Ethyl 4-hydroxybenzoate

Structural formula
General
Surname	Ethyl 4-hydroxybenzoate
other names	Ethyl 4-hydroxybenzoate ( IUPAC , Ph.Eur. ) Ethyl p -hydroxybenzoate Ethyl para- hydroxybenzoate PHB ethyl ester ETHYLPARABEN ( INCI ) E 214 Nipagin A
Molecular formula	C 9 H 10 O 3
Brief description	colorless, crystalline solid
External identifiers / databases
CAS number 120-47-8 EC number 204-399-4 ECHA InfoCard 100,004,000 PubChem 8434 Wikidata Q229976
properties
Molar mass	166.18 g · mol -1
Physical state	firmly
density	1.25 g cm −3 (20 ° C)
Melting point	116-118  ° C
boiling point	297 ° C (decomposition)
Vapor pressure	5.78 · 10 −2 Pa (50 ° C)
solubility	poor in water (1.7 g l −1 at 25 ° C) readily soluble in diethyl ether, methanol, ethanol, propylene glycol and acetone
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	3000 mg kg −1 ( LD 50 ,  mouse ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

4-hydroxybenzoic acid ethyl ester , also para -Hydroxybenzoesäureethylester ( PHB ethyl ester ) is the ethyl ester of the aromatic carboxylic acid 4-hydroxybenzoic acid and one of the parabens .

properties

The melting point is 115.8 ° C with a melting enthalpy of 158.6 J · g ⁻¹ . The compound crystallizes in a monoclinic crystal lattice with the space group C2 / c . The vapor pressure function results according to August according to ln (P) = −A / T + B (P in Pa, T in K) with A = 34.7 ± 0.2 and B = 12132 ± 80 in the temperature range from 40 ° C to 53 ° C. A molar enthalpy of sublimation of 100.9 kJ · mol ⁻¹ can be derived from the vapor pressure function . The solubility in water is low, in organic solvents it is rather very good.

The absorption maximum λ _max is 256 nm.

Solubility in various solvents (at 25 ° C, in g / 100 g solvent)
solvent	water	Water (80 ° C)	Methanol	Ethanol	Propylene glycol	acetone	Diethyl ether	peanut oil
solubility	0.17	0.86	115	70	25th	84	43	1.0

The ethyl 4-hydroxybenzoate forms eutectic melting mixtures with other 4-hydroxybenzoic acid esters .

Eutectics for mixtures of 4-hydroxybenzoic acid esters
	Methyl paraben	Propyl paraben	Butyl paraben
Mole fraction of ethyl paraben	0.54	0.40	0.24
Eutectic melting point	88.5 ° C	76.0 ° C	58.3 ° C

use

Ethyl 4-hydroxybenzoate is used as a preservative and can be found, for example, in shampoos , shower gels and other cosmetics . It is also used in research to prevent undesirable fungal growth on bacteriological agar plates . In the food industry, the PHB ester is one of the conditionally approved preservatives and antioxidants.

PHB ethyl ester is approved in the EU as a food additive with the number E 214 . The sodium salt ( sodium ethyl p- hydroxybenzoate , E 215 ) is usually used because of its better solubility .

Parabens in general can cause pseudo- allergic reactions in humans, especially asthmatics , such as: B. hives or asthmatic attacks.

Safety instructions / toxicology

4-Hydroxybenzoic acid ethyl ester was included in 2017 by the EU in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation in the Community's ongoing action plan ( CoRAP ). The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The reason for the uptake of ethyl 4-hydroxybenzoate was concerns as a potential endocrine disruptor . The reassessment is to be carried out by Germany from 2021 .

Individual evidence

1. ↑ Entry on ETHYLPARABEN in the CosIng database of the EU Commission, accessed on December 28, 2019.
2. ↑ ^{a b c d e f} Entry on ethyl 4-hydroxybenzoate in the GESTIS substance database of the IFA , accessed on December 16, 2019(JavaScript required) .
3. ↑ ^{a b c d e} Giordano, F .; Bettini, R .; Donini, C .; Gazzaniga, A .; Caira, MR; Zhang, GGZ; Grant, DJW: Physical properties of parabens and their mixtures: Solubility in water, thermal behavior, and crystal structures in J. Pharm. Sci. 88 (1999) 1210-1216, doi : 10.1021 / js9900452 .
4. ↑ ^{a b c} Perlovich, GL; Rodionov, SV; Bauer-Brandl, A .: Thermodynamics of solubility, sublimation and solvation processes of parabens in Eur. J. Pharm. Sci. 24 (2005) 25-33, doi : 10.1016 / j.ejps.2004.09.007 .
5. ↑ ^{a b c} Entry on 4-hydroxybenzoates. In: Römpp Online . Georg Thieme Verlag, accessed on July 10, 2016.
6. ↑ Entry on ethyl 4-hydroxybenzoate in the ChemIDplus database of the United States National Library of Medicine (NLM) .
7. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Ethyl 4-hydroxybenzoate , accessed on March 26, 2019.