Why do dehydration reactions decrease entropy?

In the field of chemistry, dehydration reactions refer to chemical events wherein a water molecule is lost because of the presence of another reacting molecule. From the root word “dehydrate”, these chemical reactions literally refer to the taking out of water from a chemical group or solution. With this particular effect or reaction, dehydration reactions form part of a much larger chemical event called elimination reactions. In many instances, some scientists also refer to dehydration reactions as dehydration synthesis because it also refers to a process of combining the remaining molecules aside from the removal of hydrogen. This type of reaction is said to cause a decrease in entropy in various cells. Entropy within a cell refers to a state of inner instability secondary to different energies provided by the different molecular components. Heat and temperature is also present and all these will contribute to cell’s so-called randomness. By simply taking out the hydrogen, molecule, cell entropy or the energy within the cell is said to be decreased resulting to more cellular stability. This is simply due to the fact that hydrogen or water allows the spontaneous mixing of chemical and molecular components and therefore creates a chaos of energy. When the water component is removed, then there will be less molecular energy and therefore decreased entropy.

The process of dehydration reactions may be used for a variety of purposes including the mixing of similar molecules like monosaccharide for example. These simple sugars may be mixed up together to effect a dehydration reaction to create a new molecule. In this particular case, when fructose is mixed with glucose for example, it will result to two individual monosaccharide which is the new molecule or disaccharide. This is simply due to the removal of the hydrogen molecule in the process. The good thing about dehydration reactions is that it does not only result to decreased entropy but it can also be reversed in some cases. Using the same sugar examples, the resulting disaccharide may be reverted back to being simple monosaccharide through adding back water into the mixture through a process called hydrolysis.

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