Hydrogen chloride, as catalyst

Bromoacetic acid can be prepared by the bromination of acetic acid in the presence of acetic anhydride and a trace of pyridine (55), by the HeU-VoUiard-Zelinsky bromination cataly2ed by phosphoms, and by direct bromination of acetic acid at high temperatures or with hydrogen chloride as catalyst. Other methods of preparation include treatment of chloroacetic acid with hydrobromic acid at elevated temperatures (56), oxidation of ethylene bromide with Aiming nitric acid, hydrolysis of dibromovinyl ether, and air oxidation of bromoacetylene in ethanol. 

The condensation of 30 (via 69) with a-amino-a-cyano-acetamide in alcohol, using hydrogen chloride as catalyst, probably gave 2-carbamido-3-aminopyrrolo[2,3-6]indole (70) (Scheme 23) a possible normal reaction product128 would possess the structure 2-carba-mido-3-aminoimidazo[ 1,2-ajindoline (71). 

Acetals and ketals having a second junctional group ate made by these procedures. For example, acrolein reacts with ethyl orthoformate in alcohol solution with ammonium nitrate as catalyst to give acrolein diethyl acetal (73%). On the other hand, it reacts with ethyl ortho silicate with anhydrous hydrogen chloride as catalyst to furnish (i-ethoxypropionaldehyde diethyl acetal (76%). p-Bromoacetophenone and ethyl orthoformate give the corresponding ketal in 65% yield. p-Methoxy- and m-amino-benzaldehyde diethyl acetals are made in a similar way in 96% and 85% yields, respectively. a-Keto esters like ethyl a-keto-n-butytate and ethyl a-keto-tr-valetate are converted to their diethyl ketals in excellent yields by the action of orthoformic ester in ethanol-hydrochloric acid solution. If the reaction is carried out in the presence of ethylene glycol instead of ethanol and, in addition, the volatile products are removed by distillation, then the ethylene ketal is formed in almost quantitative yield (cf. method 133). 

Early studies employing hydrogen chloride as catalyst on perbenzoylated sugars showed complicated product mixtures [1,30], while Lewis acid-catalyzed mercaptolysis of peracetylated monosaccharides afforded the corresponding thioglycosides in good yields [31,32,33], However, from a preparative point of view (smell, work-up), the present use of a solvent and only a small excess of thiol is definitely an advantage. 

In a reaction analogous to one previously reported,1 di-O-acetyl-D-arabinal and adenine, in methyl sulfoxide containing hydrogen chloride as catalyst, gave37 9-(3,4-di-0-acetyl-2-de jxy-fi-D-erythro-pentopyranosyl)adenine in 7% yield. Similarly, acid-catalyzed addition of 6-chloropurine and 2,6-dichloropurine to this glycal derivative afforded other 2 -deoxynucleosides.37a... 

Use of hydrogen chloride as catalyst (100 g of anhydrous ethanol containing 3 % of HC1), boiling for 2h, and analogous working up gives 76% of the theoretical amount of ethyl benzoate. 

During World War II, the great demand for aircraft fuel necessitated the production of large quantities of isobutane, a basic raw material in the production of high octane aviation gasoline. (See chapter on Alkylation of Alkanes. ) Various processes have been developed for the isomerization of n-butane to isobutane all of them employed aluminum chloride-hydrogen chloride as catalyst. The difference between the various processes consisted either in the method of introduction of aluminum chloride to the reaction zone, the catalyst support, or the state of the catalyst. The following summary describes some of the main features of the various processes which were developed ... 

Ethyl benzoate hydrogen chloride as a catalyst). Pass dry hydrogen chloride (Section 11,48,1) into a 600 ml. round-bottomed flask containing 116 g. (145 ml.) of absolute ethyl alcohol, cooled in an ice bath, until the increase in weight is 6 g. Add 30 g. of benzoic acid and reflux the mixture for 4 hours. Isolate the pure ester, b.p. 212-214°, as described for Methyl Benzoate. The yield is 32 g. 

Using cuprous chloride as catalyst, hydrogen chloride adds to acetylene, giving 2-chloro-1,3-butadiene [126-99-8], chloroprene, C H Cl, the monomer for neoprene mbber. 

With thionyl chloride as catalyst, hydrogen peroxide adds to vinyl ethers in anti-Markovnikov fashion, as do monothioglycols with amine catalysts... 

Hydrogen Chloride as By-Product from Chemical Processes. Over 90% of the hydrogen chloride produced in the United States is a by-product from various chemical processes. The cmde HCl generated in these processes is generally contaminated with impurities such as unreacted chlorine, organics, chlorinated organics, and entrained catalyst particles. A wide variety of techniques are employed to treat these HCl streams to obtain either anhydrous HCl or hydrochloric acid. Some of the processes in which HCl is produced as a by-product are the manufacture of chlorofluorohydrocarbons, manufacture of aUphatic and aromatic hydrocarbons, production of high surface area siUca (qv), and the manufacture of phosphoric acid [7664-38-2] and esters of phosphoric acid (see Phosphoric acid and phosphates). 

Liquid-Ph se Processes. Prior to 1980, commercial hquid-phase processes were based primarily on an AIQ. catalyst. AIQ. systems have been developed since the 1930s by a number of companies, including Dow, BASF, Shell Chemical, Monsanto, SociStH Chimique des Charboimages, and Union Carbide—Badger. These processes generally involve ethyl chloride or occasionally hydrogen chloride as a catalyst promoter. Recycled alkylated ben2enes are combined with the AIQ. and ethyl chloride to form a separate catalyst—complex phase that is heavier than the hydrocarbon phase and can be separated and recycled. 

A general method for preparing acetals by treating aldehydes or ketones with the appropriate tetra-alkyl silicate, using dry hydrogen chloride as the catalyst. Helferich and Hausen, Ber. 57, 795 (1924). 

TPB is produced by the reaction of tetrapropylene (see page 65) with benzene in the presence of aluminum chloride or hydrogen fluoride as catalyst. The reaction conditions for both catalysts differ insignificantly from each other. 

Bromoacetic acid has been prepared by direct bromination of acetic acid at elevated temperatures and pressures,2-3-4 or with dry hydrogen chloride as a catalyst 6 and with red phosphorus as a catalyst with the formation of bromoacetyl bromide.6-7-8-9-19 Bromoacetic acid has also been prepared from chloroacetic acid and hydrogen bromide at elevated temperatures 6 by oxidation of ethylene bromide with fuming nitric acid 7 by oxidation of an alcoholic solution of bromoacetylene by air 8 and from ethyl a,/3-dibromovinyl ether by hydrolysis.9 Acetic acid has been converted into bromoacetyl bromide by action of bromine in the presence of red phosphorus, and ethyl bromoacetate has been... 

According to the submitters, yields of the order of 95 per cent of other acid chlorides can be obtained by the use of phthal-oyl chloride (1 mole of chloride to 1 mole of a monobasic acid, 2 moles of chloride to 1 mole of a dibasic acid). Zinc chloride, as catalyst, is not necessary in the reaction of most acids and their anhydrides with phthaloyl chloride. When acids are used, it is best to add one of the components slowly, in order to avoid a too violent evolution of hydrogen chloride on wanning. 

The method of preparation was described by Wright, Chute, Herring and Toombs [71]. They treated diethanolamine with a mixture of nitric acid and acetic anhydride in the presence of hydrogen chloride as a catalyst. Instead of hydrogen chloride, its salts such as zinc chloride may be used. The yield amounts to 90%, but is much lower without a catalyst. 

Permethylation of carbohydrates.1 Permethylation of carbohydrates in a solid-liquid system is not possible because of lack of solubility in benzene or methylene chloride. The difficulty can be circumvented by reaction of peracetylated sugars with methyl bromide in C6H6-aqueous NaOH with tetrabutylammonium hydrogen sulfate as catalyst. 

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