638-02-8

Basic information

• Product Name: 2,5-Dimethylthiophene
• Synonyms: 2,5-DIMETHYLTHIOPHENE;2,5-DIMETHYLTHIOPHENE, 98.5%;2 5-DIMETHYLTHIOPHENE 98+%;2,5-Dimethylthiophene, 98.50%;Thiophene, 2,5-dimethyl-;2,5-DIMETHYTHIOPHENE;2,5-Thioxene;2,5-DiMethylthiophene, 98.5% 25ML
• CAS NO: 638-02-8
• Molecular Formula: C₆H₈S
• Molecular Weight: 112.19
• EINECS: 211-313-9
• Product Categories: Thiophene&Benzothiophene;Heterocyclic Compounds;Thiophens;thiophene Flavor;Building Blocks;Heterocyclic Building Blocks;Thiophenes;Alphabetical Listings;C-D;Flavors and Fragrances
• Mol File: 638-02-8.mol
• Article Data: 29

Chemical Properties

• Melting Point: -63°C
• Boiling Point: 134 °C740 mm Hg(lit.)
• Flash Point: 75 °F
• Appearance: Clear colorless to slightly yellow/Liquid
• Density: 0.985 g/mL at 25 °C(lit.)
• Vapor Pressure: 8.98mmHg at 25°C
• Refractive Index: n20/D 1.512(lit.)
• Storage Temp.: Flammables area
• Water Solubility: Insoluble in water. Soluble in alcohol, ether and benzene.
• BRN: 106450
• CAS DataBase Reference: 2,5-Dimethylthiophene(CAS DataBase Reference)
• NIST Chemistry Reference: 2,5-Dimethylthiophene(638-02-8)
• EPA Substance Registry System: 2,5-Dimethylthiophene(638-02-8)

Safety Data

• Hazard Codes: Xn,F,Xi
• Statements: 10-37-20/22
• Safety Statements: 23-24/25-16-36-33-29-7/9-3/7/9
• RIDADR: UN 1993 3/PG 3
• WGK Germany: 3
• HazardClass: 3
• PackingGroup: II
• Hazardous Substances Data: 638-02-8(Hazardous Substances Data)

Usage

Chemical Properties

clear colorless to slightly yellow liquid

Uses

2,5-Dimethylthiophene is used as an intermediate in organic synthesis.

Synthesis Reference(s)

The Journal of Organic Chemistry, 20, p. 1363, 1955 DOI: 10.1021/jo01127a012

General Description

2,5-Dimethylthiophene is a volatile flavoring compound that has been identified in the essential oil of onion. It is reported to be one of the sulfur-containing compounds formed via Maillard reaction/Strecker degradation of cysteine with furaneol.

InChI:InChI=1/C6H8S/c1-5-3-4-6(2)7-5/h3-4H,1-2H3

Synthetic route

5-methylthiophene-2-carboxaldehyde (13679-70-4) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
Stage #1: 5-methylthiophene-2-carboxaldehyde With hydrazine hydrate Wolff-Kishner-Huang Minlon Reduction; Stage #2: With potassium hydroxide	96%
With potassium hydroxide; hydrazine hydrate; ethylene glycol
With potassium hydroxide; hydrazine

2,5-hexanedione (110-13-4) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With Lawessons reagent at 140℃; for 1h;	87%
With diphosphorus pentasulfide In tetrachloromethane for 4h; Heating;	76%
With diphosphorus trisulfide

2,5-dimethylfuran (625-86-5) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With hydrogenchloride; hydrogen sulfide In acetic acid Ambient temperature; further acids, solvents;	80%
With hydrogenchloride; zinc sulfide In ethanol at 40℃; Product distribution; Further Variations:; Temperatures; Reagents; concentrations of reagents; time; Substitution;	80%
With hydrogenchloride; zinc sulfide In ethanol at 40℃; Substitution;	80%

thiophene (188290-36-0) + Dimethyldisulphide (624-92-0) → 2-Methylthiophene (554-14-3) + 2,3,4-trimethylthiophene (1795-04-6) + 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With zeolite HZSM-5 at 300℃; under 760.051 Torr; for 0.00236111h; Time; Flow reactor;	A 19% B 18% C 12%
With HZSM-5 zeolite (SiO2/Al2O3 = 34) at 300℃; under 760.051 Torr; for 2h; Catalytic behavior; Temperature; Flow reactor; Gas phase; Inert atmosphere;

2-Methylthiophene (554-14-3) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With iodine; mercury(II) oxide Behandeln mit Methyljodid und Natrium in Aether;
Multi-step reaction with 2 steps 1: Einleiten von Bromdaempfen 2: sodium View Scheme
Multi-step reaction with 2 steps 1: trichlorophosphate / 20 °C 2: hydrazine hydrate View Scheme

2-bromo-5-methyl thiophene (765-58-2) + methyl iodide (74-88-4) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With sodium

5-methyl-thiophene-2-carbaldehyde semicarbazone (131392-02-4) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

hexa-2,4-diene (592-46-1) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With sulfur at 420℃;

acetylene (74-86-2) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
at 650 - 670℃; beim Durchleiten mit Leuchtgas und Schwefelwasserstoff durch Roehren aus Marquardtscher Masse;

2-hexene (592-43-8) → 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With sulfur at 420℃;

2-Methylthiophene (554-14-3) + Methyl fluoride (593-53-3) → 2,3-dimethylthiophene (632-16-6) + 2,4-dimethylthiophene (638-00-6) + 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
With oxygen; trimethylamine In gas at 37.5℃; Product distribution; Kinetics; Mechanism; radiolysis: 1.5*104 Gy at 5*105 Gy h-1; variable pressures;

2-Methylthiophene (554-14-3) → thiophene (188290-36-0) + 2,3-dimethylthiophene (632-16-6) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + toluene (108-88-3)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 15.3 % Chromat. B 1.8 % Chromat. C 4.9 % Chromat. D 1.2 % Chromat.

2-Methylthiophene (554-14-3) → thiophene (188290-36-0) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + toluene (108-88-3) + benzene (71-43-2)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 15.3 % Chromat. B 4.9 % Chromat. C 1.2 % Chromat. D 8.6 % Chromat.

2-Methylthiophene (554-14-3) → 2-ethylthiophene (872-55-9) + 2,4-dimethylthiophene (638-00-6) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + 3-Methylthiophene (616-44-4)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 11.7 % Chromat. B 0.6 % Chromat. C 4.9 % Chromat. D 9.2 % Chromat.

2,3-dimethylthiophene (632-16-6) → thiophene (188290-36-0) + 2-ethylthiophene (872-55-9) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + 3-Methylthiophene (616-44-4)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 3.1 % Chromat. B 1.5 % Chromat. C 1.0 % Chromat. D 12.8 % Chromat.

3,4-dimethylthiophene (632-15-5) → 2,3-dimethylthiophene (632-16-6) + 2,4-dimethylthiophene (638-00-6) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + 3-Methylthiophene (616-44-4)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 5.1 % Chromat. B 6.2 % Chromat. C 1.1 % Chromat. D 12.2 % Chromat.

3,4-dimethylthiophene (632-15-5) → 2,4-dimethylthiophene (638-00-6) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + 3-Methylthiophene (616-44-4) + benzene (71-43-2)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 6.2 % Chromat. B 1.1 % Chromat. C 12.2 % Chromat. D 17.6 % Chromat.

2,4-dimethylthiophene (638-00-6) → 2,3-dimethylthiophene (632-16-6) + 3,4-dimethylthiophene (632-15-5) + 2-ethylthiophene (872-55-9) + 2,5-DIMETHYLTHIOPHENE (638-02-8)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 0.6 % Chromat. B 2.9 % Chromat. C 1.2 % Chromat. D 3.5 % Chromat.

2,4-dimethylthiophene (638-00-6) → 2-Methylthiophene (554-14-3) + 3,4-dimethylthiophene (632-15-5) + 2,5-DIMETHYLTHIOPHENE (638-02-8) + 3-Methylthiophene (616-44-4)

Conditions	Yield
1.) glow discharge, 2.) -196 deg C -> -80 deg C; Further byproducts given. Title compound not separated from byproducts;	A 6.6 % Chromat. B 2.9 % Chromat. C 3.5 % Chromat. D 9.5 % Chromat.

Upstream product

• 554-14-3 2-Methylthiophene 
• 13679-70-4 5-methylthiophene-2-carboxaldehyde 
• 74-86-2 acetylene 
• 638-00-6 2,4-dimethylthiophene 
• 80243-14-7 3-(1,1-dimethylethyl)-2,5-dimethylthiophene 
• 111-65-9 octane 
• 110-54-3 hexane 
• 632-16-6 2,3-dimethylthiophene 
• 1795-05-7 2,4,5-trimethylthiophene 
• 188290-36-0 thiophene 
• 624-92-0 Dimethyldisulphide 
• 110-13-4 2,5-hexanedione 
• 765-58-2 2-bromo-5-methyl thiophene 
• 74-88-4 methyl iodide 

Downstream Products

• 6007-77-8 2,5-dimethyl-γ-oxo-3-thiophenebutanoic acid 
• 500891-66-7 1-(2,5-dimethyl-[3]thienyl)-butan-1-one 
• 80228-42-8 2-(2,5-dimethyl-3-thenoyl)benzoic acid 
• 101095-35-6 3,6-dichloro-2-(2,5-dimethyl-thiophene-3-carbonyl)-benzoic acid 
• 855620-96-1 (2,5-dimethyl-[3]thienyl)-p-tolyl ketone 
• 659719-86-5 (4-ethyl-phenyl)-(2,5-dimethyl-[3]thienyl)-ketone 
• 32427-84-2 1-(2,5-dimethyl-thiophen-3-yl)-propan-1-one 
• 2530-10-1 3-Acetyl-2,5-dimethylthiophen 
• 15271-04-2 (2,5-dimethylthiophen-3-yl)(phenyl)methanone 
• 57248-23-4 (4-chloro-phenyl)-(2,5-dimethyl-[3]thienyl)-ketone 
• 26421-44-3 2,5-dimethyl-thiophene-3-carbaldehyde 
• 651328-46-0 1-(2,5-dimethylthiophen-3-yl)-2-phenylethanone 
• 31819-37-1 3-bromo-2,5-dimethylthiophene 
• 40197-02-2 3-iodo-2,5-dimethylthiophene 

Relevant articles and documents

MECHANISM OF RECYCLIZATION OF FURANS TO THIOPHENES AND SELENOPHENES UNDER ACID-CATALYSIS CONDITIONS. 2. KINETIC INVESTIGATIONS OF THE REACTION OF 2,5-DIALKYLFURANS WITH HYDROGEN SULFIDE AND HYDROGEN SELENIDE IN AN ANHYDROUS MEDIUM

The effect of the concentration of the acidic component on the rates of recyclization of 2,5-dialkylfurans to thiophenes and selenophenes was studied.On the basis of the direct correlation of log k on (H0)I and the isotope effect of the solvent it was established that the reaction proceeds via a mechanism of specific acid catalysis.It was shown that the rates of the reactions with the participation of hydrogen sulfide and hydrogen selenide coincide at equal acidities and temperatures.A scheme for the mechanism of the reaction that includes a step involving the formation of the doubly protonated form of the substrate is proposed.

New method for synthesis of 2,5-disubstituted thiophenes

The use of hydrogen sulfide at the moment of formation is proposed for the recyclization of furans into thiophenes in acidic media. The advantages of this method are shown. 1999 KluwerAcademic/Plenum Publishers.

Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 6. Experiments with labeled atoms. Quantum chemical calculations of intermediates of recyclization and hydrolysis

The reaction of 2-methyl-5-R-furans (R = Me, Bu, 2,2-pentyl-2-methylpentyl) with H218O was investigated. Furans and the corresponding 2,5-alkanediones containing the 18O isotope were obtained. The general characteristics of the recyclization and isotope exchange reactions were established. A kinetic study of recyclization of 2,5-dimethylfuran with 16O and 18O into 2,5-dimethylthiophene was conducted. A reverse kinetic isotope effect was found. The schemes of the mechanisms of these processes were refined based on the experimental data and quantum-chemical calculations of the recyclization and hydrolysis intermediates. 1998 Plenum Publishing Corporation.

Synthesis of substituted 1,2,4-triazines based on 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione

A novel, convenient method has been developed for the synthesis of 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione, from which were prepared 5, 6-bis(2,5-dimethyl-3-thienyl)-1,2,4-triazines (analogs of the photochromic 1,2-diarylethenes). The principial possibility of using 1,2,4-triazines obtained as photochromic agents was investigated.

Catalytic Synthesis of Methylthiophenes

The gas-phase reaction of dimethyl disulfide with thiophene over Co/HZSM-5 catalyst in a helium medium under atmospheric pressure at 250–350°C gave a mixture of mono-, di-, tri-, and tetramethylthiophenes with an overall selectivity of 94–96%.

Catalytic reactions of dimethyl disulfide with thiophene and benzene

The gas-phase reaction of dimethyl disulfide with thiophene proceeds under the action of acid catalysts under atmospheric pressure at 160-350°C and a residence time of τ = 0.6-21 s to form thioalkylation and alkylation products. Dimethyl disulfide reacts with benzene to form only alkylation products. Catalysts containing both strong protic and Lewis acid sites, as well as basic sites of moderate strength, are the most active ones.

Reaction of dimethyl disulfide with thiophene catalyzed by zeolite

Reaction of dimethyl disulfide with thiophene under the action of highly siliceous zeolite at 180-350°C and contact time 0.6-14 s resulted in formation of thioalkylation products, 2-(methylsulfanyl)- and 2,5-bis(methylsulfanyl)thiophenes and also alkylate

Electrochromic properties of novel chalcones containing triphenylamine moiety

A series of novel electrochromic chalcones containing triphenylamine units were synthesized by Aldol reaction and characterized by NMR, IR and MS. Their optical, electrochemical properties were investigated using UV-vis, photoluminescence spectra and cyclic voltammetry. The molecular orbital energy levels and excitation energies were calculated by quantum chemical calculation. It was found that the fluorescence intensity is decreasing with formation of charge-transfer state. The existence of electron donating group on triphenylamine unites caused a significant bathochromic shift of the UV absorption maximum and increased EHOMO and ELUMO. The electrochromic property of the synthesized compounds was studied by spectroelectrochemical experiments. The results showed that the chalcones containing triphenylamine moiety presented good electrochromic stability, with a color change from yellow to blue as applied potentials ranging from 0.0 to 2.8 V. The coloring and bleaching time was in the range of 2.9-4.2 s and 1.7-3.3 s, respectively.

Investigation of the aroma-active compounds formed in the maillard reaction between glutathione and reducing sugars

Aroma-active compounds formed during the thermal reaction between glutathione (GSH) and reducing sugars were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry (GC-O) with aroma extract dilution analysis (AEDA). Application of AEDA to glutathione Maillard reaction products (GSH MRPs) led to the identification of 19 aroma-active compounds in the thermal reaction of glutathione with glucose or fructose. In addition, the carbohydrate module labeling (CAMOLA) approach was also employed to elucidate the formation pathways for selected target sulfur aroma compounds, such as 5-methylthiophene-2-carbaldehyde and 3-methylthiophene-2-carbaldehyde, which have not been reported previously. The intact carbon skeleton of glucose via 3-deoxyhexosone is incorporated into 5-methylthiophene-2-carbaldehyde with the hydrogen sulfide of GSH. On the other hand, the formation of 3-methylthiophene2-carbaldehyde may occur via the recombination of a C-4 sugar fragment and mercaptoacetaldehyde.

Carbon-sulfur bond cleavage of methyl-substituted thiophenes with iridium(III)

Reaction of [Cp*IrHCl]2 (Cp* = η5- C5Me5) with 2-methylthiophene and 2,5-dimethylthiophene at 120 °C in the presence of H2 results in the cleavage of the thiophene carbon-sulfur bond(s). In both cases