Fiesers' Reagents for Organic Synthesis, ..
Languange Used : en
Release Date : 2013-08-14
Publisher by : John Wiley & Sons
Description :Structured in three parts this manual recollects efficient organocatalytic transformations around clear principles that meet actual standard in asymmetric synthesis.
Advances in Organic Synthesis:: volume 3 | …
By far, RF aerogels are the most researched organic aerogels and so we’ll use them as an example of how organic aerogels are prepared. Like other kinds of aerogels, RF aerogels are prepared through a sol-gel process, starting with a solution containing small molecules with the ability to link together (polymerize) to form larger molecular clusters that can eventually grow into nanoparticles dispersed throughout the solution (a sol). These nanoparticles can then be coaxed into interconnecting (or as they say in polymer chemistry, cross-linking) to form a continuous network of interconnected nanoparticles that spans the volume of the liquid solution, namely, a gel.
This handbook offers a unique source of the in-depth knowledge of synthesis, processing, spectroscopy, physical properties and applications of organic electronic and photonic materials and has been divided into three thematic volumes:
Biocatalysis in Organic Synthesis Volume 3
For instance, if the target compound was the base in the system, the extraction with HCl should be performed first. Whatever remains in the organic layer is not of interest anymore afterwards, unless one of the other compounds has to be isolated from this layer as well. If the target compound was an acid, the extraction with NaOH should be performed first. This strategy saves steps, resources and time, and most of all, greatly reduces waste.
Practical Aspects of an Extraction
An extraction can be carried out in macro-scale or in micro-scale. In macro-scale, usually a separatory funnel (on details how to use it see end of this chapter) is used. Micro-scale extractions can be performed in a conical vial or a centrifuge tube depending on the quantities. Below are several problems that have been frequently encountered by students in the lab:
ORGANIC SYNTHESIS THEORY AND APPLICATIONS VOLUME 3 …
Although organic aerogels have been around since the first aerogels were prepared, they were, for the most part, overlooked until the 1980’s when Lawrence Livermore National Laboratory scientists began producing organic aerogels made of phenolic resins. The bulk of this work was done by scientists Dr. Rick Pekala and Dr. Joe Satcher, who synthesized the first resorcinol-formaldehyde polymer aerogels (or RF aerogels for short).-essentially, aerogels composed of the same material as the plastic “Bakelite”. Depending on their density, RF aerogels range from light orange to deep red to black in color and range from translucent to opaque. Low density organic aerogels (-3) are generally irreversibly squishy, similar in feel to green floral potting foam. High density organic aerogels (>0.5 g cm-3) can be extremely robust and very hard to squeeze, almost like a car seat cushion.
Volume 3, Fiesers' Reagents For Organic Synthesis By …
The amino acids are colorless, nonvolatile, crystalline solids, melting and decomposing at temperatures above 200Â°C. These melting temperatures are more like those of inorganic salts than those of amines or organic acids and indicate that the structures of the amino acids in the solid state and in neutral solution are best represented as having both a negatively charged group and a positively charged group. Such a species is known as a .
Other volumes in the series Reagents for Organic Synthesis Volume 1 …
After separation of the organic and the aqueous layer, the amine can be recovered by addition of a strong base like NaOH or KOH to the acidic extract i.e., lidocaine synthesis. Note that amides are usually not basic enough to undergo the same protonation (pKa of conjugate acid: ~ -0.5).
Most neutral compounds cannot be converted into salts without changing their chemical nature. Many of these neutral compounds tend to react in undesired ways i.e., esters undergo hydrolysis upon contact with strong bases or strong acids. One has to keep this in mind as well when other compounds are removed. For instance, epoxides hydrolyze to form diols catalyzed by acids and bases. Ketones and aldehydes undergo condensation reactions catalyzed by both, acids and bases. Esters also hydrolyze to form carboxylic acids (or their salts) and the corresponding alcohol. In order to separate these compounds from each other, chromatographic techniques are often used, where the compounds are separated based on their different polarities (see Chromatography chapter).
Based on the discussion above the following overall separation scheme can be outlined. Which sequence is the most efficient highly depends on the target molecule. There is obviously no reason to go through the entire procedure if the compound sought after can be isolated in the first step already. Note that many of these steps are interchangeable in simple separation problems.