Perchloric acid halides

The reaction between Fe(IlI) and Sn(Il) in dilute perchloric acid in the presence of chloride ions is first-order in Fe(lll) concentration . The order is maintained when bromide or iodide is present. The kinetic data seem to point to a fourth-order dependence on chloride ion. A minimum of three Cl ions in the activated complex seems necessary for the reaction to proceed at a measurable rate. Bromide and iodide show third-order dependences. The reaction is retarded by Sn(II) (first-order dependence) due to removal of halide ions from solution by complex formation. Estimates are given for the formation constants of the monochloro and monobromo Sn(II) complexes. In terms of catalytic power 1 > Br > Cl and this is also the order of decreasing ease of oxidation of the halide ion by Fe(IlI). However, the state of complexing of Sn(ll)and Fe(III)is given by Cl > Br > I". Apparently, electrostatic effects are not effective in deciding the rate. For the case of chloride ions, the chief activated complex is likely to have the composition (FeSnC ). The kinetic data cannot resolve the way in which the Cl ions are distributed between Fe(IlI) and Sn(ll). 

Bi(V) in aqueous perchloric acid is very strongly oxidising but kinetic studies have been confined to a few stopped-flow measurements on oxidation of iodide, bromide and chloride ions. The appearance of Bi(III)-halide complexes was first-order with respect to Bi(III) and in all cases the first-order rate coefficient,, was the same, i.e. 161 + 8 sec at 25 °C ([H30 ] = 0.5 M, p. = 2.0 A/), irrespective of the nature or concentration of the halide. A preliminary attack on solvent is compatible with these interesting results, viz. 

Perchloric acid Iodides See Other METAL HALIDES... 

Trimethylpyrylium perchlorate has been prepared from 2,6-dimethylpyrone and methylmagnesium halides 6 from mesityl oxide and sulfoacetic acid 6 from mesityl oxide (or less satisfactorily from acetone) and a mixture of acetic anhydride and perchloric acid 7 from mesityl oxide, acetyl chloride, and aluminum chloride 8 and from <-butyl chloride, acetyl chloride,... 

In general, the halide ions, namely chloride, bromide and iodide are very weakly basic in character so much so that they cannot react quantitatively with acetous perchloric acid. In order to overcome this problem, mercuric acetate is usually added (it remains undissociated in acetic acid solution) to a halide salt thereby causing the replacement of halide ion by an equivalent amount of acetate ion, which serves as a strong base in acetic acid as shown below ... 

Potentiometric non-aqueous titration (using bismuth oxyacetate and perchloric acid or trifluoromethylsulfonic acid) was used by Zakhari et al. (90) for the determination of procaine and other drugs (halides and nitrogen bases) [90], Procaine hydrochloride was dissolved in 5 1 acetic... 

Oxetanes are much less susceptible to cleavage by nucleophiles than oxiranes, except in the presence of acids. Several types of acid-catalyzed nucleophilic reactions are described in the previous section, such as reaction of hydrogen halides to give 3-halogeno-1-propanols and various acid-catalyzed solvolysis reactions. Another example of this type is the reaction of thiourea with 2-alkyloxetanes in the presence of hydrochloric or perchloric acid to give excellent yields of 3-alkyl-3-hydroxybutylisothiouronium salts (equation 39) <67CR(C)(264)1309>. 

The acylation of unsaturated ketones constitutes one of the earliest routes to pyrylium salts (19CB1195). The reaction is better achieved with acyl halides than by anhydrides, and aliphatic are preferable to aromatic acid derivatives. The presence of a Lewis or Bronsted acid is usually necessary and iron(III) chloride, aluminum chloride, boron trifluoride and perchloric acid have found frequent application. It is considered that these interact with the acid derivative to generate the actual acylating agent. 

In absence of diluent or other effective control of reaction rate, the sulfoxide reacts violently or explosively with the following acetyl chloride, benzenesulfonyl chloride, cyanuric chloride, phosphorus trichloride, phosphoryl chloride, tetrachlorosilane, sulfur dichloride, disulfur dichloride, sulfuryl chloride or thionyl chloride [1]. These violent reactions are explained in terms of exothermic polymerisation of formaldehyde produced under a variety of conditions by interaction of the sulfoxide with reactive halides, acidic or basic reagents [2]. Oxalyl chloride reacts explosively with DMSO at ambient temperature, but controllably in dichloromethane at —60°C [3]. See Carbonyl diisothiocyanate, and Dinitrogen tetraoxide, and Hexachlorocyclo-triphosphazine, and Sodium hydride, all below See Perchloric acid Sulfoxides... 

The GC of halides is considered first. Fluorides react with trialkylchlorosilanes to form volatile trialkylfluorosilanes, which can be analysed by GC. Triethylchlorosilane [571,572] was used as a reagent for the analysis of fluorides in different materials in teeth fluorides were determined after the treatment with trimethylchlorosilane [573], as follows. The sample was dissolved in 0.5 M perchloric acid and 5 jd of the solution were transferred into a polyethylene test-tube containing 50 (A of benzene in which 50 Mg of trimethylchlorosilane and 65 ng of 2-methylbutane (internal standard) had been dissolved. The sample was stirred vigorously at 4°C for 20 min and 6—8 m1 of the benzene layer were analysed (20% of DC-200/50, 80° C). With the use of an FID, less than 1 ng of fluoride could be determined in the sample. 

The general formula [RCr(OH2)s] + describes this group of complexes. Reaction of an alkyl halide with chromium(II) perchlorate in perchloric acid yields these... 

Equation (47) was suggested for the first time by Bredig and Ripley [202]. In order to establish it unambiguously, it is necessary to carry out experiments at a constant ionic strength since feH and kHX are influenced by salt effects. Studies in the presence of halides at a constant ionic strength have never been done. Other approaches have been used instead. Albery and Bell [200] measured hydrolysis rates of ethyl diazoacetate in moderately concentrated perchloric acid and hydrochloric acid solutions. Rates in hydrochloric acid were faster than those in perchloric acid at the same stoichiometric concentration. In order to verify the dependence on the chloride ion concentration, it was assumed that rates of the reaction without participation of chloride (first term in eqn. (47)) are the same in perchloric acid and hydrochloric acid if the H0 values are equal. Activity coefficients were introduced in eqn. (47) as follows ... 

Hydrolysis rates of primary diazoketones [207] and diazosulfones [208, 209] are faster in hydrochloric acid solutions than in perchloric acid solutions. Furthermore, very strong positive salt effects are caused by alkali halides at a constant concentration of strong acid [207, 209]. In the acid catalyzed hydrolysis of PhCH(OCOOMe)COCHN2, the reaction rate as well as the percentage of bromoketone in the product strongly increase with increasing bromide ion concentration [211]. 

Protonation of ketene 0,N-acetals with strong acids gives rise to the formation of iminium compounds, e.g. (98 equation 57). Ketene OA -acetals are transformed by alkyl halides or acyl halides to a-sub-stituted amides via unstable iminium salts (99 equation 58).Iminium compounds of this type are isol-able if they are immediately precipitated, e.g. as perchlorate salts (100 equation 59), Heterocumulenes such as isocyanates, isothiocyanates or S02 form 1,4-dipoles with ketene OA -acetals, which can be stabilized by protonation with perchloric acid to give salts, e.g. (101 equation 60). 

THF is useful in the malonic ester synthesis since it dissolves many sodio derivatives. Use of aqueous THF facilitates diazotization of salts of aminopolyphenyls which are sparingly soluble in water and is recommended also for the Schiemann reaction. It is superior to ether as solvent for coupling of an acetylenic Grignard reagent with a propargylic halide. Cremlyn and Chisholm found THF superior to dioxane or Cellosolve as solvent for the hydrogenation of cholesterol at ordinary temperature and pressure with perchloric acid as catalyst. 

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