Carbohydrates - Glucose - Sucrose - Amylose - Cellulose

What are carbohydrates?
Glucose is one of the most important carbohydrates. Its chemical formula is C₆H₁₂O₆. If this is re-written as C₆(H₂O)₆   it is clear that it is a hydrate of carbon and this is the origin of the name for this class of compounds. Sucrose is a disaccharide formed from glucose and fructose. It is also a carbohydrate its formula is C₁₂H₂₂O₁₁ or C₁₂(H₂O)₁₁. It is possible to remove the water from sucrose using sulfuric acid.
    C₁₂H₂₂O₁₁    +    H₂SO₄   =    12C    +    H₂SO₄(dilute)   Web Movie
This reaction is interesting for several reasons one of which is that it is the reason why Linus Pauling decided to study chemistry.

Glucose exists in a and b forms.



The best known "sugar" is sucrose which consists of a-d-glucose joined to fructose. The molecules are joined by loss of water to give the disaccharide sucrose.

Glucose Polymers

Amylose is a component of starch and is made from a-d-glucose units joined together.

There is a four unit amylose fragment in the Moilin Library under the name amylose_frg and this structure is clearly non-linear. Amylose has a spiral structure.



Cellulose is also a glucose polymer but the monomer here is b-d-glucose. In the polymer alternate glucose units are inverted.





It is clear that this is a more linear polymer. Cellolose is not digested by humans. Humans can digest starch.

These molecules are in the Moilin Library. It is possible to model disaccharides using Mopac however larger units really need to use molecular mechanics (i.e. Tinker)

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