1-(5-Methyl-2-thienyl)ethan-1-one

1-(5-Methyl-2-thienyl)ethan-1-one Property

Melting point:

24-28 °C(lit.)

Boiling point:

65-67 °C1 mm Hg(lit.)

Density 

1.106 g/mL at 25 °C(lit.)

refractive index 

n20/D 1.561(lit.)

FEMA 

4643 | 2-ACETYL-5-METHYLTHIOPHENE

Flash point:

>230 °F

storage temp. 

under inert gas (nitrogen or Argon) at 2–8 °C

form 

Low Melting Crystalline Mass, Powder or Crystals

Specific Gravity

1.119

color 

White to pale yellow

Odor

at 1.00 % in propylene glycol. sweet spicy honey hawthorn almond acacia hyacinth caramellic graham cracker

Odor Type

spicy

Sensitive 

Light Sensitive

JECFA Number

2107

BRN 

110854

LogP

2.04

CAS DataBase Reference

13679-74-8(CAS DataBase Reference)

NIST Chemistry Reference

2-Acetyl-5-methylthiophene(13679-74-8)

Safety

Hazard Codes 

Xn,Xi

Risk Statements 

20/21/22

Safety Statements 

36/37-22

RIDADR 

UN 3335

WGK Germany 

3

RTECS 

OB4972000

Hazard Note 

Irritant

HazardClass 

STENCH

HS Code 

29349990

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Warning

Hazard statements

H302Harmful if swallowed

Precautionary statements

P264Wash hands thoroughly after handling.

P264Wash skin thouroughly after handling.

P270Do not eat, drink or smoke when using this product.

P330Rinse mouth.

P501Dispose of contents/container to..…

1-(5-Methyl-2-thienyl)ethan-1-one Chemical Properties,Usage,Production

Chemical Properties

white to light yellow crystal powder

Uses

2-Acetyl-5-methylthiophene may be used in the preparation of:

• 2-ethyl-5-methylthiophene
• (5-methylthiophen-2-yl)glyoxal
• (2E)-1-(5-methylthiophen-2-yl)-3-(pyridin-3-yl)prop-2-en-1-one
• ethyl 3-(5-methylthiophen-2-yl)-3-oxopropanoate

Definition

ChEBI: 2-acetyl-5-methylthiophene is a thiophene that is substituted by acetyl and methyl groups at positions 2 and 5, respectively. It has a role as a flavouring agent. It is an aromatic ketone, a member of thiophenes and a methyl ketone.

General Description

2-Acetyl-5-methylthiophene is a volatile organic compound formed during the reaction between L-cysteine and dihydroxyacetone in glycerine or triglyceride solvent system. It can be prepared by reacting 2-methylthiophene with acetic anhydride. 2-Acetyl-5-methylthiophene undergoes palladium-catalyzed cross-coupling reaction with aryl bromides to form C-4 arylated product. It reacts with 1,2-bis(5-formyl-2-methylthiophen-3-yl)cyclopentene via Aldol condensation to form a chalcone with photochromic property. The standard molar enthalpies of combustion, formation and vaporization of 2-acetyl-5-methylthiophene are 4341.9 ± 1.8kJ/mol, 158.0 ± 2.1kJ/mol and 62.0 ± 2.6kJ/mol, respectively.

Safety Profile

A poison by intraperitoneal route. A flammable liquid. When heated to decomposition it emits toxic vapors of SOx.

Synthesis

General procedure: 2-methylthiophene and acetyl chloride were used as raw materials for the synthesis of 2-acetyl-5-methylthiophene by Friedel-Crafts acylation reaction. The procedure was as follows: a double-necked round-bottomed flask equipped with a magnetic stirrer was charged with a pre-prepared MoO4 (AlCl22 (5 wt%, 10 mg)) catalyst, which was to be activated at 150 °C for 2 hours. Subsequently, 2-methylthiophene (1 g, 9.26 mmol) and acetyl chloride (5 equiv) were added to the reaction flask. The reaction mixture was stirred at room temperature until the reaction was completed and the reaction progress was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture was filtered to isolate the solid catalyst, which could be recycled for the next Friedel-Crafts acylation reaction. The reaction mixture was washed sequentially with dichloromethane (DCM) and water and the process was repeated three times. The organic layer was collected, dried with anhydrous sodium sulfate and subsequently concentrated on a rotary evaporator to give the crude product. Finally, the crude product was purified by column chromatography to afford the target compound 2-acetyl-5-methylthiophene.

References

[1] European Journal of Organic Chemistry, 2010, # 31, p. 6033 - 6037
[2] European Journal of Organic Chemistry, 2016, vol. 2016, # 18, p. 3126 - 3129
[3] Journal of Nanoscience and Nanotechnology, 2015, vol. 15, # 10, p. 8243 - 8250
[4] Journal of Heterocyclic Chemistry, 1982, vol. 19, p. 701 - 702
[5] Chemische Berichte, 1886, vol. 19, p. 1858