Dipentaerythritol

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... 

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). 

The quantities of formaldehyde and base catalyst required to produce pentaerythritol from 1 mol of acetaldehyde are always in excess of the theoretical amounts of 4 mol and 1 mol, respectively, and mole ratios of formaldehyde to acetaldehyde vary widely. As the mole ratio increases, formation of dipen taerytbritol and pentaerythritol linear formal is suppressed. Dipentaerythritol formation may also be reduced by increasing the formaldehyde concentration, although linear formal production increases under those conditions (55,56). 

Staged reactions, where only part of the initial reactants are added, either to consecutive reactors or with a time lag to the same reactor, maybe 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 (66,67). Both batch and continuous reaction systems are used. The former have greater flexibiHty whereas the product of the latter has improved consistency (55,68). 

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

Dipentaerythritol is sold by Perstorp AB and by Hercules (United States), ditrimethylolpropane by Perstorp AB both in relatively pure form. Tripentaerythritol is also available however, the purity is limited. Trimethylolethane is produced commercially by Alcolac (United States) and Mitsubishi Gas Chemicals (Japan). 

Pentaerythritol and trimethylolpropane acryUc esters are usefiti in solventiess lacquer formulations for radiation curing (qv), providing a cross-linking capabihty for the main film component, which is usually an acryUc ester of urethane, epoxy, or polyester. Some specialty films utilize dipentaerythritol and ditrimethylolpropane (94,95). 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

Polyols. Polyols, such as pentaerythritol [115-77-5], dipentaerythritol [126-58-9], and sorbitol [50-70-4], most likely chelate the active metal centers to reduce their activity toward the undesired dehydrochlotination reaction. These additives are generally iacluded ia the stabilizer formulation, used ia the range of 0.2 to 0.7 phr. 

The basic metal salts and soaps tend to be less cosdy than the alkyl tin stabilizers for example, in the United States, the market price in 1993 for calcium stearate was about 1.30— 1.60, zinc stearate was 1.70— 2.00, and barium stearate was 2.40— 2.80/kg. Not all of the coadditives are necessary in every PVC compound. Typically, commercial mixed metal stabilizers contain most of the necessary coadditives and usually an epoxy compound and a phosphite are the only additional products that may be added by the processor. The requited costabilizers, however, significantly add to the stabilization costs. Typical phosphites, used in most flexible PVC formulations, are sold for 4.00— 7.50/kg. Typical antioxidants are bisphenol A, selling at 2.00/kg Nnonylphenol at 1.25/kg and BHT at 3.50/kg, respectively. Pricing for ESO is about 2.00— 2.50/kg. Polyols, such as pentaerythritol, used with the barium—cadmium systems, sells at 2.00, whereas the derivative dipentaerythritol costs over three times as much. The P-diketones and specialized dihydropyridines, which are powerful costabilizers for calcium—zinc and barium—zinc systems, are very cosdy. These additives are 10.00 and 20.00/kg, respectively, contributing significantly to the overall stabilizer costs. Hydrotalcites are sold for about 5.00— 7.00/kg. 

Pentaerythritol with its four primary hydroxyl groups is used for the preparation of tetraesters and presents Httie difficulty except for its high melting point of 263°C, when pure. Pentaerythritol tetraesters are used in aircraft lubes, synthetic drying oils, and alkyds. Esters derived from trimethylo1 alkanes and dipentaerythritol are also used in alkyd resins (qv). Esterification may take place in situ during preparation of the alkyd. 

Dipentaerythritol and Derivatives. See Vol 5, D1407-L to D1413-L Metriol and Its Derivatives. See Vol 8, M120-R to M122-L 1 j... 

The reaction sequence to be used as an example will be the bromination of polyhydroxyl compounds by exchange with bromide ion (eqn. 1). In particular, at Bromine Compounds, we are concerned with the bromination of pentaerythritol 1 and dipentaerythritol 2. 

Differential Scanning Calorimetry (Fig. 9) can be used to evaluate the purity of tetrabromodipentaerythritol, a tetrabrominated derivative of dipentaerythritol. Even so, the validity of the results depends on the purity of the sample. The results shown here should be considered extremely borderline. The brorainated derivatives of the pentaerythritols cannot be analyzed with this technique because of the inherent limitations of DSC. 

Further, dendritic growths with new multiarmed clusters having more flexibility and various geometries have also been considered by the authors. Thus, the hexato-sylated dipentaerythritol 39 was converted into hexaazide 40, which upon treatment with propargylated mannoside 29 under standard conditions of click chemistry and subsequent O-deacetylation afforded the hexavalent cluster 42 in good (61%) yield over two steps (Scheme 6). 

Dipentaerythritol, 2 46, 47 economic aspects, 2 52 manufacture, 2 51—52 physical properties of, 2 48t Dipentene, 24 491—492 uses for, 24 492 Diperoxides, cyclic, 18 459 Diperoxyacetals, 18 456 Diperoxycarboxylic acids, 18 464 Diperoxydodecanedioic acid, 4 62 Diperoxyketals, 14 281 18 456 boiling points of, 18 457t as free-radical initiators, 14 287-288 Diphasic solids, connectivity patterns for, 11 101... 

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