actions reaction with acids Reactions with bases Fermentation of glycosides Formation of ester Fermentation

32. 1. Osazons formation Yellowish ,crystalline substance Formed by heating of sugar solution with phenyl hydrazine

33. . Only 1 and 2 carbon is involve in reactions Sucrose do not have potential aldehyde and keton s they do not form osazones

34. monosaccharides Alcohol derivatives 1. glucose Sorbital 2. mannose Mannitol 3. Galactose Galactiol 4. Fructose sorbitol 5. R ibose Ribitol 6.Glyceraldhyde Glycerol 7. Dihydroxyacetate Glycerol

35. 3. Oxidation to produce sugar acids Aldoses oxidize under proper condition to form three types of sugar acids .in case of glucose Gluconic acid : mild oxidation bromine water oxidation a C no. 1 Glucuronic acids: Oxidation at C no. 6 3. Glucaric acids: Oxidation at C no. 1 and 6 .

36. 4.Reducing action of suger in alkaline solution Sugar that contain anomeric carbon easily oxidize in alkaline PH by oxidizing agent means they acts as strong reducing agent 5 . Reactions with acids : Resistant to hot dilute acids Strong acids remove water from hexoses converting them in releated compound they condense with phenol to give characteristic coloured product

37. 6.Reaction with bases Low temperature can bring rearrangement at anomeric carbon or adjacent carbon and change glucose in fructose and mannose High temperature cause more change Fragmentation Polymerization occur

38. 7.Fermentation of glycoside Glycoside is formed by the combination of glucose and alcoholic residue with the help of acetal linkage D- glucose react with methyl alcohol to form methyl glycoside

39. importance They use in heart diseases Glycosides which contain steroids as aglycone Digitalis , strophanthus , phlorizin , salycin,amygdalin and saponin

40. 8 . Fermentation of ester OH of sugar are esteified to ester as phosphate acetates Importance Nucleoprotein of cells also contain phosphate of ribose or deoxyribose in combination with nitrogenous bases

41. 9.Fomation of amino suger In this the OH of suger is replace by amino Group then it is called amino suger

42. 10.fermentation Some of the hexoses sugar are converted into ethyl alcohol and CO2 Glucose fructose mannose are easily fermented by bakers yeast but glactose does not

43. Disaccharide fermentation Two steps Disaccharide liberate monosaccharide Fermentation of monosaccharide Some bacteria convert lactose to form lactic acid this process occur when milk sours

44. CYCLIC OR RING STRUCTURE OF MONO SACCHARIDES WITH SPECIAL REFERENCE TO D-GLUCOSE

45. D-glucose D-glucose is a hexose due to its aldehyde group is an aldohexose Suggested by FISCHER in 1891 Aldohexos have four asymmetric carbon atoms Carbon no 2 to no.5

46. Vant hoff’s law “In organic chemistry, the Le Bel – Van 't Hoff rule states that the number of stereoisomers of an organic compound containing no internal planes of symmetry is 2 n , where n represents the number of asymmetric carbon atoms” so aldohexos are expected to have 2=16 possible isomers Characterized as allos,allrose,glucose,manose,glucose,idose,galactose and talose Each occuring in two enantiomeric forms,i.e D and L forms

47. Mutarotation: Mutarotation refers to the change in specific rotation over time due to a change between isomers. ' Muta ' means 'change' , so it literally means a change in rotation.

48. . In aqeous solution some monosaccrides behave as that they have one more asymmetric carbon atom than what is shown by their open or straight chain formula propsed by fischer Thus the property of mutarotation shows the presence of another asymmetric carbon atom in aldohexoses So, aldohexos has optical isomers equal to 25.i.e thirty two Sixteen isomers mentioned above behave as in two anomeric foms . i.e α and β As each of these compounds can behave as α D and β D, α L and β L

49. . In the “alpha” (α) anomer , the OH group on C-1 is on the  opposite side of the ring as the chain on C-5 . In the “beta” (β) anomer , the OH group on C-1 is on the same side of the ring as the C-5 substituent . The alpha (α)   anomer of D-glucose has a specific rotation of +112 degrees in water. The beta (β)   anomer of D-glucose has a specific rotation of +19 degrees.

50. Hemiacetals or H emiketals From the above it can be seen that the ( α ) and (β) forms of glucose occurs in a cyclic or ring form and don not show an aldehyde group The rings shown show hemicetals or hemiketals formation which means condenstion between aldehyde group and hydoroxl group of the same compound in 1:1 ratio

51. Haworth perspective formulas A Haworth projection is a common way of writing a structural formula to represent the cyclic structure of monosaccharides with a simple three-dimensional perspective . Formulating the Haworth Projection the Haworth projection starting with the Fischer projection (the most common method used to depict open chain sugars). Let's start with the most common simple sugar, glucose. We first rotate the bonds around carbon 5 clockwise:

52. . We still have the same molecule as before. We are simply looking at carbon 5 from a different angle. Next, we turn the molecule sideways: With the molecule sideways it is easier to do steps 3 and 4. For step 3 we simply draw a hexagon, but omit the line connecting point 6 (OH) and point 1 (CHO): in step 4 add oh and CH 2 groups if on the side way molecule the oH group is pointing down then we draw the line down and if it is pointing up then draw the line up

53. . step 5, we connect the OH and the carbon 1. Don't worry about where the extra oxygen and hydrogen atoms go right now : Step 6, we add in the hydrogen atoms on the opposite side from the OH groups: Step 7, we put the OH group onto carbon 1. Since the carbon-oxygen bond was a double bond, we don't know what side the OH group should be on so we end up with two different molecules: Step 6, we add in the hydrogen atoms on the opposite side from the OH groups: