Trimethylbenzenes
The trimethylbenzenes form a group of substances whose structure consists of a benzene ring with three methyl groups (–CH 3 ) as substituents . Their different arrangement results in three constitutional isomers with the empirical formula C 9 H 12 . Depending on the position, one speaks of vic. -, asym. - or sym. trimethylbenzene. They also belong to the group of C 3 benzenes . The sym. -Trimethylbenzene mesitylene is the best known of the three isomers.
Representative
The trimethylbenzenes group of substances includes:
- Hemellitol (1,2,3-trimethylbenzene)
- Pseudocumene (1,2,4-trimethylbenzene)
- Mesitylene (1,3,5-trimethylbenzene)
Trimethylbenzenes | |||||||||||||
Surname | Hemellitol | Pseudocumene | Mesitylene | ||||||||||
other names | 1,2,3-trimethylbenzene vic. -Trimethylbenzene |
1,2,4-trimethylbenzene asym. -Trimethylbenzene |
1,3,5-trimethylbenzene sym. -Trimethylbenzene |
||||||||||
Structural formula | |||||||||||||
CAS number | 526-73-8 | 95-63-6 | 108-67-8 | ||||||||||
25551-13-7 (unspecified isomer or mixture of isomers) | |||||||||||||
PubChem | 10686 | 7247 | 7947 | ||||||||||
Molecular formula | C 9 H 12 | ||||||||||||
Molar mass | 120.19 g mol −1 | ||||||||||||
Physical state | liquid | ||||||||||||
Brief description | colorless liquid | ||||||||||||
Melting point | −25 ° C | −44 ° C | −45 ° C | ||||||||||
boiling point | 176 ° C | 169 ° C | 165 ° C | ||||||||||
Density (20 ° C) | 0.89 g cm −3 | 0.88 g cm −3 | 0.87 g cm −3 | ||||||||||
Vapor pressure (25 ° C) | 2.25 mbar (25 ° C) | 2.8 mbar (25 ° C) | 2.69 mbar (20 ° C) | ||||||||||
solubility | insoluble in water | ||||||||||||
GHS labeling |
|
|
|
||||||||||
H and P phrases | 226-315-319-335 | 226-304-332-319-335-315-411 | 226-304-315-319-335-411 | ||||||||||
no EUH phrases | no EUH phrases | no EUH phrases | |||||||||||
261-305 + 351 + 338 | 261-273-301 + 310-331-302 + 352-304 + 340 + 312 | 210-273-301 + 310-331-302 + 352-304 + 340 + 312 | |||||||||||
MAK | Switzerland: 20 ml m −3 or 100 mg m −3 |
properties
The melting points behave rather inconsistently. Mesitylene is unusual. The most symmetrical representative in this group has a melting point of −45 ° C and is therefore the lowest of all three isomers.
literature
- HW Earhart, Andrew P. Komin: Polymethylbenzenes . In: Kirk-Othmer Encyclopedia of Chemical Technology , 2000, doi: 10.1002 / 0471238961.1615122505011808.a01 .
Web links
Commons : Trimethylbenzenes - Collection of pictures, videos, and audio files
Individual evidence
- ↑ a b c d e Entry on 1,2,3-trimethylbenzene in the GESTIS substance database of the IFA , accessed on March 4, 2020(JavaScript required) .
- ↑ a b c d e Entry on 1,2,4-trimethylbenzene in the GESTIS substance database of the IFA , accessed on March 4, 2020(JavaScript required) .
- ↑ a b c d e Entry on 1,3,5-trimethylbenzene in the GESTIS substance database of the IFA , accessed on March 4, 2020(JavaScript required) .
- ↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for trimethylbenzene (all isomers) ), accessed on March 4, 2020.