Toluidines

Toluidines
Surname	o -Toluidine	m -toluidine	p -toluidine
other names	2-methylaniline, 1,2-methylaniline, 1,2-aminotoluene, o -tolylamine	3-methylaniline, 1,3-methylaniline, 1,3-aminotoluene, m -tolylamine	4-methylaniline, 1,4-methylaniline, 1,4-aminotoluene, p -tolylamine
Structural formula
CAS number	95-53-4	108-44-1	106-49-0
PubChem	7242	7934	7813
ECHA InfoCard	100.002.209	100.003.258	100.003.095
Molecular formula	C 7 H 9 N
Molar mass	107.16 g mol −1
Physical state	liquid		firmly
Brief description	colorless to yellowish, gradually turning reddish brown when exposed to air
Melting point	−24.4 ° C (alpha) −16.3 (beta) ° C	−31 ° C	45 ° C
boiling point	200 ° C	203 ° C	200 ° C
Density (20 ° C)	0.9984 g cm −3	0.989 g cm −3	0.9619 g cm −3
Refractive index	1.5728	1.5670	1.5534
pK s value (of the conjugate acid BH + )	4.44	4.70	5.08
solubility	15 g l −1 (20 ° C)	10 g l −1 (20 ° C)	7.5 g l −1 (20 ° C)
	slightly soluble in water
Flash point	85 ° C	86 ° C	87 ° C
Ignition temperature	482 ° C	482 ° C	482 ° C
GHS labeling o ,  m ,  p	from EU regulation (EG) 1272/2008 (CLP) danger
H and P phrases	301 + 331-319-350-400	301 + 311 + 331-319-373-410	301-311-331-317-319-351-411
	no EUH phrases
	201-273-304 + 340 305 + 351 + 338-309 + 310	261-273-280-301 + 310 305 + 351 + 338-311	280-302 + 350-304 + 340 305 + 351 + 338-301 + 310-273
Tox data	670 mg kg −1 ( LD 50 ,  rat ,  oral )	450 mg kg −1 ( LD 50 ,  rat ,  oral )	336 mg kg −1 ( LD 50 ,  rat ,  oral )

The toluidines (also known as aminotoluene (aminotoluene) or methylaniline ) form a group of substances in chemistry and are aromatic compounds with a methyl group  (–CH ₃ ) and an amino group  (–NH ₂ ) as substituents on the benzene ring . The different arrangement of the substituents ( ortho , meta or para ) results in three constitutional isomers with the empirical formula C ₇ H ₉ N. They are primarily important as preliminary products in the manufacture of dyes and pigments .

presentation

The toluidines are produced from nitrotoluenes ( accessible from toluene by nitration ) by reduction. The reduction can be carried out on the one hand with iron, acetic acid and hydrochloric acid ( Béchamp reduction ). Today, catalytic hydrogenation with Raney nickel predominates . The solvents used here are often lower, aliphatic alcohols ( methanol , ethanol , n-propanol or iso-propanol ). The hydrogenation generally takes place at pressures between 3 bar and 20 bar H ₂ pressure (so-called low-pressure hydrogenation) or at 20 to 50 bar (so-called medium-pressure hydrogenation ).

properties

The toluidines have almost the same boiling points, but differ significantly in their melting points. The p because of its symmetry -Toluidin has the highest melting point and is a solid.

The Toluidine are weak bases , their (pK _s values) are in the same order of magnitude as aniline (4,603).

According to Antoine, the vapor pressure functions result from log ₁₀ (P) = A− (B / (T + C)) (P in bar, T in K) as follows:

Vapor pressure functions of the toluidines
	T (K)	A.	B.	C.
o-toluidine	391.6-473.4	4.19168	1617.232	-87.126
m-toluidine	394.9-476.5	4.19983	1618.386	−90.631
p-toluidine	315-473.5	4.71884	1961,716	−57.0

Reactions

The toluidines form stable salts with strong inorganic and organic acids .

The most important reactions are

• Acetylation
• Alkylation
• Aralkylation
• Arylation and the
• Diazotization

The chemical behavior of the toluidines is determined (as with aniline ) by the aromatic nucleus and the amino group .

use

The toluidines used to be of great importance almost exclusively as intermediate products for the production of dyes and pigments . After reductive cleavage of azo groups, ortho-toluidine must not be released from textiles or leather products that come into direct contact with human skin for a longer period of time (Appendix 1 of the Consumer Goods Ordinance ). Some herbicides are now also produced on the basis of these compounds. o - and p -Toluidin are important starting materials for the production of Chlortoluidinen and nitrided toluidines. In addition to toluidinesulfonic acids , these are used to manufacture pharmaceuticals , dyes and pigments.

The cresols can be obtained from the toluidines via diazotization (and subsequent “ boiling ”) .

literature

• JS Bowers, Jr .: Toluidines in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, doi : 10.1002 / 14356007.a27_159 .

See also

• N -methylaniline C ₇ H ₉ N, different isomer
• Dimethylanilines C ₈ H ₁₁ N, e.g. B. N , N -dimethylaniline , N , 2-dimethylaniline - N , 4-dimethylaniline , xylidines
• Trimethylanilines C ₉ H ₁₃ N, e.g. B. 2,4,6-trimethylaniline
• Tetramethylanilines C ₁₀ H ₁₅ N, e.g. B. N , N , 3,5-tetramethylaniline
• Pentamethylanilines C ₁₁ H ₁₇ N, e.g. B. N , N , 2,4,6-pentamethylaniline

Individual evidence

1. ↑ ^{a b c d e f g} Entry on o-toluidine in the GESTIS substance database of the IFA , accessed on December 27, 2019(JavaScript required) .
2. ↑ ^{a b c d e f g} Entry on m-toluidine in the GESTIS substance database of the IFA , accessed on December 27, 2019(JavaScript required) .
3. ↑ ^{a b c d e f g} Entry on p-toluidine in the GESTIS substance database of the IFA , accessed on December 27, 2019(JavaScript required) .
4. ↑ ^{a b c d e f g h i j k l} J.S. Bowers, Jr .: Toluidines in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, doi : 10.1002 / 14356007.a27_159 .
5. ↑ ^{a b} CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
6. ↑ ^{a b} R.R. Dreisbach, SA Shrader: Vapor Pressure-Temperature Data on Some Organic Compounds , in: Ind. Eng. Chem. 41 (1949), pp. 2879-2880.
7. ^ DR Stull: Vapor Pressure of Pure Substances Organic Compounds , in: Ind. Eng. Chem. 39 (1947), pp. 517-540.