HC1, reaction with

Figure 9 Original and finite-resolution densities of reactive states for the Cl + HC1 reaction with 7 = 0. (a)N"(E). (b) p°( ). (c) ( 0.027 eV). (d) p"(E 0.027 eV). The value of AT( F) is indicated at each minimum in p°( F). (Reprinted with permission from Ref. 11, copyright 1992, American Chemical Society.)...

Notice that water can act either as an acid or as a base, d.epending on the circumstances. In its reaction with HC1, water is a base that accepts a proton to give the hydronium ion, In its reaction with amide ion, -NH2, however,... 

The chemistry of alkynes is dominated by electrophilic addition reactions, similar to those of alkenes. Alkynes react with HBr and HC1 to yield vinylic halides and with Br2 and Cl2 to yield 1,2-dihalides (vicinal dihalides). Alkynes can be hydrated by reaction with aqueous sulfuric acid in the presence of mercury(ll) catalyst. The reaction leads to an intermediate enol that immediately isomerizes to yield a ketone tautomer. Since the addition reaction occurs with Markovnikov regiochemistry, a methyl ketone is produced from a terminal alkyne. Alternatively, hydroboration/oxidation of a terminal alkyne yields an aldehyde. 

Note that in the S l reaction, which is often carried out under acidic conditions, neutral water can act as a leaving group. This occurs, for example, when an alkyl halide is prepared from a tertiary alcohol by reaction with HBr or HC1 (Section 10.6). The alcohol is first protonated and then spontaneously loses H2O to generate a carbocation, which reacts with halide ion to give the alkyl halide (Figure 11.13). Knowing that an SN1 reaction is involved in the conversion of alcohols to alkyl halides explains why the reaction works well only for tertiary alcohols. Tertiary alcohols react fastest because they give the most stable carbocation intermediates. 

The elimination of HC1 from the isomeric menthyl and neomenthyl chlorides shown in Figure 11.20 gives a good illustration of this trans-diaxial requirement. Neomenthyl chloride undergoes elimination of HC1 on reaction with ethoxide ion 200 times as fast as menthyl chloride. Furthermore, neomenthyl chloride yields 3-menthene as the major alkene product, whereas menthyl chloride yields 2-nienthene. 

One of the more common methods of alcohol protection is by reaction with a chlorotrialkylsilane, CI-S1R3, to yield a trialkylsilyl ether, R -O-SilTj. Chlorotrimethylsilane is often used, and the reaction is carried out in the presence of a base, such as tciethylamine, to help form the alkoxide anion from the alcohol and to remove the HC1 by-product from the reaction. 

Conversion of Acid Halides into Esters Alcoholysis Acid chlorides react with alcohols to yield esters in a process analogous to their reaction with water to yield acids. In fact, this reaction is probably the most common method for preparing esters in the laboratory. As with hydrolysis, alcoholysis reactions are usually carried out in the presence of pyridine or NaOH to react with the HC1 formed. 

When an alkene reacts with an electrophile, such as HC1, initial addition of H+ gives an intermediate cation and subsequent reaction with Cl" yields an addition product (Section 6.7). When an enol reacts with an electrophile, however, only the initial addition step is the same. Instead of reading with Cl- to give an addition product, the intermediate cation loses the -OH proton to give an cr-substituted carbonyl compound. The general mechanism is showm in Figure 22.3. 

It is found that 19.26 mL of 0.150 M NaOH is required to titrate the excess HC1 left after reaction with the limestone. What is the mass percent of CaC03 in the limestone ... 

This is in accord with Le Chatelier s Principle. Addition of HC1 to water raises [H+]. By Le Chatelier s Principle, processes take place that tend to counteract partially the imposed change. Reaction with OH (aq) does tend to counteract the raised concentration of H+(aq). 

Merck s thienamycin synthesis commences with mono (V-silylation of dibenzyl aspartate (13, Scheme 2), the bis(benzyl) ester of aspartic acid (12). Thus, treatment of a cooled (0°C) solution of 13 in ether with trimethylsilyl chloride and triethylamine, followed by filtration to remove the triethylamine hydrochloride by-product, provides 11. When 11 is exposed to the action of one equivalent of tm-butylmagnesium chloride, the active hydrogen attached to nitrogen is removed, and the resultant anion spontaneously condenses with the electrophilic ester carbonyl four atoms away. After hydrolysis of the reaction mixture with 2 n HC1 saturated with ammonium chloride, enantiomerically pure azetidinone ester 10 is formed in 65-70% yield from 13. Although it is conceivable that... 

Telescope the Process by Combining Stages. This has been done successfully in the conversion of propylene to acrylonitrile by direct ammoxidation rather than oxidation to acrolein followed by reaction with ammonia in a separate stage, as was described in the earlier patent literature. The oxychlorination of ethylene and HC1 directly to vinyl chloride monomer is another good example of the telescoping of stages to yield an economic process. 

The formation of chloramine as an intermediate, followed by reaction with nitric acid to produce the corresponding nitramine and HOC1, may explain the catalytic action of HC1 in the nitration of amines... 

Diaminobiphenyl (former name benzidine) can be easily bisdiazotized, but is not cleanly monodiazotized by reaction with one equivalent of a nitrosating agent. However, 4-aminobiphenyl-4,-diazonium ions are formed in a triazene equilibration of a 1 1 mixture of 4,4 -diaminobiphenyl with biphenyl-4,4 -bisdiazonium salts in aqueous HC1 (Tauber, 1894 see also Sec. 13.4). Methods for mono- and bisdiazotiza-tion of 1,4-diaminobenzene (/ -phenylenediamine) have been described by Saunders and Allen (1985, p. 29 see also Sec. 2.2). 

Figure 9 A synthetic mixture of water-soluble carboxylic acids separated by anion-exchange chromatography. Column 0.3 cm x 300 cm Diaoion CA 08, 16-20 p (Mitsubishi Kasei Kogyo). Eluant 200 mM HC1. Detection reaction with Fe3-benzohy-droxamic acid-dicyclohexy carbodiimide-hydroxylamine perchlorate-triethyl amine with absorbance at 536 nm. Analytes (1) aspartate, (2) gluconate, (3) glucuronate, (4) pyroglutamate, (5) lactate, (6) acetate, (7) tartrate, (8) malate, (9) citrate, (10) succinate, (11) isocitrate, (12) w-butyrate, (13) a-ketoglutarate. (Reprinted with permission from Kasai, Y., Tanimura, T., and Tamura, Z., Anal. Chem., 49, 655, 1977. 1977 Analytical Chemistry).

The first reported porphyrin complexes of platinum(IV) date from 1980 and were obtained by hydrogen peroxide oxidation of platinum(II) porphyrin complexes in an acidic medium (HC1).479 Since then oxidation of platinum(II) complexes of other porphyrins has been achieved by the same method,480 and by chlorine,481 or bromine482 oxidation. Reaction with iodine did not lead to oxidation and treatment of platinum(IV) porphyrin complexes with iodide resulted in reduction to platinum(II). 

Retarded acids are primarily applicable to sandstone acidizing. Fluoroboric acid slowly hydrolyzes to form the more reactive hydrofluoric acid (109,110). The time required for this hydrolysis process may enable deeper penetration of the HF into the formation although one report contradicts these findings (111). Na TiF and similar salts also slowly generate HF in acid media (112). Phosphorous acid addition to hydrochloric acid has been used to reduce the HC1 reaction rate with limestone (113). 

This facile approach to the carbene chemistry of rhenium has not yet been investigated with technetium. Further reactions with the technetium cluster 44a have been performed in C6H6/HC1 to yield the compound [( 6H6)Tc(CO)3]+ (66) which previously had only been described for manganese and rhenium [81]. "Tc-NMR of the latter compound exhibits a resonance at -1983 ppm (relative to [Tc04]- ), and it therefore fits very well into the range proposed for Tc(I) complexes. 

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