Hydroxyl IR

The acid-base properties of decationated ZSM-5 zeolite have been studied in some detail using adsorption microcalorimetry, as shown in Table VIII (169-173). As the calcination temperature for HZSM-5 zeolites was increased from room temperature to 1073 K, a maximum in acidity was observed while the initial differential heat of ammonia adsorption increased continuously. Vedrine et al. (92) also found a maximum in the intensity of the IR hydroxyl bands (169) of HZSM-5 at 673 K. The IR absorption band of pyridine adsorbed on Brpnsted sites followed the same trend as that found for the hydroxyl stretching bands, confirming that above 673 K the Bronsted acidity decreased as the dehydration temperature increased. 

IR hydroxyl peak shifts have proven to be a convenient method for evaluatir site-specific interactions. IR peak shifts showed to be usefid tool to detect acid-base interactions between probe acids and model molecules containing carbonyl and other basic groiqrs. The calculated Drago constants based on OH peak shifts diowed to be more consistent widi literature data thoi constants derived from carbotQd peak drifts. Such constants allow the prediction of the strengdi of acid-base interaction. 

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" ... 

Infrared The IR spectra of phenols combine features of those of alcohols and aro matic compounds Hydroxyl absorbances resulting from O—H stretching are found m the 3600 cm region and the peak due to C—O stretching appears around 1200-1250 cm These features can be seen m the IR spectrum of p cresol shown m Figure 24 3... 

The hydroxyl number can be deterrnined in a number of ways such as acetylation, phthalation, reaction with phenyl isocyanate, and ir and nmr methods. An imidazole-catalyzed phthalation has been used to measure the hydroxyl number for a number of commercial polyether polyols and compared (favorably) to ASTM D2849 (uncatalyzed phthalation) (99). The uncatalyzed method requires two hours at 98°C compared to 15 minutes at the same temperature. 

The UV spectra of quinoxalines have been examined in several solvents. In cyclohexane, three principal absorptions are observed (Table 2). In hydroxylic solvents the vibrational fine structure disappears and in methanol or water the weak n- ir transitions are obscured by the intense ir->ir transition (79HC(35)l). 

Beyer synthesis, 2, 474 electrolytic oxidation, 2, 325 7r-electron density calculations, 2, 316 1-electron reduction, 2, 282, 283 electrophilic halogenation, 2, 49 electrophilic substitution, 2, 49 Emmert reaction, 2, 276 food preservative, 1,411 free radical acylation, 2, 298 free radical alkylation, 2, 45, 295 free radical amidation, 2, 299 free radical arylation, 2, 295 Friedel-Crafts reactions, 2, 208 Friedlander synthesis, 2, 70, 443 fluorination, 2, 199 halogenation, 2, 40 hydrogenation, 2, 45, 284-285, 327 hydrogen-deuterium exchange, 2, 196, 286 hydroxylation, 2, 325 iodination, 2, 202, 320 ionization constants, 2, 172 IR spectra, 2, 18 lithiation, 2, 267... 

In order to obtain paromomycin In free base form, the hydrochloride is dissolved in water as a 3% solution, the solution Is poured into an adsorption column containing an anion exchange resin (Amberlite IR-45 or preferably IRA-411 or IRA-400) in the hydroxyl form and the column is washed with a small amount of water. 

Primary and secondary amines can be identified by a characteristic N—H stretching absorption in the 3300 to 3500 cm"1 range of the IR spectrum. Alcohols also absorb in this range (Section 17.11), but amine absorption bands are generally sharper and less intense than hydroxyl bands. Primary amines show a pair of bands at about 3350 and 3450 cm-1, and secondary amines show a single band at 3350 cm-1. Tertiary amines have no absorption in this region because they have no N-H bonds. An IR spectrum of cyclohexylamine is shown in figure 24.7. 

In an effort to make productive use of the undesired C-13 epimer, 100-/ , a process was developed to convert it into the desired isomer 100. To this end, reaction of the lactone enolate derived from 100-) with phenylselenenyl bromide produces an a-selenated lactone which can subsequently be converted to a,) -unsaturated lactone 148 through oxidative syn elimination (91 % overall yield). Interestingly, when 148 is treated sequentially with lithium bis(trimethylsilyl)amide and methanol, the double bond of the unsaturated lactone is shifted, the lactone ring is cleaved, and ) ,y-unsaturated methyl ester alcohol 149 is formed in 94% yield. In light of the constitution of compound 149, we were hopeful that a hydroxyl-directed hydrogenation52 of the trisubstituted double bond might proceed diastereoselectively in the desired direction In the event, however, hydrogenation of 149 in the presence of [Ir(COD)(py)P(Cy)3](PF6)53 produces an equimolar mixture of C-13 epimers in 80 % yield. Sequential methyl ester saponification and lactonization reactions then furnish a separable 1 1 mixture of lactones 100 and 100-) (72% overall yield from 149). 

Table IV presents the results of the determination of polyethylene radioactivity after the decomposition of the active bonds in one-component catalysts by methanol, labeled in different positions. In the case of TiCU (169) and the catalyst Cr -CjHsU/SiCU (8, 140) in the initial state the insertion of tritium of the alcohol hydroxyl group into the polymer corresponds to the expected polarization of the metal-carbon bond determined by the difference in electronegativity of these elements. The decomposition of active bonds in this case seems to follow the scheme (25) (see Section V). But in the case of the chromium oxide catalyst and the catalyst obtained by hydrogen reduction of the supported chromium ir-allyl complexes (ir-allyl ligands being removed from the active center) (140) C14 of the...

Intramolecular hydrogen bonds between sulphinyl or sulphonyl groups and hydroxyl groups have also been described106,107. The IR shifts Vjq in these experiments were found at around 1005-1010cm 1108 U0. Several other papers which describe hydrogen bonds of sulphoxides and sulphones are given in References 111-120. 

Four IR absorption bands have been identified in the spectrum of the hydroxysulfonyl radical (HOSO 2) which has been obtained by the reaction of hydroxyl radicals with sulfur dioxide in argon matrix at 11 K16. The observed bands at 3539.9 and 759.5 cm 1 have been assigned to O—H and S—OH stretching modes while the bands at 1309.2 and 1097.3 cm-1 have been assigned to the asymmetric and symmetric stretching modes of the double bonded S02 moiety. These data are consistent with the theoretical prediction on the geometry of the hydroxysulfonyl radical12. 

Morterra and Low109,110 proposed that thermal crosslinking may occur between 300°C and 500°C where phenolic hydroxyl groups react with methylene linkages to eliminate water (Fig. 7.43). Evidence for this mechanism is provided by IR spectra which show decreased OH stretches and bending absorptions as well as increased complexity of the aliphatic CH stretch patterns in this temperature range. 

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