Mass organic compounds

Study object Small molecular weight (molar mass) organic compounds,... 

The temporal stability of OLEDs using low-molar-mass organic compounds... 

Humic acid Naturally occurring high-molecular-mass organic compounds which are acid-soluble but are precipitated by base. 

The empirically defined terms "humic acids" and "fulvic acids" have been used to denote important macromolecular constituents of aquatic systems. Even though their structures are incompletely resolved (Section 3.2.3 and 4.5.3), their association with low-molecular-mass organic compounds — and with metal cations — is important in determining the bioavailability and hence biodegradability and toxicity of organic compounds. Their role in the generation of OH radicals under anaerobic conditions is noted in Section 4.1.1, and as intermediates in electron-transfer reactions under anaerobic conditions in Section 5.5.5. 

Silica, and to a lesser extent alumina, are the most common stationary phases used for the separation of low molecular mass organic compounds. Chemically bonded silica sorbents are used for the separation of polar organic compounds in the normal-phase and reversed-phase modes. Wide-pore, chemically bonded sorbents, are used for the separation of biopolymers [18,22]. Some separations require specially prepared stationary phases, such as silica gel impregnated with silver nitrate for the isolation of unsaturated compounds capable of forming charge transfer complexes with silver [23] (section 10.6.1), or silica and chemically bonded phases coated with cellulose tris(3,5-... 

It was observed in the last section that most antioxidants and stabilisers are relatively low molar mass organic compounds which can be easily extracted by solvents or volatilised from the surface of the polymer at elevated temperature. This is a disadvantage in two ways. Firstly, the additives may migrate into the human environment, causing toxicity in foodstuffs or, as in the case of prostheses, directly in the body. Secondly, because they are lost from the polymer, their effectiveness is reduced. 

Although, today, we are faced with an ever-increasing number of tools available to the synthetic polymer chemist, even with such new tools there remain many blank spaces on the map of polymer chemistry. The main reason for this is that the number of polymers that are accessible synthetically are absolutely comparable to - if not bigger than - the world of classical low-molar mass organic compounds, which are explored to a much better extent than the universe of polymers. 

Chemical composition One fascinating point about polymer synthesis is that, apart from synthesizing polymers from only one chemical species, it is possible to copolymerize different monomers in deliberate ratios. Simply by examining the case of statistical (e.g., radical) copolymerization, the monomer ratios can be varied almost deliberately, though still in a controlled fashion - unlike the stoichiometric reactions of low-molar mass organic compounds. This permits an enormous, practically unlimited degree of freedom to a synthetic polymer chemist in order to fine-tune the chemical properties of the polymer to as precise a state as needed. 

Mycotoxins are produced in a complex matrix of macromolecules, including proteins, polysaccharides, and lipids, and many of the plant commodities most at risk of contamination contain a complex range of low-relative-molecular-mass organic compounds. Although many mycotoxins are readily soluble in water-immiscible organic solvents, it is not always... 

Water and carbon dioxide are the most used solvents due to their low price and environmental friendliness. The critical temperature of water is 473 K and it is used for reactions under extreme conditions.Carbon dioxide, on the other hand, presents a very low critical temperature and it is adequate for reactions carried out under mild conditions, for example, selective hydrogenations. Unfortunately, it is well known that CO2 is not a good solvent for high molar mass organic compounds. Liquid carbon dioxide is miscible with alkanes with up to approximately 10 carbon atoms, while the range of miscibility increases for ethane up to 18 carbon atoms, and for propane up to 30 carbon atoms. Thus, the application of CO2 as reaction media is limited to low molar mass hydrocarbons if a homogenous operation is desired, while ethane and propane are a better option for higher molar mass hydrocarbons. 

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