Freon solvents

HI/N2 in a freon solvent of —78 in the presence of catalytic amounts of added The darker... 

The mechanism of Scheme 5 accounts for these observations. Both excited diazirine 29 and carbene 20 are regarded as product precursors. A strict partition is postulated, whereby cyclobutene 30 comes only from 29, while the carbene reacts only intermolecularly, either with the freon solvent or added alkene. In Scheme 5, the excited diazirine pathway is expanded by interposition of the opened diazirine biradical, 29, as the proximate partitioning intermediate.46-48 Of course either an excited diazirine or a diazirine-derived biradical, would satisfy the need for a second intermediate in cases where curved correlation of addn/rearr vs. [alkene] require expansion of the kinetic scheme. 

The Freon solvent may be removed under reduced pressure in order to shorten the distillation time. Since phenylsulfur trifluoride attacks glass, the total time involved in the preparation and distillation in the glass equipment should be kept to a maximum of a few hours. It is recommended that the column be changed after distillation of the Freon . If the preparation cannot be completed within a day, the Freon solution of crude phenylsulfur trifluoride may be stored in polyethylene bottles overnight. 

Despite the intense investigations, data on H H bond formation rates are rather limited since the process is usually too fast for studies by standard kinetic techniqnes. Nevertheless, some estimations are possible from low-temperatnre NMR spectra, nsually recorded in Freon solutions. These Freon solvents stop MH HX bond formation even on the H NMR time scale. For example, the ReH resonance of [Cp ReH(CO)(NO)] decoalesces in the presence of acidic alcohols at 96 K, giving two resolved lines at —7.54 and —8.87 ppm, assignable to the free and dihydrogen-bonded hydride, respectively [33]. Under these conditions, the lifetime of the MH- HX complexes, x, can be calculated via... 

In the methanol-Freon solvent mixture the methylmagnesium carbonate is only about twice as tolerant to water (as measured by the volume of water necessary to cause precipitation) as magnesium methoxide, but this appears to be sufficient to eliminate most, if not all, of the problems with water sensitivity. The difference in stability is apparently a result of the lower concentration of carbon dioxide in the methanol-Freon mixture since the Freon is a much poorer solvent for carbon dioxide than is methanol. 

The solubility of carbon dioxide in the solvent also affects the rate of reaction in the preparation of methylmagnesium carbonate as shown in Table I. In pure methanol the pH became constant after carbonation for 40 min at room temperature, indicating complete reaction, whereas in the methanol-Freon solvent, the reaction takes about 2 hr. 

In spite of the longer time required, there is an advantage in using the methanol-Freon solvent mixture for the carbonation reaction since it contains a built-in indicator. The mixture becomes cloudy with precipitate and then clears as the carbonation is continued. The reaction is complete when the solution becomes clear again, and it is then ready for immediate use. 

Fluorination. In a freon solvent, this powerful fluorinating agent is able to convert compounds containing C=N (ketone oxime ethers, hydrazones) and C=S groups to gew-difluorides. Trifluoromethyl derivatives are directly obtained from alkyl dithioates. Caution must be paid to avoid the use of oxygenated solvents with which BrFi reacts violently. 

Simpler methods are also used. In the paint industry, Kauri butanol values are determined by establishing the tolerance of a standard solution of Kauri resin in n-butanol to the addition of diluents. This method is applicable to hydrocarbons (both aromatic and aliphatic) and CFCs. Figure 2.3.20 shows that there is a good correlation between the Kauri butanol number and the Hildebrand solubility parameter. The Kauri butanol number can be as high as 1000 (amyl ester of lactic acid) or 500 (Freon solvent M-162). 

B-staged epoxies and polyesters in glass cloth are used to bind and tie armatures, transformers and coils together. This reinforced material replaces previously used steel bonding, which had to be carefully insulated to eliminate shorting other electrical components. Acrylic resins on glass cloth or Nomex is used in hermetic and general purpose motors because of their resistance to DuPont s Freons, solvents, and oils. 

In the liquid-liquid extraction procedure, the water-insoluble quaternary amnonium salt tricaprylmethylanmonlum chloride dissolved in trichlorotrifluo-roethane (Freon-TF, ClgFCCClFg b.p. 47°) was used to extract periodate from neutral aqueous salt solutions. More than 992 of the periodate appeared in the organic phase after a single extraction of an iodate-periodate sample with an equal volume of the quaternary anmonium salt-Freon solvent system >942 of the iodate remained in the aqueous phase. High concentrations of sodium chloride (0.2-0.5 afforded clear, clean phase separation. 

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