The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《The optical resolution of spiroheptanedicarboxylic acid》. Authors are Backer, H. J.; Schurink, J. H. B..The article about the compound:Pentaerythrityltetrabromidecas:3229-00-3,SMILESS:BrCC(CBr)(CBr)CBr).Related Products of 3229-00-3. Through the article, more information about this compound (cas:3229-00-3) is conveyed.
According to van’t Hoff (La chimie dans l’espace, p. 29(1875)) compounds of the types I and II should be capable of being resolved into optical components (cf. Aschan, Ber. 35, 3396(1902)), and the same holds for the spirocyclic compounds of the type III. The present paper deals with the preparation and optical resolution of spiroheptanedicarboxylic acid, giving the 1st example of the optical resolution of a compound of type III. The optical activity of compounds of this type favors the tetrahedric formulation of pentaerythritol, whether regular or not (cf. Böeseken and Felix, C. A. 23, 99, 4672). Pentaerythritol was obtained in excellent yields as follows: 190 g. pulverized CaO is added to 210 g. AcH and 800 g. paraformaldehyde in 5 l. water at 60°, the temperature being kept at 60° for 2 more hrs. after the addition After cooling the solution is decolorized with charcoal, neutralized with HCl and evaporated in vacuo until Ca formate seps.; after filtering the hot solution from this precipitate, the filtrate is cooled in ice and gives a deposit of 350 g. pentaerythritol, m. 257°, while a 2nd crop of 100 g. may be obtained from the mother liquor. Sometimes the 1st product m. 200-20° but one crystallization from dilute HCl yields a product, m. 254°, the lowering of the m. p. of the crude product being probably due to the presence of acetals. For the preparation of tetrabromopentaerythritol, 1 kg. PBr3 is added slowly to 250 g. pentaerythritol, on the water bath; after the addition the mixture is heated for 20 hrs. at 160-80° in an oil bath. The crude product is first freed from the tri-Br compound by washing with cold EtOH and is then extracted with boiling EtOH; yield 86%, m. 162°. On heating 140 g. anhydrous NaI, 70 g. of the tetra-Br compound and 300 cc. acetone for 36 hrs. at 100°, tetraiodoerythritol, m. 233°, is obtained; the same result can be obtained on using MeCOEt as a solvent and boiling for 16 hrs. in an open flask. Crystallographic properties (P. Terpstra): monoclinic crystals, β = 113 ° 43′, a : c = 0.619: 1 ; forms observed : (100); (001); (1̅02) and probably (012) and (210̅); angles: (100):(001) = 66°17′; (1̅02): (001) = 47°37′; the optical axes are situated in the plane (010); the sharp bissectrix is nearly perpendicular to (100). The crystals are analogous to those of tetrabromopentaerythritol for which Jaeger (C. A. 3, 2446) found β = 112°52.5′; a:c = 0.6240: 1. The preparation of spiroheptanedicarboxylic acid has already been described by Fecht (C. A. 3, 75) but the yield could be improved considerably in the following way: 80 g. CH2(CO2Et)2 is added to 11.5 g. Na in 500 cc. AmOH; then 40 g. tetrabromopentaerythritol is added and the EtOH, formed by the replacement of the Et group by the Am group in the CH2(CO2Et)2 is removed by distillation until the b. p. reaches 128°, the mixture being finally boiled for 40-50 hrs. The larger part of the AmOH is then distilled off, the remainder being removed by distillation with steam. The remaining ester is then saponified with alc. KOH, a mixture of spiroheptanetetra- and -dicarboxylic acids being formed in which the tetra-compound predominates. On heating the mixture at 200-20°, decarboxylation takes place with the formation of spiroheptanedicarboxylic acid, m. 212°; yield, 75-80%. On carrying out the same reaction with tetraiodoerythritol, a yield of only 20% is obtained. On boiling the acid for 2 hrs. with an excess of aniline, spiroheptanedicarboxanilide, m. 228°, was obtained. After the saponification of the primary reaction product at room temperature with alc. KOH, spiroheptanetetracarboxylic acid, m. 219°, is obtained; normal Ba salt (7 H2O) shows a solubility of 0.068% at 25°. The optical resolution of the dicarboxylic acid was carried out with the normal brucine salt (6 H2O), m. 133°, either by “”cold crystallization”” (cf. Backer and Burgers, C. A. 19, 1128) or in the usual way; normal strychnine salt, m. 238°. After 9 crystallizations of the brucine salt from hot water the optically pure d-rotatory compound is obtained, the following rotations being observed for the NH4 salt: (M)656.3 1.9°, (M)589.5 2.3°, (M)546.3 2.6°, (M)486.1 3.4°. The free acid shows in ether (M)D 1.9°. The optically active compound could not be racemized either by heating the NH4 salt for 12 hrs. at 100° in H2O, or by heating with 0.75 N NaOH during the same time at that temperature
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Reference:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem