IR and MS spectra

More recently, the esterification of oxadiazolinone 89 by 4-dimethylaminobenzoic acid in dry CH2CI2 in the presence of dicyclohexylcarbodiimide (DCC) was described to afford compound 90 (70%). The structure of the product was based on NMR, IR, and MS spectra <2000JLR545>. No other similar reaction was found. 

The complementary nature of IR and MS data is illustrated in Figure 1, which compares the IR and MS spectra of four isomeric dimethylphenols. The isomers are easily distinguished in the IR, although their mass spectra are similar. Conversely, MS is better suited than IR for distinguishing a homologous series of compounds whereas IR spectra appear similar for adjacent members of the series, MS can provide a characterizing molecular ion. 

Both Soderstrom et al. (25) and Creasy et al. (26) have applied GC/FTIR together with several other hyphenated chromatographic techniques to analyze CWC-related chemicals in complex matrices. The results of the different technique have been combined to unequivocally identify the relevant chemicals in low concentrations. In both studies, IR and MS spectra have been used together in spectral interpretation. Weimaster et al. (70) studied samples collected in Iraq, using a very wide variety of instrumentation, but they could not find any scheduled chemicals. 

Compound 64 which is an epimer of compound 63 was isolated separately. The UV, IR, and MS spectra of the new compound 64 were exactly similar to those of 63, while the H and C NMR data showed chemical shift differences particularly for H-14 (8 6.35), H-15 (5 5.52) and for some methyl groups. The two methyl groups next to the ojqrgenated carbons were observed at 6 1.22 (Me-21) and... 

NIST, United States, publishes a comprehensive database of NMR, IR, and MS spectra. The NIST database is available for sale through 21 commercial distributors, such as Bio-Rad Laboratories. 

Materials DKPs were synthesized from the corresponding dipeptides by the method of Kopple and Ghazaarian [4] except cyclo(Gly-Gly), which was commercially available. Synthesized DKPs were identified by H-NMR, IR and MS spectra, and optical rotation. 

Infrared (IR) spectrophotometry and gas chromatography-mass spectrometry (GC-MS) are commonly utilized to confirm the presence of heroin. Both IR and MS of heroin are unique and are easily distinguishable from other related compounds, thus providing a high degree of confidence in the identification process. The Fourier transform (FT) IR and MS spectra of heroin are shown in Figures 3B and 3C. The major IR absorption peaks for heroin hydrochloride, prepared in potassium bromide, are 1753, 1732, 1365, and 1230 cmT. The primary spectral features of heroin by electron-impact MS are ions at miz 369, 327, 310, and 268. 

A unique feature of this text is the combination of instrumental analysis with organic spectral interpretation (IR, NMR, and MS). The NMR, IR, and MS spectra, all new in the sixth edition, courtesy of Bio-Rad Laboratories, Informatics Division (IR, NMR), Aldrich Chemical Company (NMR), Agilent Technologies, Inc., and one of the authors (MS), were obtained on modem instruments to reflect what students will encounter in modern laboratories. Additional NMR spectra have been provided by Bruker Corporation and picoSpin LLC for the seventh edition. The use of spreadsheets for performing calculations has been introduced with examples. Reflecting the ubiquitous nature of the Internet, we have included a large number of instrument manufacturers websites, which contain extensive resources for interested students. 

This reference book consists of chromatographic and spectral data on twelve hundred selected compounds. Each monograph is accompanied by UV, NMR, IR, and MS spectra and tabulation of GC aixl HPLC data where available. The information on a specific compound should be located by using the alphabetical index, the GC, IR, and MS tables or the UV maxima indexes found in the back of the book. 

Hartl and Reek ° reported the development of iron complexes 65a and 65b, bearing pyridyl and phenyl groups, respectively, at 3,3 -positions of the BINOL moiety. The syntheses of these metal complexes involved the substitution of one carbonyl ligand in [Fe2(p-pdt)(CO)6] by a phos-phoramidite ligand (pdt=S(CH2)sS). The structure was corroborated by P NMR, IR and MS spectra, revealing single CO displacement and phosphoramidite coordination to the Fe centre via the phosphorus atom. 

Specinfo, from Chemical Concepts, is a factual database information system for spectroscopic data with more than 660000 digital spectra of 150000 associated structures [24], The database covers nuclear magnetic resonance spectra ( H-, C-, N-, O-, F-, P-NMR), infrared spectra (IR), and mass spectra (MS). In addition, experimental conditions (instrument, solvent, temperature), coupling constants, relaxation time, and bibliographic data are included. The data is cross-linked to CAS Registry, Beilstein, and NUMERIGUIDE. 

Miscellaneous. NIST has a reference database of criticaUy evaluated x-ray photoelectron and Auger spectral data, which is designed to mn on PCs. It is searchable by spectral lines as weU as by element, line energy, and chemical data (82). The Nuclear Quadrapole Resonance Spectra Database at Osaka University of over 10,000 records is avaUable in an MS-DOS version (83). The NCLl system, SDBS, has esr and Raman spectra, along with nmr, ir, and ms data, as described. 

Another analysis handled effectively by use of gc/ir/ms is essential oil characterization which is of interest to the foods, flavors, and fragrances industries (see Oils essential). Even very minor components in these complex mixtures can affect taste and aroma. Figure 4 shows the TRC and TIC for Russian corriander oil which is used extensively in seasonings and perfumes (15). The ir and ms are serially configured. Spectra can be obtained from even the very minor gc peaks representing nanogram quantities in the it flow cell. 

Which bond of the ester is broken, the acyl—O or the alkyl—O bond The answer is found by the use of Hj O. If the acyl—O bond breaks, the labeled oxygen will appear in the acid otherwise it will be in the alcohol (see 10-10). Although neither compound is radioactive, the one that contains 0 can be determined by submitting both to mass spectrometry (MS). In a similar way, deuterium can be used as a label for hydrogen. In this case, it is not necessary to use mass spectrometry (MS), since IR and NMR spectra can be used to determine when deuterium has been substituted... 

Wilson et al. [662-665] have described various prototype systems for total organic analysis devices. It has proved technically feasible to obtain UV, IR, NMR and MS spectra (together with atomic composition based on accurate mass determination) following RPLC separation. The fully integrated approach offers the benefit that one chromatographic run is required, thus ensuring that all of the spectrometers observe the same separation. Such multiple hyphenations might favour the analysis of complex mixtures for both confirmation of identity and structure determination (should this represent a cost-effective approach). Table 7.72 illustrates the main features of on-flow multiple LC hyphenation. 

The series of regioisomeric amines 48-50, methamphetamine (29) and phentermine (31), can be identified in forensic screening analyses by RP-HPLC-UVD (254/280 nm dual accessory) using a Cis stationary phase and a mobile phase buffered at pH 3.0. The capacity factors and retention times increase in the order 48 < 49 < 29 < 31 < 50. Other methods for identifying these compounds failed for example, the base peak in MS is m/z = 58 for all five compounds, corresponding to a loss of a benzyl group from the molecular peak also their IR and UVV spectra are too similar to be useful for this... 

This measure is equivalent to the correlation coefficient between two sets of mean-centered data—corresponding here to the vector components of xA and xB. It is frequently used for the comparison of spectra in IR and MS. 

Elemental composition Cl 54.16%, N 21.40%, O 24.44%. The compound can be identified by its color and other physical properties. Analysis may be done by GC/MS using a diluent gas such as helium. Alternatively, it may be added to an olefinic double bond and the derivatives identified by physical properties, IR, and mass spectra. (See Reactions.)... 

The third key issue involves data handling. To take full advantage of the complementary nature of the data, it is desirable to handle all the spectral information in a single system. In our lab the IR and MS data are handled separately by the Nicolet and Hewlett Packard computer systems, respectively. Current commercial instruments also handle MS and IR data on separate systems, with only limited communications between the two computers. On our instrument, the following computer-based libraries were used to search unknown spectra IR - EPA Vapor Phase MS - National Bureau of Standards, Revision F. 

To illustrate the complementary nature of IR and MS data we will focus on three adjacent peaks near 29 minutes (Figure 5, boxed region). Note that the center peak shows a shoulder in the MS. The corresponding infrared and mass spectra are presented in Figure 6. 

Figure 6. Matrix isolation IR spectra (left) and MS spectra (right) for selected unknowns in charbroiled chicken (cf. Figure 5). Top Rt 28.821 min., C8-dienal. Middle Rt 28.986 min., mixture of 7-hexalactone and phenylacetaldehyde. Bottom Rt 29.207 min., 2-hydroxybenzaldehyde.

The IR and NMR spectra of these molecules have np unifying features. MS has been shown to be a useful technique for structural verification (77HC(30)317). 

The ultimate test of fluency in MS and IR is whether you can determine a moderately complex structure from just the MS and the IR, with no additional information. The IR and MS of a compound are shown below. Use everything you know about IR and MS, plus reasoning and intuition, to determine a likely structure. Then show how your proposed structure is consistent with these spectra. 

A student found an old bottle labeled thymol on the stockroom shelf. After noticing a pleasant odor, she obtained the following mass, IR, and NMR spectra. The NMR peak at 54.8 disappears on shaking with D20. Propose a structure for thymol, and show how your structure is consistent with the spectra. Propose a fragmentation to explain the MS peak at mJz 135, and show why the resulting ion is relatively stable. 

The UV spectrum of an unknown compound shows values of Amax at 225 nm (e = 10,000) and at 318 nm (e = 40). The mass spectrum shows a molecular ion at m/z 96 and a prominent base peak at m/z 68. The IR and NMR spectra follow. Propose a stmcture, and show how your structure corresponds to the observed absorptions. Propose a favorable fragmentation to account for the MS base peak at m/z 68 (loss of C2H4). 

The reaction of PHMS to yield PMMS-type comb polysiloxanes is essentially quantitative for methoxypoly(ethylene glycol)s of up to 500. Substitution yields diminish for longer glycols, as indicated by the presence of residual Si-H groups in the IR and NMR spectra. Si NMR spectra and GPC data revealed that PM MS-8 is contaminated with nearly 25% cyclic products and that it also contained a considerable number of branched trisiloxy units. Both cyclic products and trisiloxy units are the result of redistribution processes common in nucleophilic siloxane reactions. The hydrosilylation reaction yielding the PAGS polymers is also quantitative, but no cyclic products are formed. 

MS is often used to confirm information from IR and NMR spectra interpretation of the mass spectrum alone is very difficult, except for the simplest molecules. 

Several H NMR spectra are reported for 2-isoxazoline iV-oxide (20) systems in earlier literature, whereas C NMR spectra and MS spectra are only a very few. In IR spectra, the characteristic intense band at 1600-1660 cm is attributed to the C=N+ bond. UV spectra for a large number of 3-nitro derivatives are reported (A ax = 320 nm) <9lHC(49)l>. 

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