Isomeric mixture

Plasticizer Range Alcohols. Commercial products from the family of 6—11 carbon alcohols that make up the plasticizer range are available both as commercially pure single carbon chain materials and as complex isomeric mixtures. Commercial descriptions of plasticizer range alcohols are rather confusing, but in general a commercially pure material is called "-anol," and the mixtures are called "-yl alcohol" or "iso...yl alcohol." For example, 2-ethyIhexanol [104-76-7] and 4-methyl-2-pentanol [108-11-2] are single materials whereas isooctyl alcohol [68526-83-0] is a complex mixture of branched hexanols and heptanols. Another commercial product contains linear alcohols of mixed 6-, 8-, and 10-carbon chains. 

Mixtures containing various concentrations of mono-, di-, and polyisopropylnaphthalenes have been prepared by treating molten naphthalene with concentrated sulfuric acid and propjiene at 150—200°C followed by distillation (39). Products comprised of such isomeric mixtures have extremely low pour points, ie, ca —50° C, are excellent multipurpose solvents, and have been evaluated as possible Hquid-phase heat-transfer oils. 

If pure isomers are required, the ortho and meta compounds can be prepared by indirect methods. o-Nitrotoluene can be obtained by treating 2,4-dinitrotoluene with ammonium sulfide followed by diazotization and boiling with ethanol. / -Nitrotoluene can be prepared from -toluidine by acetylation, nitration deacetylation, diazotization, and boiling with ethanol. A fairly pure -nitrotoluene, which has been isolated from the isomeric mixture, can be purified further by repeated crystallization. 

Diesters of Tetracarboxylic Acids with Diamines. Dianhydrides react with alcohols at a moderate temperature, producing the tetracarboxyhc acid diesters. Ben2ophenonetetracarboxyhc acid diester (BTTA diester) is obtained from B I DA as a mixture of three positional isomers. Partiy because it is an isomeric mixture, the diester of BTTA is soluble in methanol at high concentrations. A state-of-the-art thermoset polyimide,... 

Union Carbide Chemicals and Plastics Company Inc. is the only producer of C-5 oxo derived alcohols (148,150) in the United States. About 75% of the 30,000 t of valeraldehyde and 2-methylbutyraldehyde produced by the oxo process was converted to the isomeric mixture of primary amyl alcohols in 1988 (150). The primary amyl alcohol mixture was available in tank car quantities for 1.02/kg in 1991. The Dow Chemical Company appears to have stopped commercial production of / fZ-amyl alcohol (151). 

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

Hop "bitter" acids are isomeric mixtures of cyclohexadienone stmctures in both keto and enol forms, substituted at various positions on the ring by hydroxyl, acyl, and alkenyl groups. See Figure 2. 

The isomeric mixture is a colodess, mobile Hquid with a sweet, slightly irritating odor resembling that of chloroform. It decomposes slowly on exposure to light, air, and moisture. The mixture is soluble ia most hydrocarbons and only slightly soluble ia water. The cis—trans proportions ia a cmde mixture depend on the production conditions. The isomers have distinct physical and chemical properties and can be separated by fractional distillation. 

Aromatic Ring Reactions. In the presence of an iodine catalyst chlorination of benzyl chloride yields a mixture consisting mostly of the ortho and para compounds. With strong Lewis acid catalysts such as ferric chloride, chlorination is accompanied by self-condensation. Nitration of benzyl chloride with nitric acid in acetic anhydride gives an isomeric mixture containing about 33% ortho, 15% meta, and 52% para isomers (27) with benzal chloride, a mixture containing 23% ortho, 34% meta, and 43% para nitrobenzal chlorides is obtained. 

In another method based on butadiene, it is dimerized ia the presence of sodium to form an isomeric mixture of disodiooctadiene (69). 

Acyl-pyrroles, -furans and -thiophenes in general have a similar pattern of reactivity to benzenoid ketones. Acyl groups in 2,5-disubstituted derivatives are sometimes displaced during the course of electrophilic substitution reactions. iV-Alkyl-2-acylpyrroles are converted by strong anhydrous acid to A-alkyl-3-acylpyrroles. Similar treatment of N-unsubstituted 2- or 3-acyIpyrroles yields an equilibrium mixture of 2- and 3-acylpyrroles pyrrolecarbaldehydes also afford isomeric mixtures 81JOC839). The probable mechanism of these rearrangements is shown in Scheme 65. A similar mechanism has been proposed for the isomerization of acetylindoles. 

An isomeric mixture of 7a-methyl- (31) and 7)5-methyl-A -3-ketones (32) is obtained by cuprous chloride-catalyzed 1,6-addition of the methyl Grignard reagent to (30). ° ... 

Perfluoroalkylation of substituted benzenes and heterocyclic substrates has been accomplished through thermolysis of perfluoroalkyl iodides in the presence of the appropriate aromatic compound Isomeric mixtures are often obtained W-Methylpyrrole [143] and furan [148] yield only the a-substituted products (equation 128) Imidazoles are perfluoroalkylated under LTV irradiation [149] (equation 129). 4-Perfluoroalkylimidazoles are obtained regioselectively by SET reactions of an imidazole anion with fluoroalkyl iodides or bromides under mild conditions [150] (equation 130) (for the SET mechanism, see equation 57)... 

The yields refer to pure isolated products, unless otherwise cited The values were measured by F NMR and represent the ratios of the lower field peaks to the higher field peaks due to the a methine fluonne in an isomeric mixture ot the product... 

A substituted a,/3-unsaturated aldehyde, cinnamaldehyde, has been observed to undergo the same type of two-step 1,3-cycloaddition reaction with a cyclohexanone enamine as acrolein does, forming in this case a stereo-isomeric mixture of substituted bicycloaminoketones in excellent yield (29a,31a,31b). 

There is some debate in the literature as to the actual mechanism of the Beirut reaction. It is not clear which of the electrophilic nitrogens of BFO is the site of nucleophilic attack or if the reactive species is the dinitroso compound 10. In the case of the unsubstituted benzofurazan oxide (R = H), the product is the same regardless of which nitrogen undergoes the initial condensation step. When R 7 H, the nucleophilic addition step determines the structure of the product and, in fact, isomeric mixtures of quinoxaline-1,4-dioxides are often observed. One report suggests that N-3 of the more stable tautomer is the site of nucleophilic attack in accord with observed reaction products. However, a later study concludes that the product distribution can be best rationalized by invoking the ortho-dinitrosobenzene form 10 as the reactive intermediate. 

Intramolecular cycloadditions of 4/f-pyrido[l,2-n]pyrimidin-4-ones 235 (R = H, Me Ph) and MeNHOH HCl gave tetracyclic isoxazolo derivatives 237. In the case of 235 (R = Me) a minor epimer 238 was also isolated (00JCR(S)414). Similar reaction of 235 (R = H, Me, Ph) and sarcosine ethyl ester HCl afforded an isomeric mixture of epimeric tetracyclic pyrrolo derivatives 239 and 240. In the reaction of 235 (R = H) and PhCHjNHCHjCOOEt only one product 241 was obtained. 

Cyclocondensation of 2-iminopiperidine hydrochloride with an E Z isomeric mixture of ethyl 2-cyano-3-methylsulfanyl-3-( 1,2,4,5-tetrahydro-3/f-benzo[r/ azepin-3-yl)acrylate in DMF in the presence of DBU at 100°C gave 2-substituted 6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-carbo-nitrile (01EUP1074549). 

Under the circumstance of catalytic hydrogenation of piperidine derivatives 190 in MeOH over Pd/C catalyst afforded an isomeric mixture of perhydropyrido[l,2-c]pyrimidines 174-177 (98TL7021, 00JA5017). The main product was 174 (66%). 

Substituted perhydropyrido[l,2-n]pyrazines were reacted with 2-fluorobenzohydroximinoyl chlorides in the presence of DBU in CHCI3 to yield a isomeric mixture of 7-substituted 2-[(hydroxyimino)phenylmethyl]-perhydropyrido[l, 2-u]pyrazines (99MIP9). 

In theory, periodate oxidation could have given a clear-cut answer as to the composition of the isomeric mixture of deoxy ribose phosphates. The 4-phosphate (73), devoid of vicinal diol groups, should be resistant to periodate the 3-phosphate (74) should reduce one and only one molar equivalent of the oxidant and yield one molar equivalent of both formaldehyde and the phosphorylated dialdehyde (75), whereas the 5-phosphate (76) could be expected to reduce one molar equivalent of periodate relatively rapidly, followed by a slower overoxidation reaction owing to the oxidation of malonaldehyde, formed as a result of the glycol cleavage. 

In some instances, with 1-methylcyclopropene as the 27t-component, isomeric mixtures of 4H-azepines, e. g. 39 and 40, are formed.84... 

This is also true for the tautomerization of 15-dihydroisobacteriochlorin 11 which can he converted into an isomeric mixture of pyrrocorphins 12 and 13.7... 

Formation of azepine derivatives by aza-[3,3]-Claisen rearrangements was first reported by Stogryn and Brois, an isomeric mixture of 2,3-divinylaziridines 166, generated by treatment of sulfonate 165 with NaOH, being converted into azepine 167 by steam distillation (Scheme 2.41) [61]. In this case, unchanged trans-azir-... 

Diene 265, substituted by a bulky silyl ether to prevent cycloaddition before the metathesis process, produced in the presence of catalyst C the undesired furanophane 266 with a (Z) double bond as the sole reaction product in high yield. The same compound was obtained with Schrock s molybdenum catalyst B, while first-generation catalyst A led even under very high dilution only to an isomeric mixture of dimerized products. The (Z)-configured furanophane 266 after desilylation did not, in accordance with earlier observations, produce any TADA product. On the other hand, dienone 267 furnished the desired macrocycle (E)-268, though as minor component in a 2 1 isomeric mixture with (Z)-268. Alcohol 269 derived from E-268 then underwent the projected TADA reaction selectively to produce cycloadduct 270 (70% conversion) in a reversible process after 3 days. The final Lewis acid-mediated conversion to 272 however did not occur, delivering anhydrochatancin 271 instead. 

Rearrangement of each isomer or isomeric mixture leads to only one of the three isomers. No side reaction such as "bromine dancing", trans-aimulare reaction etc, can be observed. 

Besides these main products, formed in incineration of 1 in polymeric matrices complex isomeric mixtures of brominated methyl-dibenzofurans and brominated condensed systems like benzo[b]naphto[2,3-d]furan have been identified by GC/MS (ref. 11). 

Chlorinated dibenzo-ip-dioxins were prepared on the gram scale for use as toxicological standards, 2,7-Dichlorodi-henzo-p-dioxin was prepared by catalytic condensation of potassium 2-bromo-4-chlorophenate in 70% yield. Thermal condensation of the potassium salt of 2,4,4 -trichloro-2 -hydroxy diphenyl ether gave a mixture of the 2,8- and 2,7-dichlorodibenzo-p-dioxins which were separated by fractional recrystallization. 2,3,7,8-T etrachlorodibenzo-p-dioxin of 99.9- -% purity was prepared by catalytic condensation of potassium 2,4,5-trichlorophenate. An isomeric mixture of hexachlorodibenzo-p-dioxins was prepared by pyrolytic condensation of sodium 2,3,4,6-tetrachlorophenate. Chlorination of pentachlorophenol (containing < 0.07% tetrachlorophenol) in trichlorobenzene gave octachlorodi-benzo-p-dioxin in 80% yield contaminated by 5-15% heptachlorodibenzo-p-dioxin. Oxidative methods were used to produce octachlorodibenzo-p-dioxin at 99.9% purity. 

---