Difluoro-1,1 -ethylene

In a definitive study of butadiene s reaction with l,l-dichloro-2,2-difluoio-ethylene, Bartlett concluded that [2+4] adducts of acyclic dienes with fluorinated ethylenes are formed through a mixture of concerted and nonconcerted, diradical pathways [67] The degree of observed [2+4] cycloaddition of fluorinated ethylenes IS related to the relative amounts of transoid and cisoid conformers of the diene, with very considerable (i.e., 30%) Diels-Alder adduct being observed in competition with [2+2] reaction, for example, in the reaction of 1,1 -dichloro-2,2-difluoro-ethylene with cyclopentadiene [9, 68]... 

As a second example of a 4N + 2 pi electron molecule we consider 1,2 difluoro-ethylene which can exist in a cis and a trans geometry. The dissection employed is shown below ... 

Fig. 56. Configuration interaction diagram for (a) 1,1-difluoroethylene and (b) 1,2-difluoro-ethylene. and n2 are sigma charge resonance configurations. Similarly, ZI3 and r14 are pi charge resonance configurations...

Kollman chose to attempt to understand the angle shrinkage of 1,1 difluoro-ethylene by comparing this molecule to ethylene itself. He then noted that, in F2C=CH2 there is a greater withdrawal of charge from the py than from the px or s carbon AO s relative to ethylene. The same trend was found for the corresponding pseudoethylene. The author proposed and intuitive interpreation ... 

To test our suspicion, we used a point charge model and ab initio calculated atomic charges in order to evaluate the electrostatic energy of 1,2-ds and 1,1-difluoro-ethylene. 

Genetron 1132A. Designation of Difluoro-ethylene or Vinylidene Fluoride, described in Vol 6 under FLUORINE DERIVATIVES, p F126ff... 

Earlier, Ruh [120a] reported a similar reaction for l,2-dichloro-l,2-difluoro-ethylene on reaction with sodium ethoxide to give ethyl chlorofluoroortho-acetate (Eq. 39). 

What are products E and F of the reaction of l,l-dichloro-2,2-difluoro-ethylene with methanol in the presence of sodium methoxide ... 

With CF3C=CCF3 or olefins with an internal double bond such as cis- or fraras-F-2-pentene, F-cyclobutene, or l,2-dichloro-l,2-difluoro-ethylene, or with a geminally disubstituted olefin such as 1,1-dichloro-2,2-difluoroethylene, only fully fluorinated products were obtained, likely through a nucleophilic fluorination mechanism. This fact, plus the necessity for a Lewis acid catalyst for addition to proceed, is evidence for an electrophilic addition mechanism. Others have suggested polar addition of BF3 to the olefin with RfBF2 as a reactive intermediate (294). 

SAFETY PROFILE A highly corrosive irritant to the eyes, skin, and mucous membranes. Mildly toxic by inhalation, Explosive reaction with alcohols + hydrogen cyanide, potassium permanganate, sodium (with aqueous HCl), tetraselenium tetranitride. Ignition on contact with aluminum-titanium alloys (with HCl vapor), fluorine, hexa-lithium disilicide, metal acetylides or carbides (e.g., cesium acetylide, rubidium ace-tylide). Violent reaction with 1,1-difluoro-ethylene. Vigorous reaction with aluminum, chlorine + dinitroanilines (evolves gas). Potentially dangerous reaction with sulfuric acid releases HCl gas. Adsorption of the acid onto silicon dioxide is exothermic. See also HYDROGEN CHLORIDE (AEROSOL) and HYDROCHLORIC ACID. 

SYNS 1,1-DiFLuoROETHENE 1.1-DiFLuoRO-ETHYLENE pOT, MAK) ETHENE, 1,1-DIFLUORO- HALOCARBON 1132A NCI-C60208 R1132a pOT) VDF VINYLIOENE DIFLUORIDE... 

With cts-l,2-difluoro ethylene, there was only one product found, cis 1,2-difluoroethylene episulfide. Hence, we are dealing here with a quantitatively stereospecific reaction. 

Staudinger and Pfenninger long ago suggested that addition of sulfur dioxide to diphenylketene gives an intermediate, 3,3-diphenyl-l,2-oxathietane-4-one 2-oxide, that decomposes to diphenylsulfene and carbon dioxide, the former yielding tetra-phenylethylene. Similar intermediates were proposed for the addition of sulfur dioxide to pentamethyleneketene, ketenimines, " ethylene, 1,1-difluoro-ethylenes, and an aluminum trichloride derivative of the 1,2,3,4-tetramethyl-cyclobutene cation. An intermediate adduct 494 actually has been isolated at... 

Solid perfluorocarbon surfaces also have extremely low surface energies Thus, poly(tetrafluoroethylene) (PTFE, Teflon) has a y value of 18.5 dyn cm which is the reason for the anti-stick and low-friction properties used for frying pans and other applications. That this effect is directly related to the fluorine content becomes obvious on comparison of the surface energies of poly(difluoro-ethylene) (25 dyn cm ), poly(fluoroethylene) (28 dyn cm ), and polyethylene (31 dyn cm Y If only one fluorine atom in PTFE is replaced by more polarizable chlorine, the surface energy of the resulting poly(chlorotrifluoroethylene) jumps to 31 dyn cm , the same value as for polyethylene [8]. 

Stereochemical investigation of the reactions of 1,1 -dichloro-2,2-difluoro-ethylene with the geometrical isomers of 2,4-hexadiene has indicated a radical addition mechanism involving intermediate formation of an open-chain diradical addition compound.57... 

Other olefins studied include trifluoro- and tetrafluoroethylene, - 1,2-difluoro-ethylene, 1,1-dlfluoroethylene, mixtures of fluoroethylenes, and octafluoro-but-2-ene.40... 

Synonyms 1,1-Difluoroethene 1,1-Difluoroethylene Ethene, 1,1-difluoro- Ethylene, 1,1-difluoro- VDF Vinylidene difluoride... 

The most comprehensive table of relative results is Table VI in which the orientation ratios for the addition of an extensive range of fluoroalkyl radicals to vinyl fluoride, 1, 1-difluoro-ethylene and trifluoroethylene are listed. Although all radicals add preferentially to the CH2- end of vinyl fluoride and 1, 1-di-fluoroethylene, the orientation of addition to trifluoroethylene depends on the radical. The "electrophilic" radicals adding preferentially to the CHF- site and the nucleophilic radicals adding preferentially to the CF2- site. In the radical series... 

This can nicely be demonstrated with the Diels-Alder reaction of 1,1-dichloro-2,2-difluoro ethylene. 

In most ionic unimolecular reactions, internal conversion to the ground electronic state is rapid compared to dissociation. In a few cases, however, evidence has been found of a rapid and specific dissociation process occurring on the potential energy surface of an excited electronic state. When such an isolated state decay occurs, a correlation exists between the branching ratio for the specific channel and the photoelectron spectrum. Ionized difluoro-ethylenes for example, dissociate statistically below the IC state but this latter state favours strongly the F loss channel. 

H. Sato, F. Hirata and S. Kato. Analytical energy gradient for the reference interaction site model multiconfigurational self-consistent-field method Application to 1,2-difluoro-ethylene in aqueons solntion. J. Chem. Phys. 105,1996, 1546-1551. 

Vlayl fluoride [75-02-5] (VF) (fluoroethene) is a colorless gas at ambient conditions. It was first prepared by reaction of l,l-difluoro-2-bromoethane [359-07-9] with ziac (1). Most approaches to vinyl fluoride synthesis have employed reactions of acetylene [74-86-2] with hydrogen fluoride (HF) either directly (2—5) or utilizing catalysts (3,6—10). Other routes have iavolved ethylene [74-85-1] and HF (11), pyrolysis of 1,1-difluoroethane [624-72-6] (12,13) and fluorochloroethanes (14—18), reaction of 1,1-difluoroethane with acetylene (19,20), and halogen exchange of vinyl chloride [75-01-4] with HF (21—23). Physical properties of vinyl fluoride are given ia Table 1. 

---