Biological Sciences
Condensation Reaction
A condensation reaction is a chemical reaction in which two molecules combine to form a larger molecule, with the simultaneous elimination of a small molecule such as water. This type of reaction is important in the formation of biological macromolecules such as proteins, nucleic acids, and carbohydrates.
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3 Key excerpts on "Condensation Reaction"
eBook - PDFProgress in Theoretical Biology
Volume 1
- Fred M. Snell(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
All of these properties and behaviors are dependent upon structural features which are built into the molecules and appear in the next stage of their evolution. IV. Dehydration Condensation Reactions In order to achieve the next stage in the evolution of the biologically important molecules, the necessity for hooking the small molecules together must be established. When you examine the biological macro-™<>™NS [ Ä F 1 carboxyl O H 0 H2N-ÇH-cH0H+HJ-lil-ÇH-C0 2 H ■* HgN-ÇH-C-NH-ÇH-CO^H —► POLYMER R| R 2 R| R2 | dipeptide | POLYSACCHARIDES. CH 2 OH ? H * 0H ____H X ,*~K JM H N C— 0 N 'OH ' X ? H 7„c' ► DISACCHARIDE — * POLYMER Η θ ' Ν ό -0 ' Ν Η H OH A OH UPIPS HOCH 2 CHOHCH 2 -Ojf ^ H O T C -( C H 2 ) X H — HOCH 2 CHOHCH 2 -0-C-(CH 2 ) x H I I ester bond FIG. 10. Dehydration condensation of amino acids. molecules which constitute the structural and much of the catalytic basis for living organisms, you can see that they are derived by a reaction common to all of them. They are made from the primitive molecules (amino acids, sugars, phosphoric acid, hydroxy acids, and the like) by a single kind of reaction, namely, a dehydration condensation. Figures 10 and 11 show the dehydration Condensation Reactions in principle, at least. Figure 10 shows the dehydration condensation of the amino acids; the carboxylic acid and the amino group interact to give the peptide linkage and then, of course, the molecule can grow from either end (the amino end or the carboxyl end) to make the polypeptides, which ulti-mately become large enough to have catalytic and structural properties CHEMICAL EVOLUTION 19 which we now recognize as characteristic of proteins. The formation of polysaccharides is also a dehydration polymerization.
eBook - PDF- Robert O. Ebewele(Author)
- 2000(Publication Date)
- CRC Press(Publisher)
Chapter 6 Condensation (Step-Reaction) Polymerization I. INTRODUCTION Condensation polymerization is chemically the same as a Condensation Reaction that produces a small organic molecule. However, as we sa w in Chapter 2, in condensation polymerization (i.e., production of a macromolecule) the functionality of reactants must be at least 2. Recall that functionality was defined as the average number of reacting groups per reacting molecule. To derive expressions that describe the physical phenomena occurring during condensation polymerization (polycondensation) — a tool vital to process design and product control — three approaches have been traditionally adopted: kinetic, stoichiometric, and statistical. Various degrees of success have been achieved by each approach. We treat each approach in the succeeding sections. Before then, we briefly discuss the overall mechanism of polyCondensation Reactions. II. MECHANISM OF CONDENSATION POLYMERIZATION The mechanism of polyCondensation Reactions is thought to parallel that of the low-molecular-weight analogs. As a result of their macromolecular nature, polymers would be expected to have retarded mobility. It was therefore predicted, purely on theoretical arguments, that the chemical reactivity of polymers should be low. • The collision rate of polymer molecules should be small due to their low kinetic velocity. This should be accentuated by the high viscosity of the liquid medium consisting of polymer molecules. • Shielding of the reactive group within the coiling chain of its molecule should impose steric restrictions on the functional group. This would lead to a reduction in the reactivity of the reactants. Flory 1 has shown from empirical data that for a homologous series the velocity constant measured under comparable conditions approaches an asymptotic limit as the chain length increases.
eBook - PDFMicrowave-Assisted Organic Synthesis
A Green Chemical Approach
- Suresh C. Ameta, Pinki B. Punjabi, Rakshit Ameta, Chetna Ameta, Suresh C. Ameta, Pinki B. Punjabi, Rakshit Ameta, Chetna Ameta(Authors)
- 2014(Publication Date)
- Apple Academic Press(Publisher)
CHAPTER 10 CONDENSATION SANYOGITA SHARMA, ABHILASHA JAIN, and RAKSHIT AMETA CONTENTS 10.1 Aldol Condensation ....................................................................... 182 10.2 Bayer Condensation ...................................................................... 184 10.3 Claisen Condensation .................................................................... 184 10.4 Claisen-Schimdt Condensation ..................................................... 185 10.5 Cyclocondensation ........................................................................ 185 10.6 Friedlander Condensation ............................................................. 190 10.7 Isay Condensation ......................................................................... 191 10.8 Knoevenagel Condensation .......................................................... 192 10.9 Pechmann Condensation ............................................................... 196 10.10 Ugi Condensation Reaction ......................................................... 196 10.11 Miscellaneous ............................................................................... 198 Keywords .................................................................................................. 203 References ................................................................................................. 203 182 Microwave-Assisted Organic Synthesis: A Green Chemical Approach Condensation is a class of organic reactions, where two molecules combine, usually in the presence of a catalyst, with elimination of water or some other simple mol-ecule. The combination of two identical molecules is known as self-condensation. Aldehydes, ketones, esters, alkynes (acetylenes) and amines are among several or-ganic compounds that combine with each other and except for amines, among them-selves to form larger molecules, many of which are useful intermediate compounds in organic syntheses.
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