Infrared initiated reactions

In comparison to the bismuth molybdate and cuprous oxide catalyst systems, data on other catalyst systems are much more sparse. However, by the use of similar labeling techniques, the allylic species has been identified as an intermediate in the selective oxidation of propylene over uranium antimonate catalysts (20), tin oxide-antimony oxide catalysts (21), and supported rhodium, ruthenium (22), and gold (23) catalysts. A direct observation of the allylic species has been made on zinc oxide by means of infrared spectroscopy (24-26). In this system, however, only adsorbed acrolein is detected because the temperature cannot be raised sufficiently to cause desorption of acrolein without initiating reactions which yield primarily oxides of carbon and water. 

The initial reaction of SO2 with OH is proposed to form HSO3 (8). The H0S02(HS03) has recently been identified and characterized by matrix-isolation infrared spectroscopy (9). Various mechanisms (10) have been proposed to account for the conversion of HSO3 to final product H2SO4. 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

The previous hypothesis was tested by working with a solution of CRh5(CO) 1 5] in 1 8-crown-6 prepared from ERhi2(C0)3qI]2-(equation I7) from which Rhg(C0)i5 has been removed prior to use. The displacement of that equilibrium (equation 18) towards the right was achieved by reduction of the concentration of Rh2(C0)g while the system was monitored by infrared spectroscopy. The Initial reaction mixture showed only the spectrum of [Rhg (C0)i 5I]- at 150° and 832 atm. of C0 H2 (1 1) (Figure 5) but further treatment with thts gas mixture under these conditions resulted in the presence of an additional band at 1900 cm assigned to ERh(C0)4]- we have also observed the spectra of Rh2(C0)g and Rh4(C0)i2 at the same time under 200 atm. of C0 H2 (1 1) and 85°. The latter cluster has been shown to be formed by the dimerization of Rh2(C0)g. 

Once deposition is complete and the initial reaction product is trapped in an inert gas matrix, characterization is carried out spectroscopically. Several spectroscopic techniques have been used the most common is infrared spectroscopy, either dispersive or Fourier transform. Raman spectroscopic studies have been carried out as well, but low signal levels have made this approach difficult. When the trapped intermediate is a free radical, electron spin resonance techniques are valuable as well. Finally, a number of researchers are employing electronic spectroscopy, when the species of interest has an absorption in the visible or ultraviolet tegion. 

The gas phase reaction proceeds very much as described for nickel carbonyl, but the product does not contain the nitrite group (10). A smoke is formed immediately the gases come into contact, but the analysis and infrared spectrum of the solid formed show it to be the oxide-nitrate Fe0(N03). It seems likely that initial reaction involves the NO2 radical, and an iron nitrite such as Fe(N02)3 may be produced initially. The oxidation-reduction properties of the ferric and nitrite ions may render them incompatible Fe0(N03) would then be left as a decomposition product. So little is known about transition metal nitrites that this must remain conjecture at present, but it may be relevant to recall that it has not yet been possible to isolate pure samples of Fe(N03)3, A1(N03)3, or Cr(N03)3. 

A novel setup was developed to study laser-driven reactions in solid matrices (e.g., polymers) using time-resolved IR spectroscopy. The first experiments have provided one of the first examples of how ultrafast infrared spectroscopy may be used to examine laser-driven reactions in polymeric matrices. The photo chemically as well as the thermally initiated reaction of a model compound has been studied in a PMMA matrix. It is remarkable that both initial reactions happen on a time scale faster than our experimental limit of 20 ps. While the initial reaction products are probably the same, the... 

It is shown,that the transcarbonation can indeed be catalysed by basic solids. Best performances are obtained with cesium salts such as CSHCO3, CS2CO3, CsF and with organic resins bearing basic functions such as N,N-dimethylbenzylamine. A key factor for the use of this type of catalysts is the irreversible adsorption of PNP which has to be avoided. In fact, in the case of cesium carbonate, the formation of para-nitrophenate species on the catalyst has been shown by infrared spectroscopy. On the other hand, a comparative study indicates a decrease by a factor of 1.5 of the initial reaction rate of 4,4 -dinitro consumption, when CS2CO3 was recycled in dichloromethane as a solvent. 

Fig. 2.5. Profile of infrared emission at 2-7 / m during shock-initiated reaction in 2 0% H2-2 0% 02-96 0% Ar mixture. Emission is downward. Time increases from left to right. Time marks 100 //sec. Initial pressure 10-0 cm Hg. Shock velocity 1T21 km sec. Mean reaction zone temperature 1435 K. Field of view defined by slits opened to 5 mm (after Blair and Getzinger ).

Several mechanisms were offered to explain steric control in polymerizations of polar monomers. Furukawa and co-workers based their mechanism on infrared spectroscopy data of interactions between the cations and the growing polymeric chains in polymerizations of methyl methacrylate and methacrylonitrile. They observed a correlation between the tacticities of the growing molecules and the carbonyl stretching frequencies. The higher the frequency, the higher is the amount of isotactic placement in the resultant chains. The adducts, as in the initiation reactions, are resonance hybrids of two structures, A and B ... 

Amongst the reactions which have been studied on this system the reaction of Fe(CO)3(PPh )2 with I2 in CHCI3 provides a good example of the type of information which can be obtained by this form of infrared spectroscopy. At a 1 1 ratio of reactants a very curious feature of the reaction was the regeneration of 50% of the starting Fe(0) complex after an initial reaction in which it nearly completely disappears. In Figure (4) the first 350 msecs of the reaction is shown for a spectrum between 1870 and 2120 cm . Note (a) the decrease and then increase at 1878 cm l for the reactant, (b) the intermediate behaving in the same fashion, only with an initial increase and then decrease at c 2050 cm", (c) the product peak increase at ca 2043 cm ... 

Figure 4.8 Low-density polyethylene (LDPE) suspected to have low levels of thermal degradation (by a deterioration of physical properties) may show negligible differences in the infrared. Initial oxidative reaction takes place adjacent to the vinylidene units [151], and treatment with SO2 will lead to a reduction in pendant methylene absorption, which can be further intensified by prior heating. This is illustrated in this figure by comparing the treatment effects on a complaint (oxidised, right) and control (left) samples. A, the samples as received B, after SO2 treatment C, heated at 100°C for 18h D, heated at 100°C for 18h then S02-treated. Reproduced from ref. 151, by permission of Elsevier Applied Science Publishers Ltd, Barking.

The time necessary for completion of the reaction may vary from 0.5 to 4 hours, depending on the actual activity of the alumina. The progress of conversion should be monitored by infrared analysis of a concentrated sample of the solution. Stirring should be continued for 15 minutes after the nitroso band at 1540 cm. has disappeared. A strong diazo band at about 2100 cm. will then be present. The carbonyl band at 1750 cm. initially due to nitrosocarbamate, will usually not disappear completely during the reaction, because some diethyl carbonate is formed in addition to carbon dioxide and ethanol. Diethyl carbonate is removed during the work-up procedure. 

A mixture consisting of 0.69 g (10.5 mmoles) of zinc-copper couple, 12 ml of dry ether, and a small crystal of iodine, is stirred with a magnetic stirrer and 2.34 g (0.7 ml, 8.75 mmoles) of methylene iodide is added. The mixture is warmed with an infrared lamp to initiate the reaction which is allowed to proceed for 30 min in a water bath at 35°. A solution of 0.97 g (2.5 mmoles) of cholest-4-en-3/ -ol in 7 ml of dry ether is added over a period of 20 min, and the mixture is stirred for an additional hr at 40°. The reaction mixture is cooled with an ice bath and diluted with a saturated solution of magnesium chloride. The supernatant is decanted from the precipitate, and the precipitate is washed twice with ether. The combined ether extracts are washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent is removed under reduced pressure and the residue is chromatographed immediately on 50 g of alumina (activity III). Elution with benzene gives 0.62 g (62%) of crystalline 4/5,5/5-methylene-5 -cholestan-3/5-ol. Recrystallization from acetone gives material of mp 94-95° Hd -10°. 

A mixture of 2.0 g (0.064 mol) of 2-fluoromethyl-3-(o-tolyl)-6-nitro-4(3H)-qulnazolinone, Oi g of 5% palladium-carbon and 100 ml of acetic acid is shaken for 30 minutes in hydrogen gas. The initial pressure of hydrogen gas is adjusted to 46 lb and the mixture is heated with an infrared lamp during the reaction. After 30 minutes of this reaction, the pressure of hydrogen gas decreases to 6 lb. After the mixture is cooled, the mixture is filtered to remove the catalyst. The filtrate is evaporated to remove acetic acid, and the residue is dissolved in chloroform. The chloroform solution is washed with 5% aqueous sodium hydroxide and water, successively. Then, the solution is dried and evaporated to remove solvent. The oily residue thus obtained is dissolved in 2 ml of chloroform, and the chloroform solution is passed through a column of 200 g of silica gel. The silica gel column is eluted with ethyl acetate-benzene (1 1). Then, the eluate is evaporated to remove solvent. The crude crystal obtained is washed with isopropylether and recrystallized from isopropanol. 0.95 g of 2-fluoromethyl-3-(o-tolyl)-6-amino-4(3H)-quinazolinone Is obtained. Yield 52.5% MP 195°-196°C. 

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