Aromatic compounds infrared spectra

Infrared The IR spectra of phenols combine features of those of alcohols and aromatic compounds. Hydroxyl absorbances resulting from O—H stretching are found in the 3600-cm region, and the peak due to C—O stretching appears around 1200-1250 cm . These features can be seen in the IR spectrum of p-cresol, shown in Figure 24.3. 

Infrared radiation, electromagnetic spectrum and, 419, 422 energy of. 422 frequencies of, 422 wavelengths of, 422 Infrared spectroscopy, 422-431 acid anhydrides, 822-823 acid chlorides, 822-823 alcohols. 428, 632-633 aldehydes, 428. 730-731 alkanes, 426-427 alkenes, 427 alkynes, 427 amides. 822-823 amines, 428, 952 ammonium salts, 952-953 aromatic compound, 427-428, 534 bond stretching in, 422... 

The presence of a phenyl group in a compound can be ascertained with a fair degree of certainty from its infrared spectrum. For example, in Figure 22-1 we see the infrared spectra of methylbenzene, and of 1,2- 1,3-, and 1,4-dimethylbenzene. That each spectrum is of a benzene derivative is apparent from certain common features. The two bands near 1600 cm-1 and 1500 cm-1, although of variable intensity, have been correlated with the stretching vibrations of the carbon-carbon bonds of the aromatic ring also, the sharp bands near 3030 cm-1 are characteristic of aromatic C-H bonds. Other bands in the... 

These compounds are suggested if sulphur is present. If nitrogen is also present the compound may be an aminosulphonic acid. The infrared spectrum will show absorption at 3400-3200 cm -1 (OH str.) and 1150 and 1050 cm-1 (S=0 str. in a sulphonic add) or at 1090cm-1 (S=0 str. in a sulphinic acid). For derivative preparations for sulphonic acids see Section 9.6.26, p. 1284. The presence of an aromatic sulphinic add may be further confirmed by dissolving in cold concentrated sulphuric add and adding one drop of phenetole or anisole when a blue colour is produced (Smiles s test), due to formation of a para-substituted aromatic sulphoxide. The reaction is ... 

Bis[dihydrobis(l-pyrazolyl)borato]nickel(II), m.p. 181-182°C., forms well-shaped orange crystals, readily soluble in methylene chloride, chloroform, and aromatic hydrocarbons. The latter are preferred since polyhalogenated hydrocarbons react slowly with this compound at room temperature and rapidly in hot solutions. Its infrared spectrum exhibits a complex BH2 multiplet in the 2200-2500-cm.-1 region. 

Products of the Reaction. A solution containing 5 X 10"2 mole/liter hydroperoxide and 2 X 10"2 mole/liter dilauryl thiodipropionate was allowed to react at 70 °C. until no hydroperoxide remained. A brown resinous precipitate was formed which was filtered, washed, and dried in vacuo. The infrared spectrum of the solid revealed the presence of —O—SOo— groups and the presence of an ortho-substituted aromatic compound, but no further details of its constitution could be obtained. This precipitate was not formed in the kinetic experiments which had a... 

The vapor pressure of /i-[(CH3)2N]B2H5 obeys the relationship log P = 2158.56/T + 1.75 log T - 0.008061T + 7.518831 (101 torr at 0°). The gas-phase infrared spectrum has been reported in detail.5 The compound is a useful intermediate in the synthesis of other boron nitrogen compounds, including those containing NBNB6 and PBNB7 chains, and Na[(CH3)2-N(BH3)2].8 The compound can be stored at 25° for months in sealed, evacuated Pyrex tubes. It is soluble in ethers and aromatic hydrocarbons, but is attacked by protic solvents. 

The absorption bands in the ultraviolet and visible part of the spectrum correspond to changes in the energy of the electrons but simultaneously in the vibrational and rotational energy of the molecule. In this way a system of bands is produced in the gaseous state. In the liquid state there is nothing of the rotational fine structure to be seen, and usually little or nothing of the vibrational structure, as a result of the interaction with the molecules of the solvent. With aromatic compounds in non-polar solvents such as hexane and carbon tetrachloride the vibrational structure is, however, still clearly visible in the ultraviolet absorption spectrum. This vibrational structure is mainly determined by the vibrations of the excited state, which therefore do not occur in the infrared and Raman spectrum of the normal molecule. 

This moderately air-sensitive niobium salt is soluble in a wide variety of solvents, such as aromatic hydrocarbons, ethers, ketones, alcohols, and water, to give very air-sensitive solutions. The solid is also somewhat light-sensitive and should be stored in the dark. It is indefinitely stable at room temperature under nitrogen. The infrared spectrum of the compound in the carbonyl region is given in Table I. 

Chlorotris(//-cyclopentadienyl)uranium(IV) is an oxygen-sensitive brown solid. It can be handled in air for brief periods of time with minimal oxidation, which is evidenced by darkening of the color. The compound is soluble in ethereal and aromatic solvents but only sparingly soluble in aliphatic hydrocarbons. Solutions are exceedingly air-sensitive. The nmr spectrum in benzene exhibits a sharp singlet 9.6 ppm to high field of the solvent (r 12.4). The infrared spectrum (Nujol mull) exhibits typical 7t-cyclopentadienyl bands at 1013 (m) and 784 (s) cm i. Oxidation is evidenced by the appearance of the antisymmetric v(OUO) stretch of the uranyl group at 930 cm-i. 

The mass spectrum gives us the formula (CJ3H16O3), which looks like an aromatic compound as there are so few hydrogens, and the base peak at M - 15 suggests that a methyl group is lost rather easily. The infrared suggests that all three oxygen atoms are present as ethers. The NMR shows us these details ... 

Infrared spectrum The broad peak at 3500 cm is OH thymol must be an alcohol. The peak at 1620 cm suggests an aromatic compound. 

To get an idea of such a prediction process, we will look at a result for the prediction of a monosubstituted benzene derivative. The data set for this experiment contains 50 benzene derivatives and their spectra-descriptor pairs. Figure 6.5 shows the infrared spectrum of the query compound reduced to 128 components by the FHT method described already. The spectrum contains some bands that may indicate the existence of an aromatic system and of halogen atoms. However, the spectrum is not particularly characteristic. 

FIGURE 6.5 The infrared spectrum of a query compound compressed by Hadamard transform for the prediction of benzene derivatives by a CPG neural networks. The spectrum exhibits some typical bands for aromatic systems and chlorine atoms. 

Aromatic compounds also show characteristic infrared and ultraviolet absorption spectra. In the mass spectrum of aromatic substances, peaks corresponding to ions such as CgH and CgHg" are often seen. A commonly observed peak occurs at m/z 91, corresponding to the stable ion CgHgCH./, These features are all helpful in assigning aromatic character. 

The most important samples for analysis by infrared spectroscopy for crude oil chemists are organic substances. For organic molecules, the infrared spectrum can be divided into three important regions. First is the absorption of infrared radiation within the wave number range of 4000 and 1300 cm 1 which is caused by functional groups and different bond types. Second is the absorption between 1300 and 909 cm 1 that is typical for more complex interactions in the molecules. And last is the absorption between 909 and 650 cm 1, which is usually associated with the presence of aromatic compounds in the sample. 

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