Solubility of ethers

Bennett, G.M. and Philip. W.G. The influence of structure on the solubilities of ethers. Part II. Some cyclic ethers. /. Chem. Soc. (London), 131 1937-1942, 1928a. 

From these two results make a general statement about the solubility of ether in water. 

Since ethers are polar, they dissolve in water by forming hydrogen bonds. The solubility of ethers decrease when the molar masses increase. Ethers dissolve many polar and nonpolar substances very well. 

Solubility of Ether in Water. Lower Layer — Aqueous. 

Predict relative boiling points and solubilities of ethers. 

For example, if a solute added decreases the mutual solubility of the two liquids, the mutual solubility eventually becomes zero and the partition coefficient becomes equal to the ratio of the solubilities of the solute in pure solvents. If the mutual solubility is increased by the solute as in the case of malonic acid increasing the mutual solubility of ether and water, the concentrations of the solute in.the two layers tend to become equal and the partition coefficient then becomes one. The concentration... 

Procedure. The test is conducted in a micro test tube. A drop of the test solution is treated with a drop of a 1 1 mixture of 1 % barium chloride and 10 % sodium nitrite, and a arop of dilute hydrochloric acid. If aminosulfonic acid is present, a precipitate or turbidity of barium sulfate will appear. With slight quantities of sulfamic acid, the BaS04 can be brought down almost immediately by adding several drops of ether and swirling the test tube. This effect is due to the considerable solubility of ether in water which thus accelerates the normally sluggish separation of small amounts of barium sulfate. 

Ether molecules are less polar than alcohol molecules, and there is no opportunity for hydrogen bonding between them. Intermolecular attractions are therefore lower, as are their respective boiling points. Up to three carbons, ethers are gases at room conditions. Diethyl ether, with four carbons, is a volatile liquid that boils at 35°C. The solubility of ether molecules in water is about the same as the solubility of isomeric alcohols, probably due to the hydrogen bonding between the ether molecules and water molecules. 

It is a pseudo mol fraction. At the left-hand side of the diagram the water partial-pressure curve starts at the vapor pressure of water, and the ether curve starts at zero, since none is present. As ether is added to the system, it first dissolves in the water, giving only one liquid phase, until a concentration of 0.9 mol per cent ether is reached, which is the solubility of ether in water at 60 C. In the... 

The solubility of diethyl ether in water is much higher than that of pentane, but the solubilities of ethers and alkanes approach one another as their molecular weights increase. The ether functional group contributes less to the overall properties of high molecular weight molecules, which resemble alkanes in their solubility. 

Oxonium salt formation. Shake up 0 5 ml. of ether with 1 ml. of cone. HCl and note that a clear solution is obtained owing to the formation of a water-soluble oxonium salt. Note that aromatic and aliphatic hydrocarbons do not behave in this way. In general diaryl ethers and alkyl aryl ethers are also insoluble in cone. HCl. 

In the isolation of organic compounds from aqueous solutions, use is frequently made of the fact that the solubility of many organic substances in water is considerably decreased by the presence of dissolved inorganic salts (sodium chloride, calcium chloride, ammonium sulphate, etc.). This is the so-called salting-out effect. A further advantage is that the solubility of partially miscible organic solvents, such as ether, is considerably less in the salt solution, thus reducing the loss of solvent in extractions. 

Alternatively, the following procedure for isolating the glycol may be used. Dilute the partly cooled mixture with 250 ml. of water, transfer to a distilling flask, and distil from an oil bath until the temperature reaches 95°. Transfer the hot residue to an apparatus for continuous extraction with ether (e.g.. Fig. II, 44, 2). The extraction is a slow process (36-48 hours) as the glycol is not very soluble in ether. (Benzene may also be employed as the extraction solvent.) Distil off the ether and, after removal of the water and alcohol, distil the glycol under reduced pressure from a Claisen flask. 

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... 

When the derivative is appreciably soluble in ether, the following alternative procedure may be employed. Dissolve the cold leaction mixture in about 60 ml. of ether, wash it with 20-30 ml. of 10 per cent, hydrochloric acid (to remove the excess of base), followed by 20 ml. of 10 per cent, sodium hydroxide solution, separate the ether layer, and evaporate the solvent [CAUTION/]. Recrystallise the residue from dilute alcohol. 

It is advisable to test a small portion of the filtrate for platinum by acidifying with hydrochloric acid and adding a few drops of stannous chloride solution a yellow or brown colour develops according to the quantity of platinum pVesent. The yellow colour is soluble in ether, thus rendering the t t more sensitive. If platinum is found, treat the filtrate with excess of formaldehyde and sodium iQrdroxide solution and heat,- platinum black septarates on standing and may be filtered and worked up with other platinum residues (see Method 3). 

Method 2. Place a 3 0 g. sample of the mixture of amines in a flask, add 6g. (4-5 ml.) of benzenesulphonyl chloride (or 6 g. of p-toluenesulphonyl chloride) and 100 ml. of a 5 per cent, solution of sodium hydroxide. Stopper the flask and shake vigorously until the odour of the acid chloride has disappeared open the flask occasionally to release the pressure developed by the heat of the reaction. AUow the mixture to cool, and dissolve any insoluble material in 60-75 ml. of ether. If a solid insoluble in both the aqueous and ether layer appears at this point (it is probably the sparingly soluble salt of a primary amine, e.g., a long chain compound of the type CjH5(CH2) NHj), add 25 ml. of water and shake if it does not dissolve, filter it off. Separate the ether and aqueous layers. The ether layer will contain the unchanged tertiary amine and the sulphonamide of the secondary amine. Acidify the alkaline aqueous layer with dilute hydrochloric acid, filter off the sulphonamide of the primary amine, and recrystaUise it from dilute alcohol. Extract the ether layer with sufficient 5 per cent, hydrochloric acid to remove all the tertiary amine present. Evaporate the ether to obtain the sulphonamide of the secondary amine recrystaUise it from alcohol or dilute alcohol. FinaUy, render the hydrochloric acid extract alkaline by the addition of dilute sodium hydroxide solution, and isolate the tertiary amine. 

This group comprises substances of the tjrpe RCONHR and RCONR R", i.e., substituted amides of the aromatic series. They are all well-defined crystalline sohds, sparingly soluble in cold but, often, appreciably soluble hi hot water and moderately soluble in ether they are generally neutral or feebly basic in reaction. 

These compounds are soluble in ether, are comparatively stable, and exhibit many of the reactions of Grignard reagents but are more reactive. Because of their greater reactivity, organohthium compounds can often be used where Grignard reagents fail thus they add to the azomethine linkage in pyridines or... 

Study of the solubility behaviour of the compound. A semi-quantitative study of the solubility of the substance in a hmited number of solvents (water, ether, dilute sodium hydroxide solution, dilute hydrochloric acid, sodium bicarbonate solution, concentrated sulphuric and phosphoric acid) will, if intelligently apphed, provide valuable information as to the presence or absence of certain classes of organic compounds. 

Solubility in ether. Use 0 -10 g. of solid or 0 -20 ml. of a liquid in a dry test-tube and proceed exactly as in testing the solubility in water, but do not employ more than 3 0 ml. of solvent. 

Reduction of a nitrosamine to a secondary amine. Proceed as for a nitro compound. Determine the solubility of the residue after evaporation of the ether and also its behaviour towards benzenesulphonyl (or p-toluenesulphonyl) chloride. 

Step 2. Extraction of the basic components. Extract the ethereal solution (Ej) with 15 ml. portions of 5 per cent, hydrochloric acid until all the basic components have been removed two or three portions of acid are usually sufficient. Preserve the residual ethereal solution (E2) for the separation of the neutral components. Wa.sh the combined acid extracts with 15-20 ml. of ether discard the ether extract as in Step 1. Make the acid extract alkaline with 10-20 per cent, sodium hydroxide solution if any basic component separates, extract it with ether, evaporate the ether, and characterise the residue. If a water-soluble base is also present, it may be recognised by its characteristic ammoniacal odour it may be isolated from the solution remaining after the separation of the insoluble base by ether extraction by distilling the aqueous solution as long as the distillate is alkahne to htmus. Identify the base with the aid of phenyl iso-thiocyanate (compare Section 111,123) or by other means. 

Ether solution (E,). This will contain any neutral compounds present. Dry with anhydrous magnesium sulphate, and distil ofi the ether. A residue indicates the presence of a neutral component. Determine the solubility of a portion in cone. HjS04. Apply any other suitable tests. 

Ck)ol the alkaline solution resulting from the distillation of the volatile neutral compounds, make it acid to litmus with dilute sulphuric acid, and add an excess of solid sodium bicarbonate. Extract this bicarbonate solution with two 20 ml. portions of ether remove the ether from the combined ether extracts and identify the residual phenol (or enol). Then acidify the bicarbonate solution cautiously with dilute sulphiu-ic acid if an acidic compound separates, remove it by two extractions with 20 ml. portions of ether if the acidified solution remains clear, distil and collect any water-soluble, volatile acid in the distillate. Characterise the acid as under 2. 

---