Reaction FTIR spectroscopic study

The Claisen-Schmidt condensation of 2 -hydroxyacetophenone and different chlorinated benzaldehydes over MgO has been investigated through kinetic and FTIR spectroscopic studies. The results indicate that the position of the chlorine atom on the aromatic ring of the benzaldehyde substantially affects the rate of this reaction. In particular, the rate increases in the following order p-chlorobenzaldehyde < m-chlorobenzaldehyde < o-chlorobenzaldehyde. The difference between the meta and para-substituted benzaldehyde can be attributed to electronic effects due to the difference in the Hammett constants for these two positions. Steric effects were found to be responsible for the higher rate observed with the o-chlorobenzaldehyde. 

PM3 calculations of the 2 + 3-cycloaddition of t-butylphosphaacetylene with 2,4,6-triazidopyridine are consistent with the dipole-LUMO-controlled reaction type. An FTIR spectroscopic study of the 1,3-dipolar cycloaddition of aryl azides with acetylenes shows that the rate of reaction increases logarithmically with pressure (below 1 GPa). The 3 -I- 2-cycloaddition between an azide (69) and a maleimide (70) has been greatly accelerated by utilizing molecular recognition between an amidopyridine and a carboxylic acid [see (71)] (Scheme 24). ... 

Niki, H., P. D. Maker, C. M. Savage, and L. P. Breitenbach, FTIR Spectroscopic Study of the Mechanism for the Gas-Phase Reaction between Ozone and Tetramethylethylene, . /. Phys. Chem., 91, 941-946 (1987). 

Barnes, I., V. Bastian, and K. H. Becker, FTIR Spectroscopic Studies of the C H, S + N02 Reaction under Atmospheric Conditions, Chem. Phys. Lett., 140, 451-457 (1987). 

Chen, J., T. Zhu, V. Young, and H. Niki, Long Path FTIR Spectroscopic Study of the Reactions of CF,0 Radicals with Alkenes, J. Phys. Chem., 97, 7174-7176 (1993b). 

Salsa, T. Pina, M.E. Teixeira-Dias, J.J.C. Crosslinking of gelatin in the reaction with formaldehyde an ftir spectroscopic study. Appl. Spectrosc. 1996, 50 (10), 1314—1318. Buice, R.G. Gold, T.B. Lodder, R.A. Digenis, G.A. Determination of moisture in intact gelatin capsules by near-infrared spectrophotometry. Pharm. Res. 1995,12 (1), 161-163. 

AJ Michell. FTIR Spectroscopic Studies of the Reactions of Wood and of Lignin Model Compounds with Inorganic Agents. Wood Sci. Tech. 27 69-80, 1993. 

An FTIR spectroscopic study by Ziolek et al. [830] of the reaction between methanol and hydrogen sulfide over Na-X as a catalyst showed that both CH3OH and H2S were adsorbed on basic and/or cationic sites methoxy groups as well as HS species were involved in the reaction. The effect of Brensted acidity of faujasite-type zeolites on the sulfurization was studied by the same group [831]. 

As was mentioned above, in 2007, it was shown that SWNT covalently functionalized with a polymer may be obtained by a bulk polymerization [33]. The reaction mechanisms that occur in the polymerization processes can be understood by Raman light scattering and FTIR spectroscopic studies, which prove the functionalization of CNTs both with monomers (e.g. N-vinyl carbazole (VK)) and polymer molecules (e.g. PVK) [33]. 

Results of FTIR spectroscopic study are in good agreement with the model acid-catalyzed reactions of n-heptane and cyclohexane isomerization. The introduction of alumina into Pt/SZ decreases the total catalyst activity in n-CzHie isomerization, which shows up as increase of the temperature of 50% n-heptane conversion from 112 to 266 (Table 9). For isomerization of cyclohexane to methylcydopentane, higher operating temperatures are thermodynamically more favorable (Tsai et al., 2011). As a result, Pt/SZA catalyst is more efficient for cyclohexane isomerization due to higher selectivity at higher temperatures (Table 10). 

With the FTIR spectroscopic method, these free radical reactions cannot be studied individually under completely isolated conditions since competing side reactions and also secondary reactions involving the molecular products must be taken into account. These mechanistic complications can be greatly reduced by appropriate selection of the method of free radical generation, as described in Section II.B. In general, to minimize the occurrence of secondary reactions, the conversion of the molecular reactants, and consequently the product yields, have to be kept as small as is permissible in order to obtain accurate concentration measurements. Also, the reaction time required for such chemical analysis must be kept as short as possible to minimize photochemical and heterogeneous losses of labile products. 

The elucidation of the reaction mechanism of the SCR reaction has been carried out using a variety of techniques. Transient studies with isotopically (oxygen-18 and nitrogen-15) labeled molecules have been performed [86,90]. Spectroscopic studies of the working catalysts were performed by Went et al. [90] and Topsoe [91] using laser Raman spectroscopy and FTIR, respectively. 

The process analytical technology described by Simon et al. [26] consists of a combination of an ATR UV-vis probe (Hellma Analytics) and a probe for FBRM (Mettler Toledo). The bulk phase is also monitored by BVI using a Sony video camera that captures 25 frames s . This system is well suited for studying the changes in solid particles. For monitoring the reactions driven by solid catalysts, additional Raman and ATR-FTIR spectroscopic probes can be immersed in the reaction mixture as shown in Figure 3.1. In principle, this concept is also applicable to reactions under pressure however, for such applications, stainless... 

In addition to simultaneous in situ spectroscopic studies, accompanying ex situ investigations also provide valuable information about the specific interaction of the substrates (imines and respective hydrogenation products) with both the chiral modifier (P-acid) and the solid catalyst. Thus, FTIR spectroscopic analysis of the catalyst after adsorption of the imine points to a strong interaction of the latter with the catalyst surface, in particular with the support, which is reflected by marked band shifts. It could be shown that the surface of the catalyst is mainly covered by the imine after use in the hydrogenation reaction, besides some small quantities of the product [11]. 

Spectroscopic studies were performed on water in supercritical CO2 microemulsions using an ammonium carboxylate PFPE surfactant (24). FTIR spec-toscopy was used to identify a bulk water phase within the microemulsion capable of solubilizing ionic species and supporting inorganic reactions. In addition, the UV-visible spectrum of the solvatochromic probe methyl orange indicated three microenvironments within the microemulsions (a) a polar microenvironment like that found in dry PFPE reverse micelles (b) bulk water microenvironment and (c) an acidic microenvironment due to CO2 dissolved in water. 

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