The hitherto undescribed 2-hexadecynoic acid (III) was prepared by the following route. Dodecylmagnesium bromide was reacted with 2,3-dibromopropene to give 2~:bromop e ntadecene (I) in 35 % yield. Refluxing the bromo compound I with freshly prepared sodium amide in xylene gave pentadecyne(II) in 49 .1 % yiel

D. E. Sunko

N. Vujanović

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ARHIV ZA KEMIJU 27 (1955) 2-Hexadecynoic Acid D. E. Sunko and N. Vujanovic Chemical Laboratory, Department of Physiology, Medical Faculty, University of Zagreb, Croatia, Yugoslavia Received November 11 , 1955 217 The hitherto undescribed 2-hexadecynoic acid (III) was prepared by the following route. Dodecylmagnesium bromide was reacted with 2,3-dibromo-propene to give 2~:bromopentadecene (I) in 350/o yield. Refluxing the bromo-COlllipound I with freshly prepared sodium amide in xylene gave pentadecyne (II) in 49.1 O/o yield. This compound was prepared by Ahmad1 from tridecyl bromide and sodium acetylide in liquid ammonia. The ,present synthesis of II closely follows the procedure for the synthesis of h eptadecyne described by Jenny and Grob2 . Carbonation of the Grignard complex of II at atmospheric pressu re with gaseous carbon dioxide afforded 2-hexadecynoic acid in 13 .. 2°/1> )'ield .. EXPERIMENTAL 2-Bromopentadecene (I) A solution of dodecylmagnesiJum bromide (from 78.4 g. , 0.315 moles of dodecyI bromide3 and 7.06 g. of magnesium) in ether (235 ml.) was added to a stirred solution od 2,3-dibromopropene4 (GO g., 0.30 moles) in dry ether (75 ml.) at such a rate that the mixture refluxed gently. The stirring and refluxing was continued for additional four hours. The mixture as cooled and decomposed by careful addition of diluted hydrochlor ic acid (1 :10, 100 ml.). The ether layer was washed w ith water, diied and evaporated. Distillation of the residue at 23 mm. rpressure removed 11 g. of low-boiling products (boiling range 5C-130'~). The residual oil was fractionated in an atmosphere of nitrogen at 0.15 mm. pressure and the fraction b. p. 92-93/0.15 mm. was collected as practically pure colorless 2-bromopentadecene (30.1 g., i. e. 35°/o based on 2,3-dibromopropene). For analysis a sample was redistilled, b · p. 92°/0.15 mm. Colorless liquid, n ~ 1.4690. Ana!. 6.765 mg. subst.: 15.29 mg. C02, 6.55 mg. H20 C1sH29Br '(289.3) calc'd C 62.29; H 10.11°/o found : C 61.68; H 10.83°/o Pentadecyne (II) A suspension of sodium amide in liquid ammonia (from 8.8 g. of sodium) was prepared according · to Vaughn, Vogt and Nieuwland.5 The ammonia was slowly evaporated while 270 ml. of dry xylene were simultaneously added. The resulting suspension of sodium amide in xylene was heated with ?tirring at 140° (bath tempe-rature), and 39 g. of I were added in the course of one hour. The evolved ammonia was led, by means of a slow stream of dry nitrogen, through the condenser, and collected in water. The liberated ammount of ammonia was measured by titration with 2 N hydrochloric acid. The heating and stir ring was continued for addition al ten hours when the evolution of ammonia practically · ceased. The reaction m ixture was co.o.Jed and [Poured on 100 g. of cracked ice and acidified with 45 ml. of concen-trated hydrochloric acid. The resulting mixture was exhaustively ext racted with ether, the combined extracts washed successively with water, 2 N sodium carbonate, and w ater. After drying, the solvent was evaporated in vacuo a t fOl. Distillation 218 D. E. SUNKO AND N. VUJANOVIC of the residue at 0.25 mm. pressure gave 11·3 g. of low-boiling products and 13.8 g. (49.10/o) of pentadecyne, b. p. 88°/0.25 mm. A sample was refractionated; colorless 1iquid, b. p. 88°/0.25 mm., ni5 1.4545. A.hmad1 recorded b. p. 99°/0.7 mm. , nio 1.4440· 2-Hexadecynoic Acid (III) Pentadecyne (13.8 g.) in dry ether (70 ml.) was added during 45 minutes to a stirred solution of methylmagnesium iodide (from magnesium, 1.66 g.) in dry ether (100 ml.). The mixture was heated under reflux for 17 hours, and then cooled in an ice-salt mixture- A stream of dry carbon dioxide w as led over the stirred solution for two hours. The resulting complex was decomposed with .ice and hydro-chloric acid, and the ethereal layer washed with w ater and dried. After evaporating the solvent, the oily residue (13 .6 g.) was dissolved in acetone (2cY ml.). After addi-tion of 5 N methanolic potassium hydroxide (12 ml.) the white potassium salt precipitated. It was filtered, w ashed with acetone and dried (yield 2.8 g. ). The salt was decomposed w ith diluted hydrochloric acid, and the product dissolved by extraction . wiith ether. The ether solution was dried, and evaiporated to dryness. Thus, 2.2 g. (13.2°/o) of pure 2-hexadecynoic acid, m . P· 54~55° were obtained. The melting point remained unchanged after recrystallization from petroleum ether. Colorless prismatic leaflets. - Anal. 8.965 mg. s ubst. : 24.96 mg. C02, 9.11 mg. H 20 C15H2s0 2 (252.4) calc'd.: C 76.14; H 11.180/o found: C 75-98; H 11.370/o Upon catalytic hydrogenation 2-hexadecynoic acid consumed exactly two moles of hydrogen, and pure palmitic acid was obtained (m. p. and mixed m. p . 61-63°). Acknowledgment . We are indebted to Mrs. M. Munk-Weinert for the micro-analyses. REFERENCES 1. K. Ahmad, J. Indian Chem. Soc. 31 (1954) 4. 2. E. F. Jenny and C. A. Grob, Helv. Chim. Acta 36 (1953) 1454. 3. 0. Kamm and C. S. Mar v e 1, Org. Syntheses Coll. Vol. I (1946) 29. 4. R. Les pie au and M. Bourgue 1, Org. Syntheses Coll. Vo!. I (1946) 209. 5· T. H. Vaughn, R. R. Vogt, and J . A. Nie u w 1 and, J . Am. Chem. Soc. 56 (1934) 2120, cf. M. T. Leff 1 er in Organic Reactions, J. Wiley & Sons, New York 1942, Vol. I, p. 99. IZVOD Heksadecin-2-kiselina-1 D. Sunko i N. Vujanovic Opisana je sinteza heksadecin-2-kiseline- 1, tkoja polazi iz dodecil bromida, koji je preveden u Gringnardov kompleks, na koji je djelovano s 2,3-dibrompropenom. Tako dobiveni 2-brom-pentadecin (I) s natrijskim amidom u ksilenu - preiazi u p entadecin (II) . Djelovanjem ugljicnog dioksida na pentadecinil-magnezijum-jodid dobivena je heksadecin-2-kiselina- 1 u obliku bezbojnih prizmatskih listica. t. t. 54---55°. MEDICINSKI FAKULTET ZA VOD ZA FIZIOLOGIJU ZAGREB Primljeno 11 . novembra 1955. 

2-Hexadecynoic Acid

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