Selenophenes spectra

Magnetic circular dichroism (MCD) has now become a tool with valuable applications to analytical and structural studies. The MCD spectrum of thiophene is only slightly perturbed by substituents, and this is also expected to be true of the quite similar MCD spectra of selenophene.18 These molecules can therefore be classified as hard chromophores. 

The photoelectron spectrum of selenophene vapor down to 1350 A has been studied. By analogy with the other heterocyclic derivatives, Rydberg-type transitions occur, leading to the first ionization potential of the molecule.23... 

The mass spectrum of selenophene has been recorded and the fragmentation pattern compared with those of the other congener heteroaromatic compounds.27 The analogous fragments observed for the four heterocycles are given in Scheme 1. 

The carbonyl reactivity of pyrrole-, furan-, thiophene- and selenophene-2- and -3-carbaldehydes is very similar to that of benzaldehyde. A quantitative study of the reaction of Af-methylpyrrole-2-carbaldehyde, furan-2-carbaldehyde and thiophene-2-carbaldehyde with hydroxide ions showed that the difference in reactivity between furan- and thiophene-2-carbaldehydes was small but that both of these aldehydes were considerably more reactive to hydroxide addition at the carbonyl carbon than A-methylpyrrole-2-carbaldehyde (76JOC1952). Pyrrole-2-aldehydes fail to undergo Cannizzaro and benzoin reactions, which is attributed to mesomerism involving the ring nitrogen (see 366). They yield 2-hydroxymethylpyrroles (by NaBH4 reduction) and 2-methylpyrroles (Wolff-Kishner reduction). The IR spectrum of the hydrochloride of 2-formylpyrrole indicates that protonation occurs mainly at the carbonyl oxygen atom and only to a limited extent at C-5. 

The NMR spectrum of selenophene (Fig. 2) shows spin-spin interaction of 77Se with the a protons, the coupling constant, J77Sc H being 22.5 Hz. 

Trombetti and Zauli12 studied the UV spectrum of selenophene and showed that selenophene is characterized by absorption at 37,500-47,500 cm-1, caused by two superimposed transitions. 

Methyl selenien-2-yl glyoxal,118 the simplest a-diketone of the selenophene series, has been obtained in two ways by oxidation of 2-propionylselenophene by selenium dioxide and by hydrolysis of the product resulting from nitrosation of that ketone. Its UV spectrum has three characteristic maxima (Amax 277, 283, and 310 mp). When... 

The behavior of benzo[6]tellurophene under electron impact has been analyzed by Buu-Hoi and co-workers.89 The mass spectrum is similar to those of benzo[6]thiophene and benzoU>]selenophene. The base peak corresponds to a detellurated species, probably benzocyclobutadiene. 

The dipole moments of some simple halogeno-, cyano-, and formyl-selenophens have been measured and the conformations of these compounds have been discussed. Through a study of the n.m.r. spectrum of selenophen in lyotropic mesophase, the ratios of the interproton distances were calculated from the direct couplings and found to be in good agreement with the corresponding values calculated from microwave data. ... 

The H n.m.r. spectrum of benzo[b]selenophen has been analysed. The thermolysis and electron cleavage of aldazines and ketazines of the benzo[b]selenophen series have been studied. ... 

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