Xylidines

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The xylidines (also called aminoxylenes or dimethylanilines ) are aromatic amines with the general formula C 6 H 3 (CH 3 ) 2 NH 2 or as a molecular formula C 8 H 11 N, of which there are six constitutional isomers . They can be as amino - derivatives of xylenes interpret. They arise u. a. as by-products of the fractional distillation of coal tar .

Structure and properties

The xylidines are usually yellowish liquids (with the exception of the solid 3,4-xylidine) and have an amine-like odor. They change color when exposed to light and in contact with air. They are sparingly soluble in water, soluble in ethanol and ether. Xylidines are mostly toxic.

Xylidines
Surname 2,3-xylidine 2,4-xylidine 2,5-xylidine 2,6-xylidine 3,4-xylidine 3,5-xylidine
other names 2,3-dimethylaniline,
1-amino-
2,3-dimethylbenzene 		2,4-dimethylaniline,
1-amino-
2,4-dimethylbenzene 		2,5-dimethylaniline,
1-amino-
2,5-dimethylbenzene 		2,6-dimethylaniline,
1-amino-
2,6-dimethylbenzene 		3,4-dimethylaniline,
1-amino-
3,4-dimethylbenzene 		3,5-dimethylaniline,
1-amino-
3,5-dimethylbenzene
Structural formula 2,3-xylidine 2,4-xylidine 2,5-xylidine 2,6-xylidine 3,4-xylidine 3,5-xylidine
CAS number 87-59-2 95-68-1 95-78-3 87-62-7 95-64-7 108-69-0
1300-73-8 (mixture of isomers)
PubChem 6893 7250 7259 6896 7248 7949
ECHA InfoCard 100.001.596 100.002.219 100.002.229
( 100.208.101 )		 100.001.599 100.002.217 100.003.280
100.013.720 (mixture of isomers)
Molecular formula C 8 H 11 N
Molar mass 121.18 g mol −1
Physical state liquid firmly liquid
Brief description colorless liquids or solids, yellowish to reddish brown when exposed to light and air, with an amine-like odor
Melting point 2 ° C −16 ° C 15.5 ° C 11.2 ° C 51 ° C 9.8 ° C
boiling point 222 ° C 214 ° C 218 ° C 215 ° C 228 ° C 220 ° C
pK s value
(of the conjugate
acid BH + ) 		4.70 4.89 4.53 3.95 5.17 4.91
solubility sparingly soluble in water, soluble in ethanol and ether
GHS
labeling
06 - Toxic or very toxic 08 - Dangerous to health 09 - Dangerous for the environment
danger
07 - Warning 08 - Dangerous to health

09 - Dangerous for the environment
Caution
06 - Toxic or very toxic 08 - Dangerous to health 09 - Dangerous for the environment
danger
H and P phrases 331-311-301-373-411 302-312-332-315-319-335-351-411 331-311-301-373-411
no EUH phrases no EUH phrases no EUH phrases
261-273-280
301 + 310-311 		273-280-301 + 310-311 273-280-302 + 352
304 + 340-308 + 310 		273-391-501 280-273-304 + 340
302 + 352-309 + 310 		261-273-280-301 + 310-311

presentation

Technically, xylidines are obtained by converting a mixture of isomers of the xylenes . By nitration therefrom forming nitroxylenes from which, by reducing the xylidines are accessible. The product is a mixture of isomers. Hydrochloric acid is added to separate this mixture ; A crystal sludge is deposited, which consists essentially of the hydrochloride of 2,6-xylidine.

use

In general, the xylidines are used in the production of dyes, pesticides and other chemicals. In addition, the 2,3-isomer is used to produce mefenamic acid , the 2,6-isomer is converted into anesthetics (e.g. lidocaine ) and the 3,4-isomer to vitamin B 2 . The technical xylidine is used almost exclusively for the preparation of azo dyes , but it was also used as a component of the rocket fuel Tonka .

Synthesis of lidocaine from 2,6-xylidine

Individual evidence

  1. ↑ Entry for CAS no. 1300-73-8 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  2. ↑ a b c Entry for CAS no. 87-59-2 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  3. ↑ a b c Entry for CAS no. 95-68-1 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  4. ↑ a b c Entry for CAS no. 95-78-3 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  5. ↑ a b c Entry for CAS no. 87-62-7 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  6. ↑ a b c Entry for CAS no. 95-64-7 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  7. ↑ a b c Entry for CAS no. 108-69-0 in the GESTIS substance database of the IFA , accessed on December 26, 2019(JavaScript required) .
  8. ↑ CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .

Web links

Commons : Xylidines  - Collection of pictures, videos, and audio files
Wiktionary: Xylidines  - explanations of meanings, word origins, synonyms, translations