Strong acid catalysts

Although acetyl chloride is a convenient reagent for deterrnination of hydroxyl groups, spectroscopic methods have largely replaced this appHcation in organic chemical analysis. Acetyl chloride does form derivatives of phenols, uncompHcated by the presence of strong acid catalysts, however, and it finds some use in acetylating primary and secondary amines. 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

Aliphatic Aldehyde Syntheses. Friedel-Crafts-type aUphatic aldehyde syntheses are considerably rarer than those of aromatic aldehydes. However, the hydroformylation reaction of olefins (185) and the related oxo synthesis are effected by strong acid catalysts, eg, tetracarbonylhydrocobalt, HCo(CO)4 (see Oxo process). 

The second and third reactions are economical, but the first is not. The second reaction is used in a process where HCN is oxidized to (CN)2 and hydrolyzed in the presence of a strong acid catalyst to give oxamide. The third reaction is employed in a newly developed process where diaLkyl oxalates are converted to oxamide by the ammonolysis reaction. This reaction easily proceeds without catalysts and quantitatively gives oxamide as a powder. 

In the presence of strong acid catalysts such as sulfuric acid, aUphatic (R CHO) aldehydes react with alkyl hydroperoxides, eg, tert-55ky hydroperoxides, to form hydroxyalkyl alkyl peroxides (1), where X = OH R, = hydrogen, alkyl and = tert — alkyl. 

In the presence of strong acid catalysts many commonly used commercial alkyl hydroperoxides decompose to acetone to some extent. Consequendy, the diperoxyketals derived from other ketones and alkyl hydroperoxides are often contaminated with small amounts of diperoxyketals derived from acetone (1, X = OOR, = methyl, R = R = tert — alkyl). 

Strong-Acid Catalysts, Novolak Resins. PhenoHc novolaks are thermoplastic resins having a molecular weight of 500—5000 and a glass-transition temperature, T, of 45—70°C. The phenol—formaldehyde reactions are carried to their energetic completion, allowing isolation of the resin ... 

THE can be polymerized by many strongly acidic catalysts, but not all of them produce the requked bitimctional polyether glycol with a minimum of by-products. Several large-scale commercial polymerization processes are based on fluorosulfonic acid, HESO, catalysis, which meets all these requkements. The catalyst is added to THE at low temperatures and an exothermic polymerization occurs readily. The polymerization products are poly(tetramethylene ether) chains with sulfate ester groups (8). 

The catalysts used in the industrial alkylation processes are strong Hquid acids, either sulfuric acid [7664-93-9] (H2SO or hydrofluoric acid [7664-39-3] (HE). Other strong acids have been shown to be capable of alkylation in the laboratory but have not been used commercially. Aluminum chloride [7446-70-0] (AlCl ) is suitable for the alkylation of isobutane with ethylene (12). Super acids, such as trifluoromethanesulfonic acid [1493-13-6] also produce alkylate (13). SoHd strong acid catalysts, such as Y-type zeoHte or BE -promoted acidic ion-exchange resin, have also been investigated (14—16). 

Acid catalysis using strong acid catalysts, especially 2eohtes which enhance selectivity because of pore si2e restrictions, has been used for a variety of alkenes and dienes (9—11). /-Butyltoluenediamine [106398-83-8] (/-BTDA) (C H gN2) is available on a semicommercial basis (12). 

Acetone also reacts with diphenylamine, in the presence of acid, to form a variety of condition-dependent products (5). Excess amine and a small amount of strong acid catalyst at 100—150°C give 2,2-[4,4 -(dianilino)diphenyl]-propane [2980-26-9] (6). With a large amount of hydrochloric acid at 250°C in the presence of excess diphenylamine, the main product is 9,9-dimethylacridan [6267-02-3]. 

On curing, amino resins not only react with the nucleophilic sites (hydroxyl, carboxyl, amide) on the other film formers in the formulation, but also self-condense to some extent. Highly alkylated amino resins have less tendency to self-condense (33,34) and are therefore effective cross-linking agents, but may require the addition of a strong acid catalyst to obtain acceptable cure even at bake temperatures of 120—177°C. 

Esterification. Extensive commercial use is made of primary amyl acetate, a mixture of 1-pentyl acetate [28-63-7] and 2-metliylbutyl acetate [53496-15-4]. Esterifications with acetic acid are generally conducted in the Hquid phase in the presence of a strong acid catalyst such as sulfuric acid (34). Increased reaction rates are reported when esterifications are carried out in the presence of heteropoly acids supported on macroreticular cation-exchange resins (35) and 2eohte (36) catalysts in a heterogeneous process. Judging from the many patents issued in recent years, there appears to be considerable effort underway to find an appropriate soHd catalyst for a reactive distillation esterification process to avoid the product removal difficulties of the conventional process. 

Methyl /-butyl ketone [1634-04-4] (pinacolone) has been prepared in 74% yield by reaction of / f/-amyl alcohol with formaldehyde in the presence of strong acid catalyst (78,79). 

Alcohol Substitution. In the early period of normal thiol production, the normal alcohols were utilized as feedstocks. The use of a strong acid catalyst results in the formation of a significant amount of secondary thiol, along with other isomers resulting from skeletal isomerization of the starting material. This process has largely been replaced by uv-initiation because of the higher relative cost of alcohol vs alkene feedstock. 

These processes have supplanted the condensation reaction of ethanol, carbon monoxide, and acetylene as the principal method of generating ethyl acrylate [140-88-5] (333). Acidic catalysts, particularly sulfuric acid (334—338), are generally effective in increasing the rates of the esterification reactions. Care is taken to avoid excessive polymerisation losses of both acryflc acid and the esters, which are accentuated by the presence of strong acid catalysts. A synthesis for acryflc esters from vinyl chloride (339) has also been examined. 

Alcohols can be dehydrated with strong acid catalysts and high reaction temperatures to produce ethers. This method is particularly useful for the preparation of symmetrical lower alkyl ethers, such as ethyl ether. 

An extensive study of the A" -3-keto steroid system reveals a number of selective exchange reactions. For example, under controlled conditions in the presence of a strong acid catalyst such as deuterium chloride, it is... 

In a situation where severe steric hindrance e.g., 16,16-dimethyl-20-keto-pregnanes) prevents enol acetate formation, an alternate scheme has been devised. Condensation of ethyl oxalate at C-21 produces, after hydrolysis, the 21-glyoxylic acid this on treatment with acetic anhydride and a strong acid catalyst such as perchloric acid gives both lactone acetates. 

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

Although the cis-trans interconversion of aikene isomers does not occur spontaneously, it can often be brought about by treating the aikene with a strong acid catalyst- If we interconvert ris-2-butene with fraus-2-butene and allow them to reach equilibrium, we find that they aren t of equal stability. The leans isomer is more stable than the cis isomer by 2.8 kj/mol (0.66 keal/moj) at room tempera-... 

Water adds to alkenes to yield alcohols, a process called hydration. The reaction takes place on treatment of the alkene with water and a strong acid catalyst (HA) by a mechanism similar to that of HX addition. Thus, protonation of an alkene double bond yields a carbocation intermediate, which reacts with water to yield a protonated alcohol product (ROH2+). Loss of H+ from this protonated alcohol gives the neutral alcohol and regenerates the acid catalyst (Figure 7.2). 

Alkyl aryl ethers (CXVII) undergo rearrangement in the presence of Lewis acid and strong acid catalysts to give the corresponding alkyl phenols (CXVIII and CXIX), viz. 

Greater success in extending kinetic measurements to higher degrees of polymerization has been achieved with polyesterifications catalyzed by a small amount of a strong acid catalyst. The catalyst concentration being constant throughout the process, the second-order rate expression... 

Direct chlorination can be carried out in the presence of C1S03H, which acts as a strong acid catalyst. These procedures use various compounds including 1,3-dinitrobenzene, chloranil, and TCNQ to inhibit competing radical chain halogenation.137... 

Many other additions, similar in type, are possible. Although acidic reagents can bring about alterations in aldrin, such reactions proceed only in the presence of strong acids or strongly acidic catalysts in the homogeneous phase and hence are without significance for the conditions under which insecticides are normally utilized. 

Phenolic novolacs, 18 760-761 Phenolic resin adhesives, 18 783-784 Phenolic resin can coatings, 18 38 Phenolic resin composites, 18 792-794 Phenolic resin drying-oil varnishes, 18 783 Phenolic resin fibers, 18 797-798 mechanical properties of, 18 798 Phenolic resin foam, 18 795-796 Phenolic resin manufacturers, U.S., 18 774 Phenolic resin polymerization, 18 760-765 alkaline catalysts in, 18 762-765 neutral catalysts in, 18 761-762 strong-acid catalysts in, 18 760-761 Phenolic resin prepregs, 18 793 Phenolic resin production unit, 18 766 Phenolic resins, 10 409 18 754-755, 756-802 22 10 26 763 in abrasive materials, 18 786-787 in air and oil filters, 18 790 additional reactants in, 18 759 analytical methods for, 18 774-779 applications of, 18 781-798 batch processes for, 18 766 from biomass and biochemical processes, 18 769-770... 

Strong-acid catalysts, in phenolic resin polymerization, 73 760-761 Strong acid cation-exchange resins, 74 381-382... 

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