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Indole Sigma CAS 120-72-9

Molecular Formula: C8H7N

Formula Weight: 117.15

ZSpharmac: Indole Sigma Supplier

Product Name: Indole Sigma
CAS No: 120-72-9
Purity: 99%

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Basic Info

Product Name:Indole Sigma
Other Names:Indole
Place of Origin:Shandong, China
Brand Name:ZSpharmac
Type:Cosmetic Raw Materials
Appearance:White to Slightly Pink Crystalline Powder
EINECS No.:204-420-7
Provide:Indole Sigma MSDS;
Indole Sigma COA

What is Indole Sigma?

Indole Sigma is an aromatic heterocyclic organic compound with a bicyclic structure in the chemical structure, including a six-membered benzene ring and a five-membered nitrogen-containing pyrrole ring, so it is also called benzopyrrole. Because the lone pair of nitrogen electrons participates in the formation of aromatic rings, Indole Sigma is not a base, and its properties are different from simple amines. It is an imine with weak basicity; the double bond of a heterocyclic ring generally does not undergo an addition reaction; Dipolymerization and trimerization can occur under the action of strong acid; under special conditions, aromatic electrophilic substitution reaction can be carried out, and the hydrogen on the 3 position is preferentially replaced. For example, 3-chloroindole can be obtained by reacting with sulfonyl chloride . A variety of reactions can also occur at the 3-position, such as the formation of Grignard reagents, condensation with aldehydes, and Mannich reactions.

Indole Sigma Property

Melting point 

51-54 °C (lit.)

Boiling point 

253-254 °C (lit.)



vapor pressure 

0.016 hPa (25 °C)

refractive index 



>230 °F

storage temp. 



methanol: 0.1 g/mL, clear


Crystalline Powder


3.17 (quoted, Sangster, 1989)


White to slightly pink


5.9 (1000g/l, H2O, 20℃)


fecal odor, floral in high dilution

Odor Threshold


Water Solubility 

2.80 g/L (25 ºC)




Indole Sigma Uses

  1. Indole Sigma is widely contained in essential oils such as bitter neroli oil, sweet orange oil, lemon oil, lime oil, mandarin oil, pomelo peel oil, jasmine oil, etc.
  2. Indole Sigma can be widely used in floral flavors such as jasmine, lilac, orange blossom, gardenia, honeysuckle, lotus, narcissus, ylang-ylang, grass orchid, and white orchid. It is often used together with methyl indole to prepare artificial civet fragrance. It can be used in chocolate, raspberry, strawberry, bitter orange, coffee, nuts, cheese, grape and fruity compound flavors in very small amounts.
  3. Indole Sigma is a food spice that is allowed to be used according to GB 27 60 . It is mainly used to prepare flavors of cheese, citrus, coffee, nuts, grapes, strawberries, raspberries, chocolate, assorted fruits, jasmine and lily.

Synthetic Method of Indole Sigma

1. Extraction from washing oil fractions In high-temperature coal tar, it contains about 0.10%-0.16% of indole. Generally, it can be extracted from coal tar and washing oil fractions. The washing oil fraction is washed with alkali and acid to obtain the methylnaphthalene fraction, which is then rectified in a high-efficiency tower with 60 theoretical plates, and the fraction at 225-256°C is cut out and melted by adding potassium hydroxide. The reaction was carried out at 170-240°C for 2-4h, and stirred until bubbling stopped. Let it stand still, release the lower layer of indole potassium to cool, break it up and wash it with benzene to remove oil at low temperature. Then hydrolyze at 50-70°C to obtain crude indole oil, which is distilled in a distillation column with 20 theoretical plates to obtain a reflux ratio of 8-10:1, cut off the fraction with a temperature of 170-256°C at the top of the tower, cool and crystallize , Centrifugal filtration, that is, refined indole. After pressing, the oil content is below 3%, and recrystallized with ethanol to obtain refined Indole Sigma with a purity of 99%.
2. It can be obtained by catalytic dehydrogenation of o-aminoethylbenzene. O-aminoethylbenzene is dehydrocyclized at 550°C in the presence of aluminum nitrate (or aluminum oxide) in a nitrogen stream, and dihydroindoline is obtained by distillation under reduced pressure. Then dehydrogenate at 640°C to obtain Indole Sigma. Other production methods include the reaction of o-nitrotoluene and oxalate to generate o-nitrophenylpyruvate and then make α-indole carboxylic acid, and finally dry distillation with lime to obtain the product; aniline and acetylene in Synthesize indole by heating at 600-650°C; synthesize Indole Sigma from o-carboxyphenylglycine through 3-hydroxy-2-indole carboxylic acid and indole acid; oxidize cyanine with concentrated nitric acid or chromic acid to obtain indole quinone, and Indole can be obtained by distillation with zinc powder. Indole can also be obtained by mixing nitrocinnamic acid and 10 parts of potassium hydroxide powder, adding iron filings and heating to melt the mixture. In the synthesis of indole and its homologues, the Fischer synthesis method is the most common. Aromatic hydrazones of ketones or aldehydes act under acidic conditions to undergo a rearrangement reaction similar to benzidine to generate Indole Sigma.

Extraction Method of Indole Sigma

There are three main methods: alkali fusion method, sulfuric acid washing method and azeotropic distillation method.
(1) Alkali fusion method. Add 1.2 times the theoretical amount of potassium hydroxide to the fraction containing about 5% of indole, stir and react to separate potassium indole, add benzene and hydrolyze to obtain a benzene solution of indole. The indole benzene solution is rectified to obtain crude indole oil, and then the Indole Sigma product is obtained through cooling crystallization, pressing and recrystallization.
(2) Sulfuric acid washing method. Add sulfuric acid with a concentration of 30-35% to the washing oil to obtain the sulfate salt of indole and quinoline after reaction, neutralize and precipitate indole and quinoline with alkali. Then use rectification to separate indole from quinoline, so that indole is concentrated in the fraction at 250-265°C. Add sulfuric acid with a concentration of 10-20% to this fraction to wash off quinoline (indole does not react at this acidity), and add an appropriate amount of benzene to obtain a benzene solution of indole. The solution is distilled to remove benzene to obtain crude Indole Sigma, and then rectified, crystallized and squeezed to obtain industrially pure indole.
(3) Azeotropic distillation. The difference between the boiling points of indole and biphenyl is 2.2°C, which is difficult to separate by distillation, but the difference in boiling points of the azeotrope formed with diethylene glycol or ethylene glycol under normal pressure is 12°C and 12.2°C, respectively. Add the above reagents to the fraction enriched in Indole Sigma and biphenyl, and then separate indole and biphenyl by azeotropic distillation. The obtained indole fraction is extracted with benzene and then rectified, crystallized and squeezed to obtain industrially pure indole. In addition, a combination of extraction and rectification can be used to separate and purify Indole Sigma. Extractants include benzene, monohydroxyethylamine and n-heptane.

About That Product:
If you need Indole Sigma, a cosmetic raw material, please contact our service staff directly, and we will provide you with high-quality products at the best price.
As an experienced Indole Sigma manufacturer and supplier, ZSpharmac will provide Indole Sigma raw materials to customers all over the world for a long time.
Over the years, the company has been adhering to the spirit of “integrity management, strict quality control, customer first”, and has won unanimous praise from domestic and foreign customers.

Company Profile and Corporate Culture

Company Profile:

ZhiShang Chemical is owned by ZhiShang Group is a professional new-type chemicals enterprise combined into research and development, production and sales .

The company’s competitive product is pharmaceutical raw materials and intermediates (especially carbohydrate derivatives Series), In recent years, the company has made a major breakthrough in food and feed additives, plant extraction, industrial chemicals industry .

The company insists on the spirit of “sincere management, strict quality control, customer as god” , get consistent high praise from customers at home and abroad.

Corporate Culture:

Help China Chemicals to benefit the happiness of human life
Become the most trusted chemical supplier in the world
Striver – oriented, enrich employees, customer first, deep service, seek development
Be prepared for danger in times of peace, forge ahead actively, unity and cooperation, and be brave to fight

About Us

The production base is located in Zhangqiu chemical industry park and Tai’an high-tech chemical industry park. laboratory and workshop in strict accordance with the GMP standard and the product fit national ISO9001 and ISO2000 standards.

“Zhishang” products are exported to Europe, North and South America, the Middle East, Asia Pacific and Africa area, so as to establish a long-term and stable cooperation relationship with customer in the world.

Company Info
  • Business Type: Manufacturer
  • Product Range: Cosmetic raw materials
  • Products/Service:Cosmetic raw materials (flavors and fragrances,antioxidant products, moisturizing and hydrating, whitening agents, cosmetic additives)
  • Total Employees: 51~100
  • Capital (Million US $): 10000000RMB
  • Year Established: 2016
Production Capacity
  • No. of Production Lines : 8
  • No. of QC Staff : 5 -10 People
  • OEM Services Provided : yes
  • Factory Size (Sq.meters) : 3,000-5,000 square meters
  • Certificate: ISO9001 , CE , GMP , API , MSDS
  • Factory Location : Diao Town Industry Park, Zhangqiu City, Jinan City, Shandong Province, China.


Pre-Sales Service

* Prompt reply and 24 hours online, professional team to provide best price and high quality product.

* Sample testing support.

* Every batch of products will be tested to ensureits quality.

*The packing also can be according the customers` requirment.

*Any inquiries will be replied within 24 hours.

*we provide Commerical Invoice, Packing List, Bill of loading, COA , Health certificate and Origin certificate. If your markets have any special requirements, let us know.


After-Sales Service

*The fact of logistics information monitoring.

* Any questions about the product can be consulted at any time.

*Product has any problem can return.


Do you accept sample order?

We will make samples before mass production, and after sample approved, we’ll begin mass production. Doing 100% inspection during production, then do random inspection before packing.



You can get free samples for some products,you only need to pay the shipping cost or arrange a courier to us and take the samples. You can send us your product specifications and requests,we will manufacture the products according to your requests.

What’s your MOQ?

Our MOQ is 1kg. But usually we accept less quantity such as 100g on the condition that sample charge is 100% paid.

Do you supply product report?

Yes. We’ll give you product analysis report before shipping.

  Is there a discount?

Different quantity has different discount.


1. ≤50kg, Express delivery recommended, usually called as DDU service;

2. ≤500kg, Air shipping recommended, usually called as FOB, CFR, or CIF service;

3. >500kg, sea shipping recommended, usually called as FOB, CFR, or CIF service;

4. For high value products, please select air shipping and express delivery for safe.

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