Compound Studies

The most effective single criterion of whether free base or conjugate acid nitrates is the comparison of a model compound in which the possibilities of prototropic and tautomeric equilibria have been eliminated. For example, the model compound for a substitued pyridinium cation is its N-methyl cation. If the nitration of the pyridine proceeds via the conjugate acid, the rate profile will have the same shape as for the N-methyl model compound. The individual rates of nitration for the model compound may or may not be exactly the same as for the pyridine itself, depending upon the effect of the methyl group upon the reactivity. If, on the other hand, nitration of the pyridine takes place on the free base, then the N-methyl cation will not be nitrated under the same conditions. 

This method is therefore the most reliable for determining the species reacting, provided that the model compound does not decompose under the experimental conditions. 

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Dewar and his co-workers, as mentioned above, investigated the reactivities of a number of polycyclic aromatic compounds because such compounds could provide data especially suitable for comparison with theoretical predictions ( 7.2.3). This work was extended to include some compounds related to biphenyl. The results were obtained by successively compounding pairs of results from competitive nitrations to obtain a scale of reactivities relative to that of benzene. Because the compounds studied were very reactive, the concentrations of nitric acid used were relatively small, being o-i8 mol 1 in the comparison of benzene with naphthalene, 5 x io mol 1 when naphthalene and anthanthrene were compared, and 3 x io mol 1 in the experiments with diphenylamine and carbazole. The observed partial rate factors are collected in table 5.3. Use of the competitive method in these experiments makes them of little value as sources of information about the mechanisms of the substitutions which occurred this shortcoming is important because in the experiments fuming nitric acid was used, rather than nitric acid free of nitrous acid, and with the most reactive compounds this leads to a... 

The demonstration unit was later transported to the CECOS faciHty at Niagara Falls, New York. In tests performed in 1985, approximately 3400 L of a mixed waste containing 2-chlorophenol [95-57-8] nitrobenzene [98-95-3] and 1,1,2-trichloroethane [79-00-5] were processed over 145 operating hours 2-propanol was used as a supplemental fuel the temperature was maintained at 615 to 635°C. Another 95-h test was conducted on a PCB containing transformer waste. Very high destmction efficiencies were achieved for all compounds studied (17). A later bench-scale study, conducted at Smith Kline and French Laboratories in conjunction with Modar (18), showed that simulated chemical and biological wastes, a fermentation broth, and extreme thermophilic bacteria were all completely destroyed within detection limits. 

Ring 1 Ring position 2 3 4 5 Examples of compounds studied... 

An extensive series of hydrocarbons has been studied in cyclohexylamine, with the use of cesium cyclohexylamide as base. For many of the compounds studied, spectroscopic measurements were used to determine the relative extent of deprotonation of two hydrocarbons and thus establish relative acidity. For other hydrocarbons, the acidity was derived by kinetic measurements. It was shown that the rate of tritium exchange for a series of related hydrocarbons is linearly related to the equilibrium acidities of these hydrocarbons in the solvent system. This method was used to extend the scale to hydrocarbons such as toluene for which the exchange rate, but not equilibrium data, can be obtained. Representative values of some hydrocarbons withpAT values ranging from 16 to above 40 are given in Table 7.2. 

The isocyanurate reaction occurs when three equivalents of isocyanate react to form a six-membered ring, as shown in the fifth item of Fig. 1. Isocyanurate linkages are usually more stable than urethane linkages. Model compound studies show no degradation of the trimer of phenyl isocyanate below 270°C [10,11]. Catalysts are usually needed to form the isocyanurate bond. Alkali metals of carboxylic acids, such as potassium acetate, various quaternary ammonium salts, and even potassium or sodium hydroxide, are most commonly used as catalysts for the isocyanurate reaction. However, many others will work as well [12]. 

The first compound studied (56) was quinolizidine (41), which can be readily converted to J >-dehydroquinolizidine (42) in 60% yield by the action of 4 moles of mercuric acetate in 5% aqueous acetic acid on 1 mole of the amine. Mercurous acetate precipitates as the reaction progresses at... 

The high diffusivity and low viscosity of sub- and supercritical fluids make them particularly attractive eluents for enantiomeric separations. Mourier et al. first exploited sub- and supercritical eluents for the separation of phosphine oxides on a brush-type chiral stationary phase [28]. They compared analysis time and resolution per unit time for separations performed by LC and SFC. Although selectivity (a) was comparable in LC and SFC for the compounds studied, resolution was consistently... 

Changes in pressure typically have a greater impact on retention than on selectivity. Most studies of CSPs have indicated little effect of pressure on stereoselectivity [28, 31]. However, Bargmann-Leyder et al. reported pressure-related changes in selectivity for an amylose-based CSP, though the magnitude of the pressure effect was not the same for all the compounds studied [58]. Pressures in the range of 15-20 MPa are common for chiral SFC. 

Figure 3.116 Platinum compounds studied for possible anti-tumour activity. I, ris-Dichlorodi-ammineplatinum(II) cisplatin, platinol NSC 119875 neoplatin platinex. II, a.s-Diammine(l,l-cyclobutanedicarboxylato)platinum(II) JM-8 paraplatin NSC 241240. Ill, Oxiplatin. IV, Tetraplatin. V, Amminediacetatodichloro(cyclohexylamine)platinum(IV). VI, cis-Dich oro-trans-dihydroxy-cis-bis(isopropylamine)platinum(IV) iproplatin JM-19 CHIP NSC 256927.

Gandini and Rieumont26,119 have carried out an extensive examination of the polymerizability of several vinyl esters of furan carboxylic acids and of the causes of the autoinhibition which most of them display with free-radical initiation. The compounds studied were the vinyl esters of 2-furoic, 2-furylacetic, 2-furylpropionic, 2-furylacrylic and sorbic acid. All these derivatives, showed the same strong indifference towards radical polymerization. Only when treated with large doses (10—30%) of initiator did they give small yields of oligomers. The structure of all these products was carefully studied by spectroscopic and other techniques. Invariably, it was... 

A positive iodinating species was postulated to account for the kinetics and isotope effect observed in the iodination of some amines by iodine in aqueous potassium iodide (in some cases in the presence of acetate, lactate, or phosphate ion). The isotope effects (kH/kD values in parenthesis) for these compounds studied were 2,4,6-trideutero-m-dimethylaminobenzenesulphonate ion, 25 °C (1.0) 2,4,6-trideutero-m-dimethyIbenzoate ion, 30 °C (1.4) 2,4,6-trideutero-dimethylaniline, 30 °C, lactate (3.0) 2,4,6-trideuteromethylaniline, 25 °C, acetate (3.2) 2,4,6-trideuteroaniline, 25 °C (3.5), phosphate (4.0) 2,4,6-trideutero-metanilate ion, 35 °C (2.0) 2,4,6-trideutero-m-aminobenzoate ion, 30 °C (4.8), phosphate (3.0) 2,6-dideutero-l-dimethylaminobenzene-4-sulphonate ion, 25 °C, phosphate (1.0) 4-deutero-l-dimethylaminobenzene-3-sulphonate ion, 25 °C, phosphate (1.0). The kinetics of these reactions was given by... 

The two principal categories of compounds studied have been diaryl or aryl alkyl sulphones (not dialkyl sulphones, which are polarographically not reducible) and S-dioxides of certain heterocyclic compounds, such as thiophene (also benzo- and dibenzothiophenes) and phenothiazines. The first named have half-wave potentials in the region of — 2.0 V, the thiophene dioxides near — 1.0 V. Some examples of each category may be given. 

Furlei and coworkers44 studied the negative ion mass spectra of several cyclic sulfones (82-98) upon dissociative electron capture and concluded that the negative molecular ions were notably stabilized by the introduction of electron-withdrawing substituents and/or unsaturation. Some difference was found in the negative ion mass spectra of configurational isomers (85 vs. 86 and 87 vs. 88) in contrast to the situation in their positive ion spectra. A strong S02 ion (m/z 64) was observed also for all the compounds studied. 

Duffield and coworkers65 studied the El- induced mass spectra of five arene- (215-219) and four alkane sulfonylthioureas (220-223) and observed two rearrangement processes, namely loss of S02 from 215-219 and the elimination of ArS02 and RS02 with the thione sulfur atom from 215-223. The other fragmentations involved simple bond cleavages with and without hydrogen transfer (equation 48). The loss of H2S was evident for all the compounds studied except 221 and 222. It was, however, found to be a thermal and not an ionization process. 

Structure Number of the compounds studied P338 P338 active (%) 210 210 active (%)... 

The results showed that the compounds studied with more frequency in the aquatic environment, and of which, logically, there is more information, are the antibiotics, analgesics and anti-inflammatories (like diclofenac, ibuprofen, naproxen, acetylsalicylic acid, and paracetamol), as well as the p-blocker atenolol. In the category of antibiotics, several families are included, like the macrolides (erythromycin), the fluoroquinolones (ofloxacin and ciprofloxacin), sulfonamides (sulfamethoxazole), penicillins (amoxicillin), the metronidazol, and trimethoprim. Other therapeutic groups also widely studied and frequently found in the environmental waters are the lipid regulators (gemfibrozil and bezafibrat), antiepileptic carbamaze-pine, and antidepressants (diazepam, fluoxetine, paroxetine) (see Table 3). 

For the final optimization, a modified factorial design involving three concentration levels of triethylamine and three pH levels was used. From these results, it was clear that the optimum conditions for the analysis of the carboxylic acid were so different from those required for the other compounds studied that it was not sensible to attempt to analyse all fonr together and indeed that carboxylic acids were better analysed by using conventional reversed-phase HPLC than by using ion-pairing. 

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