Unreacted starting materials

Tengler and Von Falkai determined diols, adipic acid and volatiles cyclomono-diol adipates qualitatively and quantitatively in aliphatic polyesters based on adipic acid. The identification of the cyclic mon-esters is accomplished with the help of coupling a gas chromatograph with a mass spectrometer, die diols were classified by gas chromatographic retention volume. 

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The small amount of precipitate in the orange solution is not unreacted starting material but triphenylphosphinemethylene. 

A solution of 1 g of (239) in 80 ml cyclohexane is irradiated as described above. After 3 hr e reaches a constant value of 4700. The solvent is evaporated and the residue chromatographed on alumina (40 g). Elution with pentane-benzene (3 1) gives 0.14 g unreacted starting material... 

Unreacted Starting Material S Intermolecular Reaction Product Keto Ester Product ... 

Relatively little has been reported regarding the determination of the purity of the halide salts other than by standard spectroscopic measurements and microanalysis. This is largely because the halide salts are rarely used as solvents themselves, but are generally simply a source of the desired cation. Also, the only impurities likely to be present in any significant quantity are unreacted starting materials and residual reaction solvents. Thus, for most applications it is sufficient to ensure that they are free of these by use of FF NMR spectroscopy. 

Volatile impurities in an ionic liquid may have different origins. They may result from solvents used in the extraction steps during the synthesis, from unreacted starting materials from the allcylation reaction (to form the ionic liquid s cation), or from any volatile organic compound previously dissolved in the ionic liquid. 

In general, if K is a very small number, the equilibrium mixture will contain mostly unreacted starting materials for all practical purposes, the forward reaction does not go. Conversely, a large K implies a reaction that, at least in principle, is feasible products should be formed in high yield. Frequently, K has an intermediate value, in which case you must make quantitative calculations concerning the direction or extent of reaction. 

Under argon, a mixture of 145 (0.046 mmol), 132 (0.046 mmol), Pd(PPli3)4 (0.2 (junol), Cul (0.2 [miol), and diisopropylamine (0.015 mmol) in THF (4 mL) was stirred in the dark at 50°C for 2 days. Ethynylbenzene (0.92 mmol) was then added and stirred at 50°C overnight. After concentration, die residue was dissolved in CHCI3 and filtered. The filtrate was subjected to preparative SEC with CHCI3 as eluent in order to remove catalyst residues and unreacted starting materials. Polymer 42 was obtained as a yellow solid in 85% yield. SEC analysis (THF, polystyrene standards) Mw = 280,000 (PDI = 6.5). 

However, exclusive primary or secondary alkyl phosphates are seldom produced. That is due not only to the expenses of production but to the fact that in practical application the mixture of both esters combined with the rest of unreacted starting material often offers most interesting properties. Changing the molecular ratio of alcohol to P4O10 from 2 1 to 4 1 results in an increase of the secondary ester in the mixture from 35% to 65%. 

As the data in Table 1 indicate, there is a strong dependence of the hydration on the electron demands of the substituents, with a rho of -4.3 in the Yukawa-Tsuno (18) equation, where logk is plotted against p[a + t a — a)]. Partial hydration of CsHsC CT and recovery of the unreacted starting material did not result in any loss of specific activity, which indicates that the protonation of the triple bond is not significantly reversible and hence is rate determining. 

Reactions that reach equilibrium well before completion are not very attractive to the industrial chemist, because unreacted starting materials must be separated from the products, an expensive process. Nevertheless, gas-phase equilibria are involved in the industrial syntheses of H2 SO4, NH3, and HNO3. 

Early attempts by Pino and Giacomelli to resolve racemic 3,7-dimethyl-l-octene (37) by treatment with 0.3 equiv. of triisobutylaluminum in the presence of bis[(S)-seobutylsaHcyhdeneiminejnickel Ni[(S)-seobusal]2 and subsequent hydrolysis gave (S)-2,6-dimethyloctane (38) with an enantiomerical excess of 1.2% along with the unreacted starting material (S)-37 with 1.8% ee, as judged by optical rotation (Schemes 2-17 and 2-18) [28]. 

It was clearly important to drive adduct formation to completion any unreacted starting material 32 was not rejected in isolation of the product 33 and the result was an impurity in the finasteride product. Excess DDQ was required to ensure complete conversion of 32, but any DDQ remaining after adduct formation produced over-oxidation products in the thermolysis. The three over-oxidation products shown in Figure 3.4 were identified. Sequential dehydrogenation in the B-ring... 

When the concentration of BF3 increased, competitive deactivation leading to the formation of 97 resulted in unreacted starting material at the end of the etherification reaction. Efforts to break up this coordination and increase the conversion by the addition of certain additives, such as water, NaPlv, KPF6, l.iPF(l, or NasSiF6, either led to no improvement in conversion or to a complete shut down in the SN2 pathway and significant erosion in the diastereoselectivity resulted. 

Recently, iodobenzoates anchored onto an ionic liquid support (6.4) were coupled to various aryl boronic acids (6.5) in aqueous media using Pd(OAc)2 as the catalyst at 80°C to give the coupled product 6.6 (Scheme 6.3). Compounds 6.6 were purified simply by washing the reaction mixture with ether, which removed the unreacted starting materials and the side product 6.7 without the need of chromatography. Compounds 6.6 were then cleaved from the ionic liquid support... 

Furfural diacetate has been prepared from furfural and acetic anhydride in the presence of various catalysts.2-4 The present method is adapted to recovery and re-use of unreacted starting materials. 

Even with the simple laboratory equipment used in these experiments, the CESS procedure allowed quantitative recovery of the product free of solvent, and with rhodium contents ranging from 0.36-1.94 ppm (determined by atomic absorption measurements). Furthermore, using this approach removal of unreacted starting material or side products from the product is possible during extraction from the catalyst, since even small structural differences can result in significant differences in... 

An interesting observation was made by Ferrier and coworkers61 during the acylation of 2,4-boronic esters of methyl a- and /3-d-xylopyranosides, in both of which the pyranoid ring must be in the C.,(d) conformation, and the 3-hydroxyl group must be axially attached. On treatment with benzoyl chloride in pyridine, the a-d-xyloside derivative gave 37% of the 3-benzoate and 19% of unreacted starting-material, but the /3-D-xyloside derivative yielded... 

Treatment with alkali removes the various acidic by-products and their salts (acetate, sulfinate, and formate) and also serves to hydrolyze and remove unreacted starting materials. 

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