Synthesis of cyclohexene

Preparation of cyclohexene

Preparation of cyclohexene by dehydrating cyclohexanol with sulfuric acid

Preparation of cyclohexene by dehydrating cyclohexanol with sulfuric acid

Preparation of cyclohexene by dehydrating cyclohexanol with sulfuric acid

20 grams of cyclohexanol and 6 ml of concentrated sulfuric acid are placed in a 250 ml round-bottomed containing 2-3 chips of porous porcelain. The flask is fitted with a fractionating column, a Liebig condenser, adapter and filter flask receiver. The flask is heated in an oil bath to a temperature of 130-140° C. The distillation is stopped when only a small residue remains and the odour of sulfur dioxide is apparent. The distillate is transferred to a small separatory funnel, saturated with sodium chloride, then treated with 2 ml of 5% sodium carbonate solution in order to neutralize traces of free sulfuric acid. The two layers are separated by discarding the lower  aqueous layer and pouring the crude cyclohexene through the mouth of the funnel into a small dry conical flask containing 3-4 g of anhydrous calcium chloride or anhydrous magnesium sulfate. Dried cyclohexene is decanted through a small funnel supporting a small fluted filter paper into a 25 or 50 ml distilling flask. Crude cyclohexene is distilled and the fraction boiling at 81-83° C is collected. Redistillation yields 12-13 grams of pure cyclohexene.

Preparation of cyclohexene by dehydrating cyclohexanol with orthophosphoric acid

Preparation of cyclohexene by dehydrating cyclohexanol with orthophosphoric acid

Preparation of cyclohexene by dehydrating cyclohexanol with orthophosphoric acid

A 500 ml three-necked flask fitted with a fractionating column carrying a thermometer at its upper end, and a separatory funnel is connected with an efficient condenser to the column and a receiving flask cooled in ice. 50 grams of 85% orthophosphoric acid are placed in the flask and heated in an oil bath at 160-170° C. Through the funnel 250 grams of cyclohexanol are added over a period of 2 hours. When all the cyclohexanol has been introduced, the temperature is raised  to about 200° C and maintained at this temperature for 20-30 minutes. The temperature at the top of the column should not rise above 90° C. The distillate is saturated with salt, the upper layer is separated, and dried with anhydrous magnesium sulfate. The crude cyclohexene is distilled through an efficient column and the fraction boiling at 81-83° C is collected. The yield of cyclohexene is 165 g.

The residue left after distillation is largely cyclohexanol. The phosphoric acid may be recovered by diluting the residue in the three necked flask with water, filtering, and then evaporating with a little nitric acid to a concentration of about 85 per cent.

A text book of practical organic chemistry, by A. I. Vogel, 243-244, 1974





InChI Key


Canonical SMILES


MeSH Synonyms


Depositor-Supplied Synonyms

CYCLOHEXENE, Tetrahydrobenzene, Cyclohex-1-ene, Benzene tetrahydride, 110-83-8, Hexanaphthylene, Benzenetetrahydride, 1,2,3,4-Tetrahydrobenzene, Cykloheksen, Benzene, tetrahydro-, 1-Cyclohexene, 3,4,5,6-Tetrahydrobenzene, Cykloheksen [Polish], NSC 24835, cyclohexen, CHEBI:36404, HSDB 1624, HGCIXCUEYOPUTN-UHFFFAOYSA-N, EINECS 203-807-8, UN2256, UN 2256, BRN 0906737, AI3-03146, 7493-04-1, Zyklohexen, cyclo hexene, cyclo-hexene, cyclohexane N, 2-cyclohexen, 3-Cyclohexenyl radical, 4-Cyclohexenyl radical, AC1Q1HIF, 1,3,4-Tetrahydrobenzene, ACMC-1BMJ1, WLN: L6UTJ, AC1L1Q7T, UNII-12L0P8F7GN, KSC177C0F, CHEMBL16396, 125431_ALDRICH, 12L0P8F7GN, CCRIS 8739, 44028_FLUKA, CTK0H7102, MolPort-001-779-794, LTBB001107, 125431_SIAL, NSC24835, ANW-16200, NSC-24835, AKOS000119959, MCULE-3564016252, RTR-002196, TRA0075448, AN-22626, BP-31020, CJ-14477, LS-57377, Cyclohexene [UN2256] [Flammable liquid], TR-002196, Cyclohexene [UN2256] [Flammable liquid], FT-0624200, 12198-EP2269990A1, 12198-EP2270010A1, 12198-EP2272832A1, 12198-EP2272972A1, 12198-EP2272973A1, 12198-EP2275403A1, 12198-EP2277872A1, 12198-EP2280009A1, 12198-EP2281817A1, 12198-EP2281818A1, 12198-EP2284148A1, 12198-EP2284149A1, 12198-EP2284165A1, 12198-EP2287155A1, 12198-EP2292611A1, 12198-EP2295429A1, 12198-EP2295503A1, 12198-EP2298731A1, 12198-EP2298732A1, 12198-EP2298767A1, 12198-EP2301913A1, 12198-EP2301914A1, 12198-EP2301983A1, 12198-EP2302015A1, 12198-EP2305627A1, 12198-EP2305641A1, 12198-EP2305672A1, 12198-EP2305683A1, 12198-EP2305808A1, 12198-EP2305825A1, 12198-EP2308510A1, 12198-EP2308562A2, 12198-EP2308812A2, 12198-EP2308839A1, 12198-EP2308840A1, 12198-EP2308865A1, 12198-EP2308877A1, 12198-EP2311796A1, 12198-EP2311797A1, 12198-EP2311798A1, 12198-EP2311799A1, 12198-EP2311839A1, 12198-EP2314583A1, 12198-EP2314587A1, 12198-EP2314589A1, 12198-EP2315303A1, 12198-EP2316837A1, 12198-EP2316974A1, 12198-EP2371811A2, 12198-EP2380568A1, 77950-EP2272846A1, 77950-EP2275408A1, 77950-EP2287158A1, 77950-EP2308866A1, 4-05-00-00218 (Beilstein Handbook Reference), A802251, 3B4-1252, S14-1475, InChI=1/C6H10/c1-2-4-6-5-3-1/h1-2H,3-6H, 15650-80-3, 33004-06-7

Removed Synonyms

CID8079, c0491

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