Ring frequencies

The infrared spectrum of the compound shows the boron-nitrogen ring frequency at 1392 cm.-"1. Its XH n.m.r. spectrum shows a sharp singlet at —3.1 p.p.m. (TMS standard). 

Yur ev et al.2b studied the Raman spectra of 2-cyclopropyl-, 2-(2-methylcyclopropyl)-, and 2-(l-propenyl)-selenophene and found ring frequencies similar to those of selenophene and its methyl homologs.24 On replacement of the w-propyl group by cyclopropyl or, particularly, by propenyl, however, the intensities of certain lines increased two- to tenfold, as a result of conjugation. 

It is principally dependent on the electronegativity of the atom attached to the ring, frequency increasing steadily with electronegativity, as shown in Table V. 

The assertion of these assignments is founded on the following criteria i) Similar single six-ring frequencies were observed in... 

The PEL emits micropulses at the storage ring frequency. The width of the laser micropulse is certainly smaller than the electron bunch length (0.5 - Ins) but has not yet been measured. A pulsed macro-temporal emission structure has been described theoretically (33) and observed experimentally (4a, 25).In the ACO case, where the electron pulses are Ins long and the repetition period 37ns, the PEL emission macro-temporal structure has a pseudoperiod of 10-20ms and a pulse duration of about 2-3ms (Pig. 19a).The laser time structure is thus similar to the relaxation oscillation of a conventional laser, but here the excursions of the electron beam energy spread about a mean value play a role equivalent to that of the excursions of an inverted population density. 

In 1,2,3-trimethoxybenzene the strongest band in the C—O region is at 1115 cm" Some other highly substituted methoxybenzenes are similar. This reflects the fact that the aryl C—O vibration interacts with ring frequencies and is therefore not completely mechanically independent of other single bonds attached to the ring. 

Fluorine atoms directly attached to an aromatic ring give rise to bands in the region 1270-1100 cm Many of these compounds including the simpler ones with one fluorine only on the ring absorb near 1230 cm Fluorine substitution does not abnormally affect the ring frequencies at 850-700 cm ... 

These models are attempts to rationalize kinetic, electron microscope, and ring formation data. Critical tests in one species are necessary to demonstrate the validity of any or all of these possibilities. A unique and specific prediction of model a, for example, is that ring frequencies with salivary gland DNA will have peaks at multiples of the 1.5 pm repeat separation length, i.e., 3.0,4.5 pm, etc. a. As we have no information on the function of these short repeat sequences, there is no logical a priori reason to discount any of the models. Indeed, different chromomeres may have quite different sequence organization. (After Laird, 1973)... 

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