Chloride ions reactions

Reaction with bromide ion has a rate expression similar to that for the chloride ion reaction, but when studied in the presence of arsenite ° so that the overall reaction is... 

Studies of the chloride ion reaction required careful attention to impurities which at first gave rise to rates of hydrogen peroxide decomposition comparable to those under study. The reaction obeys the rate law... 

Representative examples of pharmaceutically important acidic drugs are listed in Table 2-1. Each acid, or proton donur. yields a conjugate base. The latter is the product after the proton is lost from the acid. Conjugate ba-ses range frum the chloride ion (reaction a), which does not accept a proton in aqueous media, to ephedrine (reaction h). which is an excellent proton acceptor. 

The very similar onsets for reactions 11b and 11c reflect the fact that they have the same barrier at the PCI5 CP transition state. After the transition state, there is a competition between PCI3 and CI2 for the chloride ion. Reaction 11c is less endothermic than reaction 11b by the difference between D(Cl2-CP) = 99 5 kJ/mol and D(PCl3-CP) = 91 7 kJ/mol, or 8 9 kJ/mol. Fits to the data, which show slightly more Cp than PCI4 near threshold, are consistent with this small energy difference. 

The acidity of the solutions in which 50 mg and 500 mg of H-alg. prepared using IN HCl was immersed in 50 ml of water were pH 3.3 and pH 2.7, respectively, but for fresh H-alg. the pH was 4.2-4.5. The granular sample was washed with water until the rinsing no longer gave a chloride ion reaction in the preparation, although it showed some evidence of the presence of Cl". 

In some of our earlier work it was reported that electron exchange also occurred between 10" " and chloride and bromide ion, leading only to the formation of 10 ( ). We now think that this is not entirely correct. We now know that the chloride ion reaction leads to 3-chloro- (22) and a dichlotopetylene (23), presumed to be the 3,9-isomer (40). Whether or not their formation... 

The first step in the reaction sequence is a regioselective and stereoselective franj-acetoxypalladation of one of the double bonds, thus forming a jr-allylpalladium(II) intermediate, which is then attacked by a second nucleophile. By variation of the concentration of chloride ions, reactions selective for either the franj-diacetate or the cw-diacetate (eq 9) can be accomplished. The use of other chloride salts resulted in poor selectivity. The selectivity for the trans product at chloride-free conditions is further enhanced if the reaction is carried out in the presence of a sulfoxide co-catalyst. Enzymatic hydrolysis of the cis-meso-diacetate yields cw-l-acetoxy-4-hydroxy-2-cyclohexene in more than 98% ee, thus giving access to a useful starting material for enantios-elective synthesis. ... 

The development of scanning probe microscopies and x-ray reflectivity (see Chapter VIII) has allowed molecular-level characterization of the structure of the electrode surface after electrochemical reactions [145]. In particular, the important role of adsorbates in determining the state of an electrode surface is illustrated by scanning tunneling microscopic (STM) images of gold (III) surfaces in the presence and absence of chloride ions [153]. Electrodeposition of one metal on another can also be measured via x-ray diffraction [154]. 

The strongly electronegative (p. 49) chlorine atom becomes a chloride ion, the proton accepting the electron pair donated by the nitrogen atom. A similar reaction occurs when ammonia is passed into water, but to a much lesser extent as oxygen in water is a poorer donor of the electron pair ... 

When either hydrogen ions or hydroxide ions participate in a redox half-reaction, then clearly the redox potential is alTected by change of pH. Manganate(Vir) ions are usually used in well-acidified solution, where (as we shall see in detail later) they oxidise chlorine ions. If the pH is increased to make the solution only mildly acidic (pH = 3-6), the redox potential changes from 1.52 V to about 1.1 V, and chloride is not oxidised. This fact is of practical use in a mixture of iodide and chloride ions in mildly acid solution. manganate(VII) oxidises only iodide addition of acid causes oxidation of chloride to proceed. 

For this reaction, charcoal is a catalyst if this is omitted and hydrogen peroxide is used as the oxidant, a red aquopentammino-cobalt(lll) chloride, [Co(NH3)jH20]Cl3, is formed and treatment of this with concentrated hydrochloric acid gives the red chloro-p0itatnmino-coba. t(lll) chloride, [Co(NH3)5Cl]Cl2. In these latter two compounds, one ammonia ligand is replaced by one water molecule or one chloride ion it is a peculiarity of cobalt that these replacements are so easy and the pure products so readily isolated. In the examples quoted, the complex cobalt(III) state is easily obtained by oxidation of cobalt(II) in presence of ammonia, since... 

Nickel forms yellow anhydrous halides NiXjlX = F. Cl. Br) and a black iodide Nil2 all these halides are made by direct combination of the elements, and the chloride by reaction of sulphur dichloride oxide with the hydrated salt. All dissolve in water to give green solutions from which the hydrates can be crystallised the solutions contain the ion [NifHjOls], and the chloride crystallises as NiCl2.6H2O, nickel(II) chloride hexahydrate. 

Chandrasekhar, J., Smith, S,F,m Jorgensen, W.L. Theoretical examonation of the Stv2 reaction involving chloride ion and methyl chloride in the gas phase and aqueous solution. J. Amer. Chem. Soc. 107 (1985) 154-163. 

Figure 5.21 reprinted with permission from Chandrasekhar J, S F Smith and W L Jorgensen. Theoretical Examination of the 5 2 Reaction Involving Chloride Ion and Methyl Chloride in the Gas Phase and Aqueous Solution. The Journal of the American Chemical Society 107 154-163. 1985 American Chemical Society. 

In the Wacker process, the reaction is actually carried out in dilute HCl at a high concentration of chloride ion and an elevated temperature. The high concentration of CUCI2 shifts the equilibrium further to the right. 

Carbonyiation of butadiene gives two different products depending on the catalytic species. When PdCl is used in ethanol, ethyl 3-pentenoate (91) is obtained[87,88]. Further carbonyiation of 3-pentenoate catalyzed by cobalt carbonyl affords adipate 92[89], 3-Pentenoate is also obtained in the presence of acid. On the other hand, with catalysis by Pd(OAc)2 and Ph3P, methyl 3,8-nonadienoate (93) is obtained by dimerization-carbonylation[90,91]. The presence of chloride ion firmly attached to Pd makes the difference. The reaction is slow, and higher catalytic activity was observed by using Pd(OAc) , (/-Pr) ,P, and maleic anhydride[92]. Carbonyiation of isoprcne with either PdCi or Pd(OAc)2 and Ph,P gives only the 4-methyl-3-pentenoate 94[93]. 

Step 3 Reaction of tert butyl cation with chloride ion... 

Friedel-Crafts acylation of aromatic compounds (Section 12 7) Acyl chlorides and carboxylic acid anhydrides acylate aromatic rings in the presence of alumi num chloride The reaction is electrophil ic aromatic substitution in which acylium ions are generated and attack the ring... 

The component electrochemical reactions are the discharge of chloride ions, Cl , at the anode. 

Preparation of Pillared Clay Catalysts. PAG products are used for the preparation of zeolite-like catalysts by intercalation, the insertion of Al polycations molecules between the alurninosiHcate sheets of clay (3,33). Aqueous clay suspensions are slowly added to vigorously stirred PAG solutions, and the reaction mixture is aged for several hours. The clay is separated from the PAG solution and washed free of chloride ion. The treated clay is first dried at low temperature and then calcined in air at 450—500°G, producing a high surface area material having a regular-sized pore opening of about 0.6 to... 

Qualitative. The classic method for the quaUtative determination of silver ia solution is precipitation as silver chloride with dilute nitric acid and chloride ion. The silver chloride can be differentiated from lead or mercurous chlorides, which also may precipitate, by the fact that lead chloride is soluble ia hot water but not ia ammonium hydroxide, whereas mercurous chloride turns black ia ammonium hydroxide. Silver chloride dissolves ia ammonium hydroxide because of the formation of soluble silver—ammonia complexes. A number of selective spot tests (24) iaclude reactions with /)-dimethy1amino-henz1idenerhodanine, ceric ammonium nitrate, or bromopyrogaHol red [16574-43-9]. Silver is detected by x-ray fluorescence and arc-emission spectrometry. Two sensitive arc-emission lines for silver occur at 328.1 and 338.3 nm. 

All lation. In alkylation, the dialkyl sulfates react much faster than do the alkyl haHdes, because the monoalkyl sulfate anion (ROSO ) is more effective as a leaving group than a haHde ion. The high rate is most apparent with small primary alkyl groups, eg, methyl and ethyl. Some leaving groups, such as the fluorinated sulfonate anion, eg, the triflate anion, CF SO, react even faster in ester form (4). Against phenoxide anion, the reaction rate is methyl triflate [333-27-7] dimethyl sulfate methyl toluenesulfonate [23373-38-8] (5). Dialkyl sulfates, as compared to alkyl chlorides, lack chloride ions in their products chloride corrodes and requires the use of a gas instead of a Hquid. The lower sulfates are much less expensive than lower bromides or iodides, and they also alkylate quickly. 

Cyanide compounds are classified as either simple or complex. It is usually necessary to decompose complex cyanides by an acid reflux. The cyanide is then distilled into sodium hydroxide to remove compounds that would interfere in analysis. Extreme care should be taken during the distillation as toxic hydrogen cyanide is generated. The cyanide in the alkaline distillate can then be measured potentiometricaHy with an ion-selective electrode. Alternatively, the cyanide can be determined colorimetricaHy. It is converted to cyanogen chloride by reaction with chloramine-T at pH <8. The CNCl then reacts with a pyridine barbituric acid reagent to form a red-blue dye. 

Oxidation of Chlorides. Hypochlorite can also be formed by the in situ oxidation of chloride ions by potassium peroxymonosulfate [25482-78-4] (36). Ketones like acetone cataly2e the reaction (37). The triple salt of potassium peroxymonosulfate is a stable powder that has been combiaed with chloride salts and sold as toilet bowl cleaners. Bromides can be used ia place of chlorides to form hypobromites, and such combiaations are used to disiafect spas and hot tubs. 

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