The molar refractions (polarizabilities) and dipole moments of fourteen 2‐arylmethylene‐1,3‐indandiones (I) and the electronic absorption spectra of twenty‐one representatives of this series have been measured. From these data certain features of the fine structure of the compounds have been deduced; inter alia, the carbonyl groups in I are bent away from the benzene ring of the indane moiety, and the 4‐dimethylaminophenyl compound II exists to a significant extent in the zwitterionic form IIA.

Limonene and isoprene were irradiated at various pressures by means of a continuous wave C02 laser. The results show that it is possible under controlled conditions to obtain reactions in the electronic ground state under nonequilibrium conditions. The possibility of carrying out reactions obeying symmetry selection rules of thermal reactions and having thermodynamic and kinetic properties of photochemical reactions by means of infrared laser light is discussed.

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A large number of 2‐arylmethylene‐1,3‐indandiones have been prepared and their nuclear magnetic resonance and infrared spectra have been measured. The measurements have been used to elucidate some details of the fine structure of these compounds.

The mass spectra of 1,2-dichloro-3,4-bis(dichloromethylene)cyclobutene (IV) and of hexachloropentafulvene (11) have been studied. Compound IV cannot be an intermediate in the formation of I1 from octachloro-l,2-dimethylenecyclobutane (111) under electron-impact , as previously suggested. In the mass spectra of I1 and IV the species [Celt. and [CJ+ occur, obviously through cleavage of the semicyclic C-C bond.The mass spectrum of pentachlorofulvalene (VI) shows strikingly that successive elimination of an even number of C1 atoms is preferred over that of an odd number of C1 atoms; probably corresponding C-Cl bonds in the two rings are broken simultaneously. Amongst the fragments, the species [Clo]+* and [C,]+and possibly also [C,]+* and [C,]+* have been observed.