Pentaerythritols

Pentaerythritol tetranitrate ( nitropentaerythrite ) also has numerous trade names which are different in various countries PETN, Penthrite, Penta (English speaking countries), Pentrit, Niperyth, Nitropenta, NP (Germany), Pentryt, NP (Poland), Ten (U.S.S.R.). PETN was first obtained by the Rheinisch-Westfalische Sprengstoff A.G. in 1894 [1], by nitrating pentaerythritol. 

Pentaerythritol was obtained by Tollens and Wigand in 1891 [2] from acetaldehyde and formaldehyde according to the following reaction  

Addition of copper salts permits substantial improvement of yield. The reaction appears to proceed in two stages. Initially an aldol condensation occurs between three molecules of formaldehyde and one molecule of acetaldehyde  

Afterwards the pentaerythrose reacts with a fourth molecule of formaldehyde according to Cannizzaro s reaction  

This reaction scheme was proposed by Tollens and Wigand [2]. 

Pentaerythritol is produced by reacting acetaldehyde with formaldehyde in the presence of calcium hydroxide (or caustic soda) [31.27]. Pentaerythritol is used in the production of alkyd resins. 

The most important polyhydric alcohols (Fig. 1) are white solids, ranging from crystalline pentaerythritol to the waxy trimethylol alkyls. The trihydric alcohols are very soluble in water, as is ditrimethylol propane. Pentaerythritol is moderately soluble and dipentaerythritol anti-tripentaerythritol are less soluble. 

Pentaerythritol is manufactured by reaction of formaldehyde and acetaldehyde in the presence of a basic catalyst, generally an alkali or alkaline-earth hydroxide. 

In the process (Fig. 2), the main concern in mixing is to avoid loss of temperature control in this exothermic reaction, which can lead to excessive byproduct formation and/or reduced yields of pentaerythritol. The reaction time depends on the reaction temperature and may vary from about 0.5 to 4 hours at final temperatures of about 65 and 35°C, respectively. The reactor product, neutralized with acetic or formic acid, is then stripped of excess formaldehyde and water to produce a highly concentrated solution of pentaerythritol reaction products. This is then cooled under carefully controlled crystallization conditions so that the crystals can be readily separated from the liquors by subsequent filtration. 

Staged reactions, where only part of the initial reactants is added, either to consecutive reactors or with a time lag to the same reactor, may be used to reduce dipentaerythritol content. This technique increases the effective formaldehyde-to-acetaldehyde mole ratio, maintaining the original stoichiometric one. It also permits easier thermal control of the reaction. Both batch and continuous reaction systems are used. 

Dipentaerythritol and tripentaerythritol are obtained as by-products of the pentaerythritol process and may be further purified by fractional crystallization or extraction. 

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Lithium fluoride is the optimum crystal for all wavelengths less than 3 A. Pentaerythritol (PET) and potassium hydrogen phthalate (KAP) are usually the crystals of choice for wavelengths from 3 to 20 A. Two crystals suppress even-ordered reflections silicon (111) and calcium fluoride (111). 

Peroxide-decomposing antioxidants destroy hydroperoxides, the sources of free radicals in polymers. Phosphites and thioesters such as tris(nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, and dialkyl thiodipropionates are examples of peroxide-decomposing antioxidants. 

Another interesting structure with a high degree of ring character along the backbone is the product obtained by the reaction of 1,4-cyclohexanedione [XIV] and pentaerythritol [XV] ... 

Pentaerythritol, 2,2p [methylenebis(oxymethylene)]bis(2-hydr oxymethyl-l,3-propanediol) [6228-26-8]... 

Acetaldehyde, first used extensively during World War I as a starting material for making acetone [67-64-1] from acetic acid [64-19-7] is currendy an important intermediate in the production of acetic acid, acetic anhydride [108-24-7] ethyl acetate [141-78-6] peracetic acid [79-21 -0] pentaerythritol [115-77-5] chloral [302-17-0], glyoxal [107-22-2], aLkylamines, and pyridines. Commercial processes for acetaldehyde production include the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, the partial oxidation of hydrocarbons, and the direct oxidation of ethylene [74-85-1]. In 1989, it was estimated that 28 companies having more than 98% of the wodd s 2.5 megaton per year plant capacity used the Wacker-Hoechst processes for the direct oxidation of ethylene. 

The base-catalyzed reaction of acetaldehyde with excess formaldehyde [50-00-0] is the commercial route to pentaerythritol [115-77-5]. The aldol condensation of three moles of formaldehyde with one mole of acetaldehyde is foUowed by a crossed Cannizzaro reaction between pentaerythrose, the intermediate product, and formaldehyde to give pentaerythritol (57). The process proceeds to completion without isolation of the intermediate. Pentaerythrose [3818-32-4] has also been made by condensing acetaldehyde and formaldehyde at 45°C using magnesium oxide as a catalyst (58). The vapor-phase reaction of acetaldehyde and formaldehyde at 475°C over a catalyst composed of lanthanum oxide on siHca gel gives acrolein [107-02-8] (59). 

Figure 3 shows the production of acetaldehyde in the years 1969 through 1987 as well as an estimate of 1989—1995 production. The year 1969 was a peak year for acetaldehyde with a reported production of 748,000 t. Acetaldehyde production is linked with the demand for acetic acid, acetic anhydride, cellulose acetate, vinyl acetate resins, acetate esters, pentaerythritol, synthetic pyridine derivatives, terephthaHc acid, and peracetic acid. In 1976 acetic acid production represented 60% of the acetaldehyde demand. That demand has diminished as a result of the rising cost of ethylene as feedstock and methanol carbonylation as the preferred route to acetic acid (qv). 

The nameplate capacities for acetaldehyde production for the United States in 1989 are shown in Table 5 (120). Synthetic pyridine derivatives, peracetic acid, acetate esters by the Tischenko route, and pentaerythritol account for 40% of acetaldehyde demand. This sector may show strong growth in some products but all of these materials maybe prepared from alternative processes. 

The most important polyhydric alcohols are shown in Figure 1. Each is a white soHd, ranging from the crystalline pentaerythritols to the waxy trimethylol alkyls. The trihydric alcohols are very soluble in water, as is ditrimethylol-propane. Pentaerythritol is moderately soluble and dipentaerythritol and tripen taerythritol are less soluble. Table 1 Hsts the physical properties of these alcohols. Pentaerythritol and trimethyl olpropane have no known toxic or irritating effects (1,2). Finely powdered pentaerythritol, however, may form explosive dust clouds at concentrations above 30 g/m in air. The minimum ignition temperature is 450°C (3). 

Property Pentaerythritol Dipentaerythritol Tripentaerythritol Trim ethyl o1 eth a n e T rimethylolprop an e Ditrimethylolpropane... 

Long-chain esters of pentaerythritol have been prepared by a variety of methods. The tetranonanoate is made by treatment of methyl nonanoate [7289-51-2] and pentaerythritol at elevated temperatures using sodium phenoxide alone, or titanium tetrapropoxide in xylene (12). PhenoHc esters having good antioxidant activity have been synthesized by reaction of phenols or long-chain aUphatic acids and pentaerythritol or trimethyl olpropane (13). 

Another ester synthesis employs the reaction of a long-chain ketone and pentaerythritol in xylene or chlorobenzene (14). Mixed esters have been produced using mixed isostearic and cyclohexane carboxyUc acids in trihromophosphoric acid, followed by reaction with lauric acid (15). 

Polyhydric alcohol mercaptoalkanoate esters are prepared by reaction of the appropriate alcohols and thioester using -toluenesulfonic acid catalyst under nitrogen and subsequent heating (16,17). Organotin mercapto esters are similarly produced by reaction of the esters with dibutyltin oxide (18). Pentaerythritol can be oxidized to 2,2-bis(hydroxymethyl)hydracryhc acid [2831-90-5] C H qO, ... 

Borolane products of mixed composition can be synthesized by direct addition of boric acid to pentaerythritol (23). 

Reaction between pentaerythritol and phosphorous trichloride [7719-12-2] yields the spkophosphite, 3,9-dichloro-2,4,8,10-tetraoxa-3,9,-diphosphaspii o[5,5]-undecane [3643-70-7] C HgCl20 P2,... 

The commercially important explosive pentaerythritol tetranitrate [78-11-5] (PETN), C HgN40 2>... 

Aminoalkoxy pentaerythritols are obtained by reduction of the cyanoethoxy species obtained from the reaction between acrylonitrile, pentaerythritol, and lithium hydroxide in aqueous solution. Hydrogen in toluene over a mthenium catalyst in the presence of ammonia is used (34). The corresponding aminophenoxyalkyl derivatives of pentaerythritol and trimethyl olpropane can also be prepared (35). 

Tosylates of pentaerythritol and the higher homologues can be converted to their corresponding tetra-, hexa-, or octaazides by direct reaction of sodium azide (36), and azidobenzoates of trimethyl olpropane and dipentaerythritol are prepared by reaction of azidobenzoyl chloride and the alcohols in pyridine medium (37). 

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