Checked by William S. Johnson and H. C. Dehm.
1. Procedure
Into a
3-l. three-necked round-bottomed flask fitted with a
mechanical stirrer,
dropping funnel, and
reflux condenser provided with a
calcium chloride drying tube is placed
1260 ml. (approximately 900 g.) of anhydrous ether. Stirring is commenced, and
153.0 g. (0.7 mole) of lauroyl chloride (Note
1) is added rapidly through one of the flask openings. The solution is cooled in ice water, and
70.7 g. (0.7 mole) of triethylamine (Note
2) is added over a period of 10 minutes through the dropping funnel in a fine stream. Stirring is discontinued after 1 hour, and the mixture is allowed to come to room temperature. After 12 to 24 hours, the mixture of
decylketene dimer (Note
3) and
triethylamine hydrochloride is extracted once with
125 ml. of an aqueous 2% sulfuric acid solution to remove the amine salt.
Procedure A. The wet
ether layer is transferred to a
3-l. distillation flask and distilled to remove most of the solvent. The warm oily residue is transferred to a
1-l. beaker and mixed with
500 ml. of 2% potassium hydroxide solution. The mixture is heated on a
steam bath for 1 hour with occasional stirring and is then chilled in ice water. The waxy cake which settles out on top of the aqueous suspension is skimmed from the surface and dissolved in a mixture of
400 ml. each of acetone and
methanol. The hot solution is filtered through a
steam-jacketed funnel and cooled in ice water, and the precipitate is collected on a
Büchner funnel with suction. The product is washed on the funnel with cold
methanol; after air drying overnight it amounts to
55–65 g. (
46–55%), m.p.
62–64°.
Procedure B. The following alternative isolation procedure yields a somewhat purer product. The wet
ether layer which has been washed with dilute
sulfuric acid to remove amine salt is transferred to a 3-l. distillation flask,
150 ml. of 2% sulfuric acid is added, and the mixture is distilled until nearly all the
ether is removed. The hot, oily layer is separated in a
separatory funnel and distilled (Note
4). The yield of the fraction distilling at
215–230°/3 mm. is
64–75 g. (
54–63%). After recrystallization from
750 ml. of acetone, the
laurone weighs
55–65 g. (
46–55%), m.p.
68–69° (Note
5).
2. Notes
1. A commercial
lauric acid, such as that available from Armour and Company, was converted into the acid chloride by reaction with
thionyl chloride. The checkers employed
1 kg. of thionyl chloride for 1201 g. of acid. The product was distilled through a
12-in. Vigreux column, giving
1145 g. (
87%) of colorless acid chloride, f.p. −15° to −18°.
2.
Triethylamine was purified by the following procedure: fractional distillation, addition of about
2% phenyl isocyanate to the distillate, and redistillation.
3. If desired,
decylketene dimer can be isolated at this point by filtering the reaction mixture and concentrating the filtrate. The mixture should be handled at all times under anhydrous conditions. The filtration should be carried out by the inverted filtration method.
2 Difficulties are usually encountered in the filtration step since the amine salt frequently separates as a gel. Seeding the
ether solution of
lauroyl chloride with
triethylamine hydrochloride usually aids in preventing this gel formation. It is necessary to rinse the amine salt several times with ether to extract the dimer, which is usually contaminated with traces of
triethylamine hydrochloride.
4. The electrically heated
fractionating column used by the submitter for distilling
laurone is pictured in part in
.htmFig.11. This still, with a column length of 8 in., was designed by Dr. H. J. Sampson of the Rayon Department of E. I. du Pont de Nemours and Company, Inc., Waynesboro, Virginia.
Fig. 11.
5. Other acid chlorides of the type RCH
2COCl can be similarly dehydrochlorinated. For example,
caproyl chloride (1.2 moles) was converted to
di-n-amyl ketone, b.p.
98–102°/15 mm., in
60–71.5% yield. In this case, it was found preferable to remove the amine salt from the reaction mixture by washing with
2% sulfuric acid. The
butylketene dimer was then extracted from the reaction mixture by washing with
5% sodium hydroxide solution; the alkaline solution was acidified with
sulfuric acid and steam-distilled. The oily layer in the distillate was separated and fractionated.
3. Discussion
Copyright © 1921-2002, Organic Syntheses, Inc. All Rights Reserved