Same solvent

After the main filtrate has been removed, the crystals should be washed in order to remove the mother liquor which, on drying, would contaminate the crystals. The wash liquid will normally be the same solvent as was used for recrystallisation, and must be used in the smallest possible... 

While the same solvent may serve throughout, it is often necessary to use different solvents at different stages of the chromatographic separation. 

Reference has already been made to the choice of solvent for introducing the mixture to the column. Generally speaking, adsorption takes place most readily from non-polar solvents, such as petroleum ether or benzene, and least from highly polar solvents such as alcohols, esters and pyridine. Frequently the solvent for introducing the mixture to the column and the developer are so chosen that the same solvent serves the dual purpose. 

Anilides. Dilute the acid chloride with 5 ml. of pure ether (or benzene), and add a solution of 2 g. of pure aniline in 15-20 ml. of the same solvent until the odour of the acid chloride has disappeared excess of aniline is not harmful. Shake with excess of dilute hydrochloric acid to remove aniline and its salts, wash the ethereal (or benzene) layer with 3-5 ml. of water, and evaporate the solvent [CAUTION ] Recrystallise the anilide from water, dilute alcohol or benzene - light petroleum (b.p. 60-80°). 

Method 2. Place 90 g. of sodium benzenesulphonate (Section IV,29) (previously dried at 130-140° for 3 hours) and 50 g. of powdered phosphorus pentachloride (1) in a 500 ml. round-bottomed flask furnished with a reflux condenser heat the mixture in an oil bath at 170-180° for 12-15 hours. Every 3 hours remove the flask from the oil bath, allow to cool for 15-20 minutes, stopper and shake thoroughly until the mass becomes pasty. At the end of the heating period, allow the reaction mixture to cool. Pour on to 1 kilo of crushed ice. Extract the crude benzenesulphonyl chloride with 150 ml. of carbon tetrachloride and the aqueous layer with 75 ml. of the same solvent. Remove the solvent under atmospheric pressure and proceed as in Method 1. The yield is about 170 g., but depends upon the purity of the original sodium benzenesulphonate. 

In a Lewis-acid catalysed Diels-Alder reaction, the first step is coordination of the catalyst to a Lewis-basic site of the reactant. In a typical catalysed Diels-Alder reaction, the carbonyl oxygen of the dienophile coordinates to the Lewis acid. The most common solvents for these processes are inert apolar liquids such as dichloromethane or benzene. Protic solvents, and water in particular, are avoided because of their strong interactions wifti the catalyst and the reacting system. Interestingly, for other catalysed reactions such as hydroformylations the same solvents do not give problems. This paradox is a result of the difference in hardness of the reactants and the catalyst involved... 

It has already been noted that, as well as alkylbenzenes, a wide range of other aromatic compounds has been nitrated with nitronium salts. In particular the case of nitrobenzene has been examined kinetically. Results are collected in table 4.4. The reaction was kinetically of the first order in the concentration of the aromatic and of the nitronium salt. There is agreement between the results for those cases in which the solvent induces the ionization of nitric acid to nitronium ion, and the corresponding results for solutions of preformed nitronium salts in the same solvent. 

The equation does not take into account such pertubation factors as steric effects, solvent effects, and ion-pair formation. These factors, however, may be neglected when experiments are carried out in the same solvent at the same temperature and concentration for an homogeneous set of substrates. So, for a given ambident nucleophile the rate ratio kj/kj will depend on A and B, which vary with (a) the attacked electrophilic center, (b) the solvent, and (c) the counterpart cationic species of the anion. The important point in this kind of study is to change only one parameter at a time. This simple rule has not always been followed, and little systematic work has been done in this field (12) stiH widely open after the discovery of the role played by single electron transfer mechanism in ambident reactivity (1689). 

They are prepared by the addition of an alcoholic solution of thiazole to the metal salt in the same solvent. 

The (thermal) decomposition of thiazol-2-yldiazonium salts in a variety of solvents at 0 C in presence of alkali generates thiazol-2-yl radicals (413). The same radicals result from the photolysis in the same solvents of 2-iodothiazole (414). Their electrophilic character is shown by their ability to attack preferentially positions of high rr-electron density of aromatic substrates in which they are generated (Fig. 1-21). The major... 

When a dilute solution of 6 phenylhexanoyl chloride in carbon disulfide was slowly added (over a period of eight days ) to a suspension of aluminum chloride in the same solvent it yielded a product A (C12H14O) in 67% yield Oxidation of A gave benzene 1 2 dicarboxyhc acid... 

A sample of the protein, horse heart myoglobin, was dissolved in acidified aqueous acetonitrile (1% formic acid in HjO/CHjCN, 1 1 v/v) at a concentration of 20 pmol/1. This sample was injected into a flow of the same solvent passing at 5 pl/min into the electrospray source to give the mass spectrum of protonated molecular ions [M + nH] shown in (a). The measured ra/z values are given in the table (b), along with the number of protons (charges n) associated with each. The mean relative molecular mass (RMM) is 16,951,09 0.3 Da. Finally, the transformed spectrum, corresponding to the true relative molecular mass, is shown in (c) the observed value is close to that calculated (16,951.4), an error of only 0.002%. 

In discussing mechanism (5.F) in the last chapter we noted that the entrapment of two reactive species in the same solvent cage may be considered a transition state in the reaction of these species. Reactions such as the thermal homolysis of peroxides and azo compounds result in the formation of two radicals already trapped together in a cage that promotes direct recombination, as with the 2-cyanopropyl radicals from 2,2 -azobisisobutyronitrile (AIBN),... 

The assumption that k values are constant over the entire duration of the reaction breaks down for termination reactions in bulk polymerizations. Here, as in Sec. 5.2, we can consider the termination process—whether by combination or disproportionation to depend on the rates at which polymer molecules can diffuse into (characterized by kj) or out of (characterized by k ) the same solvent cage and the rate at which chemical reaction between them (characterized by kj.) occurs in that cage. In Chap. 5 we saw that two limiting cases of Eq. (5.8) could be readily identified ... 

The second CO2 removal is conducted using the same solvent employed in the first step. This allows a common regeneration stripper to be used for the two absorbers. The gases leaving the second absorption step stiU contain some 0.25—0.4% CO and 0.01—0.1% CO2 and so must be methanated as discussed earlier. The CO, CO2, and possibly small amounts of CH, N2, and Ar can also be removed by pressure-swing adsorption if desired. 

JSlonhydrocarbon and Oxygenated Solvents. Most kidustrial solvents that are not hydrocarbons are pure chemical compounds. As such, they have sharp boiling pokits and weU-defined properties. Specifications for these solvents focus mosdy on impurities such as water and other contaminants. This also means that a solvent from one manufacturer should perform the same as the same solvent from another manufacturer any differences are probably the result of impurities, stabiLker content, etc, rather than the properties of the overall solvent. 

Catalyst Cation. The logarithms of extraction constants for symmetrical tetra- -alkylammonium salts (log rise by ca 0.54 per added C atom. Although absolute numerical values for extraction coefficients are vastly different in various solvents and for various anions, this relation holds as a first approximation for most solvent—water combinations tested and for many anions. It is important to note, however, that the lipophilicity of phenyl and benzyl groups carrying ammonium salts is much lower than the number of C atoms might suggest. Benzyl is extracted between / -propyl and -butyl. The extraction constants of tetra- -butylammonium salts are about 140 times larger than the constants for tetra- -propylammonium salts of the same anion in the same solvent—water system. 

Consider using the same solvent in the next step (i.e. eliminate the co-distillation)... 

A substance is usually taken to be of an acceptable purity when the measured property is unchanged by further treatment (especially if it agrees with a recorded value). In general, at least two different methods, such as recrystallisation and distillation, should be used in order to ensure maximum purity. Crystallisation may be repeated (from the same solvent or better from different solvents) until the substance has a constant melting point or absorption spectrum, and until it distils repeatedly within a narrow, specified temperature range. 

Nitrobenzyl bromide [100-11-8] M 216.0, m 98.5-99.0 . Recrystd four times from abs EtOH, then twice from cyclohexane/hexane/ benzene (1 1 1), followed by vac sublimation at 0.1mm and a final recrystn from the same solvent mixture. [Lichtin and Rao J Am Chem Soc 83 2417 1961.] Has also been crystd from pet ether (b 80-100°, lOmL/g, charcoal). It slowly decomposes even when stored in a desiccator in the dark. IRRITANT. 

To the cooled reaction mixture, 200 ml. of water is added carefully with stirring. Potassium carbonate is added with continued stirring until the water layer is saturated the mixture is now transferred to a separatory funnel and extracted three times with 60-ml. portions of ether. The combined ether extracts are dried over solid sodium hydroxide and are then transferred to a simple distillation apparatus. Distillation is commenced with a steam bath as source of heat when most of the ether has been removed, the steam bath is replaced by a flame. Distillation is continued until most of the piperidine (b.p. 106°) has been removed. The cooled residue in the distillation flask is recrystallized from petroleum ether (boiling range 30-60°) with the use of charcoal. There is obtained 30.0 g. (71%) of N-/3-naphthyl-piperidine as tan crystals, m.p. 52-56°. An additional recrystallization from the same solvent gives crystals, m.p. 56-58°, with about 10% loss in weight (Note 6). 

The column used in the upper chromatogram was 24 cm long, 4.6 mm I.D. the solvent was tetrahydrofuran, the solute benzene and the flow rate 1 ml/min. The column used in the lower chromatogram was 1 m long, 1 mm I.D. using the same solvent and solute but at a mobile phase flow rate of 40 ml/min. It is seen that the reduction in cell volume has a dramatic effect on peak shape. The large 25 pi cell... 

Samples and reference substances should be dissolved in the same solvents to ensure that comparable substance distribution occurs in all the starting zones. In order to keep the size of the starting zones down to a minimum (diameter TLC 2 to 4 mm, HPTLC 0.5 to 1 mm) the application volumes are normally limited to a maximum of 5 xl for TLC and 500 nl for HPTLC when the samples are applied as spots. Particularly in the case of adsorption-chromatographic systems layers with concentrating zones offer another possibility of producing small starting zones. Here the applied zones are compressed to narrow bands at the solvent front before the mobile phase reaches the active chromatographic layer. 

A cold (0°) solution of 15 g (0.039 mole) of cholest-4-en-3-one, mp 79-80°, in 200 ml of ether-benzene (8 1) is added dropwise to 0.05 mole of lithium tri-t-butoxyaluminum hydride in ether-diglyme at —40° to —50°. The mixture is allowed to stand overnight at 0° and then hydrolyzed by treatment with ice, 5 N sodium hydroxide and Rochelle salt. Evaporation of the washed and dried ether extracts and crystallization of the residue from ethyl acetate affords 13 g (87 % yield) of nearly pure cholest-4-en-3j9-ol, mp 126-129°. One recrystallization from the same solvent gives the pure product as large needles mp 131-132°, [a]o 46° reported mp 132° [a]c, 44° (benzene). 

P,17P-Dihydroxyestr-4-en-3-one 1-acetate. The 6-hydroxy compound is removed from the column with 15-17% acetone. Recrystallization of the crude product (1.92 g) from acetone-hexane gives 1.25 g of crystals melting at 165-166° and 0.13 g melting at 162-164° (12.1% yield). When the analytical sample was prepared from the same solvent mixture, the melting point rose to 192-193° (Lit 166° 189-190°) [a] -59.5° (CHCI3) 2, 236 m/i (fi 14,500). 

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