By F. Scheinmann
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The molecular constitution hypothesis--that a molecule is a set of atoms associated by way of a community of bonds-- presents the significant technique of ordering and classifying observations in chemistry. despite the fact that this speculation isn't really similar on to the physics which governs the motions of atomic nuclei and electrons.
Prof. Dr. -Ing. Reinhard Seeling - Rheinisch-Westfälische Technische Hochschule Aachen
Extra info for An Introduction to Spectroscopic Methods for the Identification of Organic Compounds. Nuclear Magnetic Resonance and Infrared Spectroscopy
6) The magnitude of proton-proton couplings across double bonds depends upon the stereochemistry. Typical values are 15-17 Hz for J (trans) and 12-14 Hz for J(cis). Cis- and ircws-isomers of olefinic compounds can therefore be characterized readily by proton magnetic resonance spectroscopy. (a) The dimethyl ester (XXIII) of the well-characterized trans-trans-ß-methylmuconic acid showed the expected 7-proton resonance lines. There were three singlets, at τ 640 (2 χ C02Me), 7-75 (C—Me), and 400 (=C ) and two doublets, at 3-88 and 2-75.
D . W. Mathieson, Academic Press, London, 1966, p. 195. (b) J. A. ELVIDGE, Nuclear magnetic resonance spectroscopy, in Interpretation of Organic Spectra, ed. D. W. Mathieson, Royal Institute of Chemistry and Academic Press, London, 1965, pp. 3 - 7 3 . (c) J. S. BURTON, J. A . ELVIDGE, and R. STEVENS, / . Chem. Soc, 7. (a) F. , 1965, 1276. 1893, 26, 747. (b) G. A. R. K O N and H. R. NANJI, / . Chem. Soc, 1932, 2557, and earlier papers cited therein. NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 57 8. M.
Considerable simplification of the spectrum is achieved and this can be seen from Fig. 27 using the case of allyl bromide as an example. The low field vinyl absorptions are complicated by spin coupling with the allylic protons : when the allylic protons are irradiated in a frequency swept double resonance experiments the vinyl protons are seen to become a simple AMX system. When the nucleus being decoupled is of the same species as that being observed then the technique is known as homonuclear spin decoupling.
An Introduction to Spectroscopic Methods for the Identification of Organic Compounds. Nuclear Magnetic Resonance and Infrared Spectroscopy by F. Scheinmann