Chloroformate preparation

Terminal and disubstituted internal alkenes react rather slowly with HC1 in nonpolar solvents. The rate is greatly accelerated in the presence of silica or alumina in noncoordinating solvents such as dichloromethane or chloroform. Preparatively convenient conditions have been developed in which HC1 is generated in situ from SOCl2 or (ClCO)2.2 These heterogeneous reaction systems also give a Markovnikov orientation. 

B) Benzyl Carbamate.—A measured aliquot (suitably 10 cc.) of the solution of benzyl chloroformate, prepared as described above, is added slowly and with vigorous stirring to five volumes of cold concentrated ammonium hydroxide (sp. gr. 0.90), and the reaction mixture is allowed to stand at room temperature for thirty minutes. The precipitate is filtered with suction, washed with cold water, and dried in a vacuum desiccator. The yield of practically pure benzyl carbamate, melting at 85-86°, is 7.0-7.2 g. (91-94 per cent of the theoretical amount based on the benzyl alcohol used in. 4). Pure benzyl carbamate melting at 87° is obtained by recrystallizing the slightly impure material from two volumes of toluene. 

EPA (U.S. Environmental Protection Agency), 1985. Health Assessment Document for Chloroform. Prepared by the Office of Health and Environmental Assessment, Environmental Criteria and Assessment Office, Research Triangle Park, NC, for the Office of Air Quality Planning and Standards. EPA 600/8—84—004F. 

For nonquantitative -C-NMR techniques, this could be the extent of the analysis possible. However, the combination of F-NMR with C-NMR allowed us to quantitatively calculate the isomer composition and to investigate solvent effects on isomer formation. Figure 17.5 illustrates these concepts. Two possible isomers (structures in Figure 17.5) can be formed from the reaction of 3-fluorophthalic anhydride with 4-fluoroaniline. Upon formation of the amic acid based on 3-fluorophthalic anhydride with 4-fluoroaniline, two isomers were found in both NMP and chloroform reactions as shown by the F-NMR spectra in Figure 17.5a and b, respectively. Two signals were observed for each type of fluorine atom, labeled as Fi and F2 for the anhydride and amine fluorine atoms respectively. Ortho and meta isomers were formed in a ratio of 4.75 1 in solution in NMP, while the same ratio was 1.04 1 in chloroform, where the product precipitated. The major isomer was the ortho in each case as determined by C-NMR of the chloroform prepared amic acid (Table 17.1). 

Method. The sample is spotted on to a TLC plate (silica gel) followed by 2 d of a solution of TFA (50% in chloroform, prepared fresh each day). The reaction is allowed to proceed for 5 min, after which time the plate is dried with a stream of nitrogen or air. The plate is then developed with chloroform—acetone (in various ratios such as 9 1 or 4 1), benzene-ethanol-water (43 35 19) or ethyl acetate-methanol-water (96 3 1). The plate is removed from the tank and dried in the dark. The spots are observed visually under UV light at long wavelength. The derivative of aflatoxin Bt appears blue, while the derivative of aflatoxin Gi is green. This confirmation technique has been applied to peanuts, brazil nuts, pistachio nuts, walnuts, barley, corn and other foods. 

Chloroformates, prepared by controlled reaction of phosgene with alcohols, are decar-boxylated in presence of ammonium, phosphonium or sulfonium salt catalyst (equation 170)1092. 

Remove 0.3 ml ofyour extracted lipids in chloroform prepared on Day 1 and place in a 1.5-ml microcentrifuge tube. Dry the sample under a stream of N2 and resuspend the lipids in 40 pi of chloroform. 

In PBLG-chloroform preparation, the V, mode often shows the (f —90 pattern under no external field, showing that the maximum polarizabili direction of the molecular cluster is at 45° with respect to the cluster axis (see Section II). Even in such a case, this pattern turns to the 45 pattern in external lds the 45 Vn pattern is often seen in liquid crystalline solutions when shearing stresses are suspected to have operated on the solutioiL... 

The 2,2,2-trichloroethoxycarbonyl group is stable to acid, but somewhat labile to base. A superior protective group is the 2,2,2-trichloro-t-butyloxycarbonyl group, which is stable to both acid and base. The group is introduced by means of the stable chloroformate, prepared from chloretone (equation II). This protecting group is cleaved by the anion 2 in about 1 minute in approximately 90% yield. It is also... 

A mixture of the azole (50 mmol), aryl halide (50 mmol), anhydrous potassium carbonate (7g) and copper(II) oxide (0.25 g) in pyridine (10 ml) is refluxed for some hours. The cooled mixture is filtered, extracted with benzene or chloroform, and the combined extracts and filtrate are rotary evaporated to give a residue which is chromatographed on alumina, eluting with benzene or benzene-chloroform. Prepared in this way are the following 1-substitutcd imidazoles (1-substituent, heating time, yield given) o-nitrophenyl, 11 h, 64% m-nitrophenyl, 19.5h, 30% p-nitrophenyl, lOh, 54% o-cyanophenyl, 50h, 43% tw-cyanophenyl, 50.5 h, 13% p-cyanophenyl, 50h, 73% o-acctylphenyl, 7h, 33% m-acetylphenyl, 48h, 68% p-acetylphcnyl, 48h, 82% a-pyridyl, 19h, 37% 3-pyridyl, 24h, 51% y-pyridyl, 12h, 30%. 

Furthermore, the same a mmetric addition reaction in chloroform was studied by Ueyanagi and Inoue (22) using as catalyst the terminal amino group of poly(S-alanine), insoluble in chloroform, prepared by the polymerization of the NCA initiated with butylamine in acetonitrile. As Table 5 ows, the optical rotation of the addition product obtained by poly(S-alanine) as catalyst was larger than that obtruned by its terminal model, ethyl S-alaninate or S-alaninepropylamide, similarly to the case of PBLG. When poly(S-alanine) was used as catalyst, however, the largest optkal rotation of the product was obtained when n-3,n being the ratio of the NCA to the initiator in the preparation of the polymer (Table 5). 

The solvent used for nearly all measurements was a mixture of diethyl ether, isopentane, ethanol and chloroform prepared from analytical reagent grade solvents in the volnme ratio of 75 75 30 20. Stock 1000 ppm solutions of these compounds were prepared by direct dissolution in the solvent mixture, or by dissolution in chloroform followed by dilution with ether, isopentane and ethanol. Nonox Cl was dissolved in diethylamine to prepare a 1000 ppm solution - 1 ml was then diluted to 10 ml with a mixture of ether, isopentane and ethanol. 

INSTRUCTOR PREPARATION. The active brominating reagent in this reaction is liquid Br2 dissolved in chloroform. Prepare a solution of200 /tL (624 mg) of bromine dissolved in 8 ml of chloroform multiplied by the number of students carrying out the experiment. The reagent should be prepared, dispensed, and added to the reaction HOOD in the hood. 

An early review on the chemistry of chloroformates ( esters of chloroformic acid ) covered the methods of synthesis, physical and chemical properties and highlighted the possibility of polymer synthesis from chloroformates [10]. An example of a classical chloroformate preparation by phosgenation of benzylic alcohol with phosgene gas is given in [11]. An improved procedure for the synthesis of benzyl chloroformate (1, Z-Cl) in 97% yield is given in [12]. 

Tab. 4.2. Hydantoins 26 synthesized from non-commercially available alkyl and aryl chloroformates prepared with triphosgene [24],...

Tab. 4.3. Unstable chloroformates prepared with diphosgene and triphosgene [44].

Azidoformates have also been applied to polymeric substrates. Polymeric and non-polymeric compounds, p-RC6H4NEt(CH2)20CON3, useful as azo dyes or oil-, laundry-, and waterproofing agents for polyamide and polyester fibres, have been manufactured by treatment of a variety of chloroformates (prepared in situ with phosgene) with sodium azide [284]. 

Hydroxyquinoline (C9H7NO) in chloroform Prepare a solution of 0.3g8-hydroxyqui-noline (oxin) in 500 mL of chloroform, redistilled. Store the reagent cool and in the dark. It should be prepared weekly. 

A soln. of glutarimide and dinitrogen pentoxide in chloroform prepared at — 15° allowed to warm slowly to room temp., and the product isolated after 15hrs. N-nitroglutarimide. Y 88%. F. e. s. J. Runge and W. Treibs, J. pr. 15, 223 (1962). 

With tertiary amines, phosgene-amine complexes can be formed. Warming results in decomposition to an N,N-dialkylchloroformamide by elimination of alkyl chloride. This has been utilized for the mild and high yielding deprotection of A-methyl amines (eq 8). a-Chloroethyl chloroformate, prepared... 

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