Condensation preferential

Also, because the boiling points of these cryogenic liquids are lower than that of oxygen, if exposed to air they can cause oxygen to condense preferentially, resulting in hazards similar to those of liquid oxygen. 

Condensation reactions between carbonyl compounds and primary amines have played a central role in the synthesis of new macrocyclic ligands [28-34]. Usually, though not in all cases, such reactions are conducted in the presence of metal ions which can serve to direct the condensation preferentially to cyclic rather than oligomeric/polymeric products and to stabilize the macrocycle once formed. The relative atomic radius of the templating ion has a considerable effect on the size of the macrocycle formed. For instance, in what is now classic work, cations such as Mg(Il) (r = 0.72 A) were found to stabilize the formation of macrocycles such as 60 from 1 1 condensations [35], while larger cations such as Sr(II)... 

Most commercial enone synthesis methods are not applicable to all desired enones. The acetylene condensation/hydration method can only make enones with even numbers of carbons, while formaldehyde condensation preferentially gives branched products at higher molecular weights. Other methods use expensive oxidation reagents and start with the allylic alcohols. Yet other methods use even more expensive reagents, " or electrochemical methods... 

MCA requires a continual source of monomers, which, because of physical or chemical factors, condense preferentially with higher molecular weight species rather than themselves. Because growth occurs monomer-by-monomer under reaction-limited conditions, all potential growth sites are accessible the result is compact, uniform (nonfractal) objects characterized by P = — 4. Si NMR... 

Monomer-cluster growth requires a continual source of monomers which, for either chemical or physical reasons, condense preferentially with clusters rather than each other. Examination of the Si NMR spectra of TEOS-derived silicates (Fig. 33) shows that substantial concentrations of monomer are available even at t/t = 0.9 for systems prepared at pH 5 and 7, whereas the system prepared at pH 1 is composed almost completely of species. 

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