Assignment of spectra

If the superimposed sextet is subtracted from the original spectrum a triplet remains which must be due to a scission product of the above molecule. The exclusive breakage of bonds 3 and 4 can be ruled out immediately since it would only lead to radicals of type III. Breakage of bonds 6 and 7 was eliminated after comparison with capron deuterated in the imino groups breakage of bond 1 would not lead to a radical with a triplet spectrum. After inspection of all other possibilities, including secondary radicals, there remain as likely scission points only the bonds 2 and 5. After having studied a and e methyl substituted caprolactam the authors [10] finally were able to state that in a stressed 6 polyamide molecule both the bonds 2 and 5 do break and with equal probability. The rupture of a PA 6 molecule, therefore, leads to three primary radicals  

Upon slowly rising the temperature from 77 K radical III begins to disappear leaving at 120 K only IV and V. At higher temperatures IV and V are gradually transformed into I which prevails above 240 K. Within the experimental limits mentioned above with respect to comparing the absolute numbers of radicals of different species there seems to be no loss of radicals during conversion of III, IV, and V into radical I. 

In the following Sections and Tables the experimental conditions are reported which were employed during mechanical production and ESR investigation of free radicals. The assignments of primary and/or secondary radicals are given. For a discussion of the nature and kinetics of possible transfer reactions the reader is referred to the recent and comprehensive reviews of Ranby et al. [2] and of Sohma et al. [64]. Special problems in view of polymer morphology and of the reduction of chain strengths will be treated in Chapters 7 and 8. 

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Figure 2.10 ESR spectra of o-, m-, and p-xylene radical anions (see text for assignment of spectra). Spectrum (a) was simulated with permission using hyperfine parameters from Ref. 17b, copyright (1964) American Institute of Physics spectra (b) and (c) were simulated with permission using hyperfine parameters from ref. 17a, copyright (1961) Taylor and Francis (www.tandk. co.uk).

Care also needs to be taken with the interpretation of UV-visible spectra in concentrated acid solutions. Richard and Amyes have shown that p fR2° = —16.6 for the 9-methylfluorenyl cation involves an incorrect assignment of spectra and that a value based on azide clock measurements (see below) is —11.9.69... 

The alkaloids of this group are renowned for their pharmacological activity and it is not surprising therefore that several groups have examined their spectra or those of derivatives (32-34). The first complete assignment of spectra to these alkaloids was made by Terui et al. (32), and shortly thereafter a more comprehensive report by Carroll et al. (55) appeared. The alkaloids and model compounds that are discussed are shown in Fig. 7 and 13C data are recorded in Table VII. 

Cholesteryl acetate was used as a model to illustrate the application of tailored detection to the assignment of spectra of complex molecules. The noise-decoupled spectrum contains several regions where signals almost overlap, so that off-resonance decoupling, aimed at ascertaining the multiplicity of individual signals as a result of coupling, can cause much confusion. The tailored... 

An appropriate range of spectroscopic and chromatographic data which is sufficient to characterize the compound. Full assignments of spectra should be entered in the data sheets as soon as the information is obtained, then when it comes to report writing most of the information required is on hand... 

Degraded polymer Sample prepared by milling at°K ESR spectra Assignment of spectra to taken at °K Primary radicals Secondary radicals Ref. 

Figure 8. Zero quantum and double quantum transitions in the AMX system oj 2-jurancarboxylic acid methyl ester, a, 2D spectrum, b. Projection of the 2D spectrum onto the a, axis. ZQT s and 2QT s are labeled by 0 and 2, respectively. The middle doublet of 2QT s has been folded at the Nyquist frequency, —88J2 Hz. Otherwise forbidden zero quantum and double quantum transitions provide connectivity information valuable for the analysis and assignment of spectra, and relaxation information useful for the study of molecular motional processes. (Reproduced, with permission, from Ref. 35. Copyright 1977, North-Holland Publishing Company.)...

Decomposition and Assignment of Spectra. Following the method as applied to the decomposition of absorption and CD spectra for the DP 100 In the previous gapers (10. 11), eight bands were Isolated from both spectra of I, In amylose with DP below 1000 In the slowly mixed system, regafaless of q. Those bands were named S], 2, S3. Sg going from the long to the short wave-... 

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