Sulfonic acid residues

The Bucherer carbazole synthesis was first demonstrated when 7 was heated in the presence of phenylhydrazines 8, sodium hydroxide and sodium bisulfite after acidic work-up, the benzocarbazole product 9 was isolated (-70% yield). When 2-naphthol was used the reaction was significantly slower with the yield of benzocarbazole being only 46% after several days at 130 °C Bucherer and co-workers investigated this reaction extensively concluding, incorrectly, that intermediate products were probably carbazole-Al-sulfonic acids due to the ease with which they lost the sulfonic acid residues to yield benzocarbazoles. 

Water soluble (contain mostly sulfonic acid residues) and water insoluble (penetrate mostly biological membranes)... 

The basis of the separation of amino acids by AAA lies in the interaction between acids - present in the elution buffer - and the stationary phase. This resin is made up of small sulfonated polystyrene particles. The negative charge of the sulfonic acid residues is counterbalanced by the Li+ -cations of the elution buffer. As the whole separation process takes place at a weakly acidic pH, the carboxylic acid residues are protonated and the interaction with the stationary phase of the column is achieved by the protonated (and thus positively charged) amino group(s) of the amino acids. The more basic the amino acid is, the stronger the interaction with the stationary phase and - consequently - the longer the retention time. So it is easily understood... 

The tosyl esters react like the halogen compounds. Methyl 4-tosyl-2,3,6-triacetyl- 9-D-glucopyranoside (XLVIII), which may be obtained from methyl 6-trityl-/3-D-glucopyranoside (see page 92), did not give a 4-tosyl derivative even on very careful deacetylation. The sulfonic acid residue was split off simultaneously and a peculiar anhydride was formed. Mtiller suggested a methyl 3,4-anhydro-n-hexoside structure (XLIX) for this substance. 

Photocontrol of the transport property was also studied for poly(L-glutamic acid) membrane with azobenzene-4-sulfonic acid residues [61]. 

Proton conduction in Nafion requires water to ionize the sulfonic acid groups and establish percolation paths through the membrane [2]. The water uptake by the PEM, X = number of water molecules per sulfonic acid residue, and the membrane resistivity, R, are functions of the water activity, aw they have negligible dependence on temperature [21, 22]. 

A one-dimensional PEM fuel exhibited steady state multiplicity, resulting from positive feedback between proton conduction in the membrane and water production from the fuel cell reaction. The critical membrane water activity necessary for ignition of the fuel cell current was identified. The time for current ignition is 100-1000 s, resulting from the titration of the sulfonic acid residues in the polymer membrane from the water formed by the fuel cell reaction. 

Fluorescent probes used as labels should have high quantum yield, emission wavelengths longer than 500 nm, and Stokes shifts of over 50 nm. They must possess suitable functional groups such as carboxylic acid, amino, hydroxyl, sulfonic acid residues, acid anhydride, acid chloride, diazonium, isocyanate, isothiocyanate, AT-hydroxysuccinimide, maleimide. 

To determine whether CW has a catalytic effect of the resinification of FA, in a typical experiment, 0.75-1.0 phr freeze-dried CW was redispersed in FA by means of a brief ultrasonication treatment (Fisher 500W, 25-50% amphtude, 15 min bursts) followed by heating to 50 °C for additional dispersion. At 50 °C, the sulfonic acid residues are stable and de-esterification is not expected. After 1 h at 50 °C, the mixture was heated to the target reaction temperature untQ resinification of FA to PFA occurred. 

The monobactams have a single beta-lactam ring structure. The only clinically used monobactam is aztreonam. Replacement of the 1-sulfonic acids residue in monobactam with an Af-sulphonylated carbonyl amino moiety yields monocarbams [71, 72 ]. So far, however, no monocarbam derivative is on the market, probably because their antimicrobial moiety is not optimal. Since micro-organisms need iron for growth, some siderophore-conjugated monocarbams are now under evaluation [73 ]. It is reasonable to assume that it will take some time until they are marketed. One of the many problems not yet solved is the in vivo fate of the siderophore itself, since it may create some new adverse effects of its own. 

A new type of biobased material was synthesized from cellulose nano whiskers (CW) and furfuryl alcohol by employing in-situ polymerization method to produce polyfur-furyl alcohol (PFA)/cellulose nanocomposites without the use of solvents or surfactants. Furfuryl alcohol (FA) played a dual role, serving both as an effective dispersant for the cellulose whisker (CW) and as the matrix precursor for the in-situ polymerization. The filler, CW also served multiple functions, by first catalyzing the polymerization of FA, and then acting as an effective matrix modifier, increasing the thermal stability of the consolidated PFA nanocomposite. The polymerization was catalyzed by sulfonic acid residues at the CW surface left over from the whisker preparation [67]. 

The surface of poly(tetrafluoroethylene) materials may be etched with potassium or liquid ammonia to produce double bonds.These double bonds are usable as grafting sites for MA. Grafting is achieved with free-radical initiators, using neat polymerization conditions. Grafted tubes were tested for thrombogenetic activity by exposure to animal blood. Thrombogenicity of the poly(tetrafluoroethylene) surface was improved, but carboxyl groups were inferior to sulfonic acid residues. 

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