Spectrum methylene chloride

Quinoxalin-2-ones are in tautomeric equilibrium with 2-hydroxy-quinoxalines, but physical measurements indicate that both in solution and in the solid state they exist as cyclic amides rather than as hydroxy compounds. Thus quinoxalin-2-one and its A -methyl derivative show practically identical ultraviolet absorption and are bases of similar strength. In contrast, the ultraviolet spectra of quinoxalin-2-one and its 0-methyl derivative (2-methoxyquinoxaIine) are dissimilar. The methoxy compound is also a significantly stronger base (Table II). Similar relationships also exist between the ultraviolet absorption and ionization properties of 3-methylquinoxalin-2-one and its N- and 0-methyl derivatives. The infrared spectrum of 3- (p-methoxy-benzyl)quinoxalin-2-one (77) in methylene chloride shows bands at 3375 and 1565 cm" which are absent in the spectrum of the deuterated... 

B) Acylation of 6-Aminopenicillanic Acid To a solution of the aryl halocarbonyl ketene (0.1 mol) in methylene chloride (sufficient to provide a clear solution and generally from about 5 to 10 ml per gram of ketene) there is added the proper alcohol RjOH (0.1 mol), in this case 5-indanyl alcohol. The reaction mixture is maintained under an atmosphere of nitrogen and stirred for a period of from 20 minutes to 3 hours, care being taken to exclude moisture. The temperature may range from about -70° to about -20°C. The infrared spectrum of the mixture is then taken to determine and confirm the presence of the ketene ester. A solution of 6-aminopenicillanic acid-triethylamine salt (0.1 mol) in methylene chloride (50 ml) is added and the mixture stirred at -70° to -20°C for 10 minutes. The cooling bath is then removed and the reaction mixture stirred continuously and allowed to warm to room temperature. 

The Na salt of MEDINA was fluorinated in w, the sain extd with methylene chloride, and the solv evapd to give a yellow oil whose IR spectrum showed absence of NH and the presence of NF absorption, and analysis indicated was a mixt (Ref 22). Nitramines in the presence of sulfuric acid are capable of nitrating reactive aromatic compds, but when acetanilide was treated with MEDINA in the presence of this acid, no nitroacetanilide was isolated. Instead compds indicating that the MEDINA had been fragmented and the fragments reacted with the acetanilide were isolated (Ref 12)... 

A proton decoupled 13C NMR spectrum of the resin-peptide sample swollen in methylene chloride is shown in Figure A. The spectrum obtained in DMF is quite similar. The strong line at 175 ppm is from the lie carbonyl, and the six intense resonances between 60 and 10 ppm are due, in order of increasing field to the... 

The spectrum was run in 10% methylene chloride in carbon tetrachloride with use of benzoic acid as an internal standard, using the N-CH3 protons of methimazole at 3.566 and the aromatic protons of benzoic acid at 7.5 and 8.136 as criteria for analysis (29). 

When a solution is tested, both analyte and solvent absorption bands will be present in the spectrum, and identification, if that is the purpose of the experiment, is hindered. Some solvents have rather simple IR spectra and are thus considered more desirable as solvents for qualitative analysis. Examples are carbon tetrachloride (CC14, only C-Cl bonds), choloroform (CHC13), and methylene chloride (CH2C12). The infrared spectra of carbon tetrachloride and methylene chloride are shown in Figure 8.21. There is a problem with toxicity with these solvents, however. For quantitative analysis, such absorption band interference is less of a problem because one needs only to have a single absorption band of the analyte isolated from the other bands. This one band can be the source of the data for the standard curve since the peak absorption increases with increasing concentration (see Section 8.11 and Experiment 25). See Workplace Scene 8.2. 

Much chemistry, perhaps most chemistry, is carried out not in the gas phase, but in solution. A wide variety of solvents are available to chemists. At one end of the spectrum is water which is both highly polar and highly structured. Water is unique among common solvents in that it is capable of forming hydrogen bonds to both (proton) donors and acceptors. At the other end of the spectrum are hydrocarbons such as decane, and relatively non-polar molecules such as methylene chloride. In the middle are a whole range of solvents such as tetrahydrofuran which differ both in their polarity and in their ability to act either as hydrogen-bond donors or acceptors. 

Stade observed an interesting oxidation with tetrachloro-p-benzoquinone. In methylene chloride an intense red coloration appears, but no signal in the ESR spectrum. Apparently only a charge-transfer complex 61 is formed, without electron transfer. A similar observation has been made in the reaction of N, N, N, N -tetramethyl-p-phenylenediamine with tetrachloro-p-benzoquinone in non-polar solvents Here, as in our case, electron transfer does not take place until a polar solvent such as acetonitrile is added. The ESR spectrum initially shows the doublet of 55 (23,2 Gauss) overlapping with the sharp sin et of tetrachloro-semi-quinone 62 (which has a somewhat smaller g factor). The semiquinone signal slowly disappears until finally only the doublet of 58 remains. The following scheme summarizes the reaction course ... 

Treatment of cyclopropane 1 with one equivalent of dry BiCl3 in methylene chloride results in an exothermic reaction producing monoakylbismuth derivative 16 in 80% yield Eq. (19) [11]. Addition of another equivalent of the cyclopropane then affords the dialkylated bismuth species 17, which in turn reacts with BiCl3 to give the monoalkyl species. IR absorptions due to the carbonyl groups indicate the chelate structures shown. The two propionate moieties in the dialkylated compound 17 give rise to two distinctive carbonyl bands in the IR spectrum,... 

Graves, R.J., Trueman, P, Jones, S. Green, T. (1996) DNA sequence analysis of methylene chloride induced HPRT mutations in CHO cells comparison with the mutation spectrum obtained for 1,2-dibromomethane and formaldehyde. Mutagenesis, 11, 229-233... 

Specific examples illustrate that similar principles affect the absorption spectra. For example, as we have pointed out above, the neutral form of the C-2 benzyl ester is red in MeOH and orange in methylene chloride. Thus it has the spectrum of the ionized form in the polar, protic solvent and of the nonionized form in the nonpolar solvent methylene chloride [248]. The tributyl ammonium salt of the C-2 octyl ester is soluble in solvents ranging from ethanol-water to toluene. Its spectrum in an essentially nonionizing solvent such as toluene is that of the ionized xanthene [249], The spectrum of the pyrillium salt in ethanol is concentration dependent. In dilute solution the compound is totally ionized and is red, whereas in concentrated solution the compound is not fully ionized and the orange form predominates, as predicted by the law of mass action. 

As expected, the 15N spectrum of [Fe2S2(,5NO)4]2 consists of a singlet, as all the nitrosyl ligands are equivalent (63). However, in methylene chloride solution, [Fe2S2(NO)4]2 is rapidly and cleanly converted to [Fe4S3(NO)7], which is then the sole species detectable in solution using 15N NMR (25, 63) and by-products remain uncharacterized. 

The UV spectrum of the 3-oxide in ethanol exhibits maxima at 254 nm (e = 19300) and 320 nm (e = 3000), the latter appearing as a shoulder. On irradiation (A = 250 nm, in methylene chloride), benzo-nitrile and phenyl isothiocyanate are formed in 65% and 3% yields, respectively. A similar result is obtained on photolysis of 5-phenylthiatri-azole (Section III, C). The major part of the products was shown to be formed from the singlet excited state.23... 

At —80° a yellow precipitate is obtained, which on heating evolves the gases. An infrared spectrum of a 1% solution in methylene chloride at —80° indicates, in striking contrast to the formation of ordinary... 

The homopolymer of DMP dissolves readily in methylene chloride but precipitates on standing as a crystalline polymer-CH2Cl2 complex, providing a method for distinguishing between block copolymers and mixtures of homopolymers. Random copolymers prepared by methods a and b form stable solutions in methylene chloride. Copolymers with a 1 1 ratio of DMP and DPP prepared by methods c and d also yield stable methylene chloride solutions. Since the NMR spectrum shows that the DMP portion of these materials is present as a block and the solubility in methylene chloride shows that DMP homopolymer is absent, these copolymers have the block structure. They can be separated by crystallization from m-xylene into an insoluble DPP-rich fraction and a soluble DMP-rich fraction, both fractions having the NMR spectra characteristic of block copolymers. A typical 1 1 copolymer prepared by adding DMP to growing DPP polymer yielded 35% of insoluble material... 

Oxidation of a mixture of equivalent weights of the two low-molecular-weight homopolymers at 25°C with a diethylamine-cuprous bromide catalyst yielded a copolymer that formed stable solutions in methylene chloride and could not be caused to crystallize by stirring with a 3 1 methanol/toluene mixture, a procedure that results in crystallization of DMP homopolymer or of the DMP portion of DMP-DPP block copolymers. The NMR spectrum was identical with that of the polymer obtained by simultaneous oxidation of the two monomers. 

Every polymer, no matter what the rose bengal concentration, shows a maximum absorption for the rose bengal moiety at 571-2 nn when the spectrum is taken in a non-polar solvent such as methylene chloride. RB benzyl ester, on the other hand, shows a maximum absorption at 564 nm in MeOH. This phenomenon is explained by a relatively large influence of hydrogen bonding solvents on the absorption maxima. The absorption maximum of RB benzyl ester (essentially a monomeric rose bengal polymer unit) in different solvents was measured. The positions of the absorption maxima, as a function of solvent, are shown in Thble IV. 

The allenes bearing four tert-butyl or four trimethylsilyl groups at the terminal carbons react in methylene chloride with antimony pentachloride. The cation radicals formed contain an unpaired electron delocalized along the neighbouring -rr-bonds. The conclusion is based on the analysis of 1H, 13C, and 29Si ESR spectra (Bolze et al. 1982) as well as on photoelectron spectra (Elsevier et al. 1985 Kamphius et al. 1986). These data have found corroboration in a recent study (Werst Trifunac 1991). The tetramethylallene cation radical spectrum was observed by fluorescent-detected magnetic resonance. The well-resolved multiplet due to this cation radical consists of a binomial 13-line pattern owing to 12 equivalent methyl protons. This is in full accord with Scheme 3-60. 

The extent of sulfonation of 8% crosslinked styrene divinylbenzene co-polymer beads (Biorad Bio Bead SX 8) was investigated by comparing the surface composition after sulfonation of the beads using chlorosulfonic acid, sulfuric acid and fuming sulfuric (54). Each reagent was refluxed in methylene chloride for a similar period of time. A wide-scan spectrum indicates the presence of sulfur 2p and 2s electrons, indicative of sulfonation. The surface sulfur content was fairly similar in the surface region analyzed by XPS. The composition determined from beads sulfonated by the three methods is indicated in Table VI. 

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