Solvent adduction

The oxidation reaction of 1-bromosilatrane (50) or its 3,7,10-trhnethyl derivative (50a) and tin dibromide leads to the formation of adduct/solvent complexes 63a,b (equation 82). Acetonitrile, DMF or methanol are used as the solvent315. 

Bhattacharyya, A. Banerjee, S. Mohapatra, P.K. Basu, S. Manchanda, V.K. Role of ligand structure and basicity on the extraction of uranyl isoxazolonate adducts, Solvent Extr. Ion Exch. 22 (2004) 13-29. 

Time course of product of PBN adduct Solvent used in extraction ESR parameters (G) Nature of trapped radical (R )... 

Solid adducts Isolated amine products, in particular, offer advantages such as low colour, low free amine content and low irritation potential they also provide non-yellowing, bloom-free films with good chemical and solvent resistance Amine adducts solvent-based, two-pack coatings, e.g. primers, finishes and coal tar epoxy coatings... 

Catalyst Adducts Solvent Temp. 1°C] (time [h]) Yield [%] (based on butadiene) Lactones Esters Buta- Ref. diene dimers ... 

The monomers are electron pair acceptors, and donor molecules are often able to split the dimeric halide molecules to form adducts thus, whilst the dimeric halides persist in solvents such as benzene, donor solvents such as pyridine and ether appear to contain monomers since adduct formation occurs. Aluminium halides, with the one exception of the fluoride, resemble the corresponding boron halides in that they are readily hydrolysed by water. 

Theoretical work by the groups directed by Sustmann and, very recently, Mattay attributes the preference for the formation of endo cycloadduct in solution to the polarity of the solvent Their calculations indicate that in the gas phase the exo transition state has a lower energy than the endo counterpart and it is only upon introduction of the solvent that this situation reverses, due to the difference in polarity of both transition states (Figure 1.2). Mattay" stresses the importance of the dienophile transoid-dsoid conformational equilibrium in determining the endo-exo selectivity. The transoid conformation is favoured in solution and is shown to lead to endo product, whereas the cisoid conformation, that is favoured in the gas phase, produces the exo adduct This view is in conflict with ab initio calculations by Houk, indicating an enhanced secondary orbital interaction in the cisoid endo transition state . 

In conclusion, the special influence of water on the endo-exo selectivity seems to be a result of the fact that this solvent combines in it three characteristics that all favour formation of the endo adduct (1) water is a strong hydrogen bond donor, (2) water is polar and (3) water induces hydrophobic interactions. 

Due to the prolonged reaction times in organic solvents, cKmerisation of the diene occurs during the reaction, resulting in contaminated product mixtures after work-up. In contrast the reactions in water yield quantitatively the H-NMR-pure Diels-Alder adducts. 

Endo-exo ratios of the micelle-catalysed reactions have been determined by adding 0.25 mmol of 5.1c and 0.5 mmol of 5.2 to a solution of 5 mmol of surfactant and 0.005 mmol of EDTA in 50 ml of water in carefully sealed 50 ml flasks. The solutions were stirred for 7 days at 26 C and subsequently freeze-dried. The SDS and CTAB containing reaction mixtures were stirred with 100 ml of ether. Filtration and evaporation of the ether afforded the crude product mixtures. Extraction of the Diels-Alder adducts from the freeze-dried reaction mixture containing C12E7 was performed by stirring with 50 ml of pentane. Cooling the solution to -18 C resulted in precipitation of the surfactant. Filtration and evaporation of the solvent afforded the adduct mixture. Endo-exo ratios... 

A mixture of 0.20 mol of the adduct from cyclooctene and dibromocarbene (note 1) and 250 ml of dry diethyl ether was cooled to -65°C. A solution of 0.23 mol of ethyllithium (note 2) in 200 ml of diethyl ether (see Chapter II, Exp. 1) was added in 15 min with cooling between -60 and -50°C. The reaction was very exothermic (note 3). After the addition the cooling bath was removed and the temperature was allowed to rise to about -10°C and the reaction mixture was poured into 200 ml of ice-water. The aqueous layer was extracted twice with diethyl ether. After drying, the solvent was removed in a water-pump vacuum and the remaining liquid was distilled through a 40-cm Vigreux column. 1,2-Cyclononadiene, b.p. 62°C/22 mmHg, 1.5059, was obtained in 86 yield. 

Furfuryl alcohol is used alone or in combination with other solvents for various cleaning and paint removing operations. The ethylene oxide adduct of furfuryl alcohol is especially useful in this type of appHcation (80—83). 

Since double bonds are no longer present, these compounds are more stable than the corresponding furan derivatives. Tetrahydrofurfuryl alcohol—ethylene oxide adducts [31692-85-0] are also usehil solvents for paint stripping formulations (136,141,143). 2-Methylfuran is a good solvent, but... 

A method for making ben2onitri1e by dehydrogenation of the Diels-Alder adduct of butadiene and acrylonitrile also has been described (79). Ben2onitri1e also can be made on a small scale by the dehydration of ben2amide ia an iaert solvent with phosphoms oxychloride or ben2enesulfonyl chloride and an organic amine (80,81). 

Aqueous mineral acids react with BF to yield the hydrates of BF or the hydroxyfluoroboric acids, fluoroboric acid, or boric acid. Solution in aqueous alkali gives the soluble salts of the hydroxyfluoroboric acids, fluoroboric acids, or boric acid. Boron trifluoride, slightly soluble in many organic solvents including saturated hydrocarbons (qv), halogenated hydrocarbons, and aromatic compounds, easily polymerizes unsaturated compounds such as butylenes (qv), styrene (qv), or vinyl esters, as well as easily cleaved cycHc molecules such as tetrahydrofuran (see Furan derivatives). Other molecules containing electron-donating atoms such as O, S, N, P, etc, eg, alcohols, acids, amines, phosphines, and ethers, may dissolve BF to produce soluble adducts. 

Boron trifluoride catalyst may be recovered by distillation, chemical reactions, or a combination of these methods. Ammonia or amines are frequently added to the spent catalyst to form stable coordination compounds that can be separated from the reaction products. Subsequent treatment with sulfuric acid releases boron trifluoride. An organic compound may be added that forms an adduct more stable than that formed by the desired product and boron trifluoride. In another procedure, a fluoride is added to the reaction products to precipitate the boron trifluoride which is then released by heating. Selective solvents may also be employed in recovery procedures (see Catalysts,regeneration). 

Beryllium Hydride. BeryUium hydride [13597-97-2] is an amorphous, colorless, highly toxic polymeric soHd (H = 18.3%) that is stable to water but hydroly2ed by acid (8). It is insoluble in organic solvents but reacts with tertiary amines at 160°C to form stable adducts, eg, (R3N-BeH2 )2 (9). It is prepared by continuous thermal decomposition of a di-/-butylberylhum-ethyl ether complex in a boiling hydrocarbon (10). 

Borane—dimethyl sulfide complex (BMS) (2) is free of these inconveniences. The complex is a pure 1 1 adduct, ca 10 Af in BH, stable indefinitely at room temperature and soluble in ethers, dichioromethane, benzene, and other solvents (56,57). Its disadvantage is the unpleasant smell of dimethyl sulfide, which is volatile and water insoluble. Borane—1,4-thioxane complex (3), which is also a pure 1 1 adduct, ca 8 Af in BH, shows solubiUty characteristics similar to BMS (58). 1,4-Thioxane [15980-15-1] is slightly soluble in water and can be separated from the hydroboration products by extraction into water. 

DiphenyhnethyUithium [881-42-5] can be prepared by the metalation reaction of butyUithium with diphenyknethane in addition, the adduct of butyUithium and 1,1-diphenylethylene is convenientiy prepared in either hydrocarbon or polar solvents such as THF as shown in equation 18. 

MIBK is a highly effective separating agent for metals from solutions of their salts and is used in the mining industries to extract plutonium from uranium, niobium from tantalum, and zirconium from hafnium (112,113). MIBK is also used in the production of specialty surfactants for inks (qv), paints, and pesticide formulations, examples of which are 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its ethoxylated adduct. Other appHcations include as a solvent for adhesives and wax/oil separation (114), in leather (qv) finishing, textile coating, and as a denaturant for ethanol formulations. 

Chlorendic anhydride is the common name of the Diels-Alder adduct of maleic anhydride and hexachlorocyclopentadiene, 3,4,5,6,7,7-hexachloroendomethylene-l,2,3,6-tetrahydrophthahc anhydride (HET). The resultant resins from HET contribute to the flame retardancy of the alkyd coatings. HET gives a greater reaction rate than phthaUc anhydride, to the extent that at 204—210°C the reaction rate approximates that of phthaUc anhydride at a temperature of 238°C (8). However, the resins tend to develop darker color, particularly at high processing temperature. Tetrachlorophthahc anhydride [117-08-8] made by conventional chlorination of phthaUc anhydride, would also impart flame retardancy to its alkyds. However, it is appreciably less soluble in the usual processing solvents than is phthaUc anhydride, and is reported to be of appreciably lower chemical reactivity (8). 

Activated tertiary amines such as triethanolamine (TEA) and methyl diethanolamine (MDEA) have gained wide acceptance for CO2 removal. These materials require very low regeneration energy because of weak CO2 amine adduct formation, and do not form carbamates or other corrosive compounds (53). Hybrid CO2 removal systems, such as MDEA —sulfolane—water and DIPA—sulfolane—water, where DIPA is diisopropylamine, are aqueous alkaline solutions in a nonaqueous solvent, and are normally used in tandem with other systems for residual clean-up. Extensive data on the solubiUty of acid gases in amine solutions are available (55,56). 

Isoquinoline can be reduced quantitatively over platinum in acidic media to a mixture of i j -decahydroisoquinoline [2744-08-3] and /n j -decahydroisoquinoline [2744-09-4] (32). Hydrogenation with platinum oxide in strong acid, but under mild conditions, selectively reduces the benzene ring and leads to a 90% yield of 5,6,7,8-tetrahydroisoquinoline [36556-06-6] (32,33). Sodium hydride, in dipolar aprotic solvents like hexamethylphosphoric triamide, reduces isoquinoline in quantitative yield to the sodium adduct [81045-34-3] (25) (152). The adduct reacts with acid chlorides or anhydrides to give N-acyl derivatives which are converted to 4-substituted 1,2-dihydroisoquinolines. Sodium borohydride and carboxylic acids combine to provide a one-step reduction—alkylation (35). Sodium cyanoborohydride reduces isoquinoline under similar conditions without N-alkylation to give... 

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). 

Sulfur dioxide acts as a dienophile ia the Diels-Alder reaction with many dienes (253,254) and this reaction is conducted on a commercial scale with butadiene. The initial adduct, sulfolene [77-79-2] is hydrogenated to a solvent, sulfolane [126-33-0] which is useful for selective extraction of aromatic hydrocarbons from... 

Titanium oxide dichloride [13780-39-8] TiOCl2, is a yellow hygroscopic soHd that may be prepared by bubbling ozone or chlorine monoxide through titanium tetrachloride. It is insoluble in nonpolar solvents but forms a large number of adducts with oxygen donors, eg, ether. It decomposes to titanium tetrachloride and titanium dioxide at temperatures of ca 180°C (136). 

Titanium Tetraiodide. Titanium tetraiodide [7720-83 ] forms reddish-brown crystals, cubic at room temperature, having reported lattice parameter of either 1200 (149) or 1221 (150) pm. Til melts at 150°C, boils at 377°C, and has a density of 440(0) kg/m. It forms adducts with a number of donor molecules and undergoes substitution reactions (151). It also hydrolyzes in water and is readily soluble in nonpolar organic solvents. 

These effects can be attributed mainly to the inductive nature of the chlorine atoms, which reduces the electron density at position 4 and increases polarization of the 3,4-double bond. The dual reactivity of the chloropteridines has been further confirmed by the preparation of new adducts and substitution products. The addition reaction competes successfully, in a preparative sense, with the substitution reaction, if the latter is slowed down by a low temperature and a non-polar solvent. Compounds (12) and (13) react with dry ammonia in benzene at 5 °C to yield the 3,4-adducts (IS), which were shown by IR spectroscopy to contain little or none of the corresponding substitution product. The adducts decompose slowly in air and almost instantaneously in water or ethanol to give the original chloropteridine and ammonia. Certain other amines behave similarly, forming adducts which can be stored for a few days at -20 °C. Treatment of (12) and (13) in acetone with hydrogen sulfide or toluene-a-thiol gives adducts of the same type. 

The mean chemical shifts of A- unsubstituted pyrazoles have been used to determine the tautomeric equilibrium constant, but the method often leads to erroneous conclusions (76AHC(Sl)l) unless the equilibrium has been slowed down sufficiently to observe the signals of individual tautomers (Section 4.04.1.5.1). When acetone is used as solvent it is necessary to bear in mind the possibility (depending on the acidity of the pyrazole and the temperature) of observing the signals of the 1 1 adduct (55) whose formation is thermodynamically favoured by lowering the solution temperature (79MI40407). A similar phenomenon is observed when SO2 is used as solvent. 

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