steps where addition of each iteration produces a higher generation of dendrimer (Tomalia and Frechet, 2001). The synthesis method used for dendrimer preparation permit almost entire control over the critical molecular design parameters such as size, shape, surface/interior chemistry, flexibility, and topology. The dendrimers can be synthesized by using three different approaches (Crespo et al., 2005).
1. Divergent approach
2. Convergent approach
3. Double stage convergent approach
Divergent approach
In this method, dendrimer grows outwards from a multifunctional core molecule towards periphery. As a result of this growth, each new iterative reaction is characterized by the generation of an exponentially increasing number of functional groups on the periphery and double the molecular weight than the previous layer (Vogtle et al., 1978). The reaction steps can be repeated to increase the size of dendrimers as required. Many problems occur from side reactions and incomplete reactions of the end groups that lead to structural defects. To prevent side reactions and for completion o...
The goal of this lab is to synthesize maleic anhydride with polyethylene glycol of 200g/mol molecular weight (PEG 200) and 2,3-dimethyl-1,3-butadiene to get 4,5-dimethylcyclohexane-1,2-dicarboxylic acid anhydride and its diacid by using Diels-Alders reaction and hydrolysis, respectively. The crystals were determined using melting point determination and IR spectroscopy.
David and John Free. (26 Nov 2006). MadSci Network: Chemistry. Retrieved on March 6, 2011, from http://www.madsci.org/posts/archives/2007-02/1171045656.Ch.r.html
The compound was synthesized according to Experiment 8.2 from the Microscale and Miniscale Organic Chemistry
Acknowledgements. Special thanks go to the Department of Chemistry and Chemical Biology at IUPUI, Dr. Ryan E. Denton, Professor and Dan Preston, TA.
[9] 2009, “CRC Handbook of Chemistry and Physics, 90th edition,” American Chemical Society CNC Press, Boca Raton, pp. 631-637
All the reagents and solvents were obtained from standard suppliers. The 2:1 water:methanol was prepared by the Carleton College stockroom and methanol was degassed with argon with the use of a Schlenk Line, but the rest of the reagents and solvents were used with no further purification. The final step of the synthesis was performed in an inert atmosphere provided by a Schlenk Line. The 1H and 13C spectrums and COSY, DEPT, and HMQC experiments were collected with a Bruker Avance III HD 400 MHz High-Performance Digital NMR Spectrometer.
W. A. Konig, D. H. Hochmuth, D. Joulain, Library of MassFinder 2.1 University of Hamburg, Institute of Organic Chemistry, Hamburg 2001
...Coauthor, ChemBioChem 2006, 7, 1-10; b) A. Author, B. Coauthor, Angew. Chem. 2006, 118, 1-5; Angew. Chem. Int. Ed. 2006, 45, 1-5.))
Monomers that are combined by condensation polymerization have two functional groups. A carboxylic acid and an amine can form an amide linkage, and a carboxylic acid and an alcohol can construct an ester linkage. So as each monomer has two reactive sites, they can form long chain polymers by making multiple amide or ester links and releasing a small molecule. Examples of the mentioned mechanism are illustrated below.
As we progress towards the future, it is evident that methyl ethyl ketone will continue to act as a key player in the chemical industry. New processes are being developed to produce methyl ethyl ketone in a much safer and faster manner, with less energy consumption and less environmental impact, as was exemplified by Maruzen Petrochemical Co.’s patented process. As more and more applications and uses of methyl ethyl ketone are discovered, the demand for the chemical compound will increase and thus inspire chemical manufacturing companies to research and develop new methods and tools in producing methyl ethyl ketone.
Polymerization of cyclic esters has attracted a lot of interest for the synthesis of biodegradabale/ biocompatible polymeric materials, such as polylactide, polyglycolide and also other polymer compound such as linear polycarbonate. Ring opening polymerization of cyclic ester compounds is better than step polymerization for obtaining high Mw polymers in a controlled “living” fashion, while avoiding the formation of by-products.
2, 4-dihydroxy benzaldehyde (2.83 g), Cl-SBA-15 (2 g) and triethylamine (2 g) in 50 mL of toluene was refluxed for 3 hours at 80-90 ºC in the water bath. Then, the solid was filtered, rinsed sequentially with ethanol and dried in a vacuum oven at 80 oC. Then, 1.96 mL of ethanolamine was added on the resulting substance in 50 mL of toluene and refluxed at 110ºC for 48 hours in oil bath under a nitrogen atmosphere. The product was centrifuged, washed with 50 mL of ethanol, diethyl ether, distilled water and dried in vacuum for 10 h at 90ºC. Finally, any residual template and organosilane was removed by Soxhlet extraction over diethylether and dichloromethane (1:1) at 100 ºC for 24 h and heated for 10 h at 40ºC under vacuum. Synthesis steps are presented in Scheme 1.
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
The Knorr synthesis of the pyrrole, 2,4-diethoxycarbonyl-3,5-dimethylpyrrole, was achieved using an α-amino ketone, ethyl acetoaminoacetate and reacting it with its predecesso r, ethyl acetoacetate in a double condensation reaction . The product was analysed by 1H NMR, 13C NMR, mass spectrometry and IR spectroscopy giving positive results .
Development of specific ethers has been inactive and fruitful area of investigation in the past few decades.2The strategy of ether catalysis General encompasses synergistic activation of a ethers an electrophile by two or more reactive centers through the combination of a Lewis acid and Lewis base working in concert. Such approach results in high reaction rates and excellent ethers. Hydrogen bonding plays a crucial role in this catalysis. Hydrogen bonding to an electrophile decreases the electron density of this species, activating it toward nucleophilic attack. Recently chemists have begun to appreciate the tremendous potential offered by hydrogen bonding as a tool for electrophile activation in synthetic catalytic systems. In particular, ethers donors have emerged as a broadly applicable class of catalysts for ethers synthesis. An amide unit, the key functional group of peptides, plays an important role in catalyst design and modification. Based on the understanding of different asymmetric catalytic reaction mechanisms, the creation of amide structure-based ether and was realized by rational arrangement of hydrogen-bond networks. According to their model, two water molecules simultaneously establish H-bonds to the carbonyl oxygen of the substrate for optimal transition state stabilization. The concept of explicit double H-bonding activation was no longer restricted to one type of reaction or catalyst, but became a generally applicable principle. The simultaneous donation of two hydrogen bonds has proven to be a highly successful strategy for electrophile activation. Such interactions benefit from increased strength and directionality compared to a single hydrogen bond. Ethers containing double hydrogen bond ethers are capable of directing the assembly of molecules with similar control as