Reaction Of Difluorocarbene Research Articles

Fluorine-containing azoles. 2. Reaction of imidazole, benzimidazoles, and perimidines with difluorocarbene

The reaction of difluorocarbene, generated from difluorochloromethane in an alkaline medium or from sodium trifluoroacetate in a neutral medium, with imidazole, tetrahydrobenzimidazole, benzimidazoles, and perimidines leads to the production of their N-difluoromethyl-substituted derivatives.

The Reaction of Difluorocarbene with Bicyclo[2.2.2]octadiene

AbstractThe addition of difluorocarbene to bicyclo[2.2.2]octa‐2,5‐diene gave the exo and endo 1:1 cyclopropane adducts. In contrast to norbornadiene, no homo‐1,4 adduct was formed. The adducts were thermally stable under the conditions of their formation and separation (<170°). However, smooth equilibration was achieved on heating at 250° for 36 h. The same mixture resulted from either isomer. At 250° ΔΔG = 1.83 kcal/mol; the endo isomer being the more stable. Heating to higher temperatures caused decomposition, rather than further reaction to the intramolecular [2+2]cyclization products. The kinetic and thermodynamic product compositions were essentially the same on extrapolating to the same temperature, viz. endo/exo = 19–22 at 25°. The mechanisms by which the cyclo‐addition and the stereomutation of the cis‐fused cyclopropane moiety occur are discussed.

Kinetic study of reaction of difluorocarbene with cyclopentadiene

1. The kinetics of the copyrolysis of chlorodifluoromethane with cyclopentadiene was studied and a mechanism was presented. 2. A mathematical model of the process was composed. 3. The rate constants and the activation energies for the addition of difluorocarbene to cyclopentadiene and the dissociation of tetrafluoroethylene were determined.

Surface photopolymerization of tetrafluoroethylene

The formation of thin (< 1000 A) polymeric films from tetrafluoroethylene in a pre-evacuated (10–6 Torr) system by surface-photopolymerization has been monitored by quartz crystal microbalance, mass spectrometric, and infra-red techniques. Film growth rate was found (1) to depend upon ultra-violet light intensity to the 1.6 power at wavelengths of about 2100A; (2) to vary inversely with the surface temperature over the range 10 to 60°C; (3) to vary positively with monomer pressure from 0.5 to about 10 Torr. Depositions using selected wavelengths demonstrated that the growth could not be initiated or maintained with light above 2150 A, the effective cutoff for absorption by C2F4 in the gas phase. Adsorption on the surface does not perturb the TFE molecule to the extent that the photolysis can be initiated by less energetic photons. For irradiation at wavelengths < 2150A, film growth terminated on removal of the light soure. Approximately one monomer unit was polymerized for each photon ∼ 2000 A incident on the deposition cell. Evacuation of the photolysis system after deposition resulted in film weight loss as high as 50 % depending upon the experimental conditions. Mass spectral analysis of gas phase by-products identified higher molecular weight species up to C9F18. Infra-red analysis of the gas phase also indicated the presence of cyclic fluorocarbons. A proposed mechanism for the surface-photopolymerization process invokes the photodissociation of C2F4 followed by reactions of difluorocarbene and its higher homologues both in the gas phase and on the surface. Polymeric film growth on the surface then results from interaction of the higher molecular weight components.