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Toshiro Shimada/Getty Images A dehydration reaction is a chemical reaction between two compounds where one of the products is water. For example, two monomers may react where a hydrogen (H) from one monomer binds to a hydroxyl group (OH) from the other monomer to form a dimer and a water molecule (H2O). The hydroxyl group is a poor leaving group, so Bronsted acid catalysts may be used to help to protonate the hydroxyl to form -OH2+. The reverse reaction, where water combines with hydroxyl groups, is termed hydrolysis or a hydration reaction. Chemicals commonly used as dehydrating agents include concentrated phosphoric acid, concentrated sulfuric acid, hot ceramic and hot aluminum oxide. A dehydration reaction is the same as a dehydration synthesis. A dehydration reaction may also be known as a condensation reaction, but more properly, a dehydration reaction is a specific type of condensation reaction. Dehydration Reaction Examples Reactions that produce acid anhydrides are dehydration reactions. For example acetic acid (CH3COOH) forms acetic anhydride ((CH3CO)2O) and water by the dehydration reaction Other examples include:
Dehydration reaction
What is dehydration synthesis? A dehydration reaction is a form of biochemical reaction wherein a water molecule is lost or removed from the reacting molecules. Dehydration synthesis, in particular, is the building up of compounds or molecules while losing water molecules. In particular, it is a type of condensation reaction in which the monomers join together into polymers while losing water molecules. In contrast, the addition of a water molecule into a compound or a substance is called a hydration reaction. Hydrolysis, in particular, is the process of combining a water molecule with a compound, e.g. a disaccharide, which when hydrolyzed converts into two monosaccharides. Let’s define dehydration synthesis to further understand it. Read more information below. Dehydration Synthesis DefinitionDehydration synthesis is the reaction at which two small molecules react together to form a new large molecule by removing a water molecule or water molecules. What is the result of a dehydration reaction? Dehydration synthesis leads to the formation of polymers from small monomers where monomers are combined together by the removal of small molecules such as water. Dehydration reaction results in the formation of a covalent bond. Therefore, it is a type of condensation reaction. Thus, water is a common byproduct of condensation reactions in biological systems. A common example of dehydration reactions is the formation of ethers from the condensation of alcohols. This reaction takes place in an acidic medium since it is catalyzed by the presence of an acid. This reaction is reversible. Therefore, dehydrating chemicals are used to collect water from the system so that the reaction can proceed in one direction only. Watch this vid about dehydration reaction and how it is biologically important: Biology definition: i.e., A-OH + B-H → AB + HOH Etymology: Latin dē-, meaning “remove” + Ancient Greek ὕδωρ (húdōr), meaning “water”) and Latin reāctiō, reagō, i.e., re-, meaning “again” + agō, meaning “to act” Types of Dehydration SynthesisThere are the types of dehydration synthesis reactions depending on what happens in a dehydration reaction…
Dehydration synthesis reactions may be classified according to the type of the used catalyst. Because most dehydration reactions are reversible, a catalyst is used to drive the reaction in one direction only. Examples of conditions changed as a result of using catalysts are salt concentration, pH, temperature, and water availability in the system. What is the Substitution Reaction?Substitution reaction is the reaction at which one group of one reactant is replaced by another group of another reactant to form two new compounds. There are two main types of substitution reaction as the following;
Examples of Dehydration SynthesisDehydration synthesis reactions are numerous, they are included in many industries as well as biological systems. Examples of dehydration synthesis include:
Formation of glycosidic bondsGlycoside or carbohydrate is a simple ring of sugar molecule which is formed of 5 or 6 carbon atoms. The interaction between two glycoside rings results in the formation of a covalent glycosidic bond. For example, sucrose is formed by the interaction of glucose and fructose, water is released during the dehydration reaction and a glycosidic bond is formed between them. Consequently, glucose polymers such as glycogen, cellulose, and starch are formed in the same manner by condensation of small sugar molecules and the formation of glycosidic bonds between them. Glycosidic bonds are formed chemically by a condensation reaction where one water molecule is released during the reaction. A condensation reaction occurs when the hydroxyl group (OH) attacks the anomeric carbon of a sugar. Anomeric carbon is the carbon in a sugar ring that is found between two oxygen atoms and attached by a single bond to each oxygen atom- releasing water molecule and forming a glycosidic bond between the oxygen atom in the ring of sugar and the other oxygen which is found in the hydroxyl group. This linkage chemically forms an ether linkage as the oxygen attaches to two atoms of carbon of each ring of sugars. Are all glycosidic bonds the same? There are three different types of glycosidic bonds. They are the N-glycosidic bond, S-glycosidic bond, and O-glycosidic bond. DNA dehydration synthesis or RNA dehydration synthesis are biochemical examples of glycosidic bonds, as sugar units are connected to nucleobases by N-glycosidic bonds. Moreover, glucuronic acid attaches to different substances by a glycosidic bond to increase their water solubility to facilitate excretion and metabolism inside animals’ bodies. Triglyceride formationHow are triglycerides formed chemically? Triglycerides are chemically formed by connecting three carboxylic groups of a glycerol molecule with three carboxylic groups of a fatty acid-forming ester bond with the release of three water molecules. The length of triglycerides may vary depending on the length of the fatty acid chain between 16 to 20 carbon moieties. Therefore, This reaction is chemically considered a condensation reaction. Triglyceride can be metabolized by the hydrolysis of the ester bond which is connected between glycerol and fatty acids by pancreatic lipase enzymes and this hydrolysis is done to provide energy for the body. Triglyceride is one of the most abundant fats in the body. Triglyceride can be found and detected as a ratio in the bloodstream. The reason for their existence in the bloodstream is to supply cells with energy and may be stored in the body to give energy when needed. Animals and humans store triglycerides as solid fats whereas plants store triglycerides as liquid oils. Triglycerides stores cause obesity in humans, therefore, the higher the triglycerides level in the bloodstream, the higher the risk of obesity. Elevated levels of triglycerides in the blood are medically known as hypertriglyceridemia and this condition directly increases the risk of cardiovascular diseases and metabolic syndrome. How can you detect if the triglyceride is harmful or harmless? Triglyceride ratio can be detected by blood tests in mmol/L as follows:
How can triglyceride be higher than the normal ratio?
What Happens in Dehydration Synthesis Reaction?A dehydration synthesis reaction is a process in which a condensation reaction takes place. Dehydration synthesis reaction leads to the formation of big molecules from two small molecules with the elimination of water molecules. A dehydration reaction is a process in which reactants lose one oxygen atom and two hydrogen atoms in the form of water molecules or molecules. Consequently, water is a byproduct of dehydration reaction, other products of dehydration reaction are usually polymers which form due to the connection of two reactants and the formation of a double bond or a ring structure in organic molecules. On the other hand, molecules of inorganic chemistry that are involved in dehydration reactions are usually hydrates which are not covalently bonded to water molecules but complexed to them. Dehydration is usually reversible, they proceed in dehydration and hydrolysis pathways as long as water is available in the system. Therefore, dehydrating agents are chemicals commonly used to shift the reaction to the dehydration pathway. There are many examples of dehydration synthesis processes such as the formation of di or polysaccharides from monosaccharides. Another example is the formation of ether from dehydration of alcohols. Dehydration Synthesis and HydrolysisDehydration synthesis is a chemical reaction in which a condensation reaction takes place with the elimination of one or more water molecules. On the other hand, hydrolysis is a hydration reaction that reverses the dehydration reaction. Hydrolysis is the process at which there is a cleavage of bonds of large molecules to form small molecules with the introduction of water. To sum up, the main differences between dehydration synthesis and hydrolysis chemical reactions are shown in the table below:
Data Source: Nadine Omar of Biology Online Frequently Asked Questions on Dehydration Synthesis
Answer the quiz below to check what you have learned so far about dehydration synthesis. References
What is used for dehydration in chemistry?Chemicals commonly used as dehydrating agents include concentrated phosphoric acid, concentrated sulfuric acid, hot ceramic and hot aluminum oxide. A dehydration reaction is the same as a dehydration synthesis.
What is an example of dehydration reaction?For example; the elimination of water molecules from alcohol forms alkene. It is an example of a dehydration reaction. Similarly, the elimination of hydrogen molecules forms unsaturated compounds and is called a dehydrogenation reaction.
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