Dehydration synthesis

FIGURE 1.9 (a) Amino acids build proteins by connecting the n-carboxyl C atom of one amino acid to the n-amino N atom of the next amino acid in line, (b) Polysaccharides are built by combining the C-1 of one sugar to the C-4 O of the next sugar in the polymer, (c) Nucleic acids are polymers of nucleotides linked by bonds between the 3 -OH of the ribose ring of one nucleotide to the 5 -P04 of its neighboring nucleotide. All three of these polymerization processes involve bond formations accompanied by the elimination of water (dehydration synthesis reactions). 

FIGURE 11.15 Formadoii of ADP and ATP by the successive addition of phosphate groups via phosphoric anhydride linkages. Note the removal of equivalents of H9O in these dehydration synthesis reactions. 

Peptides are short chains of amino acids linked by peptide bonds. Most biologically active peptides contain two to ten amino acids. Peptide bonds are formed between the carboxyl carbon of one amino acid and the amino nitrogen of another. Since water is released, this is an example of dehydration synthesis. The bond forms as illustrated in Figure 16.7. 

General Procedure for the Hydroformylation/Carbonyl ene Reaction/O,O-acetal Forma-tion/Dehydration. Synthesis of Chromane Derivatives. A solution of the substrate (1 eq) RhCl(PPh3)3 (1 mol %) and PPh3 (3 mol %) in dry dioxane was heated for 70 h to 120 °C und an atmosphere of CO/H2 (1 1, 100 bar). The crude product was filtered through basic alumina (eluated with MTBE). After evaporation of the solvent further purification by column chromatography (silica, PE/MTBE) furnished the title compounds. 

Claisen condensation-dehydration. Synthesis of tripeptide anaiogs C6z-G/y-iA[(Z)-CF=CH]LeuXaa (10)... 

In this reaction the H and OH highlighted in bold have been removed to form a molecule of water. The carbonyl of the amino acid on the left formed a bond with the nitrogen atom in the amino acid on the right. The amide functional group was formed in this dehydration synthesis reaction. Notice the ends of the newly formed dipeptide. There exists another amine group and carboxylic acid group at the ends of this chain to join with other amino acids and lengthen the chain. 

A fat molecule consists of one molecule of glycerol, bonded by dehydration synthesis (the loss of water) to three fatty acid molecules (this is a triacylglycerol. Figure 1.4). Fatty acids are... 

Condensation is the process of bonding together separate monosaccharide subunits into a disaccharide and/or a polysaccharide. It is also called dehydration synthesis as one molecule of water is lost in the process. It is carried out by specific enzymes. 

Amino acids are linked by peptide bonds. These bonds are formed by a dehydration synthesis reaction between the ceirboxyl group of the first amino acid and the amino group of the second amino acid. 

The reaction that produces ethers is an example of a dehydration synthesis in which two molecules are joined and a new functional group is generated by the removal of a water molecule. Dehydration synthesis is important in living organisms because it is part of the formation of carbohydrates, fats, proteins, and many other essential substances. 

Dehydration synthesis A chemical reaction that builds complex organic molecules. 

Two amino acids can react with each other in an acid-base type of reaction. The basic amino group of one amino acid reacts with the acidic carboxylic acid group of another amino acid to form a peptide, and a molecule of water is lost. This reaction, shown below, is classified as a condensation reaction, or a dehydration synthesis, and the two amino acid molecules join together. The bond formed is called a peptide bond, and the product is a dipeptide because it is made up of two amino acid units. Longer chains are called polypeptides, and chains of 50 or more amino acids are called proteins. 

Notice that a water molecule is formed from the hydrogen atom on the acid and the -OH group on the alcohol. This reaction is called esterification, and is just one example of what chemists call dehydration synthesis, where the word dehydration means to remove water, or a condensation reaction, because water condenses as the reaction proceeds. 

To form protein molecules, the amino ends of amino acid molecules link together with the acid ends of other molecules. The reaction is another example of a dehydration synthesis, similar to what we have already encountered when sugars link together to form starch and cellulose. The bond that forms is called a peptide bond. Each different kind of protein molecule is characterized by the particular amino acids of which it is composed as well as the sequence in which they appear. 

Peptide Bond—a covalent chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, causing the release of a molecule of water. The process is a dehydration synthesis reaction (also... 

Dehydration.. Synthesis of isocyanides from formamides (eq 6) is the only example of a dehydration reaction reported for triphosgene to date. ... 

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