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2,3,5-Trimethylpyrazine

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2,3,5-Trimethylpyrazine
Names
IUPAC name 2,3,5-Trimethylpyrazine
Other names Pyrazine, 2,3,5-trimethyl-;2,3,5-Trimethyl pyrazine;2,3,5-Trimethyl pyrazine (natural);2,3,5-Trimethylpyrazine;2,3,6-Trimethylpyrazine;5-23-05-00419 (Beilstein Handbook Reference);AI3-34442;BRN 0002423;CCRIS 2932;FEMA No. 3244;Pyrazine, trimethyl-;Trimethylpyrazine
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.035.178 Edit this at Wikidata
EC Number
  • 238-712-0
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C7H10N2/c1-5-4-8-6(2)7(3)9-5/h4H,1-3H3Key: IAEGWXHKWJGQAZ-UHFFFAOYSA-N
SMILES
  • CC1=CN=C(C(=N1)C)C
Properties
Chemical formula C7H10N2
Molar mass 122.171 g·mol
Appearance colourless to slightly yellow liquid
Odor roasted nut, baked potato odour
Density 0.979 g mL
Boiling point 173.1 °C (343.6 °F; 446.2 K)
Solubility in water Alcohol, oils, water (1.521e+004 mg/L at 25 °C (est)
Refractive index (nD) 1.5030 to 1.5050
Hazards
GHS labelling:
Pictograms GHS02: FlammableGHS07: Exclamation mark
Signal word Warning
Hazard statements H226, H302
Precautionary statements P210, P233, P240, P241, P242, P243, P264, P270, P280, P301+P312, P303+P361+P353, P330, P370+P378, P403+P235, P501
Flash point 54.4 °C (129.9 °F; 327.5 K)
Lethal dose or concentration (LD, LC):
LD50 (median dose) 806 mg/kg rat
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references
Chemical compound

2,3,5-Trimethylpyrazine (chemical formula C7H10N2) is one of the most broadly used edible synthesis fragrances. It comes from baked food, fried barley, potatoes, and peanuts. 2,3,5-Trimethylpyrazine is used for the flavor in cocoa, coffee, chocolate, potato, cereal, and fried nuts.

Physical properties

The specific gravity depends on the quality and the producer and ranges from 0.967 to 0.987.

Synthesis

2,3,5-Trimethylpyrazine can be synthesized from 2,3-butanedione and 1,2-diaminopropane. First, 1,2-diaminopropane is synthesized by amination of isopropanolamine in the presence of ammonia and a hydrogenation catalyst: Raney Ni. The effect of the amount of Raney Ni catalyst, the molar ratio of materials, reactions are as follows: the molar ratio of isopropanolamine to ammonia is 1:3.5,the reaction temperature is 160 °C, the reaction is 5 hours, the molar ratio of hydrogen to isopropanolamine is 1:5. Then the reaction consists of synthesis of 2,3,5-trimethyl-5,6-dihydropyrazine and 2,3,5-trimethylpyrazine. The optimum conditions of 2,3,5-trimethyl-5,6-dihydropropyrazine synthesis are established:2,3-butanedione which is mixed with anhydrous ethyl alcohol (the mass ratio of anhydrous ethyl alcohol to 2,3-butanedione was 5:1) is dropped to the mixture of anhydrous ethyl alcohol and 1,2-diaminopropane (the mass ratio of anhydrous ethyl alcohol to 1,2-diaminopropane was 6:1) at the even pace for four hours, the molar ratio of 2,3-butanedione to 1,2-diaminopropane is 1:1.1, the condensation reaction temperature is -5 °C. The best dehydrogen oxidation conditions are as follows: air is used as oxidant, the molar ration of potassium hydroxide and 2,3,5-Trimethyl-5,6-dihydro-pyrazine is 3:1, the mass ratio of ethanol to 2,3,5-trimethyl-5,6-dihydro-pyrazine 10:1,reaction temperature 68 °C, reaction time seven hours.

There are several other ways to synthesis 2,3,5-trimethylpyrazine:

Piperazine gas phase catalytic dehydrogenation
  • N-(β alkane alcohol)ethanediamine gas phase catalysis
N-(β alkane alcohol)ethanediamine gas phase catalysis
Ethanediamine and methyl aldehyde gas phase catalysis
  • Diamine and diol gas phase catalysis
Diamine and diol gas phase catalysis


Use limit in food

FEMA (mg/kg)
Soft drinks 5.0～10
Candy 5.0～10
Baked food 5.0～10
Cereal 2.0
Seasoning 2.0
Meat 2.0
Dairy 1.0
Soup 2.0

References

  1. "2，3，5-三甲基吡嗪的合成研究" [Study on the synthesis of 2,3,5-trimethylpyrazine]. {{cite journal}}: Cite journal requires |journal= (help)

Additional references

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