Neopentyl glycol carbonate

The third type of reaction for polyester polyols synthesis is the ring opening polymerisation of cyclic esters, such as -caprolactone (reaction 8.4) or cyclic carbonates, such as ethylene glycol carbonate, propylene glycol carbonate, neopentyl glycol carbonate, etc., (reaction 8.5) initiated by diols (or polyols) and catalysed by specific catalysts [7, 16]. 

Cychc carbonates are prepared in satisfactory quaUty for anionic polymerization by catalyzed transesterification of neopentyl glycol with diaryl carbonates, followed by tempering and depolymerization. Neopentyl carbonate (5,5-dimethyl-1,3-dioxan-2-one) (6) prepared in this manner has high purity (99.5%) and can be anionically polymerized to polycarbonates with mol wt of 35,000 (39). 

Fumaric and itaconic acids are also used as the diacid component. Most reaction formulations involve a mixture of a saturated diacid (iso- and terephthalic, adipic) with the unsaturated diacid or anhydride in appropriate proportions to control the density of crosslinking (which depends on the carbon-carbon double-bond content of the prepolymer) for specific applications [Parker and Peffer, 1977 Selley, 1988], Propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, and bisphenol A are also used in place of ethylene glycol as the diol component. Aromatic reactants are used in the formulation to improve the hardness, rigidity, and heat resistance of the crosslinked product. Halogenated reactants are used to impart flame resistance. 

An additional evaluation [18] of the extension of rutile Ti02 by different fillers was conduded by assessing blister resistance in two types of liquid, thermosetting polyester resins (namely ortho- and ortho-neopentyl glycol (NPG). The performance of the filler/pigment portion of the cured polyester gel coat was compared after exposure to water at 65 °C for 1150 h (Table 13.12). Untreated kaolin provided better blister resistance than untreated talc or calcium carbonate. Vinylsilane surface-treated kaolin gave the best blister resistance, reducing the size and extent of blisters... 

Diethyl chloroacetal refluxed with an equimolar amount of neopentyl glycol in the presence of 1 mole-% p-toluenesulfonic acid under a fractionating column with distillation of the resulting ethanol, benzene added when most of the ethanol has been removed after ca. 2 hrs., the remaining ethanol removed as benzene azeotrope, the catalyst destroyed with solid K-carbonate, and the product distilled 2-chloromethyl-5,6-dimethyl-m-dioxane. Y 95%. Numerous e., mostly m-dioxanes and other cyclic acetals, also direct acetalation of 0x0 compounds, e. g. acrolein, s. C. S. Rondestvedt, Jr., J. Org. Chem. 26, 2247 (1961) transaeetalation s. a. S. J. Angyal and R. M. Hoskinson, Soc. 1962, 2985 N. B.Lorette and W. L. Howard, Org. Synth. A2, 1 (1962). 

Newkome et al. were the first to synthesise symmetrical, quater-directionaF cascade molecules with a carbon scaffold bearing 36 terminal carboxyl groups -all at an equal distance from the neopentyl core (Fig. 6.20a). The carboxyls were converted into the corresponding ammonium and tetramethylammonium car-boxylates. Synthesis of these dendritic unimolecular micelles with hydrophobic core and hydrophilic shell was accomplished up to the fourth generation by coupling of a dendritic hypercore (constructed from 4,4-bis(4 -hydroxyphenyl)-pentanol monomer) and PEG mesylate (PEG = polyethylene glycol). Dyes such... 

---