Dihydroxytoluenes

The dihydroxytoluenes form a group of aromatic compounds that are derived from both toluene and dihydroxybenzenes . The structure consists of a benzene ring with two attached hydroxyl groups  (-OH) and a methyl group  (-CH ₃ ) as substituents . Their different arrangement results in six constitutional isomers with the empirical formula C ₇ H ₈ O ₂ , the best known being 3,5-dihydroxytoluene ( orcin ).

A uniform naming is difficult because the dihydroxytoluenes do not form a common common name. They can therefore be understood as derivatives of catechol (2 isomers), resorcinol (3 isomers) and hydroquinone (1 isomer). Conversely, they can be viewed as dihydroxy derivatives of toluene. They are therefore referred to as dihydroxytoluenes , since only -toluene forms a common new common tribe name .

Occurrence

The 3,4- isomer homopyrocatechin (also homobrenzcatechin, 4-methylpyrocatechin) is found as 2-methylether creosol , on the one hand in creosote , in wood tar and in ylang-ylang oil . The 3,5-isomer orcin was isolated in 1829 from lichens of the genus Rocella . It is also found in the flowers of mosses such as Ditrichia viscosa and the leaves of tree heather ( Erica arborea ).

properties

All substances are sparingly soluble in water. Chemically, they typically behave like phenols, for example in alkaline solution they form phenolates, which have a significantly higher water solubility.

Dihydroxytoluenes
Surname	2,3-dihydroxytoluene	2,4-dihydroxytoluene	2,5-dihydroxytoluene	2,6-dihydroxytoluene	3,4-dihydroxytoluene	3,5-dihydroxytoluene
other names	3-methyl- 1,2-dihydroxybenzene, 3-methylpyrocatechol	4-methyl- 1,3-dihydroxybenzene, 4-methylresorcinol	2-methyl- 1,4-dihydroxybenzene, 2-methylhydroquinone, toluhydroquinone	2-methyl- 1,3-dihydroxybenzene, 2-methylresorcinol	4-methyl- 1,2-dihydroxybenzene, 4-methylpyrocatechol, homopyrocatechol	5-methyl- 1,3-dihydroxybenzene, 5-methylresorcinol, orcin , orcinol
Structural formula
CAS number	488-17-5	496-73-1	95-71-6	608-25-3	452-86-8	504-15-4
PubChem	340	10333	7253	11843	9958	10436
ECHA InfoCard	100.006.975	100.007.117	100.002.222	100.009.233	100.006.559	100.007.259
Molecular formula	C 7 H 8 O 2
Molar mass	124.14 g mol −1
Physical state	firmly
Brief description	crystalline solids
Melting point	65-68 ° C	104-108 ° C	126-127 ° C	114-120 ° C	67-69 ° C	56-58 ° C
boiling point	241 ° C	270 ° C	297 ° C	264 ° C	251 ° C	290 ° C
solubility	slightly soluble in water
GHS labeling	Caution	Caution	Caution	danger	Caution	Caution
H and P phrases	315-319-335	315-319-335	302-315-319-335	301-315-319-335	315-319-335	302-315-319-335
	no EUH phrases	no EUH phrases	no EUH phrases	no EUH phrases	no EUH phrases	no EUH phrases
	261-305 + 351 + 338	261-305 + 351 + 338	261-305 + 351 + 338	261-301 + 310-305 + 351 + 338	261-305 + 351 + 338	261-305 + 351 + 338

Individual evidence

1. ↑ H. Hager et al .: Hagers Handbook of Pharmaceutical Practice , Springer 1999, ISBN 3-540-52640-4 , p. 681.
2. ↑ J. Falbe, M. Regitz (ed.): Römpp Lexikon Chemie , 10th edition, Thieme, Stuttgart a. New York 1996-1999, p. 2642.
3. ↑ ^{a b c} data sheet 3-methylcatechol from Sigma-Aldrich , accessed on December 26, 2019 ( PDF ).
4. ↑ ^{a b} Data sheet 4-methylresorcinol from Sigma-Aldrich , accessed on December 27, 2019 ( PDF ).
5. ↑ ^{a b c} data sheet methylhydroquinone from Sigma-Aldrich , accessed on December 26, 2019 ( PDF ).
6. ↑ ^{a b c} data sheet 2-methylresorcinol from Sigma-Aldrich , accessed on December 26, 2019 ( PDF ).
7. ↑ ^{a b c} data sheet 4-methylcatechol from Sigma-Aldrich , accessed on December 26, 2019 ( PDF ).
8. ↑ ^{a b c} data sheet Orcinol monohydrate from Sigma-Aldrich , accessed on December 26, 2019 ( PDF ).
9. ↑ David R. Lide: CRC Handbook of Chemistry and Physics A Ready-reference Book of Chemical and Physical Data . CRC Press, 1995, ISBN 978-0-8493-0595-5 , pp. 370 ( limited preview in Google Book search).

Web links

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