DOI: 10.15227/orgsyn.000.0005
2-THIOPHENEALDEHYDE
Submitted by Kenneth B. Wiberg
Checked by Cliff S. Hamilton and J. L. Pauley.
1. Procedure
A.
2-Thienylmethylhexamethylenetetrammonium chloride. In a
1-l. round-bottomed flask are placed
67 g. (0.5 mole) of 2-chloromethylthiophene (p. 197),
400 ml. of chloroform, and
70 g. (0.5 mole) of hexamethylenetetramine. The flask is fitted with a
reflux condenser, and the mixture is boiled gently for 30 minutes. The mixture is cooled, and filtered on a
Büchner funnel. The precipitate is washed with
100 ml. of cold chloroform, drained thoroughly, and air-dried. The yield is
128–136 g. (
94–99%) of a white powder.
B. 2-Thiophenealdehyde. The hexamethylenetetrammonium salt is placed in a 2-l. round-bottomed flask containing 400 ml. of warm water. The flask is fitted for steam distillation, and steam is passed in until all the aldehyde has distilled (Note 1). The distillate is cooled, 10 ml. of 6 N acetic acid is added (Note 2), and the aldehyde is extracted with two 100-ml. portions of ether. The ether solution is dried over anhydrous calcium chloride, and the ether is evaporated on a steam bath until the volume of the solution has decreased to about 50 ml. The solution is placed in a 100-ml. Claisen flask, the ether is removed by distillation, and the aldehyde distilling at 89–91°/21 mm., n25D 1.5880, is collected. The yield is 27–30 g. (48–53%) of a colorless oily liquid which darkens slowly on standing (Note 3) and (Note 4).
2. Notes
1.
About 1.5 l. of distillate is collected before all the
thiophenealdehyde is distilled over.
2.
The
acetic acid is added to remove traces of amines that come over in the steam distillation. This method of purification must be used because of the high solubility of the bisulfite addition compound of the aldehyde.
3.
If the aldehyde is to be stored for any period of time, the addition of a small amount of
hydroquinone is advisable.
4.
It has been reported (S. J. Angyal and D. F. Penman) that the procedure for
1-naphthaldehyde [Org. Syntheses, 30, 67 (1950)] may also be followed with slight modification for the preparation of
2-thio-phenealdehyde. A mixture of
41.5 g. (0.31 mole) of 2-chloromethylthiophene,
88 g. (0.60 mole) of hexamethylenetetramine,
130 ml. of glacial acetic acid, and 130 ml. of water is swirled until, with considerable evolution of heat, the mixture has become homogeneous. The mixture is heated under reflux for 4 hours; at the end of this period,
125 ml. of concentrated hydrochloric acid is added, and heating under reflux is continued for 5 minutes. After cooling, the mixture is extracted with three
100-ml. portions of ether. The combined
ether extracts are dried (with anhydrous
sodium or magnesium sulfate), and the
ether is removed. The crude product is distilled through a
short column under reduced pressure; after a fore-run of
acetic acid the product is collected at 63–66°/6 mm. or 115–118°/65 mm. The yield is
25–26 g. (
71–74%).
Working with Hazardous Chemicals
The procedures in Organic Syntheses are intended for use only by persons with proper training in experimental organic chemistry. All hazardous materials should be handled using the standard procedures for work with chemicals described in references such as "Prudent Practices in the Laboratory" (The National Academies Press, Washington, D.C., 2011; the full text can be accessed free of charge at http://www.nap.edu/catalog.php?record_id=12654). All chemical waste should be disposed of in accordance with local regulations. For general guidelines for the management of chemical waste, see Chapter 8 of Prudent Practices.
In some articles in Organic Syntheses, chemical-specific hazards are highlighted in red "Caution Notes" within a procedure. It is important to recognize that the absence of a caution note does not imply that no significant hazards are associated with the chemicals involved in that procedure. Prior to performing a reaction, a thorough risk assessment should be carried out that includes a review of the potential hazards associated with each chemical and experimental operation on the scale that is planned for the procedure. Guidelines for carrying out a risk assessment and for analyzing the hazards associated with chemicals can be found in Chapter 4 of Prudent Practices.
The procedures described in Organic Syntheses are provided as published and are conducted at one's own risk. Organic Syntheses, Inc., its Editors, and its Board of Directors do not warrant or guarantee the safety of individuals using these procedures and hereby disclaim any liability for any injuries or damages claimed to have resulted from or related in any way to the procedures herein.
The paragraphs above were added in September, 2014. The statements above do not supersede any specific hazard caution notes and safety instructions included in the procedure.
3. Discussion
2-Thiophenealdehyde has been prepared by the decarboxylation of
2-thienylglyoxalic acid,
1 by the action of
2-thienylmagnesium iodide on
ethyl orthoformate followed by hydrolysis of the
acetal,
2 in small yields by the Rosenmund reduction of
2-thiophenecarboxylic acid chloride,
3 in small yields by the action of
hydrogen cyanide,
hydrogen chloride, and
aluminum chloride on
thiophene, using
benzene as a solvent,
4 by a series of reactions from
1-chloro-2,3-diketocyclopentane,
5 by the hydrolysis of
2-thenylmethylhexamethylenetetrammonium chloride in neutral solution,
6 by the action of
N-methylformanilide on
thiophene in the presence of
phosphorus oxychloride,
7 by the acid hydrolysis of
N-(2-thenyl)-2'-thenaldimine,
8 and by the oxidation of
N,N-di-(2-thenyl)hydroxylamine with alkaline
potassium permanganate.
9
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
2-thio-phenealdehyde
N-(2-thenyl)-2'-thenaldimine
ACETAL (105-57-7)
calcium chloride (10043-52-4)
hydrogen chloride,
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
Benzene (71-43-2)
ether (60-29-7)
chloroform (67-66-3)
hydroquinone (123-31-9)
potassium permanganate (7722-64-7)
hydrogen cyanide (74-90-8)
Phosphorus Oxychloride (21295-50-1)
aluminum chloride (3495-54-3)
sodium (13966-32-0)
Ethyl orthoformate
hexamethylenetetramine (100-97-0)
Thiophene (110-02-1)
magnesium sulfate (7487-88-9)
2-thienylmagnesium iodide
N-methylformanilide (93-61-8)
2-Chloromethylthiophene (765-50-4)
hexamethylenetetrammonium
2-Thiophenealdehyde,
thiophenealdehyde (98-03-3)
2-thienylglyoxalic acid (4075-59-6)
2-thiophenecarboxylic acid chloride (5271-67-0)
1-chloro-2,3-diketocyclopentane
2-thenylmethylhexamethylenetetrammonium chloride
N,N-di-(2-thenyl)hydroxylamine
1-Naphthaldehyde (66-77-3)
2-Thienylmethylhexamethylenetetrammonium chloride
Copyright © 1921-2025, Organic Syntheses, Inc. All Rights Reserved