Halocarbon solvents

The aluminium-solvent slurry produced by metal atom/solvent co-condensation at — 196°C is so reactive that oxygen is abstracted from the solvent ether as the mixture is allowed to melt. Hydrocarbon solvents are more suitable (but halocarbon solvents would react explosively). 

An attempt to mill a slurry of metal in the solvent caused a violent explosion. Experiment showed violent interaction of the freshly ground metal surfaces with the halocarbon solvent. 

Upon sonication in halocarbon solvents, metal carbonyls undergo facile halogenations (186). The rates of halogenation are solvent dependent, but independent of choice of metal carbonyl or its concentration, and represent the products of secondary reactions occurring from the sonolytic decomposition of the halocarbon solvent, as shown in Eqs. (16)-(20). Alkanes and other halogen atom traps suppress the halogenation of the metal carbonyls. 

Figure 4 shows the behavior that is observed when a solution of cationic radon in 1,1,2-trichlorotrifluoroethane is passed through a column packed with KPF. The radon displaces potassium ion and adheres in a narrow band at the top of the column. It can be washed repeatedly with dilute BrF in the halocarbon solvent, then eluted rapidly with 1.0 M BrF in sulfuryl chloride. The radon daughters remain on the column during elution and decay in situ new daughters are generated in the radon-containing eluant fractions. 

With the exception of chlorobenzene and 1,2-dichloroethane, halocarbon solvents are unsuitable diluents, as carbon tetrachloride and chloroform may react violently with alkylalumimum derivatives. The hazards of individually mixing 7 alkyla-luminiums with 7 chlorinated solvents have been assessed comparatively. Most of a series of cyclic coordination complexes between triethylaluminium and a-iminoketones decomposed violently when dissolved in halogenated solvents. 

The preparation of metal dithiophosphate complexes usually involves the reaction of metal halides or acetates with dithiophosphoric acids or their salts. The metal complexes are generally purified by repeated fractional crystallization from halocarbon solvents such as chloroform. The reactions of mixtures of alcohols and alcohols and phenols with phosphorus(V) sulfide allegedly,... 

Alcohols, water and even acetic acid are useful solvents for some radical reactions. However, they cannot be employed with organometallics that are basic. Conversely, halocarbon solvents are popular for many types of ionic reactions but they are not generally useful for radical reactions. Chloroform and carbon tetrachloride (and to a lesser extent, dichloromethane) can interfere by donating either hydrogen or halogen atoms to intermediate radicals and they are used only in atom transfer reactions where the solvent is also a reagent. 

A paste of zinc powder and carbon tetrachloride (with kieselguhr as thickener) will readily burn after ignition by a high-temperature primer [1]. Intimate mixtures of chlorinated rubber with powdered zinc (or its oxide) in presence or absence of hydrocarbon or halocarbon solvents react violently or explosively at about 216°C... 

Fewer examples of heterolysis of silane Si-H bonds are known as compared to splitting of H-H bonds. However, the Si is highly activated toward nucleophilic attack by trace water, hydroxylic or halocarbon solvents, and even fluoride from anions when silanes are coordinated to electrophilic cationic centers (103). 

Halocarbons, a class of polar solvents, are hydrocarbons with an attached halogen. There are commonly three types of halocarbon solvents those based on chlorine, fluorine, and a combination of the two. They are all powerful degreasing materials and can be particularly effective in removing polar contaminants from glass. The chlorofluorocarbons are currently under review because they cause environmental damage to the ozone layer.1... 

Photochemical oxidation of square-planar bis(l,2-dithiolene) complexes of Ni, Pd, and Pt is by no means limited to IPCT excitation. Photooxidation also occurs in halocarbon solvents. In 1982, two separate reports addressed the photochemistry of metal bis(l,2-dithiolene) complexes. Vogler and Kunkely (80) investigated complexes of the type M(S2C2R-2)2, where M = Ni, Pd, Pt,... 

The long lifetimes of CT excited states of the Pt(diimine)(dithiolate) complexes allow for bimolecular photochemistry, often involving oxidation of the complex. The earliest report of photoreactivity of these complexes dealt with the photooxidation of Pt(bpy)(tdt) (20) following excitation at 577 nm in chloroform (118). The reaction proceeds with a quantum yield of < ) = 0.03 and was attributed to ET to the halocarbon solvent (Eq. 8) similar to the CTTS photooxidation chemistry of the platinum bis(dithiolate) dianions described above. 

The yellow crystalline material is very air sensitive. When stored for long periods of time, it should be kept cold, or it will darken and become tacky. The compound is very soluble in hydrocarbon and ether solvents and is slightly proton-ated by alcohols. It decomposes when exposed to halocarbon solvents. 

Tn other studies, reaction of [MnX(TPP)] (X = Nf or OCN ) with iodosylbenzene in hydrocarbon or halocarbon solvents yielded products formulated as yi-oxo dimers, [MnlvX(TPP)]20.678 [Mn,vN3(TPP)]20 has been characterized by X-ray diffraction (see Section 41.5.7.1). Infrared evidence supports678,679 the formulation of the dimers as being metal-centred oxidized products rather than containing porphyrin cation radicals the possibility of ligand-centred versus metal-centred oxidation in higher-valent metallo porphyrins has been discussed by several authors.680-682... 

Izatt, R.M., McBride, D.W., Brown, P.R., Lamb, J.D., and Christensen, J.J., The influence of halocarbon solvent on macrocycle-mediated cation transport through liquid membranes. J. Membr. Sci., 1986, 28 69-76. 

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