Org. Synth. 1941, 21, 36
DOI: 10.15227/orgsyn.021.0036
n-DODECYL (LAURYL) MERCAPTAN
Submitted by G. G. Urquhart, J. W. Gates, Jr., and Ralph Connor.
Checked by Lee Irvin Smith, R. T. Arnold, and Kenneth Stevenson.
1. Procedure
A mixture of 125 g. (0.5 mole) of n-dodecyl bromide (Note 1), 38 g. (0.5 mole) of thiourea, and 250 ml. of 95% ethanol is refluxed on a steam cone for 3 hours (Note 2), (Note 3), and (Note 4). A solution of 30 g. (0.75 mole) of sodium hydroxide in 300 ml. of water is added, and the mixture is refluxed for 2 hours. During this period the mercaptan separates as a pink to red oil. The layers are separated, and the aqueous layer is acidified with dilute sulfuric acid (7 ml. of concentrated acid to 50 ml. of water) and then extracted with one 75-ml. portion of benzene (Note 5). The extract is added to the crude mercaptan layer, and the whole is washed twice with 200-ml. portions of water and then dried over 20 g. of anhydrous sodium sulfate (Note 6). The solvent is removed and the residual oil distilled from a modified Claisen flask. There is no appreciable fore-run (Note 6). The yield of n-dodecyl mercaptan, b.p. 165–169°/39 mm., is 80–84 g. (79–83%) (Note 7) and (Note 8).
2. Notes
1.
The preparation of
lauryl bromide has been described
[Org. Syntheses Coll. Vol. 1, 29 (1941)], but the following modification avoids the emulsion formed in washing
lauryl bromide with
sulfuric acid. The crude bromide from the reaction mixture is washed thoroughly with water and then with
potassium carbonate solution. The washing with water must be thorough enough to remove most of the acid in order to prevent the formation of heavy foam by the carbonate. The bromide is then dried over
calcium chloride and distilled. The distillate is washed with concentrated
sulfuric acid and treated as described (
loc. cit.). The checkers, however, found the method using anhydrous
hydrogen bromide [Org. Syntheses Coll. Vol. 2, 246 (1943)] to be preferable.
2.
The intermediate
laurylisothiourea hydrobromide may be obtained by cooling the
ethanol solution in ice and filtering the precipitate. It may be further purified by washing with
ether. An alternative method gives more satisfactory results. The
ethanol solution is diluted with 150 ml. of water and heated until the solution is homogeneous, and then, after cooling slightly,
200 ml. of concentrated hydrochloric acid is added; the
laurylisothiourea hydrochloride separates quantitatively as a waxy white solid.
3.
The reflux period required for complete reaction varies considerably with the structure of the halide. Some alkyl bromides require more than 3 hours. Alkyl chlorides frequently require 16 hours and occasionally as much as 24 hours.
4.
This procedure is useful for the preparation of other mercaptans. The yields are of the same order. The boiling points are as follows:
|
n-Heptyl
|
|
174–176°
|
|
n-Octyl
|
198–200°;
|
98–100°/22 mm.
|
|
n-Nonyl
|
220–222°;
|
98–100°/15 mm.
|
|
n-Decyl
|
88–91°/2 mm.;
|
96–97°/5 mm.
|
|
n-Undecyl
|
|
103–104°/3 mm.
|
|
n-Octadecyl
|
|
170–175°/4 mm.
|
|
5.
Although
benzene is the most satisfactory solvent for this extraction, emulsions are sometime produced when it is used for the extraction of other mercaptans. To obviate this difficulty the same amount of ether may be used, provided that the
ethanol is first removed by distillation on a
steam bath.
6.
If the
ether extracts are not thoroughly dry, the mercaptan appears slightly cloudy on subsequent distillation. The checkers found that this cloudiness was frequently due to colloidal
sulfur. The
sulfur can be removed by shaking an
ether solution of the cloudy product with bone black, then filtering and distilling.
7.
The odor of
lauryl mercaptan is not disagreeable, and no unusual precautions need be taken in working with it. With lower-molecular-weight mercaptans a
trap containing alkaline potassium permanganate solution will prevent the escape of unpleasant odors.
8.
Other boiling points:
107–109°/2 mm.;
133–135°/7 mm.;
145–147°/15 mm.;
150–152°/20 mm.;
158–160°/28 mm.;
168–170°/38 mm.
3. Discussion
n-Dodecyl mercaptan has been prepared by the action of alkali on the salts of
S-n-dodecyl thiourea1 and by reduction of
di-n-dodecyl disulfide.
2,3
It has also been prepared from
lauryl alcohol by the action of
thiourea in the presence of
hydrobromic acid, followed by alkaline hydrolysis.
4This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ethanol (64-17-5)
calcium chloride (10043-52-4)
potassium carbonate (584-08-7)
sulfuric acid (7664-93-9)
hydrochloric acid (7647-01-0)
Benzene (71-43-2)
ether (60-29-7)
sodium hydroxide (1310-73-2)
HYDROBROMIC ACID,
hydrogen bromide (10035-10-6)
Lauryl Bromide,
n-DODECYL BROMIDE (143-15-7)
Lauryl alcohol (112-53-8)
sodium sulfate (7757-82-6)
sulfur (7704-34-9)
thiourea (62-56-6)
laurylisothiourea hydrobromide
laurylisothiourea hydrochloride
lauryl mercaptan,
n-dodecyl mercaptan (112-55-0)
n-DODECYL (LAURYL) MERCAPTAN
S-n-dodecyl thiourea
di-n-dodecyl disulfide
n-Heptyl mercaptan
n-Nonyl mercaptan
n-Decyl mercaptan
n-Undecyl mercaptan
n-Octadecyl mercaptan
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