Water, amide reactions detection

Besides the alkyl ether carboxylates the amidether carboxylates are used as mild surfactants in cosmetic formulations [35-37,68,69,71,80]. As described by Meijer [68,69], the ether carboxylate mixture derived from the monoethanol-amide of coconut oil is a mild product in shampoos and showerbaths, and the stearylmonoethanolamidether carboxylate an oil-in-water emulsifier for creams and lotions. The NDELA content of these products is below the detection level of 10 ppb because of the use of monoethanolamine and the further chemical reactions after amidation. 

Acrylamide polymers in aqueous solution undergo thermal hydrolysis and cyclic imide formation. Acrylate, acrylamide and cyclic imide functional groups were detected when a poly(acrylamide) is heated at 150°C in water. The formation of intramolecular imide has been reported in literature. Moradi-Araghi, Hsieh and Westerman reported the formation of cyclic imide in acid, neutral and slightly basic media at 90° C.7 In acidic media, imide formation is favored. In neutral and basic media, both hydrolysis to acrylate and imide formation do occur, but hydrolysis is the dominant reaction. We speculate the high conversion of amine to amide is the result of transamidation, amidation and the nucleophilic addition of the amine to the glutarimide intermediate (Reaction 1). 

Khurgin et al. (1977) measured the chymotrypsin-catalyzed breakdown of the amide substrate A -succinyl-L-phenylalanine-/>-nitroaniline at low hydration levels. For this substrate the acylation process is rate limiting. Figure 28 shows the extent of reaction for 1 1 enzyme-substrate mixtures, of nominal pH 7.5, reacted for 5—7 days. The intent of the experiments was to define the critical water concentration at which activity could first be detected. This was determined as the intercept of the linear region of the response with the abscissa. For chymotrypsin with no added buffer, the critical hydration level was at relative humidity 0.48, which corresponds to 0.12 A (Luescher-Mattli and Ruegg, 1982a). The reaction grows explosively (Fig. 28) above this hydration level. Addition of 0.57 g of sodium acetate per g of chymotrypsin reduced the critical hydration level by about half. This may reflect the hydration of the the salt, rather than a specific effect on the enzyme. 

When the enzyme is used to catalyse the synthesis of a peptide bond, the solvent is either non-aqueous or contains only a low concentration of water. In addition, of course, an amino component such as an amino acid or peptide ester replaces the water in the second step. Obviously, the amino component must be unprotonated for reaction to succeed. Synthesis is favoured over hydrolysis of the resultant peptide because an amide is kinetically a much worse substrate for a proteinase than is an ester. The rapid acylation of a proteinase by an TV-protected amino acid or peptide aryl ester can be demonstrated experimentally using a stopped-flow apparatus with spectrophotometric facilities. A rapid burst of phenol is followed by steady-state release, showing that acylation of the enzyme is faster than hydrolysis of the acy-lated enzyme. No such burst is detectable if, for example, an TV-acylated amino acid anilide is used as substrate. In fact, acylation is the rate-determining step with amide substrates. 

The amide is a colourless, odourless, neutral liquid at room temperature with a high dielectric constant. The amount of water present can be determined directly by Karl Fischer titration, GLC and NMR have been used to detect unreacted propionic acid. Commercial material of high quality is available, probably from the condensation of anhydrous methylamine with 50% excess of propionic acid. Rapid heating to 120-14(P with stirring favours the reaction by removing water either directly or as the ternary xylene azeotrope. The quality of the distillate improves during the distillation. 

There are different fashions how to induce water removal in condensation reactions. By simply heating amino acids with or without potent agents of condensations such as hydrogen cyanide, HC=N, cyan amide, N=C-NH2, and carbon-oxy-sulfide COS, oligomers and polymers, called proteinoids, readily formed. The detection of enzymatic activities in these polymeric proteinoids was unsuccessful except for about ten degrading enzymatic activities. Synthetic activities that build up molecules, for instance, kinase, ligase, and polymerase, were not detectable. The disadvantage of these mixtures of proteinoids is that they do not exhibit a distinct structure or a function. 

The work-up conditions for the condensation step (Scheme 12.6) were also modified to accommodate commercial operations. Sodium carbonate was used in the initial chemical development pilot plant batches to absorb the by-product HCl from the reaction. The quantities of carbon dioxide produced from the neutralization made this approach impractical in a commercial plant. To complicate matters, the amide bond formed during the condensation was subject to hydrolysis under strongly acidic conditions. Solid sodium acetate was added to the reaction mixture as a buffer to address this issue. A significant quantity of the diacetylation product (18) was also detected in the reaction mixture before work-up. However, this material rapidly hydrolyzes to the condensation product (6) and 2-chloronicotinic acid upon exposure to water (Scheme... 

Formation of the anhydride was shown unambiguously with FT-IR spectroscopy. No fluorine was detected by XPS and FT-IR methods, which supports formation of the interchain product339. The monolayer anhydride is quite stable and can survive treatment with water for at least 1-2 min. It can further react with aliphatic amines producing mixed anhydride of amide and acid. The reaction is rapid and quantitative the ratio of amide and acid in the resultant monolayer i s ca 1 1. 

Free fatty acids in human serum were derivatized with 1-naphthylamine after being converted to acyl chlorides [109], Serum (0.5 ml) was mixed with 0.1 ml of methanol containing an internal standard and 1.4 ml of 1/15 M phosphate buffer and poured into a column packed with Ig of Extrelut. The adsorbed fatty acid was recovered by elution with 10 ml of chloroform. After removal of solvent, the residue was dissolved in 0.6 ml of benzene. A solution of oxalyl chloride in benzene (2%) was added to the fatty acids and the mixture was allowed to react at 70 °C for 30 min. The solvent was removed at reduced pressure. Then naphthylamine solution (0.1ml) and triethylamine solution (0.01ml) were added. The reaction was carried out at 30 °C for 15 min, and 2 fi of the mixture was injected onto a pBondapak Cjg column at 40 °C. The mobile phase was methanol/water (81 19 v/v) and detection was at 280 nm Each fatty acid was quantitatively converted into its acid chloride and the overall recovery of naphthyl amides by this method was 94-106%. The main free fatty acids in human serum (14 0,16 0,16.1,18 0,18 1,18 2) and the internal standard (17 0) were separated in 30 min. 

More recently, Chatani and his researchers developed the ruthenium-catalyzed carbonylation at the ortho-C-H bonds of aromatic amides [65] to give phthali-mides as their products. Analogously, this reaction can also be transferred to even inactivated C(sp )-H bonds and yield the corresponding succinimides. (Scheme 6.20) [66] In both cases, the presence of 2-pyridinylmethylamino moiety is necessary for these transformations, because it plays an important role as a N,N-bidentate ligand to form a dinuclear ruthenium complex with Ru3(CO)i2. Interestingly, in the absence of ethylene, no carbonylation product could be detected while the efficiency of the reaction decreased in the absence of water. In the latter case, a long reaction time (5 days) is still needed. 

Detecting peroxides. There may be times when you need to know the peroxide content of a chemical and there are several methods that test for the presence of peroxides, including iodide methods, ferrous thiocyanate methods, titanium sulfate methods, and test strip methods. These methods each have their limitations—some will not detect the presence of all peroxide forms. These methods should not be used to test alkali metals or amides since they react violently with water. Test strips offer some advantages in that they detect a wide group of different peroxides, can be used easily, and are convenient. However, they have limited shelf life and may be beyond the budget of some. For example, potassium iodide-starch test strips are available that can detect peroxides below 100 ppm. The presence of peroxides is detected by deep dark blue (virtually black) color on the test strip from the reaction of iodine (from potassium iodide reaction with peroxide) and starch. We will not discuss these peroxide test methods in detail here, but you should know that they are available. 

Sulphonyl ylides usually are obtained by proton removal from a sulphone. Jarvis and Saukaitis" have found that the reaction of an a-bromo- or o-chloro-sulphone with triphenylphosphine resulted in abstraction of the halc en and formation of the sulphonyl ylide as an intermediate, which was trapped by protons from the water present. Benzyl phenyl sulphone was converted into the aa-dilithio-carbanion by treatment with n-butyl-lithium in THF-heptane," and Bosworth and M nus " have reported that a bicyclic phenylsulphone, upon treatment with n-butyl-lithium and then D2O, was converted into the ao-dideuteriosulphone, and that it was not possible to obtain the mono-deuteriosulphone by that method. Kaiser et al. have found that using sodium, lithium, or potassium amide with dimethyl sulphone or with dibenzyl sulphone resulted in formation of the aa -dicar-banion, as detected by deuteriation or by reaction with benzophenone. Amel and Marek determined the pK. s of a series of phenylphenacyl sulphones and concluded that the sulphone group provided less stabilization for the phenacylide than did a sulphonium group. The p value for substituents on the phenacyl portion was similar to that obtained for sulphonium, phosphonium, arsonium, and pyridinium phenacylides. 

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