Infrared spectra carbonyl stretching bands

Compound A undergoes hydrolysis of its acetal function in dilute sulfuric acid to yield 1,2-ethanediol and compound B (CgHg02), mp 54°C. Compound B exhibits a carbonyl stretching band in the infrared at 1690 cm and has two singlets in its H NMR spectrum, at 8 2.9 and 6.7, in the ratio 2 1. On standing in water or ethanol, compound B is converted cleanly to an isomeric substance, compound C, mp 172—173°C. Compound C has no peaks attributable to carbonyl groups in its infrared spectrum. Identify compounds B and C. 

The electronic and vibrational spectra of benzoquinones are very diagnostic. Of the two possible isomers remaining, the 2,5-substituted quinone (5) would be expected to give two different electronic transitions of equal intensity around 280 nm, and only one carbonyl stretching band. The Fourier transform infrared spectrum (CH2CI2) of the haustorial Inducer showed strong absorptions at 1698 (vC=0), 1646 (vC=0) and 1597 cm (vC=C). These spectroscopic data established the haustorial inducer as 2,6-diraethoxy-2"benzoquinone (2,6-DMBQ, 4). 

The carbonyl stretching band in the infrared spectrum of isotactic poly (a,a-dimethylbenzy 1 methacrylate) prebaked at 142°C for 1 hr indicated the formation of a small amount of acid group during the prebake, while the atactic polymer showed no change in the spectrum at this temperature. This may be the reason why the isotactic polymer showed a lower 7-value than the atactic polymer (Table III). 

The product is a green crystalline solid and is air sensitive in solution or in the solid state. Its infrared spectrum contains strong bands at 1860 and 1960 cm that are assigned to carbonyl stretching frequencies. In most preparations the infrared spectrum of the final product also contains a weak band at 2020 cm , which may be due to slight contamination with Mo(CO)3 [S2PO-C3117)2] 2-... 

M is a First Transition Series element. It forms a carbonyl F of empirical formula MICO) which reacts with sodium amalgam in tetrahydrofuran to give a solution G. Treatment of G with 3-chloro-l-propene gives a compound H of molecular formula CgHgOgM. The infrared spectrum of H shows carbonyl stretching bands between 2110 and 2004cm the n.m.r. spectrum of H indicates protons in four chemically distinct environments. 

In the infrared spectrum of pyrolysed polymethacrylic acid a carbonyl stretching band is clearly visible at 5.73 p.m. Also evident is the ester stretching band at 9.82 i,m (Figure 3.5). 

IR and NMR spectra of N-acetyl-norheroin. The infrared spectrum of N-acetyl-norheroin indicated that it contained a tertiary amide and two ester groups. The carbonyl stretching bands of the phenolic acetate (1760 cm " ) and the allylic acetate (1735 cm ) were observed in heroin and N-acetyl-norheroin. In addition, the IR of ( -1) indicated a strong amide I band at 1632 cm" which was not sensitive to solution concentration or change of phase. Since the presence of free N-H stretching bands was not observed in the regions 3500-3400 cm (in dilute solution) and 3340-3060 cm" ... 

The infrared spectrum of erythromycin is commonly used for its identification. Figure 2 shows the spectrum of a 75 mg./ml. chloroform solution. The bands at 1685 and 1730 cm- are due to the ketone carbonyl and the lactone carbonyl, respectively. The absorption peaks between 1000 and 1200 cm-1 are due to the ethers and amine functions. The CH2 bending is evidenced by peaks between 1340 and 1460 cm-, and alkane stretching peaks appear between 2780 and 3020 cm-. Hydrogen bonded OH and water appear as bands between 3400 and 3700 cm-1. 

The infrared spectrum of y-crotonolactone shows two bands in the carbonyl r on at 5.60 and 5.71 fi in carbon tetrachloride (5%) [shifted to 5.61 and 5.71 fi in chloroform (5%)] and carbon-carbon stretching absorption at 6.23 fjt. The nuclear magnetic resonance spectrum shows olefinic peaks centered at 2.15r (pair of triplets) and 3.85r (pair of triplets), each due to one proton, and a two-proton triplet centered at 5.03t (in CCU). 

The C=0 in all carbonyl groups has a very intense band in the 1,700 cm region of its infrared spectrum. In many cases this band is the most prominent feature of the spectrum. Table 9-1 shows some typical carbonyl stretches. (See Chapter 5 for a discussion of IR stretches and peaks.)... 

One of the main routine uses of infrared spectroscopy is identification of specific functional groups present in an unknown molecule and, as a result, further characterization of the unknown. By far the most common example involves the carbonyl group. Location of a strong band in the infrared in the vicinity of 1730cm is almost certain proof that carbonyl functionality is present. This confidence is based on the fact that the characteristic frequency (the CO stretch in this case) is isolated, that is to say, it is sufficiently far removed from the other bands in the infrared spectrum to not be confused with them. It also assumes that carbonyl groups in different chemical environments will exhibit similar characteristic... 

The infrared spectrum in the carbonyl stretching region is very useful in characterizing these complexes (Table I). Three infrared active bands are predicted 18 however, limited solubility may preclude observation of the weaker bands. Dimer formation is easily detected by the presence of characteristic bands.12... 

Another member of this series is bis(cyclopentadienylnickel carbonyl), (CsHaNiCO it is dimeric, diamagnetic, and must, therefore, contain a nickel-nickel bond (79). The dipole moment, quoted (79) as 0 0.38 Debye unit, indicates that the molecule must be very nearly centro-sym-metric in benzene. The infrared spectrum, however, shows two carbonyl stretching frequencies in the solid state and in solution, but the vapor at 100°C shows only one band (173, 199). The wave-numbers are shown in Table IV. 

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