Phthalic acid crystallization

The solvent was evaporated off under reduced pressure, and the residual gum refluxed with concentrated hydrochloric acid (50 g) for 6 hours. The solution was aliowed to cool overnight. It was filtered from the phthalic acid crystals, and freeze-dried, and to the pink residue was added acetone (160 g) and ethyl acetate (50 g). The mixture was left in the cold room overnight and the clear pink supernatant liquid poured off. The pink gummy hydrochloride remaining in the flask was dissolved in water (20 g), saturated sodium acetate solution added until precipitation was complete, and the product collected and dried in a desiccator. The crude p-bis-(2-chloroethyl)-aminophenylalanine (3.6 g) was crystallized from methanol giving colorless needles, MP 172° to 174°C (decomp.) of p-bis-(2-chloroethyl)-aminophenylalanine. 

The author has observed repeatedly that, in such mixtures with pH less than 3.0, phthalic acid crystals separate out. This difficulty is encountered especially during the winter months when the temperature drops below 15°. 

A mixture of dimethyl a,8-diphthalimidoadipate 76 (50 g), hydrobromic acid (100 mL, 40%), and glacial acetic acid (100 mL) was heated under reflux until a clear solution resulted (10 days). On cooling, most of the phthalic acid crystallized. After filtration, the filtrate and water washes were concentrated under reduced pressure practically to dryness. The residue was dissolved in H20 (100 mL), filtered, and neutralized with concentration ammonia. After crystallization at 0 °C for 12 h, a,8-diaminoadipic acid (17.3 g, 91.2%) was obtained. 

Phthalic acid crystallizes from hot water. It does not possess a definite melting point, as it slowly decomposes into its anhydride and water when heated. Melting points can be obtained from 180° to 213°, the higher temperatures being observed when the acid is heated rapidly. 

Phthalein reaction. Fuse together carefully in a dry test-tube a few crystals of phthalic acid or of a phthalate and an equal quantity of ph tol moistened with 2 drops of cone. H2SO4. Cool, dissolve in water and add NaOH solution in excess the bright red colour of phenolphthalein in alkaline solution is produced. 

Raw Materials. Eor the first decade of PET manufacture, only DMT could be made sufficiently pure to produce high molecular weight PET. DMT is made by the catalytic air oxidation of -xylene to cmde TA, esterification with methanol, and purification by crystallization and distillation. After about 1965, processes to purify cmde TA by hydrogenation and crystallization became commercial (52) (see Phthalic ACID AND OTHER... 

D. ci - -Thiabicyclo[4 .. Q]nonan S,S-Dioxide [Benzo[c]thiophene 2,2-dioxide, cis-octahydro-]. A solution of the sulfide (43.0 g., 0.303 mole) in 11. of ether is cooled to 0° and treated dropwise while magnetically stirred with 1.01. of 0.65iV ethereal monoperphthalic acid (0.65 mole). The mixture is kept overnight at 0°, after which time the precipitated phthalic acid is separated by filtration and the filtrate concentrated with a rotary evaporator. Bulb-to-bulb distillation of the residual oil at 0.05-0.1 mm. affords the sulfone as a eolorless liquid (48.5-50 g., 92-95%) (Note 11). This product is crystallized from ether-hexane to give a colorless solid, m.p. 39-41° (Note 12). 

A solution of 10 g (0.023 mole) of cholesteryl acetate (mp 112-114°) in ether (50 ml) is mixed with a solution containing 8.4 g (0.046 mole) of monoperphthalic acid (Chapter 17, Section II) in 250 ml of ether. The solution is maintained at reflux for 6 hours, following which the solvent is removed by distillation (steam bath). The residue is dried under vacuum and digested with 250 ml of dry chloroform. Filtration of the mixture gives 6.7 g of phthalic acid (87% recovery). The solvent is evaporated from the filtrate under reduced pressure and the residue is crystallized from 30 ml of methanol, giving 6.0 g (58% yield) of -cholesteryl oxide acetate. Recrystallization affords the pure product, mp 111-112°. Concentration of the filtrate yields 1.55 g (15% yield) of a-cholesteryl oxide acetate which has a mp of 101-103° after crystallization from ethanol. 

Tschujaeff and Fromm have shown that by the recrystallisation of the cinchonine salt of the phthalic acid ester, and hydrolysis of the crystal- line salt, thujyl alcohol can be obtained of specific rotation -p 116-9°,... 

It is a solid body melting at 112° to 114°, forming exceedingly fine prismatic crystals. It forms a compound with phthalic acid, melting at 140°. 

Fig. 11 Binary phase diagram between phthalic acid and decyloxystilbazole. (Crc and Cra are the crystal phase of the complex and the acid, respectively E is the crystal smectic E phase). Adapted from [35]...

However, the formation of these products does not appear to play a critical role in the decision as to whether the 425 nm and 480 nm maxima are due to different states of the same molecule or to different compounds. It was reported that special care was taken to ensure the purity of luminol and of 3-aminophthalate 109>. In commercially available 3-amino-phthalic acid a yellowish impurity exhibiting brilliant green fluorescence was detected 109> this substance also formed in neutral solutions of pure 3-amino phthalic acid and crystallized from these solutions in yellow crystals. The structure of this substance was determined to be 53 its absorption spectrum has a maximum at 388 nm the fluorescence maximum is at 475 nm, with a fluorescence quantum yield of about 0.75 in DMF i 9). 

The direct reaction of [TCO4] in ethanolic solution with dppe and oxalic acid produces the red Tc" complex [Tc(ox)(dppe)2] (552). Attempts to prepare similar complexes with succinic acid, phthalic acid, or salicylic acid failed, or the complexes were stable in solution only. " Similarly, cationic complexes of Tc" are produced by reaction of the versatile precursor [TcO(OH)(dppe)2] (204) with various dithiocarbamates, which produces several complexes of general formula [Tc(dtc)(dppe)2] (553). For this reaction the reductant formamidine sulphinic acid (510) was required in an alkaline solution. The X-ray crystal structure of [Tc(S2CNMe2)(dppe)2] (554) shows a distorted octahedral geometry. Cyclic voltammetry reveals a reversible reduction wave Tc"/Tc couple at —0.53 V, and a reversible oxidation at +0.3 V for the Tc" /Tc" couple. The same compound (554) was also prepared from the thiourea precursor [TcO(tmtu)4] + (91).The reaction of this precursor in dmf in the presence of dppe produced a mixture of brown [TcO(dtc)(tmtu)2] and the Tc" complex (553). The first compound is probably an intermediate... 

The typical polyesters from dicarboxylic acids and polyalcohols, espedally glycols, which have no tendency to crystallize, are suitable as plastidzers for PVC. The well known polyesters of the alkyd type obtained from glycerol or glycol with phthalic acid have been recommended for PVC by I.G. Farben but have not found practical application. 

Organic Adsorbents. (a) Organic crystal compounds (e.g., benzophenone on firebrick, anthraquinone on graphitized carbon black, phthalic anhydride and/or phthalic acid isomers on Chromo-sorb G). (b) Liquid phases below their melting point (e.g.,... 

Bentone-34 has commonly been used in packed columns (138—139). The retention indices of many benzene homologues on squalane have been determined (140). Gas chromatography of C —C aromatic compounds using a Ucon B550X-coated capillary column is discussed in Reference 141. A variety of other separation media have also been used, including phthalic acids (142), liquid crystals (143), and Werner complexes (144). Gel permeation chromatography of alkylbenzenes and the separation of the Cg aromatics treated with zeolites are described in References 145—148. 

Akzo has been instrumental in developing a new process for the stereospecific synthesis of trans- 1,4-cyclohexane diisocyanate [7517-76-2] (21). This process, based on the conversion of polyethylene terephthalate) [25038-59-9], circumvents the elaborate fractional crystallization procedures required for the existing -phenylenediamine [108-45-2] approaches. The synthesis starts with polyethylene terephthalate) (PET) (32) or phthalic acid, which is converted to the dimethyl ester and hydrogenated to yield the cyclohexane-based diester (33). Subsequent reaction of the ester with ammonia provides the... 

A 2.0-gram sample of the oil was boiled with 50 ml. of N sodium hydroxide for 4 hours under reflux, and then the mixture was distilled to yield 20 ml. of distillate. Ethanol was identified in the distillate by gas chromatography. The alkaline aqueous residue was acidified with dilute sulfuric acid and extracted with ether. The ether was evaporated to yield a solid mass, which was recrystallized from water to yield colorless crystals, melting at 199°-201°C. and not depressing the melting point of a mixture with authentic o-phthalic acid. An infrated spectrum of this compound was identical with that of authentic o-phthalic acid. 

It is important to use rather pure acid esters for the resolution step. The hydrogen phthalates are usually solids that may be crystallized from petroleum ether, benzene, or acetic acid. Phthalic acid is the usual major impurity and may interfere with the crystallization of the ester. If it does, or if the ester is liquid, it is convenient to extract the crude product with chloroform or benzene, in which phthalic acid is nearly insoluble. Distillation of the solvent from the dried extract usually leaves the ester pure enough to crystallize or to use directly. 

The reaction mixture is now diluted to 60° by slowly adding a mixture of 150 grams of concentrated sulfuric acid and 130 cc. water. It is then cooled thoroughly and poured onto ice. The precipitated boric acid ester is filtered off and mixed with 1 liter water. The suspension is boiled for 10 minutes with good stirring, filtered hot, and the precipitate is washed with 1 liter hot water. The mother liquor and wash water are collected separately, since the excess phthalic acid is crystallized from the former (about 40 per cent of the anhydride is recovered as phthalic acid). 

If any crystals of phthalic acid are present, crystallization will occur on cooling. 

T. G. D. van Schalkwyk. Acta Cryst. 7, 775 (1954). Crystal structure phthalic acid. 

The process of crystallization can be observed readily using phthalic acid. In the reference book The Handbook of Chemistry and Physics, in the table Physical Constants of Organic Compounds, the entry for phthalic acid gives the following solubiUty data (in grams of solute per 100 mL of solvent). The superscripts refer to temperature in °C ... 

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