Infrared spectra butenes

The trapped product gave an immediate test with KI in acetic acid. Its infrared spectrum was similar to that of 3-butene-2-ol with major absorption peaks at 3, 8.7, 9.5, 10.3, and 10.8 microns and minor peaks at 6.3, 7.2, 7.7, 11.6, 12.4, and 12.6 microns. There was no absorption arising from carbonyl. In a 25% solution of hydroperoxide in carbon tetrachloride, the hydroperoxide proton gave rise to a broad band at 8.7 p.p.m. (referred to TMS) in the NMR spectra. 

This mechanism is consistent with the observation of significant yields of epoxide products and N02 for some alkenes (Olzmann et al., 1994). For example, Fig. 6.7 shows the infrared spectrum of the minor products from the reaction of N03 with 2,3-dimethyl-2-butene at... 

FIGURE 6.7 Infrared spectrum of products of the reaction of 2,3-dimethyl-2-butene with N03 (spectra of acetone, N02, and HN03 have been subtracted out) (adapted from Skov et al., 1994). 

Figure 10-1 Infrared spectrum of 1-butene showing the vibrational assignments made to the various absorptions...

Such a reaction has been shown to give 1-butene and carboxyl groups in equivalent yields (about 2 x 10-2) in the liquid-phase photolysis of undiluted di-n-butylterephthalate [116]. From Table 4 it can be seen that the quantum yields of chain scission and of carboxyl group formation are almost identical this suggests that reaction (22) is the main cause of chain scission in the photolysis of polyethylene terephthalate. It must also be pointed out that reactions (19) and (21) do not necessarily yield chain scission, since the probability of the macro-radicals escaping the cage is rather low in a rigid matrix. Indeed, the appearance of an absorption maximum near 775 cm-1 in the infrared spectrum of polyethylene terephthalate irradiated at 313 nm has been ascribed to... 

Bell, S., Drew, B. R., Guirgis, G. A., Durig, J. R. (2000). The far infrared spectrum, ab initio calculations and conformational energy differences of 1-butene. Journal of Molecular Structure, 555(1-3), 199-219. (b) Broeker, J. L., Hoffmann, R. W., Houk, K. N. (1991). Conformational analysis of chiral aUcenes and oxonium ions ab initio molecular orbital calculations and an improved MM2 force field. Journal of the American Chemical Society, 775(13), 5006-5017. 

Brako and Wexler [122] have described a useful technique for testing for the presence of unsaturation in polymer films such as polybutadiene and styrene-butadiene. They expose the film to bromine vapour and record its spectrum before and after exposure (Figure 3.12). This results in marked changes in the infrared spectrum. Noteworthy is the almost complete disappearance of bands at 13.691,10.99,10.36, and 6.10 pm associated with unsaturation. A pronounced band possibly associated with a C-Br vibration appears at 12.02 pm which is due to exposure to bromine vapour. Exposure of butadiene-styrene copolymer (Figure 3.12) to bromine vapour results in the disappearance of bands at 10.99 and 10.36 pm associated with unsaturation in the butene component of the copolymer. Some alteration of the phenyl bands at 14.28 and 10.37 pm is evident. The loss of a band at 6.45 pm and the appearance of a band at 5.88 pm are probably due to the action of acidic vapours on the carboxylate purifactant of the latex. 

Figure 5-18. The infrared spectrum of ra 5-2-butene. (Courtesy API Project 44.)...

The investigation of the 300 MHz spectrum of poly(3-methyl-l -butene) indicates that the conclusions drawn by previous workers (2—4) concerning the structures of the crystalline and amorphous polymers are essentially correct the crystalline polymer being almost entirely of the 1,3-structure and the amorphous polymer being a mixture of both 1,2- and 1,3-structures. Further, it has indicated that this method is useful for analysis of the composition of the polymer. Quantitative composition determination, however, has not been carried out, since it is felt that the accuracy of the previous estimates utilizing near infrared spectroscopy were satisfactory. 

Figure 27. Difference infrared spectra (before and after photolysis) of l-butene and oxygen in BaY. (a) X > 400 nm at -20 °C for 5 h followed by warm-up at 24 °C for 18 h without O2 (b) X > 400 nm at room temperature for 1.5 h (c) X > 495 nm at 45 °C for 14 hours (d) reference spectrum of methyl vinyl ketone in BaY. Asterisks indicate the loss of l-butene.

Following are infrared spectra of methylenecyclopentane and 2,3-dimethyl-2-butene. Assign each compound its correct spectrum. 

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