Formaldehyde reaction with bases

Second-order kinetics were also established for base-catalyzed formaldehyde reactions with m-cresol " and p-cresol. However, Fitzgerald and Martin reported fractional orders for reactions of 2,3,4,5-tetramethylphenol and 2,6-xylenol. ... 

Five reactions are included for formaldehyde reaction with OH and NO3 and the two photolysis channels. Reaction with 0( P) is also included, because of the close association between CB4 and chamber studies, where 0( P) reactions can be important. The chemistry of ALD2 is based on that of acetaldehyde. It reacts with O, OH, and NO3 to generate the species C2O3, which represents an acyl peroxy radical. Photolysis is written as ... 

Which giyes formaldehyde as one of the starting materials. Base-catalysed reactions with this yery reacfiye aldehyde often giye poor yields because of polymerisation and other side reactions. The Marmich reaction is used instead ... 

Uses, cx-Aminonitriles may be hydrolyzed to aminoacids, such as is done in producing ethylenediaminetetracetate (EDTA) or nittilotriacetate (NTA). In these cases, formaldehyde is utilized in place of a ketone in the synthesis. The principal use of the ketone-based aminonitriles described above is in the production of azobisnittile radical initiators (see below). AN-64 is also used as an intermediate in the synthesis of the herbicide Bladex. Aminonitriles are also excellent intermediates for the synthesis of substituted hydantoins by reaction with carbon dioxide however, this is not currently commercially practiced. 

Reactions with Ammonia and Amines. Acetaldehyde readily adds ammonia to form acetaldehyde—ammonia. Diethyl amine [109-87-7] is obtained when acetaldehyde is added to a saturated aqueous or alcohoHc solution of ammonia and the mixture is heated to 50—75°C in the presence of a nickel catalyst and hydrogen at 1.2 MPa (12 atm). Pyridine [110-86-1] and pyridine derivatives are made from paraldehyde and aqueous ammonia in the presence of a catalyst at elevated temperatures (62) acetaldehyde may also be used but the yields of pyridine are generally lower than when paraldehyde is the starting material. The vapor-phase reaction of formaldehyde, acetaldehyde, and ammonia at 360°C over oxide catalyst was studied a 49% yield of pyridine and picolines was obtained using an activated siHca—alumina catalyst (63). Brown polymers result when acetaldehyde reacts with ammonia or amines at a pH of 6—7 and temperature of 3—25°C (64). Primary amines and acetaldehyde condense to give Schiff bases CH2CH=NR. The Schiff base reverts to the starting materials in the presence of acids. 

Fig. 2. Functional groups on modified polyacrylamides (a) formed by reaction with dimethylamine and formaldehyde (Mannich reaction) (b), quatemized Mannich amine (c), carboxylate formed by acid or base-cataly2ed hydrolysis or copolymerization with sodium acrylate and (d), hydroxamate formed by...

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

The resihency and dyeabihty of poly(vinyl alcohol) fibers is improved by a process incorporating -hydroxybenzaldehyde to provide a site for the formation of a stable Mannich base. Hydroxyl groups on the fiber are converted to acetal groups by -hydroxybenzaldehyde. Subsequent reaction with formaldehyde and ammonia or an alkylamine is rapid and forms a stable Mannich base that is attached to the polymer backbone (94). 

The in situ process is simpler because it requires less material handling (35) however, this process has been used only for resole resins. When phenol is used, the reaction system is initially one-phase alkylated phenols and bisphenol A present special problems. As the reaction with formaldehyde progresses at 80—100°C, the resin becomes water-insoluble and phase separation takes place. Catalysts such as hexa produce an early phase separation, whereas NaOH-based resins retain water solubiUty to a higher molecular weight. If the reaction medium contains a protective coUoid at phase separation, a resin-in-water dispersion forms. Alternatively, the protective coUoid can be added later in the reaction sequence, in which case the reaction mass may temporarily be a water-in-resin dispersion. The protective coUoid serves to assist particle formation and stabUizes the final particles against coalescence. Some examples of protective coUoids are poly(vinyl alcohol), gum arabic, and hydroxyethjlceUulose. 

Quinone Methides. The reaction between aldehydes and alkylphenols can also be base-cataly2ed. Under mild conditions, 2,6-DTBP reacts with formaldehyde in the presence of a base to produce the methylol derivative (22) which reacts further with base to eliminate a molecule of water and form a reactive intermediate, the quinone methide (23). Quinone methides undergo a broad array of transformations by way of addition reactions. These molecules ate conjugated homologues of vinyl ketones, but are more reactive because of the driving force associated with rearomatization after addition. An example of this type of addition is between the quinone methide and methanol to produce the substituted ben2yl methyl ether (24). 

Methylphenol is converted to 6-/ f2 -butyl-2-methylphenol [2219-82-1] by alkylation with isobutylene under aluminum catalysis. A number of phenoHc anti-oxidants used to stabilize mbber and plastics against thermal oxidative degradation are based on this compound. The condensation of 6-/ f2 -butyl-2-methylphenol with formaldehyde yields 4,4 -methylenebis(2-methyl-6-/ f2 butylphenol) [96-65-17, reaction with sulfur dichloride yields 4,4 -thiobis(2-methyl-6-/ f2 butylphenol) [96-66-2] and reaction with methyl acrylate under base catalysis yields the corresponding hydrocinnamate. Transesterification of the hydrocinnamate with triethylene glycol yields triethylene glycol-bis[3-(3-/ f2 -butyl-5-methyl-4-hydroxyphenyl)propionate] [36443-68-2] (39). 2-Methylphenol is also a component of cresyHc acids, blends of phenol, cresols, and xylenols. CresyHc acids are used as solvents in a number of coating appHcations (see Table 3). 

Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). 

The manufacture of alkyl cyanoacrylate monomers, 1, involves the Knoevenagel reaction of formaldehyde, 2, with an alkyl cyanoacetate, 3, and a base, such as a secondary amine, as the catalyst, shown in Eq. 1. 

Novolacs are often modified through alkylations based on reactions with monomers other than, and in addition to, aldehydes during their manufacture. Examples might be inclusion of styrene, divinyl benzene, dicyclopentadiene, drying oils, or various alcohols. Despite significant production of all of these variants, most novolac volume is produced using phenol and formaldehyde. 

In a modified approach, the carbolinyl acetate 393 underwent a Mannich reaction with formaldehyde and acetone to give the keto ester 396 which, with base, cyclized to the diketone 397. This diketone (397) has recently been used to prepare a number of interesting pentacyclic compounds. 

We compared a variety of reducing agents and found that in most cases the reaction did not go to completion (see Table 3). In those instances in which all the starting material was consumed, the coupling performance was poorer than that obtained with 4. Interestingly, formaldehyde showed two distinct modes of action. When pretreated with bases it promoted coupling, whereas by itself (in the presence of base but without pretreatment) its activity was reversed leading mostly to reduction. 

Another versatile approach, which nicely complements these Mannich-based procedures, incorporates a preformed symmetrical hexahydro-l,3,5-triazine (HHT) intermediate. In this case the phosphorus reagent reacts with HHT as a trimeric form of the normal aldimine species generated in situ between the amine or amino acid and formaldehyde. These HHT reagents can often be puritied and isolated prior to the reaction with phosphites. They are reasonably stable under neutral or slightly basic conditions, but they can readily revert back to the original amine and formaldehyde after heating with aqueous acid (25). Several can be purchased commercially. 

Several earlier methods (55,56) utilized a piperazinedione derivative in an Arbuzov-based sequence as a more stable source of the requisite iV-chloromethyl intermediate 51. Treatment of piperazine-1,4-dione with formaldehyde and phosphorus trichloride provided convenient access to this starting material. Subsequent reaction with either trimethyl or triethyl phosphite produced the iV-phosphonomethyl tetraester derivative 52, which has been hydrolyzed to GLYH3. 

Phenol was originally recovered during the coking of coal, essentially being a by-product. Eventually, commercial routes were developed based on benzene (from coal or petroleum) for example, sulfonation of benzene to ben-zenesulfonic acid followed by reaction with water to phenol plus regenerated sulfuric acid. Phenol is used to make plastics (phenol-formaldehyde and epoxy resins) and textile fibers (nylon). Phenol is also used in solution as a general disinfectant for cleaning toilets, stables, floors, drains, etc. and is used both internally and externally as a disinfectant for animals. 

Examples Over-reaction and reduction are the problems with formaldehyde condensations in base (page T158). In acid solution over-reaction and acetal formation, e.g, to give (41), occur.The Mannlch Reaction avoids all these problems. 

Quantitative analysis can be carried out by chromatography (in gas or liquid phase) during prolonged electrolysis of methanol. The main product is carbon dioxide,which is the only desirable oxidation product in the DMFC. However, small amounts of formic acid and formaldehyde have been detected, mainly on pure platinum electrodes. The concentrations of partially oxidized products can be lowered by using platinum-based alloy electrocatalysts for instance, the concentration of carbon dioxide increases significantly with R-Ru and Pt-Ru-Sn electrodes, which thus shows a more complete reaction with alloy electrocatalysts. 

Scheme 2.12 shows some representative Mannich reactions. Entries 1 and 2 show the preparation of typical Mannich bases from a ketone, formaldehyde, and a dialkylamine following the classical procedure. Alternatively, formaldehyde equivalents may be used, such as l>is-(di methyl ami no)methane in Entry 3. On treatment with trifluoroacetic acid, this aminal generates the iminium trifluoroacetate as a reactive electrophile. lV,A-(Dimethyl)methylene ammonium iodide is commercially available and is known as Eschenmoser s salt.192 This compound is sufficiently electrophilic to react directly with silyl enol ethers in neutral solution.183 The reagent can be added to a solution of an enolate or enolate precursor, which permits the reaction to be carried out under nonacidic conditions. Entries 4 and 5 illustrate the preparation of Mannich bases using Eschenmoser s salt in reactions with preformed enolates. 

Although the condensation of phenol with formaldehyde has been known for more than 100 years, it is only recently that the reaction could be studied in detail. Recent developments in analytical instrumentation like GC, GPC, HPLC, IR spectroscopy and NMR spectroscopy have made it possible for the intermediates involved in such reactions to be characterized and determined (1.-6). In addition, high speed computers can now be used to simulate the complicated multi-component, multi-path kinetic schemes involved in phenol-formaldehyde reactions (6-27) and optimization routines can be used in conjunction with computer-based models for phenol-formaldehyde reactions to estimate, from experimental data, reaction rates for the various processes involved. The combined use of precise analytical data and of computer-based techniques to analyze such data has been very fruitful. 

Formaldehyde reacts with proteins to form adducts and cross-links.31516 Metz et al.3 have identified three types of chemical modifications after treatment of proteins with formaldehyde (a) methylol (hydroxymethyl) adducts, (b) Schiff bases, and (c) methylene bridges. The reaction of formaldehyde with proteins is summarized in Figure 19.1, but briefly, formaldehyde reacts primarily with lysine and cysteine to form methylol adducts. The methylol adduct can subsequently undergo a dehydration reaction to form a Schiff base. Adducted primary amine and thiol groups can undergo a second reaction with arginine,... 

Hydrazide-based cyanine dyes are reactive with common formaldehyde fixatives for cell and tissue studies. This enables these dyes to function as general stains for protein-rich areas within cells, and they get crosslinked into place by the formaldehyde reaction process. 

In the framework of this concept a series of new mixed P/N ligands was prepared, employing the phosphorus-analogous Mannich reaction (Scheme 9). This transformation permits the substitution of primary or secondary amines by methylenephos-phine residues -CH2PRR (R, R = alkyl, aryl) through reaction with a secondary phosphine and formaldehyde (46). Based on the... 

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