Usually, polymers are organic (but not necessarily).
Dehydration Synthesis - Biology As Poetry
It is the long chains that give polymers their unique properties.
In summary, we developed a concise and highly enantioselective synthesis of colchicine (>99% ) in eight steps in 9.3% overall yield without the need for protecting groups. An unusual Wacker oxidation was used for enabling the regioselective construction of the highly oxidized tropolone C-ring. β-Lumicolchicine was prepared through a 4π-electrocyclization reaction with a much-improved yield compared with existing procedures, and the allocolchicinoid NCME was synthesized from β-lumicolchicine through a novel decarbonylation/electrocyclic ring-opening cascade reaction.
Owing to their unusual structural motifs and promising pharmacological properties, colchicine (1) and NCME (2) have attracted considerable attention from synthetic chemists, which has resulted in several elegant total syntheses of 1 and 2. Recently, we developed an enantioselective synthesis of colchicine (1) from commercially available and inexpensive 2,3,4-trimethoxybenzaldehyde (5). The challenging tricyclic 6–7–7 core of colchicinoids was efficiently introduced using an intramolecular oxidopyrylium-mediated [5 + 2] cycloaddition reaction. In our continuing efforts toward the synthesis of biologically active natural products, we herein describe a modified concise and highly enantioselective synthesis of colchicine using the Wacker oxidation for the regioselective construction of the highly oxidized tropolone C-ring. Moreover, asymmetric total syntheses of β-lumicolchicine and NCME were also achieved.
There are many monomer molecules.
Subsequently, the proposed transition-metal-catalyzed decarbonylation/electrocyclic ring-opening cascade reaction of 3 was attempted using several different catalysts (Rh, Ni, and Pd) in a variety of different solvents, as reported previously. However, these conditions failed to afford any of the desired product of 2. To our delight, the irradiation of a solution of β-lumicolchicine (3) in 10:1 (v/v) CH3CN/acetone (0.0024 mol/L) with a 125 W high-pressure mercury arc lamp surrounded by a Pyrex water jacket for 20 min gave 2 in 54% yield instead of α-lumicolchicine (4) and colchicine. The outcome of this transformation suggested that under the irradiation compound 3 had probably undergone a decarbonylation process to generate the intermediate B, followed by the anticipated retro-4π-electrocyclization reaction to give 2, which has been reported to exhibit greater inhibitory activity toward tubulin than colchicine. The 1H and 13C NMR spectra of synthetic 2 and 3, as well as their optical rotation, were identical to those of the natural products. We also have tried to extend the time of irradiation for one-pot synthesis of compound 2 from 1, but a trace of 2 was detected. Probably, other unidentified compounds made the reaction more complex, with the time extended and the temperature of the solution increased. So, after many attempts, we found that 25 min is the best time length for the first irradiation and the two-step sequence is more efficient than the one-pot procedure for the preparation of 2 from 1.
The heavier fraction contains substituted phenols and aromatic oligomers (small polymers of 3-8 monomers) and on passing the liquid and their vapours over a heated catalyst in a a high concentration of aromatic hydrocarbons, benzene, methylbenzene (toluene) and the three methylbenzenes (xylenes), known as BTX, are recovered (Figure 2, route 10). Alternatively the vapours can be mixed with hydrogen and passed over a catalyst such as a cobalt- molybdenum sulphide on alumina.
Let's see if you can spot them.
Basically, an organic aerogel is any aerogel with a framework primarily comprised of organic polymers. Generally, organic aerogels have very different properties from inorganic aerogels such as silica aerogel and metal oxide aerogels. They are generally less friable and less fragile than inorganic aerogels, instead squishing when compressed. The term “organic aerogel” can refer to one of many different kinds of aerogels, each with properties arising from the polymer which makes up the aerogel’s framework.
Organic aerogels can be made from resorcinol formaldehyde, phenol formaldehyde, melamine formaldehyde, cresol formaldehyde, phenol furfuryl alcohol, polyacrylamides, polyacrylonitriles, polyacrylates, polycyanurates, polyfurfural alcohol, polyimides, polystyrenes, polyurethanes, polyvinyl alcohol dialdehyde, epoxies, agar agar, agarose, and many others (see C. S. Ashley, C. J. Brinker and D. M. Smith, Journal of Non-Crystalline Solids, Volume 285, 2001).
Organic aerogels have been around as long as any aerogel-in fact, the first aerogel Samuel Kistler is believed to have prepared was aerogel made from jelly (which is composed of the organic heteropolysaccharide pectin). Kistler also prepared aerogels of gelatin and rubbers, both of which are composed of organic polymers.
Look again at the first four monomers:
The double bond is a common feature of each of these monomers.
Ether - Wikipedia
Now, let's look at those other four monomers.
Nitrile - Wikipedia
That is, they are difunctional.
Biology | CourseNotes
There are two main routes using thermochemical processing:
Polyurethanes (PUs) were synthesised using methylene diphenyl diisocyanate (MDI), polytetrahydrofuran ether diol (PTMG), and chain extenders containing different amounts of aliphatic side chains. Hybrid materials were then prepared by reacting the PUs with nano-TiO2. The effects of different molecular structures of the chain extenders on the surface properties of PU coatings and the hybrid materials were investigated.
There are several ways in which methanol is made from biomass.
A series of carbon-based solid acid catalysts derived from biomass was prepared and used for the conversion of fructose to 5-HMF, which is a very important platform chemical due to its unique chemical structure. The results suggest that sulfonated carbon materials exhibit remarkable catalytic capability for fructose dehydration to 5-HMF.
Figure 1. Structures of colchicine, NCME, and β-lumicolchicine.
The present paper reports a new hybrid cyclohexaphosphate which was characterized by different techniques (NMR, IR, UV-vis) and evaluated (electrical and biological). This reported compound exhibits an acidic character which is rarely observed with this type of condensed phosphate. In addition, this material is distinguished from others by its higher thermal stability and more pronounced antioxidant activity.
Figure 2. Retrosynthetic analysis of 1–3.
Crystal structures of tetraiodoallene, C3I4, and 2,2-diiodoacrylic acid, I2C=CH(CO2H), are reported.
X.L., Y.-J.H., and B.C. contributed equally.
The co-operative stabilizations associated with the bending of the σC–C toward C–F bonds and total hyperconjugative generalized anomeric effect in the -configuration of 1,2-difluoroethene overcome the destabilizations associated with the exchange component and dipole–dipole interactions, leading to the preference of the -configuration in the compound.
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