Chloroform spectrum

Figure 7. Emission and absorption spectra of IrMe(CO)(PPh3)2(mnt) (46-Me). Spectrum (a) is the electronic absorption spectrum in chloroform spectrum (b) (—) is the emission spectrum with A..vl.

Much more pronounced effects were reported by Sojka (15) who compared the l3C chemical shifts of a number of coumarin derivatives in chloroform and in 96% sulphuric acid and by Yufit et al. (74) for some 4,7-diaminocoumarins in 10-25% and 40% sulphuric acid solutions. For coumarin itself the differences are C-2, 13.2 C-3, -5.3 C-4, 16.5 C-5, 4.3 C-6, 7.1 C-7, 8.0 C-8, 3.4 C-9, 0.6 and C-10, 3.7 ppm, when the data of the chloroform spectrum are subtracted from those in sulphuric acid (15). Even the j(C,H) values are sensitive, and vary up to 16 Hz. These dramatic effects are explained by protonation of the carbonyl group and by considering a different balance of mesomeric forms of the molecule. They are not constant in their magnitude, however, when coumarin is substituted in different positions. 

We will illustrate the process of simple quantitative analysis by using the example of aspirin dissolved in chloroform. The best peak to choose in this example is the C=0 stretching band of aspirin observed at 1764 cm because it is an intense peak and lies in a region where there is no interference from the chloroform spectrum. 

Although no chemical reaction occurs, measurements of the freezing point and infra-red spectra show that nitric acid forms i i molecular complexes with acetic acid , ether and dioxan. In contrast, the infrared spectrum of nitric acid in chloroform and carbon tetrachloride - is very similar to that of nitric acid vapour, showing that in these cases a close association with the solvent does not occur. 

Solutions of dinitrogen pentoxide in nitric acid or sulphuric acid exhibit absorptions in the Raman spectrum at 1050 and 1400 cm with intensities proportional to the stoichiometric concentration of dinitrogen pentoxide, showing that in these media the ionization of dinitrogen pentoxide is complete. Concentrated solutions in water (mole fraction of NgOg > 0-5) show some ionization to nitrate and nitronium ion. Dinitrogen pentoxide is not ionized in solutions in carbon tetrachloride, chloroform or nitromethane. ... 

Figure 13 7 shows the H NMR spectrum of chloroform (CHCI3) to illustrate how the terminology just developed applies to a real spectrum... 

IR spectra can be recorded on a sample regardless of its physical state—solid liquid gas or dissolved m some solvent The spectrum m Eigure 13 31 was taken on the neat sample meaning the pure liquid A drop or two of hexane was placed between two sodium chloride disks through which the IR beam is passed Solids may be dis solved m a suitable solvent such as carbon tetrachloride or chloroform More commonly though a solid sample is mixed with potassium bromide and the mixture pressed into a thin wafer which is placed m the path of the IR beam... 

In the infrared, 2-hydroxycyclobutanone has a carbonyl band at 1780 cm in chloroform solution. Kept in nitrogen-filled screw-capped vials in the freezing compartment of a refrigerator, 2-hydroxyoyolo-butanone slowly but completely solidifies as its dimer. The infrared spectrum of the solid in a KBr disk shows no carbonyl. However, a chloroform solution of the solid does show the characteristic 1780 em band, indicating rapid equilibration with the monomer. 

The infrared spectrum (chloroform) shows bands at 2230 (medium strong), 1348, and 940 (medium) cm. The proton magnetic resonance spectrum (chloroform-d) shows absorption at 3 5.73 and 7.33 (AA XX pattern). 

Dobbie and Tinkler suggested that, sipce hydrastinine in solution in ether or chloroform has an absorption spectrum almost identical with that of hydrohydrastinine, whilst the absorption spectra of its solutions in water or alcohol resemble those of the salts, it may exist in two forms, represented by formula I (solid state or dissolved in ether or chloroform), and II (dissolved in water or alcohol) these conclusions have been confirmed by Steiner. No evidence for the existence of Roser s aldehydic form was obtained. 

FIGURE 13.7 The200-MHz H NMR spectrum of chloroform (HCCb). Chemical shifts are measured along the x-axis in parts per million (ppm) from tetramethylsilane as the reference, which is assigned a value of zero. 

The UV spectrum of 5-phenyl-3 hydroxythiophene is very similar to that of its methyl ether in alcoholic solution, indicating that it exists largely in the enol form in this solvent. The same coincidence of the wavelength maxima was also obtained for 5-phenyl-2-hydroxy-thiophene and its methyl ether. In chloroform solution, the maxima were shifted toward longer wavelengths, suggesting that the tautomeric equilibrium in this solvent is displaced more toward the keto form. ... 

In 1951, Witkop et al. interpreted the infrared spectra of quinol-2-and -4-ones to favor the oxo formulation. Since then, many investigators, especially Mason, have reported that potential a- and y-hydroxy compounds show infrared absorption bands in the vN—H (3500-3360 cm ) and vC—O (1780-1550 cm ) regions of the spectrum and, hence, exist predominantly in the oxo form references to this work appear in Table I. A study of the bands which occur in the NH-stretching region of the infrared spectra of a series of substituted pyrid-2-ones and quinol-2-ones also supported an oxo formulation for these compounds. Detailed band assignments have been published for pyrid-2- and -4-one. Mason has reported that solutions of j8-hydroxy compounds in chloroform or carbon tetrachloride show... 

Hydroxypyridine 1-oxide is insoluble in chloroform and other suitable solvents, and, although the solid-state infrared spectrum indicates that strong intermolecular hydrogen bonding occurs, no additional structural conclusions could be reached. Jaffe has attempted to deduce the structure of 4-hydroxypyridine 1-oxide using the Hammett equation and molecular orbital calculations. This tautomeric compound reacts with diazomethane to give both the 1- and 4-methoxy derivatives, " and the relation of its structure to other chemical reactions has been discussed by Hayashi. ... 

Mason has determined the infrared spectrum of pyrido[3,2-d]-pyrimidin-4(3ff)-one (149, N in position 5) in chloroform solution and as a KBr disc and has suggested that the low frequency of th e NH band (3389 cm ) and high frequency of the C=0 band (1745 cm i) in the solution spectra are indicative of a quasi o-quinonoid form. The infrared spectra of the four pyridopyrimidin-4(377)-ones (149), the four 2,4(ljff,3//)-diones (150), and a number of substituted derivatives, have been determined, as Nujol mulls, in these laboratories. ... 

The tautoraerism of certain difunctional derivatives of l-thia-3,4-diazole has received considerable attention. Pala assigned structure 156 to 2,5-dimercapto-l-thia-3,4-diazole on the basis of infrared spectral data, and Thorn" reached the same conclusion by comparing its ultraviolet spectrum (measured in ethanol) with those of the four possible methylated derivatives. However, the infrared spectrum of a chloroform solution of the parent compound showed bands at 2600-2550 cm indicating an SH group and the probable occurrence of form 157 under these conditions, and this conclusion is supported by the occurrence of SH bands in solid state spectra obtained by Swiss investigators. For a summary of earlier work on these compounds, see reference 187. 

A suspension of 4.00 g (6.75 mmol) of 3, 5 - bis-0-(p-nitrobenzoyl)-2 -deoxy-5-(trifluoro-methyDuridine in 250 ml of methanol was treated with 10 ml of diisopropylamine and refluxed until it had dissolved (about IB minutes), and the solution was concentrated. The dry residue was partitioned between 50 ml of chloroform and 50 ml of water. The chloroform layer was washed with 20 ml of water, and the combined aqueous layers were concentrated. A low ultraviolet extinction ( 7200 and 262 m/U pH 1) and the presence of isopropyl signals in the NMR spectrum (two singlets at 78.73 and B.B5) indicated the dry residue contained diisopropylamine, probably as a salt with the relatively acidic heterocyclic N-H in 14. 

Figure 2. Partial 100 MHz P.M.R. Spectrum of 3,4,6-tri-O-acetyl-v-glucal (1) measured for a chloroform -d solution (A normal spectrum of the Hi and H2 resonances respectively (B) frequency sweep spin-decoupled spectrum of the Hi and H2 resonances, with a strong decoupling field centred on the Hs resonance (C), as in (B) above, but with an additional weak radiofrequency field centred on the high field transition of the H2 resonance (D), as in (B) above, but with a weak radiofreauency field centred on the low field transition...

When the H NMR spectrum of an alcohol is run in dimethyl sulfoxide fDMSO) solvent rather than in chloroform, exchange of the O—H proton is slow and spin-spin splitting is seen between the O-H proton and C-H protons on the adjacent carbon. What spin multiplicities would you expect for the hydroxyl protons in the following alcohols ... 

The PL spectrum and onset of the absorption spectrum of poly(2,5-dioctyloxy-para-phenylene vinylene) (DOO-PPV) are shown in Figure 7-8b. The PL spectrum exhibits several phonon replica at 1.8, 1.98, and 2.15 eV. The PL spectrum is not corrected for the system spectral response or self-absorption. These corrections would affect the relative intensities of the peaks, but not their positions. The highest energy peak is taken as the zero-phonon (0-0) transition and the two lower peaks correspond to one- and two-phonon transitions (1-0 and 2-0, respectively). The 2-0 transition is significantly broader than the 0-0 transition. This could be explained by the existence of several unresolved phonon modes which couple to electronic transitions. In this section we concentrate on films and dilute solutions of DOO-PPV, though similar measurements have been carried out on MEH-PPV [23]. Fresh DOO-PPV thin films were cast from chloroform solutions of 5% molar concentration onto quartz substrates the films were kept under constant vacuum. 

The purity and the depth of the color of phthalocyanines arise front an isolated band (Q band) in the far-red end of the visible spectrum of light near 670 nm, with a molar absorption often exceeding 10s cm2 mol-1.77 321 A second absorption (B band), near 340 nm, extending to the blue of the visible spectrum is generally much less intense. Absorption spectra of 1,4-oc-tahcxyl-substitutcd PcNi322 and 1,4-octahexyl-substituted PcH2,323 both dissolved in chloroform, are shown below. 

Properties of panal (Nakamura etal., 1988a). Purified panal is a colorless, amorphous solid, soluble in alcohols, water, ethyl acetate, and chloroform. The absorption spectrum (Fig. 9.3) shows a single peak (A.max 217nm, e 15,300). Optical rotation [a]D —17° (c 0.9, methanol). Mass spectrometry and NMR analysis showed that panal is a sesquiterpene aldehyde, C15H18O5 (Mr 278.30), with the structure shown below. 

---