Hydrochloric acid scavengers

Traces of HCI (moisture) inhibit the reaction because HCI2- anion exhibits much less nudeophilicity than Cf. Including hydrochloric acid scavenger such as little toluene diisocyanate in the mixture generally solves the problem. 

Peroxidation with peracetic acid is used to produce a number of other epoxides that are commercially available. These include epoxidized soybean oil and linseed oil used as vinyl plasticizers and hydrochloric acid scavengers in processing aliphatic halogen-containing polymers and cycloaliphatic diepoxides that are used in epoxy polymers for electrical and electronic applications. This process has also been used to make a large number of alkylene epoxides, the polymers of which have been described in the literature, but which have never reached commercial status. 

THPC—Amide Process. The THPC—amide process is the first practical process based on THPC. It consists of a combination of THPC, TMM, and urea. In this process, there is the potential of polymer formation by THPC, melamine, and urea. There may also be some limited cross-linking between cellulose and the TMM system. The formulation also includes triethanolamine [102-71-6J, an acid scavenger, which slows polymerization at room temperature. Urea and triethanolamine react with the hydrochloric acid produced in the polymerization reaction, thus preventing acid damage to the fabric. This finish with suitable add-on passes the standard vertical flame test after repeated laundering (80). 

The reaction can be driven to the tetraalkoxide stage by addition of an amine or ammonia to scavenge the Hberated hydrochloric acid. The amine or ammonium hydrochloride that forms can be filtered from the reaction mass and the tetraalkyl titanate purified by distillation. If the reaction is mn in the starting alcohol as solvent, the chloride salts formed are in a finely divided state and difficult to filter. When the reaction is mn in the presence of an inert hydrocarbon solvent such as heptane or toluene, a much more readily filterable salt is obtained. The solution of cmde tetraalkyl titanate can be distilled to remove solvent and give a pure product (1,2). 

Chloroaluminate laboratory preparations proved to be easily extrapolated to large scale. These chloroaluminate salts are corrosive liquids in the presence of protons. When exposed to moisture, they produce hydrochloric acid, similarly to aluminium chloride. However, this can be avoided by the addition of some proton scavenger such as alkylaluminium derivatives. In Difasol technology, for example, carbon-steel reactors can be used with no corrosion problem. 

Upon carefully controlled hydrolysis with hydrochloric acid at room temperature, the corresponding serine methyl esters 4 are obtained in reasonable yields. Higher yields of 4 arc obtained by hydrolyzing with dilute trifluoroacetic acid5. In some cases, the diastereomeric ratio of 4 does not exactly correspond to the d.r. of the adduct 3, which is attributed to different kinetics in the hydrolysis of the diastereomers 4. Subsequent treatment of the methyl ester with excess 5 N hydrochloric acid and methyloxirane as an acid scavenger results in the free amino acid 54,7. 

Is unstable under certain conditions. For example, this popular Industrial refrigerant and aerosol, In the presence of moisture, will react with steel or aluminum forming free hydrochloric acid As a result, efforts are made to maintain anhydrous conditions or provide acid scavengers. Although not widely known. Freon 11 will react with primacy and secondary alcohols Including polyols to liberate aldehydes, ketones and hydrochloric acid All the above... 

Olofson and coworkers discovered a relatively simple process of thermal elimination of hydrochloric acid from 1-chloroethyl carbamates to produce vinyl carbamates in high yields (Ref. 126). In a typical example, N-(vinyloxy-carbonyl) piperidine was obtained in 89 % yield just by refluxing N-(l-chloroethyloxycarbonyl) piperidine for 3 h in o.dichlorobenzene containing 1.2 eq. recyclable 2,4,6-collidine as an acid scavenger [see scheme 97]. 

On a weight-to-weight basis, approx 1.34 parts of sodium metabisulfite are required to remove one part of free chlorine. Upon reaction with water, sodium metabisulfite produces sodium bisulfate and hydrochloric acid. Dechloramination using sodium metabisulfite produces NH3 or NH4+, depending on pH. Sodium metabisulfite is a considerable oxygen scavenger. Its scavenging properties are comparable to that of sodium bisulfite. 

In some cases, acid scavenging is not used to stop further reactions of the acid, but to shift an existing equilibrium to the favored side. This is true for elimination reactions or the formation of ylids that are further used in Wittig reactions. Hydrochloric acid (HCI) is the acid most commonly formed. Usually, tertiary amines such as triethylamine are added to scavenge the acid. With the acid, these substances form solid salts which turn the reaction mixture into a suspension. The solid byproduct must then be removed. This can be done via a filtration step which requires expensive equipment, especially for precipitates vrith high filter resistances or continous filtration. If the product is inert to and insoluble in water, one can dissolve the solid by adding water to the reaction mixture, and remove the organic phase by a simple liquid-liquid separation. If the product is sensitive to acids and moisture, until now only filtration was left as a suitable means. 

In a typical reaction, a chlorosilane is reacted with the silanols on the silica surface in the presence of a basic scavenger of the hydrochloric acid (3,4) ... 

The most popular reversed-phase columns today are manufactured from silica-based bonded phases, and among those the Cjg-type bonded phase is most frequently used. As we have seen in Section 6.2, these bonded phases are prepared by reacting silica with a reactive silane that carries the ligand after which the phase is named. Commonly, chlorosilanes are used as the reactive silane in the presence of a scavenger of the hydrochloric acid, which is a byproduct of this reaction ... 

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