Comparison of Alpha and Beta Fructose

Fructose is present in fruits and is also known as fruit sugar. It is also present in honey and sweet fruits, along with glucose. It is present in a combined state as well as present in disaccharide sucrose and polysaccharide (inulin).

 It is obtained along with glucose by the hydrolysis of cane sugar with dilute sulphuric acid.

 H2SO4(dil.)

C12H22O11     + H2O                →           C6H12O6     +     C6H12O6

            Cane-sugar                                                 Warm                   D- Glucose                  D- Fructose

The naturally occurring fructose is laevorotatory, and it is also known as levulose. Fructose is a ketohexose.

 The excess sulphuric acid is neutralised by adding milk of lime. On adding more lime, it converts both glucose and fructose into calcium gluconate and calcium fructosate, respectively. Calcium fructosate is insoluble in water, and it can be separated out. Carbon dioxide decomposes calcium fractosate and breaks it down into fructose and calcium carbonate. The calcium carbonate is eliminated by filtration, and the filtrate is concentrated under reduced pressure.

C6H11O5  — O — CaOH   +  CO2    ⟶     C6H12O6     +    Ca

     Calcium fructosate                     Fructose 

Properties of Fructose

• Dry Fructose is a colourless crystalline compound.

• It melts at 102 °C.

• It is soluble in water, but it is soluble in benzene and ether.

• It is the sweetest of all sugars, and its solution is levorotatory.

• Like glucose, it shows mutarotation.

• Fructose is 1.2 to 1.8 times sweeter than sucrose.

• The fructose metabolism does not require insulin and has a low impact on blood glucose levels. 

    CH2OH

    |

             C  =  O

     |

         HO— C— H

                          |

                H  —  C  — OH

        |

    H   —  C  — OH

      |

     CH2OH

      Open structure Of 

    D – (—) – Fructose 

Structure of Fructose

• Fructose is a Penta hydroxy ketone, and it has both a kind chain that is the open chain and closed chain structure.

Comparison Between Alpha and Beta Fructose

Fructose also undergoes mutarotation.

α – D  – Fructose      ⇌      Equilibrium mixture         ⇌       β – D – Fructose

  [α ]D   = -21°             [α ]D   = -92°                      [α ]D   = -133°

• In the combined state, fructose is present as furanose from alpha and beta. The two forms of D-fructose are shown by the Fischer Haworth projection formula.

• In the beta structure, the alcoholic group is present on the same side of the ring as the carbon at 6.

• In the alpha structure, the alcoholic group is present on the opposite sides of the ring as the carbon at 6, it will lead to the down projection of -OH at carbon.

Uses of Fructose

Fructose helps in enhancing the taste in foods and beverages.

Fructose, which is present in crystalline form, are the natural sweeteners that are used in energy drinks, chocolate milk, cereals, yoghurt and many other low-calorie foods. 

When glucose and fructose combine, it forms a product like high fructose corn syrup.

This high fructose corn syrup is used as a sweetener as well as it is used in adult medicine such as cough suppressants and decongestant liquid.

Isomerism 

In isomerism, the atoms of a molecular formula can be rearranged in different ways to give some other compounds called isomers, but these compounds have different physical and chemical properties.

 There are two types of isomerism: structural isomerism and stereoisomerism.

 Structural isomerism are the molecules that have the same molecular formula, or they have the same number of atoms of each element, but the arrangement of bonds in the molecules is different. It consists of position isomers, functional group isomers and chain isomers. 

 Stereoisomers are the isomers that have the same composition or the same molecular formula and the same sequence of bonded atoms, but they have different three-dimensional orientations of their atom space. Stereomerisum includes conformational isomers, configurational isomers, optical isomerism, and geometrical isomerism.

Types of Isomerism

 In position isomerism, isomers have the same functional group but in a different position on the same carbon chain.

 In functional group isomerism, the atoms are from different functional groups.

In chain isomerism, I may differ in the rearrangement of carbon chains that may be branched or straight.

 In conformational isomerism, the stereoisomerism can be interconverted by rotations of a single bond.

 Configurational isomers are stereoisomers that can be converted into one another just by rotating a molecule around a single bond.

 Optical isomers are compounds that have the different spatial arrangements of an atom having the same number of atoms.

 Geometric isomers have the same structural formula but a different arrangement of groups in a single atom.

Conclusion

All monosaccharides are reducing sugar, for example, glucose and fructose.

Fructose contains a ketonic group, yet it reduces Fehling’s solution and Tollen’s reagent.

 Fructose enhances glucose metabolism, and it acts as a part of a healthy meal through several mechanisms which facilitate the disposal of dietary carbohydrates.

Fructose is harmful when taken in large amounts, and it is very difficult to get access to the amount of fructose from fruit.

Unlike glucose and other types of sugar, fructose is exclusively broken down by the liver. In the liver, fructose is converted into energy and stored in the form of glycogen.