J. Org. Chem. 1982,47, 3569-3570 (8.1 g, 50 mmol) in THF (100 mL). The mixture was stirred at room temperature for 1h, and then a solution of 4-acetylpyridine (6.05 g, 50 mmol) in THF (20 mL) was added at -78 “C. The mixture was graduallywarmed to room temperature. After stirring had been continued at the same temperature for 3 h, the mixture was poured into water and extracted with CHC13. The extract was washed with water, dried over NazS04,and evaporated to give 5e (9.9 g, 70%). Properties of this compound are shown in the Table I. General Procedure for the Preparation of 5f-i. To a -78 “C stirred solution of LDA [prepared from diisopropylamide (1.0 g, 10 mmol) and n-BuLi (6.7 mL of 1.5 M hexane solution, 10 mmol) in THF] was added a solution of 4d-g (10 mmol) in THF (10 mL). After 0.5 h, a solution of 4-acetyl-3-methylpyridine (1.2 g, 10 “01) in THF (10 mL) was added at -78 “C. After stirring had been continued for 1 h, the mixture was poured into water and extracted with CHC1,. The extract was washed with water, dried over NaZSO4,and evaporated to give 5f-i. For the preparation of 5i, lithiation of thieno[3,2-c]pyridine (4g)was carried out at 0 “C instead of -78 “C. Yields and physical data are summarized in the table I. Pyrolysis of 5. Alcohol 5 (200-500 mg) was placed in a 10-mL round-bottomed flask equipped with a 30-cm glass tube without a seal and was heated at 400 “C for 7 min. The solid 5 immediately melted and decomposed, accompanied by the formation of water vapor. During the reaction, the reaction mixture mildly refluxed. The dark brownish reaction mixture was chromatographed on silica gel (5-10 9). Isolation of 8a, 7a, and 6a. Hexane-ethyl acetate (3:2) was used as an eluent. The f i i t fraction (30 mL) gave a dark brownish resin. The second (30 mL) afforded 8a, the third one (15 mL) gave 6a, and the succesive fraction (20 mL) yielded 7a. Isolation of 6b and 7b. Hexane-ethyl acetate (3:2) was used as an eluent. Removal of the first fraction (40 mL) gave dark brownish resin, the second one (15 mL) gave 6b, and the third fraction (20 mL) gave 7b. Isolation of 9 and 10. Hexane-ethyl acetate (3:2) was used as an eluent. The first fraction (30-35 mL) was discarded. Removal of the second one (30 mL) gave 10,and the third one (25 mL) gave 9. Isolation of 12,11, and 7b. Hexane-ethyl acetate (3:2) was used as an eluent. After the first fraction (35 mL) was discarded, removal of the second one (15 mL) gave 12. The third one (20 mL) yielded 11, and removal of the successive fraction (15 mL) afforded 7b. Isolation of 14 and 11 (or 13). Hexane-ethyl acetate (1:l) was used as an eluent. The first fraction (35 mL) was discarded, and removal of the second one (20 mL) afforded 14. The third one (30 mL) yield 11 (or 13). Isolation of 15 and 16. Hexane-ethyl acetate (7:3) was used as an eluent. The first fraction (15 mL) was discarded, and removal of the second one (15 mL) gave 16. Evaporation of the third one (20 mL) yielded 15. Isolation of 17 and 18. CHC13-MeOH (97:3) was used as an eluent. After the first fraction (20 mL) was discarded, the second one (15 mL) was removed and gave, 16, and removal of the third one (25 mL) yielded 15. Yields and physical properties of these products are summarized in Table 11. 2-Methyl-3-[a-(3-pyridyl)vinyl]benzo[ b ]thiophene (19). A mixture of 5a (2.7 g, 10 mmol) and KHS04 (1.35 g, 10 mmol) in toluene (100 mL) was stirred under reflux for 14 h. The solution was diluted with benzene, washed with water, dried over Na2S04, and evaporated to give 19 (2.4 g, 96%) as an oil: ‘H NMR 6 2.37 (3 H, s), 5.36 (1H, d, J = 1.5 Hz), 5.97 (1H, d, J = 1.5 Hz); mass spectrum, mle 251.0772 (M+,calcd for C16H13NS251.0768). Registry No.4a,10243-15-9;4b,64860-32-8;4c,31283-14-4;4d, 95-15-8;4e, 271-89-6; 4f, 110-02-1; 4g,272-14-0; 5a, 82351-75-5;5b, 82351-76-6; 5c, 82351-77-7; 5d, 82351-78-8; 5e, 82351-79-9; 5f, 82351-80-2; 5g, 82351-81-3; 5h, 82351-82-4; 5i, 82351-83-5; 6a, 82351-84-6; 6b, 82351-85-7; 7a, 82351-86-8; 7b, 21339-68-4; 8a, 82351-87-9; 9a, 82351-88-0;9b, 23018-34-0; loa, 82351-89-1; lob, 82351-90-4; 11, 25121-97-5; 12, 82351-91-5; 13, 82351-92-6; 14a, 82351-93-7; 14b, 82351-94-8; 15, 82351-95-9; 16, 82351-96-0; 17, 82351-97-1; 18,82351-98-2; 19,82351-99-3; 2-acetylpyridine, 112262-9; 3-acetylpyridine, 350-03-8; 4-acetylpyridine, 1122-54-9; 4acetyl-3-methylpyridine, 82352-00-9.
3569
The Myth of Saturated Aqueous Sodium Chloride Solution (Brine) for Drying Organic Solutions James B. Ellern Department of Chemistry, University of Southern California, University Park, Los Angeles, California 90089 Received February 24, 1982 Perusal of t h e experimental sections of this Journal reveals that many workers use saturated brine for preliminary drying of water-saturated organic extracts in the apparent belief t h a t such treatment removes much dissolved water. A t least two recent organic laboratory texts assert this to be SO.^ In fact, saturated brine can remove no more than about 25% of dissolved water, as the following analysis shows. An organic solvent (OS) saturated with water must have the same partial pressure of water, P H 2 0 , as does water saturated with t h e OS (both phases at t h e same temperature). This is merely a specific case of the principle that a component distributed between two phases at equilibrium must have the same partial pressure in each phase.2 For an OS very slightly soluble in water, P H z o in the OSrich phase is very slightly less than the vapor pressure of pure water, POH20. Between 15 and 50 O C , P H Z O of saturated brine is 0.75-0.76 PHO3 By the vapor pressure equality principle2 adduced above, P H , o in any phase in equilibrium with saturated brine must therefore be -0.75 PH20. Since for the common extracting solvents, water is dilute even when the OS is saturated, the mole fraction of water, XHzO,is proportional t o its partial pressure, or nearly so, in its solutions in these solvents (Henry’s law).4 Thus, treating a water-saturated solution with brine can reduce the water concentration only by about a factor of 0.75 P H 2 0 / P H 2 0 , OS satd. Since the denominator must be < p H & , the factor is
