Absorption hydroxyl

Hydrolysis of a compound A in dilute aqueous hydrochlonc acid gave (along with methanol) a compound B mp 164—165°C Compound B had the molecular formula CigHig04 it exhibited hydroxyl absorption in its IR spectrum at 3550 cm but had no peaks in the carbonyl region What IS a reasonable structure for compound B" ... 

When levuhnic acid (CH3CCH2CH2CO2H) was hydrogenated at high pressure over a nickel catalyst at 220°C a single product C5Hg02 was isolated in 94% yield This compound lacks hydroxyl absorption in its IR spectrum and does not immediately liberate carbon dioxide on being shaken with sodium bicarbonate What is a reasonable structure for the compound" ... 

The configuration was assigned after oxidation of (43) and (44) to the corresponding 3,20-diketones. The diketone obtained from (44) showed an intramolecular bonded hydroxyl absorption at 3450 cm h Inspection of molecular models indicates that only a 12 -hydroxyl function can form an internal hydrogen bond to the 20-carbonyl group. 

Infrared Hydroxyl Absorption Bands and Hydrogen-bonding Strength (Xv cm ) for Various Sugars and Their Relative Sweetness ... 

Fig. 15.—Hydroxyl Absorption Bands in the Infrared Spectra of Three Free Sugars. ...

The relatively low percentage of ring substitution can be attributed to several side reactions 1,4-addition of Li to 2-cyclopentenone, incomplete dehydration of 4 as evidenced by the presence of a small hydroxyl absorption (3425 cm ) in the IR spectrum of 5, and reduction of the polymer-bound cyclopentadiene in its reaction with Co2(C0)8 (26,27,32). 

Characterization of the donor bound polymers follows from their spectroscopic (ir and uv-vis KBr) properties in comparison with the starting donor monomers, and from elemental analyses. That the donors are covalently bound to the polymer and not present as unreacted monomers can be seen by the absence of the characteristic monomer functional group absorption (i.e. -OH, COzH) in the donor bound polymer. For example in Figure 1, the comparative ir spectra of p-hydroxyphenyl-TTF monomer and this donor covalently bound to linear and to cross-linked polysytrene are given. Except for the presence of the hydroxyl absorption in the monomer, all three spectra are essentially identical, indicating a rather clean polymer attachment reaction. 

Fig. 1. Hydroxyl absorption bands for several smectites pillared with aluminum chlorhydroxide (ACH) soluctions A) Wyoming ACH-bentonite B) Texas ACH-bentonite C) Fe-bentonite D) ACH- Fe bentonite) E) (ACH, Fe)-bentonite and F) ACH-nontronite. Samples a) have been dried at 200 C and then loaded with pyridine and degassed at b) 200 C, c) 300 C, d) 400 C and e) 500 C in vacuo for 2 hours at each temperature.

The shift in the surface hydroxyl absorption band fabout 65 cm ) and the simultaneous presence of an adsorption band at 1623 cm reasonably attributed to vc=c shifted by about 30 cm" in respect to vc=c he gaseous propylene due to the coordination to an unsaturated cation, indicates the formation of propylene coordinated to the surface in the form of a 7t-complex with the CH3 group bonded to a hydroxyl group (9) ... 

An infrared spectrum of a film of peroxide between rock salt plates showed the presence of carbonyl and hydroxyl absorption from decomposition products. There was a wide region of C—O stretching absorption... 

The molecular coefficient for hydroxyl absorption, n , as measured by Avramenko and Kondratiev6 permitted determination of the absolute values for small concentrations of free hydroxyl. 

Avramenko6 specified the value of the hydroxyl absorption molecular coefficient in a form convenient for use in the determination of hydroxyl concentrations under flame conditions. 

It should be mentioned that the described spectroscopic method for determining absolute concentrations of hydroxyl is very reliable. As spectral determinations do not interrupt the reaction course, and as identification of OH by the specific hydroxyl absorption spectrum may be carried out simultaneously, the spectroscopic method should be given preference over other methods. 

The absence of hydroxyl absorption in the reaction of oxygen atoms with hydrocarbons is evidence that oxygen atom reactions did not interfere with studying free-hydroxyl reactions, even if oxygen atoms were pumped out from the discharge zone in water vapor. 

The main feature of the spectra of 3- and 4-chromanols is the hydroxyl absorption band which occurs in the range 3625-3200 cm-1. Some derivatives show two peaks in this region, whilst others exhibit just a single band (70BSF1139, 70JOC2282). 

Nature of acidic sites. The location of the acidic hydroxyl groups in the faujasite structure has been the subject of numerous investigations and much discussion. The results of adsorption experiments with several molecules led Eberly (170) to conclude that the 3550-cm-1 hydroxyl absorption band represented hydroxyl groups located in the hexagonal prisms of the faujasite framework [(Si sites (171)], where they were relatively inac-... 

The spectra of alkaline earth ion-exchanged samples, with the exception of the barium form (211), have hydroxyl absorption bands at 3645 and 3540 cm-1, similar to those found in H—Y zeolite. The barium form behaves like the alkali-exchanged zeolites. The similarity of the spectra of the alkaline earth forms with that of the hydrogen form suggests that the acidic hydroxyls are associated with the same structural features (151). Band frequencies in the region of 3600 to 3560 cm-1 vary with the cations and are thought to result from hydroxyl groups associated with the divalent cations (211). They are weakly acidic or inaccessible to adsorbate molecules since the band intensity is not affected by adsorption of pyridine (209). 

Infrared spectral studies of rare earth (RE) ion-exchanged faujasites have been reported by Rabo et al. (214), Christner et al. (217), Ward (211, 212), and Bolton (218). Distinct hydroxyl absorption bands are observed at 3740, 3640, and 3522 cm-1 after calcination at temperatures in the range of 340° to 450°C. As previously discussed, the hydroxyl groups at 3740 cm-1 are attributed to silanol groups either located at lattice termination sites or arising from amorphous silica associated with the structure. The hydroxyl groups that form the 3522 cm-1 band are nonacidic to pyridine or piperidine and are thought to be associated with the rare earth cations. 

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