Ether infrared absorption

Synthesis of Perfluoro(4-Carbomethoxybutyl Vinyl Ether). The parent ester was prepared from perfluoroglutaryl fluoride and hexa-fluoropropylene oxide by the reactions shown in Figure 2. This ester had a boiling point of 146 °C, and showed characteristic vinyl ether infrared absorptions at 5.42/, 5.55/. (carbonyl group), and 10.0/. (-OCH3 group). 

Dipropyl ketoxime (heptan-4-one oxime). Heat a mixture of 20 g (0.18 mol) of heptan-4-one, 17 g (0.25 mol) of hydroxylamine hydrochloride, 19.6 g (20 ml, 0.25 mol) of pyridine and 150 ml of ethanol under reflux for 1 hour in a 500-ml round-bottomed flask. Rearrange the condenser for downward distillation and remove the ethanol on the water bath. Allow the residue in the flask to cool and add 150 ml of water. Extract the oxime with three 50 ml portions of ether. Wash the combined extracts with water and dry over magnesium sulphate. Remove the ether on the rotary evaporator and distil the residue at atmospheric pressure. Collect the fraction having b.p. 192-195 °C the yield is 18.2g (80%). The oxime shows infrared absorptions at 3300 cm-1 (O—H stretch) and 1655 cm-1 (C=N stretch). 

The butadiene (80%)-acrylonitrile(17%)-aerylamidoxime(3%) terpolymer was prepared by reacting 2.5g butadiene 80%)-acrylo-nitrile(20%) copolymer (Aldrich) in 150 ml xylene with 1.61g hydro-xylamine hydrochloride in 12 ml n-butanol (freed of HC1 immediately before addition by method of Hurd (4) by dropwise addition under nitrogen. Reaction time and temperature were 23 hr. and 90-95°C. The polymer product was worked up by slowly adding the reaction mixture to 500 ml ether with rapid stirring. The precipitated polymer was allowed to settle, the supernate decanted and the polymer resuspended and washed with two 100 ml portions of ether followed by vacuum drying. Yield 2.04g (81%). Conversion of nitrile functional groups to amidoxime groups was 15% by infrared absorption. 

Brown, A.C., Canosa-Mas, C.E., Parr, A.D., Wayne, R.P (1990) Laboratory studies of some halogenated ethanes and ethers measurements of rates of reaction with OH and of infrared absorption cross-sections. Atmos. Environ. 24A, 2499-2511. 

Potutkin and associates (14) report changes in the lignin isolated from hot-pressed particleboards compared to that from raw birchwood from which the boards were made. Lignin isolated from boards pressed at 180C showed increased infrared absorption at 800 cirri and 1300-1500 cm"1, which is interpreted to indicate condensation and demethoxylation, respectively. An appearance of a new band at 1370 cm""1 is assigned to aryl-alkyl ether bonds formed by reactions of lignin with other wood breakdown products to yield pseudolignin. 

Independent synthesis of the crystalline amide LXVII established its identity and its configurational relationship to L-(+)-mandelic acid. The latter acid was converted to ethyl L-(+)-mandelate (LXVIII), and the ether linkage introduced by reaction with ethyl bromoacetate in the presence of silver carbonate, under conditions such that Walden inversion was impossible. The resulting ethyl D-(+)-2-phenyldiglycolate (LXVI), was subjected to ammonolysis, giving a crystalline product, m. p. 174-174.5°, [a]26D 106.2°. This showed no mixed melting point depression and an identical infrared absorption spectrum with the sample of LXVII obtained from /3-D-xylopyranosylbenzene. The enantiomorphic l-(—)-2-phenyldiglycolamide was also prepared by identical synthetic steps from d-( —)-mandelic acid. 

According to the British Pharmacopoeia 2002 [2] and Indian Pharmacopoeia [6], mefenamic acid in capsule and tablet preparations are identified by examination using infrared absorption spectrophotometry as the following procedure. Extract a quantity of the capsule contents (or powdered tablets) containing 0.25 g of mefenamic acid with two 30 mL quantities of ether. Wash the combined extracts with water, evaporate to dryness on a water bath, and dry the residue at 105°C. Dissolve a sufficient quantity in the minimum volume of absolute ethanol, and evaporate to dryness on a water bath. The infrared absorption spectrum is concordant with the reference spectrum of mefenamic acid. 

Infrared absorption data for the compounds considered have been reported more often. Absorption of such vinyl ethers as 150a at 5.9-6.9 /xm corresponds to the vinylic fragment.28 33,86 Additional bands in the spectrum of 151 at 10.7 /am (Ref. 33) and of 152 at 10.18 /am (Ref. 86) show the presence of trans isomers. Alkene absorption of vinylthio ethers was observed29 83 84 between 6.1 and 6.2 /am, the upper limit corresponding83 84 to absorption by a terminal olefinic bond in such compounds as 154a or 159. 

Bromobis[2,3-butanedione dioximato( 1 -)] (4-terf-butylpyridine)cobalt(lIl) is a tan, microcrystalline solid with greatly enhanced solubility in organic solvents compared to the chloro(pyridine) analogue. It is also the compound of choice in preparing alkylcobaloximes by the subsequent procedure because of the ease of isolation of the resultant products. In addition, the bromo(4-ferf-bupy) species react directly with electron-rich olefins, such as ethyl vinyl ether, in the presence of ethanol to yield, in this case, bis[2,3-butanedione dioximato(l-)]-(2,2-diethoxyethyl)(pyridine)cobalt(III).1J Conversion of the dimethyl sulfide compound to the pyridine derivatives is readily detected by a characteristic infrared absorption at 1600 cm 1 (pyridine stretch). The H nmr spectrum of bromobis[2,3-butanedione dioximato(1 -)] (4-ferf-butylpyridine)cobalt (III) has absorptions in the alkane region in the ratio of 3 4 at 6 1.25 ppm [Py—C (CH3)3 ] and 6 2.43 ppm (dh—CH3) from tetramethylsilane. 

The other compound, called Zl, which was much more acid-labile, was hydrolyzed to equimolar amounts of pyruvate and shikimate, and was tentatively assigned the structure of shikimate 3- or 5-enolpyruvate ether. In a more recent study, it was found that the barium salt of Zl does not absorb in the carbonyl region of the infrared absorption spectrum (no ester structure), and that it has a strong band at 8.2iu characteristic of a vinyl ether. It is oxidized very rapidly by periodate, giving rise to an unstable compound with maximum absorption at 235 m i ( = 4000). A similar unstable chromophore, most likely having the structure XVII, was produced by periodate oxidation of shikimate 3-phosphate but not of shikimate 5-phosphate. (3-Methyl-crotonaldehyde shows Xm 235, t = 6700. ) These observations suggest that Zl is shikimate 3-enolpyruvate ether (XVIII). 

The synthesis of the allyl ethers in nitrogen heterocyclic systems presents an element of complication in that the allylation could occur on the oxygen atom or the basic nitrogen atom. This is a feature of alkylation of ambident anions.3 However, this applies only when the allylation is effected by reacting the oxo or hydroxy derivative of the compound with an allyl halide in the presence of a base.3 The alternative method is to react the appropriate halo derivative with sodium allyloxide in allyl alcohol. The latter approach provides not only better yields of the allyl ethers but also certainty of the constitution of the ethers obtained. A diagnostic tool in deciding between the 1-allyl derivative and the O-allyl compound that has commonly been employed is the infrared absorption of the amide carbonyl in the case of the former which is clearly absent in the latter. 

Molecules which are capable of undergoing conversion to an i.somer of similar thermodynamic stability via a low activation barrier (>10 kJ mol ) may be quenched in a matrix which has the composition of the vapor prior to deposition. The distribution of isomers in a matrix can be influenced by changing the temperature of a heated nozzle. By analyzing the intensities of relevant infrared absorptions, the molar ratio between two conformers can be determined as a function of the gas temperature. On this basis, the enthalpy difference between the two forms can be obtained by a van t Hoff plot. On the basis of matrix studies for the conversion of the s-cis to the s-gauche form of methyl vinyl ether, a value of AH = 6.62 kJ mol was found (Gunde et al., 1985). 

The hydrogen-bonding group of each polymer has been taken as equivalent to that of the parent mononrer. (The hydrogen-bonding tendency can be assigned qualitatively in the order alcohols > ethers > ketones > aldehydes > esters > hydrocarbons or setniquantitatively from infrared absorption shifts of CH rOD in a reference solvent and in the liquid of interest (7J.)... 

Relative basicities of cyclic ethers have been determined by several methods [146,152,153]. By one method Wirth and Slick [152] obtained relative basicities by infrared from a study of the equilibrium constant at 27°C for the distribution of BF3 between two ethers in benzene solution. In another case, Yamashita et al. [146], following a method similar to that of Gordy and Stanford [154], measured the infrared absorption spectra of cyclic ethers in the presence of 0.1 mole r methanol-d. They then calculated the basicity of the monomers from the shift value of O—D stretching band. Nuclear magnetic resonance measurements of the equilibrium constant between BF3. Et O and the cyclic ether were also used [146]. 

The ether layer is washed successively with 5% hydrochloric acid, 5% sodium carbonate aqueous solution and water, and then dried over sodium sulfate. Upon evaporation of ether, the residue is subjected to fractional distillation in vacuo, thereby to yield 8.9 g. of N-methyl linseed oil fatty acid amide, B.P. 178-190° C./0.03 mm. Hg, I.R. 1,650 cm.-l. (I.R. means wave number of the infrared absorption spectrum.)... 

Attenuated total reflectance infrared spectroscopy was employed to determine the possible chemical modification of the PVC specimen exposed to t-butyl alcohol and methyl t-butyl ether. Infrared spectroscopy has been used to study solvent absorption (17), oxidation (18) and other degradation reactions of polymers (19). In the studies of the hostile effects of methyl t-butyl ether and acetone, the solvent was concentrated and examined using conventional infrared techniques. 

To ensure that photolysis is the only loss process for the aldehyde experiments can be carried out in the presence of an excess concentration of a radical scavenger such as cyclohexane. In cases where the high concentration of a scavenger is undesirable, e.g. because it causes saturation in the infrared absorption spectrum, a tracer compound, such as di-n butyl ether, can be used to correct for the measured decay of the aldehyde in order to obtain the j value. Typical starting concentrations used in photolysis experiments at EUPHORE are [aldehyde] = 0.5-1.5 ppmv, [scavenger] = 10-50 ppmv or [tracer] = 0.1-02. ppmv (Wenger et ai, 2004 and Magneron et al, 2002). 

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