Alkyl halides solubility

Cold concentrated sulphuric acid will remove unsaturated hydrocarbons present in saturated hydrocarbons, or alcohols and ethers present in alkyl halides. In the former case soluble sulphonated products are formed, whilst in the latter case alkyl hydrogen sulphates or addition complexes, that are soluble in the concentrated acid, are produced. 

Higher alcohols (> C3) react comparatively slowly with sodium because of the slight solubility of the sodium alkoxide in the alcohol a large excess (say, 8 mols) is therefore employed. The mixed ether is distilled off, and the process (formation of alkoxide and its reaction with the alkyl halide) may be repeated several times. The excess of alcohol can be recovered. cj/cloAliphatic alcohols form sodio compounds with difficulty if small pieces... 

Solubility in Water Alkyl halides and alcohols differ markedly from one another m their solubility m water All alkyl halides are insoluble m water but low molecular weight alcohols (methyl ethyl n propyl and isopropyl) are soluble m water m all pro portions Their ability to participate m mtermolecular hydrogen bonding not only affects the boiling points of alcohols but also enhances their water solubility Hydrogen bonded networks of the type shown m Figure 4 5m which alcohol and water molecules asso ciate with one another replace the alcohol-alcohol and water-water hydrogen bonded networks present m the pure substances... 

Phosphorous acid is water soluble and may be removed by washing the alkyl halide with water or with dilute aqueous base... 

To ensure that reaction occurs m homogeneous solution solvents are chosen that dis solve both the alkyl halide and the ionic salt The alkyl halide substrates are soluble m organic solvents but the salts often are not Inorganic salts are soluble m water but alkyl... 

In the absence of die polyether, potassium fluoride is insoluble in benzene and unreactive toward alkyl halides. Similar enhancement of solubility and reactivity of other salts is observed in the presence of crown ethers The solubility and reactivity enhancement result because the ionic compound is dissociated to a tightly complexed cation and a naked anion. Figure 4.13 shows the tight coordination that can be achieved with a typical crown ether. The complexed cation, because it is surrounded by the nonpolar crown ether, has high solubility in the nonpolar media. To maintain electroneutrality, the anion is also transported into the solvent. The cation is shielded from interaction with the anion as a... 

The higher solubility of several quaternary ammonium salts of glyphosate in polar aprotic organic solvents such as acetonitrile was discovered (2), which permitted their reaction in solution with various alkyl halides. For example, GLY(n-Bu4N)2H reacted with either o-xylylene dichloride or 1,5-dibromopentane to produce the interesting quaternary glyphosate derivatives 81 and 82, whose structures have been confirmed by x-ray analysis (2). 

Notes on the preparation of secondary alkylarylamines. The preparation of -propyl-, ijopropyl- and -butyl-anilines can be conveniently carried out by heating the alkyl bromide with an excess (2-5-4mols) of aniline for 6-12 hours. The tendency for the alkyl halide to yield the corresponding tertiary amine is thus repressed and the product consists almost entirely of the secondary amine and the excess of primary amine combined with the hydrogen bromide liberated in the reaction. The separation of the primary and secondary amines is easily accomplished by the addition of an excess of per cent, zinc chloride solution aniline and its homologues form sparingly soluble additive compounds of the type B ZnCl whereas the alkylanilines do not react with sine chloride in the presence of water. The excess of primary amine can be readily recovered by decomposing the zincichloride with sodium hydroxide solution followed by steam distillation or solvent extraction. The yield of secondary amine is about 70 per cent, of the theoretical. 

Especially for large-scale work, esters may be more safely and efficiently prepared by reaction of carboxylate salts with alkyl halides or tosylates. Carboxylate anions are not very reactive nucleophiles so the best results are obtained in polar aprotic solvents45 or with crown ether catalysts.46 The reactivity order for carboxylate salts is Na+ < K+ < Rb+ < Cs+. Cesium carboxylates are especially useful in polar aprotic solvents. The enhanced reactivity of the cesium salts is due to both high solubility and minimal ion pairing with the anion 47 Acetone is a good solvent for reaction of carboxylate anions with alkyl iodides48 Cesium fluoride in DMF is another useful... 

Alternatively, the Sn2 nucleophilic substitution reaction between alcohols (phenols) and organic halides under basic conditions is the classical Williamson ether synthesis. Recently, it was found that water-soluble calix[n]arenes (n = 4, 6, 8) containing trimethylammonium groups on the upper rim (e.g., calix[4]arene 5.2) were inverse phase-transfer catalysts for alkylation of alcohols and phenols with alkyl halides in aqueous NaOH solution to give the corresponding alkylated products in good-to-high yields.56... 

The reaction of alkyl halides with metal nitrites is one of the most important methods for the preparation of nitroalkanes. As a metal nitrite, silver nitrite (Victor-Meyer reaction), potassium nitrite, or sodium nitrite (Kornblum reaction) have been frequently used. The products are usually a mixture of nitroalkanes and alkyl nitrites, which are readily separated by distillation (Eq. 2.47). The synthesis of nitro compounds by this process is well documented in the reviews, and some typical cases are listed in Table 2.3.92a Primary and secondary alkyl iodides and bromides as well as sulfonate esters give the corresponding nitro compounds in 50-70% yields on treatment with NaN02 in DMF or DMSO. Some of them are described precisely in vol 4 of Organic Synthesis. For example, 1,4-dinitrobutane is prepared in 41 -46% yield by the reaction of 1,4-diiodobutane with silver nitrite in diethyl ether.92b 1-Nitrooctane is prepared by the reaction with silver nitrite in 75-80% yield. The reaction of silver nitrite with secondary halides gives yields of nitroalkanes of about 15%, whereas with tertiary halides the yields are 0-5%.92c Ethyl a-nitrobutyrate is prepared by the reaction of ethyl a-bromobutyrate in 68-75% yield with sodium nitrite in DMF.92d Sodium nitrite is considerably more soluble in DMSO than in DMF as a consequence, with DMSO, much more concentrated solutions can be employed and this makes shorter reaction times possible.926... 

We have already mentioned that the mixed alkyl halide compounds of aluminum dimerize, and the solubility parameters shown in Table 12.1 for these compounds are consistent with that assessment. The solubility parameters for triethylboron and diethylzinc are 15.4 and 18.2 in J cm 3/2, respectively. These values are indicative of liquids that are not strongly associated, which is known to be the case. 

Similarly, it was also found that radical polymerization was induced in the Ni(CO)3(PPh3)/CBrCl3 redox system [155]. This complex is soluble in the polymerization medium, and the polymerization proceeded in a homogeneous system. This redox iniferter system has been intensively developed to the recent successful living radical polymerization using transition-metal complexes in combination with alkyl halides by several independent research groups (see Sect. 6.2). 

Interestingly, Et3B/02 initiation can be performed in aqueous solution [13]. For instance, a wide range of aryl and alkyl halides are reduced in water by water-soluble organosilanes using Et3B/02 initiation (Scheme 4) [14]. 

The formation of S-alkyl thiosulfate (Bunte salt) by the reaction of alkyl halide and sodium thiosulfate has been well known. Whereas a patent claimed the formation of Bunte salt from PECH and sodium thiosulfate (23), the reaction hardly proceeded in DMF owing to low solubility of sodium salt. On the other hand, both ammonium thiosulfate and PECH were soluble in HMPA-H20 (7 1 vol/vol) and the reaction proceeded homogeneously. Water soluble Bunte salt (j2, v(S0), 1200, 1020 cm-1) was isolated by pouring the reaction mixture into water and salting out with ammonium chloride. The DS based on the mercuric nitrate titration was in nearly accord with that on elemental analysis. The DS values depended on the thiosulfate concentration were shown below. 

The synthesis of aliphatic nitro compounds from the reaction of alkyl halides with alkali metal nitrites was discovered by Kornblum and co-workers and is known as the modified Victor Meyer reaction or the Kornblum modification. The choice of solvent in these reactions is crucial when sodium nitrite is used as the nitrite soiuce. Both alkyl halide and nitrite anion must be in solution to react, and the higher the concentration of nitrite anion, the faster the reaction. For this reason, both DMF and DMSO are widely used as solvents, with both able to dissolve appreciable amounts of sodium nitrite. Although sodium nitrite is more soluble in DMSO than DMF the former can react with some halide substrates.Urea is occasionally added to DMF solutions of sodium nitrite to increase the solubility of this salt and hence increase reaction rates. Other alkali metal nitrites can be used in these reactions, like lithium nitrite,which is more soluble in DMF than sodium nitrite but is also less widely available. 

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