Amines pure organic solvents

Direct addition of ammonia to olefmic bonds would be an attractive method for amine synthesis, if it could be carried out smoothly. Like water, ammonia reacts with butadiene only under particular reaction conditions. Almost no reaction takes place with pure ammonia in organic solvents. The presence of water accelerates the reaction considerably. The reaction of aqueous ammonia (28%) with butadiene in MeCN in the presence orPd(OAc)i and PhjP at 80 C for 10 h gives tri-2,7-octadienylamine (47) as the main product, accompanied by a small amount of di-2,7-octadienylamine (46)[46,47], Isomeric branched... 

It s often possible to lake advantage of their basicity to purify amines. For example, if a mixture of a basic amine and a neutral compound such as a ketone or alcohol is dissolved in an organic solvent and aqueous acid is added, the basic amine dissolves in the water layer as its protonated salt, while the neutral compound remains in the organic solvent layer. Separation of the water layer and neutralization of the ammonium ion by addition of NaOH then provides the pure amine (Figure 24.2). 

Table 1.3 Influence ofthe organic solvent on the enantioselectivity of the protease subtilisin in the kinetic resolution ofthe racemic amine (9) (expressed as the ratio ofthe initial rate of acylation of the pure enatiomers, Vs/vr).

In ad fume hood, wash the amine-surface with organic solvent to remove any contaminants or water (especially when working with particles). Suggested solvents to use for this reaction are highly pure and dry DMAC, DMSO, or DMF. Particles can be washed by repeated centrifugation and resuspension. 

The NHS ester compounds are sensitive to hydrolysis in aqueous solution, and they likely will hydrolyze faster than more hydrophobic biotinylation compounds due to their hydrophilic-ity. If a stock solution is made at a higher concentration to facilitate the addition of a small amount to a reaction solution, the initial solution should be made in a water-miscible organic solvent that is dried with a molecular sieve. Suitable solvents include DMAC, DMSO, or DMF. If using DMF, use only highly pure solvent, as it may contain amines that can react with the NHS ester groups (Figure 18.13). 

The similarity in the rate laws does not allow a clear choice to be made between mechanisms, but Mechanism A is required in H20 by the observation of general base catalysis. However, the relative stability of the (red) T° intermediate in Me2SO (this is dependent on the nature of the AA side chain, cf. Section III,C) in the absence of proton-ated amine makes us prefer Mechanism B for reaction in this solvent, since the solvent is unable to assist the departure of MeOH. The similar catalytic rate constants found for B = imidazole, Af-methylimidazole (26) suggest that transfer of the proton from T+ to the alcohol function remains stepwise (i.e., via T°) since N-methylimidazole cannot carry out a concerted transfer. Such general acid-catalyzed loss of MeOH from T° supports a suggestion made many years ago by Burnett and Davies relating to purely organic esters (62). 

The pure compound is a pale yellow, nearly odourless oil, soluble in organic solvents, but almost insoluble in water. Averell and Norris2 describe the detection of minute quantities of parathion (20 /ig.) in spray and dust, by reduction with zinc, diazotization and coupling with an amine to give an intense magenta colour. It is effective (at concentrations of 25-600 p.p.m.) against many insect species, but of course, like the majority of organo-phosphorus insecticides, it is toxic to man and to animals. 

One possibility to separate the enantiomers of rac- 1-phenylethanamine is to form diastereomeric salts with an enantiomerically pure chiral acid, e.g. (R,R) tartaric acid or (S)-2-hydroxysuccinic acid. These can be separated from each other by recrystallisation as a consequence of their different solubilities. Note, however, that the separation process is not complete at this stage since the amines are now present as salts. The separated salts must be treated with a strong base, e.g. aqueous sodium hydroxide, to convert them back to the free amines which can then be extracted into an organic solvent. After drying the extract distillation of the solvent leaves the pure amine. 

To a mixture of HC02H (3 mmol, 0.11 mL) and ZnO (0.5 mmol, 0.04 g) was added an amine (1 mmol), and then the reaction mixture was heated in an oil bath at 70 °C and stirred with a magnetic stirrer. The progress of the reaction was monitored by TLC. After the reaction was complete, CH2CI2 or EtOAc was added to the reaction mixture and ZnO was removed by filtration. The organic solvent was then washed with H20 (2x10 mL) and a saturated solution of NaH-C03 and dried over anhydrous Na2S04. After removal of the solvent, the pure product was obtained. 

To a mixture of the acid (la-f, 2.5 mmol) and racemic 2-ethyIhexyl amine (2, 5.0 mmol), CAL-B (300 mg) was added. The reaction mixture was heated at 90 °C in vacuo with stirring and the progress of the reaction was monitored by IR spectroscopy. When the acid was consumed completely, the reaction mixture was diluted with dichloromethane and quenched by filtering off the enzyme. The organic solvent was evaporated in vacuo and the residue was subjected to column chromatography using petroleum ether-ethyl acetate as eluent to afford the pure amide and the unreacted amine in optically enriched forms. 

Acetonyltriphenylphosphonium bromide (0.05 mmol) was added to a mixture of the alcohol, or phenol, or amine or thiol (1 mmol) and acetic anhydride (1.5-2.0 mmol) and the mixture was stirred at room temperature for ca. 0.5-3.5 h. After complete disappearance of the starting material, as monitored by TLC, the mixture was quenched with a saturated hydrogencarbonate solution (2mL). Finally, the reaction mixture was extracted with ethyl acetate (20mLx3). The combined organic extract was washed with water and dried over anhydrous sodium sulfate. After removal of the organic solvent in a rotary evaporator, the crude residue was passed through a silica gel column to isolate the desired pure acetate. 

Pure ioxynil is a colourless crystalline compound insoluble in water and poorly soluble in organic solvents. Owing to its acid character (pK. 3.96) it forms salts with alkali metals, which are readily soluble in water. Its amine salts are also readily soluble in water. 

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