Infrared spectroscopy hydroxylation

Analysis of oligomers for phenolic hydroxyl end groups was conducted by quantitative infrared spectroscopy. Hydroxyl absorbance at 3580 cm-1 was measured for a number of synthetic mixtures of bisphenol-A and bisphenol-A homopolycarbonate. A calibration curve for hydroxyl absorbance vs. weight percent hydroxyl end groups was constructed. Hydroxyl content of bisphenol-A oligomers was calculated from the calibration data. 

Infrared spectroscopy can also be used incisively to identify the six main varieties of asbestos fibers. Specific absorption bands in the infrared spectmm can be associated with the asbestos fibers, first in the 3600 3700 cm range (specific hydroxyl bands) and, second, in the ranges 600—800 and 900 1200 cm (specific absorption bands for various siUcate minerals (10)). 

The acetyl content of cellulose acetate may be calculated by difference from the hydroxyl content, which is usually determined by carbanilation of the ester hydroxy groups in pyridine solvent with phenyl isocyanate [103-71-9J, followed by measurement of uv absorption of the combined carbanilate. Methods for determining cellulose ester hydroxyl content by near-infrared spectroscopy (111) and acid content by nmr spectroscopy (112) and pyrolysis gas chromatography (113) have been reported. 

A noteworthy feature of the photoacoustic spectra shown in Figure 2 Is the presence of water librations. These are frustrated rotations and have been observed for ice (24) by infrared spectroscopy, as well as for water adsorbed on Ft and Ag surfaces by electron energy loss spectroscopy (25-27). The three libration modes have been associated with the bands at 600, 538 and 468 cm" > this set of peaks occurs for water adsorbed on both the hydroxylated and methoxylated silica. 

Several assumptions were made in order to analyze kinetic data in terms of this expression (2). First it was assumed that k 2 m kj, k2 k 3, and kj/k j k /k ( - If). Second it was assumed that the rate constants were independent of the extent of reaction i.e., that all six functional groups were equally reactive and that the reaction was not diffusion controlled. The concentration of polymer hydroxyl functionality was determined experimentally using infrared spectroscopy as described elsewhere (7). A major unknown is the instantaneous concentration of methanol. Fits to the kinetic data were made with a variety of assumptions concerning the methanol concentration. The best fit was achieved by assuming that the concentration of methanol was initally constant but decreased at a rate proportional to the concentration of residual polymer hydroxy groups towards the end of the reaction. As... 

The carbonyl index is not a standard technique, but is a widely used convenient measurement for comparing the relative extent and rate of oxidation in series of related polymer samples. The carbonyl index is determined using mid-infrared spectroscopy. The method is based on determining the absorbance ratio of a carbonyl (vC = 0) band generated as a consequence of oxidation normalised normally to the intensity of an absorption band in the polymer spectrum that is invariant with respect to polymer oxidation. (In an analogous manner, a hydroxyl index may be determined from a determination of the absorbance intensity of a vOH band normalised against an absorbance band that is invariant to the extent of oxidation.) In the text following, two examples of multi-technique studies of polymer oxidation will be discussed briefly each includes a measure of a carbonyl index. 

In addition to the simple chemical methods for following these processes, infrared spectroscopy may also be used. In Fig. 9 is shown the spectrum of silica dried at 200°C before and after reaction with Zr(allyl)4- The characteristic absorption bands of the transition metal-allyl group are clearly displayed, also a significant reduction in the number of hydroxyl groups (3740 cm-1) is also clearly evident. 

Note that in all the examples discussed so far, infrared spectroscopy gives its information on the catalyst in an indirect way, via hydroxyl groups on the support, or via the adsorption of probe molecules such as CO and NO. The reason why it is often difficult to measure the metal-oxide or metal-sulfide vibrations of the catalytically active phase in transmission infrared spectroscopy is that the frequencies are well below 1000 cm-1, where measurements are difficult because of absorption by the support. Infrared emission and Raman spectroscopy, discussed later on in this chapter, offer better opportunities in this respect. 

Using infrared spectroscopy, Yates (299) proved the existence of hydroxyl groups on anatase as well as on rutile. Both forms still contained some adsorbed molecular water after evacuation at 150°, as evidenced by the bending vibration at 1605 cm b After outgassing at 350°, no free water was detected. There remained two OH stretching absorptions in the case of anatase (at 3715 and 3675 cm ) and one weak band at 3680 cm with rutile. This is indication of the existence of two different types of OH groups on anatase. These results were confirmed by Smith (300). 

Glemser and Rieck (317) demonstrated by infrared spectroscopy that most of the aluminum oxides intermediate between the hydroxides and ot-AlaOg contain hydroxyl groups which may be removed reversibly by heating. This result was confirmed by proton magnetic resonance measurements (318). 

Russell, J.D. (1979) Infrared spectroscopy of fer-rihydrite evidence for the presence of structural hydroxyl groups. Clay Min. 14 109—114 Russell, J.D. Parfitt, R.L., Eraser, A.R. Farmer,... 

Thermal analysis, and to a lesser extent infrared spectroscopy, has shown that grinding kaolin reduces the number of structural hydroxyls and increases the amount of sorbed water. However, the infrared studies have been restricted to... 

Infrared Spectroscopy. The spectrum of the solid C showed only weak and unresolved hydroxyl bands (Figure 5). The introduction of CO under an equilibrium pressure of 50 torr did not modify the i>oh bands. After evacuation of the carbon monoxide at room temperature, the IR spectrum showed two bands at 2135 and 2110 cm-1 caused by strongly chemisorbed... 

Few authors considered the reactivity of hydroxyl groups at catalyti-cally interesting temperatures. In situ infrared spectroscopy showed that in the cumene cracking reaction the 3550 cm-1 hydroxyls in a HY sample are only affected above 325° C. The 3650 cm-1 hydroxyl decreased in intensity at 250° C (6). During the cracking of hexane on a similar sample the gradual deactivation of the catalyst is accompanied by the progressive... 

Infrared Spectroscopy. The following bands are seen in the ir spectrum of PPG 2970, 2940, 2880 cm-1 (C—H stretch, m) 1460,1375 cm-1 (C—H bend, m) 1100,1015 cm-1 (C—O stretch, m) of which the 2940 and 1015 band are specific. The latter are also present in copolymers of EO and PO. Absorptions due to unsaturated end groups are found at 1650 cm-1 (allyl ether) and 1672 cm-1 (1-propenyl ether). The O—H stretching band at 3470 cm-1 shows the greatest variation for different hydroxyl number polyols and has been used to estimate the hydroxyl number (169). 

J. Loertscher and F. Weesner, Determination of Hydroxyl Number in Polyols by Mid-Infrared Spectroscopy, Nicolet FT-IR Application Note (AN-9146), Nicolet Instrument Corp. 

Reed 332) has reported that reaction of ethylene oxide with the a,(a-dilithiumpoly-butadiene in predominantly hydrocarbon media (some residual ether from the dilithium initiator preparation was present) produced telechelic polybutadienes with hydroxyl functionalities (determined by infrared spectroscopy) of 2.0 + 0.1 in most cases. A recent report by Morton, et al.146) confirms the efficiency of the ethylene oxide termination reaction for a,ta-dilithiumpolyisoprene functionalities of 1.99, 1.92 and 2.0j were reported (determined by titration using Method B of ASTM method E222-66). It should be noted, however, that term of a, co-dilithium-polymers with ethylene oxide resulted in gel formation which required 1-4 days for completion. In general, epoxides are not polymerized by lithium bases 333,334), presumably because of the unreactivity of the strongly associated lithium alkoxides641 which are formed. With counter ions such as sodium or potassium, reaction of the polymeric anions with ethylene oxide will effect polymerization to form block copolymers (Eq. (80) 334 336>). 

Moffat and Neeleman (139) investigated the adsorption of ammonia on boron phosphate by means of infrared spectroscopy. Ammonia appear to dissociate on this solid. Although absorption bands arising from NH4+ and coordinated ammonia were obtained, the authors feel that the presence of NH + does not necessarily indicate that Br0nsted sites were initially present on the BP04 surface. Hydroxyl groups that might be formed when ammonia dissociates could react with dry ammonia to form NHi+. 

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