Methoxyphenols

Methoxyphenols

Surname

2-methoxyphenol

3-methoxyphenol

4-methoxyphenol

other names

o -Methoxyphenol,
pyrocatechol
monomethyl ether
guaiacol

m -Methoxyphenol,
resorcinol
monomethyl ether

p -Methoxyphenol,
hydroquinone monomethyl
ether
MEHQ

Structural formula

CAS number

90-05-1

150-19-6

150-76-5

PubChem

9015

C ₇ H ₈ O ₂

124.14 g mol ⁻¹

firmly

liquid

firmly

Melting point

28-32 ° C

−17.5 ° C

56 ° C

boiling point

205 ° C

243-244 ° C

pK _s value

9.98

9.65

10.20

GHS
labeling

Caution

danger

Caution

H and P phrases

302-315-319

302-311-315-318-332

302-317-319-361d-412

no EUH phrases

305 + 351 + 338

280-305 + 351 + 338-312

201-273-280-308 + 313-333 + 313-337 + 313

The methoxyphenols (also hydroxyanisols ) form a group of substances that are derived from both anisole and phenol . The structure consists of a benzene ring with attached methoxy (–OCH ₃ ) and hydroxy (–OH) groups as substituents . Their different arrangements ( ortho , meta or para ) result in three constitutional isomers with the empirical formula C ₇ H ₈ O ₂ . First and foremost, they can be viewed as methoxy-substituted phenols. They can also be understood as monomethyl ethers of dihydroxybenzenes ( pyrocatechol , resorcinol and hydroquinone ). The 2-methoxyphenol is known by its common name guaiacol .

properties

4-methoxyphenol has the highest melting point due to the greatest molecular symmetry. The methoxy group has little influence on the acidity of the phenolic OH group , the pK _s values have only minor differences to the phenol (9.99) on.

presentation

The methoxyphenols can be prepared from the anisidines by boiling their diazonium salts .

They can also be prepared from the dihydroxybenzenes ( pyrocatechol , resorcinol and hydroquinone ) by etherification with dimethyl sulfate . Dimethoxybenzenes are also formed as by-products .

use

4-methoxyphenol is used as an inhibitor to stabilize monomeric acrylates . The abbreviation MEHQ is also used for this.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
↑ Guaiacol data sheet from Sigma-Aldrich , accessed on May 3, 2011 ( PDF ).

↑ 3-Methoxyphenol data sheet from Sigma-Aldrich , accessed on November 7, 2016 ( PDF ).

↑ Data sheet 4-methoxyphenol from Sigma-Aldrich , accessed on November 7, 2016 ( PDF ).

^ Association of authors: Organikum , 19th edition, Johann Ambrosius Barth, Leipzig · Berlin · Heidelberg 1993, ISBN 3-335-00343-8 , p. 564.

^ Association of authors: Organikum , 19th edition, Johann Ambrosius Barth, Leipzig · Berlin · Heidelberg 1993, ISBN 3-335-00343-8 , p. 209.

[CRC-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .

[Sigma_2-2] Guaiacol data sheet from Sigma-Aldrich , accessed on May 3, 2011 ( PDF ).

[Sigma_3-3] 3-Methoxyphenol data sheet from Sigma-Aldrich , accessed on November 7, 2016 ( PDF ).

[Sigma_4-4] Data sheet 4-methoxyphenol from Sigma-Aldrich , accessed on November 7, 2016 ( PDF ).

[ORGANIKUM_19_564-5] Association of authors: Organikum , 19th edition, Johann Ambrosius Barth, Leipzig · Berlin · Heidelberg 1993, ISBN 3-335-00343-8 , p. 564.

[ORGANIKUM_19_209-6] Association of authors: Organikum , 19th edition, Johann Ambrosius Barth, Leipzig · Berlin · Heidelberg 1993, ISBN 3-335-00343-8 , p. 209.