Overtone cyclic molecules

Cyclopentane, cyclobutane, cyclopropane, and many other cyclic molecules have been studied, hi the fundamental region, the frequency increases as the ring becomes more strained, and the first overtones reflect this trend. Cyclopentane s two strongest first overtone peaks are at 5730 cm (1745 nm) and 5834 cm (1714 nm) for example, as compared to cyclohexane s 5697 and 5791 cm . ... 

Representative diterpene structures are shown in Fig. 18. Diterpenes can be classified on a biogenetic basis (Ruzicka et al., 1953 McCrindle and Overton, 1965 Hanson, 1972a). There are a few open-chain diterpenes. Phy-tol, in an ester linkage, is found as a side chain on the chlorophyll molecule. Most diterpenes are cyclic compounds. A few diterpenes are formed by cy-clizations analogous to those involved in the synthesis of cyclohexanoid monoterpenes. The result is a macrocyclic structure such as that of cem-... 

In the IR spectrum of the gas at 60 to 400Torr, the rotational subbands of the three fundamental vibrations and of the overtone 2v2(see p. 150) of HOF and DOF we re observed [7]. The spectrum of matrix-isolated HOF was studied at HOF N2 ratios of -1 3000 and -1 20000. The fundamental vibrations (see p. 149) were observed as well as a small band at 1393 cm definite only in the more concentrated matrix and presumably due to the bending mode of an HOF molecule hydrogen-bonded to HF, a product of thermal decomposition of HOF [8]. The complex spectra in N2 and Ar matrices are also partly due to HF HOF [9]. IR spectra of solid films were studied at -195°C, and the intramolecular vibrations v, V2, V3, 2v2, and 2v3 of HOF, DOF, and H OF were found. Bands at 628 and 448 cm" for HOF were ascribed to a simple cyclic dimer. But infinite planar zigzag chains could not be ruled out [10], and this latter interpretation is supported by the Raman spectrum (see table p. 154). 

For molecules containing a weak bond, say, HOOH, it is possible to provide enongh energy by an overtone excitation of an O—H bond so as to dissociate the molecnle. For exoergic processes it is only necessary to provide enough energy to surmount the barrier. A well-studied example is the dissociation of die cyclic peroxide tetramethyl dioxane (TMD) that fragments over a barrier of about 110 kJ mol (about three quanta of C—H stretch) to two acetone molecules... 

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