Methylparaben Chemical Properties
- Melting point:
- 125-128 °C(lit.)
- Boiling point:
- 298.6 °C
- vapor pressure
- 0.000005 hPa (20 °C)
- 2710 | METHYL P-HYDROXYBENZOATE
- refractive index
- 1.4447 (estimate)
- Flash point:
- storage temp.
- ethanol: soluble0.1M, clear, colorless
- pKa 8.15(H2O,t =20.0) (Uncertain)
- Crystalline Powder
- White to almost white
- 5.8 (H2O, 20°C) (saturated solution)
- Water Solubility
- Slightly soluble in water.
- Stable. Incompatible with strong oxidizing agents, strong bases.
- CAS DataBase Reference
- 99-76-3(CAS DataBase Reference)
- NIST Chemistry Reference
- Benzoic acid, 4-hydroxy-, methyl ester(99-76-3)
- EPA Substance Registry System
- Methylparaben (99-76-3)
Methylparaben Usage And Synthesis
Method one: determinate according to the content analysis method in "butyl p-hydroxybenzoate (07002)". Per mL 1 mol/L sodium hydroxide is equivalent to the product (C8H8O3) 152.2mg.
Method two: Take 0.1 g (accurate to 1 mg) of the sample previously dried on silica gel for 5 h and move into a 300 ml flask with a glass plug. Plus l mol/L sodium hydroxide 10ml, heated in the water bath for 15min. After cooling, add 0.1mol/L potassium bromate 0.00ml, potassium bromide 5.0g and l mol/L hydrochloric acid 30ml. Put 15min in the dark room after sealing. Add potassium iodide 1 g, shake the flask vigorously, with 0.1mol/L sodium thiosulfate titration, with starch test solution (TS-235) as an indicator. Per ml 0.1mol/L potassium bromate is equivalent to the product (C8H8O3) 25.36mg.
FAO/WHO (1984): Jam, jelly, 1000mg/kg (single or with benzoate, sorbic acid and potassium sorbate).
EEC(1990,mg/kg): For use in pigment solutions, flavor syrups, coffee extracts, frozen drinks, fruit, glucose and soft drinks, pickled fish, salad, sauce, snack food, concentrated soup and so on, limited to GMP; Beer 70; Snack cereals and soup concentrate 175, the same as "07018 p-hydroxybenzoate".
HACSG is listed as a restricted list.
White needle crystal; Slightly soluble in water, easily soluble in ethanol, ether, acetone and other organic solvents.
- Antimicrobial agents for medicine and organic synthesis.
- Anti-mildew in food, cosmetics and pharmaceutical industries.
- As a preservative antiseptic agents in the pharmaceutical industry, also for organic synthesis and food, spices, film and other preservative additives.
- Similar products produced by similar production methods, like ethyl p-hydroxybenzoate (paraben B) and propyl p-hydroxybenzoate (Nepalese c), are also disinfectant preservatives.The products are irritating to the skin.
The drug is esterified with p-hydroxybenzoic acid and methanol. The p-hydroxybenzoic acid was added to excess methanol to dissolve, stirring and adding concentrated sulfuric acid slowly. After heating and refluxing 10h, pour into the water to precipitate crystallization, then washed with water, sodium carbonate solution and water, finally obtain the crude product. Recrystallize from water or 25% ethanol to obtain finished product. The yield was 85%. Raw material consumption (kg/t): p-hydroxybenzoic acid 1200, methanol 1000.
Abdomen-mouse LD50: 960 mg/kg
Flammability hazard characteristics
Combustible, excretes spicy smoke from fireground
Ventilated , low temperature and dry warehouse.
Water, carbon dioxide, dry powder, sand.
Colorless crystals or white, crystallinepowder; odorless or faint characteristic odor; slightburning taste. Soluble in alcohol,ether; slightly soluble in water, benzene, and carbontetrachloride.
Methylparaben occurs as colorless crystals or a white crystalline powder. It is odorless or almost odorless and has a slight burning taste.
Methyl p-hydroxybenzoate is odorless or has a faint characteristic odor and a slight burning taste. Methyl p-hydroxybenzoate is more commonly known as methyl paraben and is an ester of p-hydroxybenzoic acid.
Reported present in cloudberry, yellow passion fruit juice, white wine, botrytised wine and Bourbon vanilla.
It is used as preservative in foods, beverages and cosmetics.
As preservative in foods, beverages and cosmetics.
parabens is one of the most commonly used group of preservatives in the cosmetic, pharmaceutical, and food industries. Parabens provide bacteriostatic and fungistatic activity against a diverse number of organisms, and are considered safe for use in cosmetics, particularly in light of their low sensitizing potential. An evaluation of preservatives for use in leave-on cosmetic preparations lists parabens among the least sensitizing. The range of concentrations used in cosmetics varies between 0.03 and 0.30 percent, depending on the conditions for use and the product to which the paraben is added.
Methylparaben is an antimicrobial agent which is a white free-flowing powder. it is active against yeast and molds over a wide ph range. see parabens.
ChEBI: A 4-hydroxybenzoate ester resulting from the formal condensation of the carboxy group of 4-hydroxybenzoic acid with methanol. It is the most frequently used antimicrobial preservative in cosmetics. It occurs naturally in several fruits, particularly in blu berries.
Produced by the methanol esterification of p-hydroxybenzoic acid in the presence of sulfuric acid. The materials are heated for distillation in a glass-lined reactor under reflux. The acid is then neutralized with caustic soda and the product is crystallized by cooling. The crystallized product is centrifuged, washed, dried under vacuum, milled and blended, all in corrosion-resistant equipment to avoid metallic contamination.
Methylparaben is prepared by the esterification of p-hydroxybenzoic acid with methanol.
Aroma threshold values
Detection: 2.6 ppm.
Toxic. Use in foods restricted to 0.1%.
Methylparaben is widely used as an antimicrobial preservative in
cosmetics, food products, and pharmaceutical formulations; see
Table I. It may be used either alone or in combination with other methylparaben is the most frequently used antimicrobial preservative.
The parabens are effective over a wide pH range and have a broad spectrum of antimicrobial activity, although they are most effective against yeasts and molds. Antimicrobial activity increases as the chain length of the alkyl moiety is increased, but aqueous solubility decreases; therefore a mixture of parabens is frequently used to provide effective preservation. Preservative efficacy is also improved by the addition of propylene glycol (2–5%), or by using parabens in combination with other antimicrobial agents such as imidurea;
Owing to the poor solubility of the parabens, paraben salts (particularly the sodium salt) are more frequently used in formulations. However, this raises the pH of poorly buffered formulations.
Methylparaben (0.18%) together with propylparaben (0.02%) has been used for the preservation of various parenteral pharmaceutical formulations;
This substance is one of the parabens family. Parabens are esters formed by p-hydroxybenzoic acid and an alcohol. They are largely used as biocides in cosmetics and toiletries, medicaments, or food. They have synergistic power with other biocides. Parabens can induce allergic contact dermatitis, mainly in chronic dermatitis and wounded skin.
Methylparaben and other parabens are widely used as antimicrobial
preservatives in cosmetics and oral and topical pharmaceutical
formulations. Although parabens have also been used as preservatives
in injections and ophthalmic preparations, they are now
generally regarded as being unsuitable for these types of formulations
owing to the irritant potential of the parabens. These
experiences may depend on immune responses to enzymatically
formed metabolites of the parabens in the skin.
Parabens are nonmutagenic, nonteratogenic, and noncarcinogenic. Sensitization to the parabens is rare, and these compounds do not exhibit significant levels of photocontact sensitization or phototoxicity.
Hypersensitivity reactions to parabens, generally of the delayed type and appearing as contact dermatitis, have been reported. However, given the widespread use of parabens as preservatives, such reactions are relatively uncommon; the classification of overstated. Immediate hypersensitivity reactions following injection of preparations containing parabens have also been reported.
Delayed-contact dermatitis occurs more frequently when parabens are used topically, but has also been reported to occur after oral administration.
Unexpectedly, preparations containing parabens may be used by patients who have reacted previously with contact dermatitis provided they are applied to another, unaffected, site. This has been termed the paraben paradox.
Concern has been expressed over the use of methylparaben in infant parenteral products because bilirubin binding may be affected, which is potentially hazardous in hyperbilirubinemic neonates.
The WHO has set an estimated total acceptable daily intake for methyl-, ethyl-, and propylparabens at up to 10 mg/kg bodyweight.
LD50 (dog, oral): 3.0 g/kg
LD50 (mouse, IP): 0.96 g/kg
LD50 (mouse, SC): 1.20 g/kg
The carcinogenic potential of methyl paraben has been studied in rodents. Several studies are available, but none that expose animals via oral or dermal routes. No evidence of a carcinogenic effect was observed following intravenous or subcutaneous injection .
Aqueous solutions of methylparaben at pH 3–6 may be sterilized by
autoclaving at 120°C for 20 minutes, without decomposition.
Aqueous solutions at pH 3–6 are stable (less than 10%
decomposition) for up to about 4 years at room temperature, while
aqueous solutions at pH 8 or above are subject to rapid hydrolysis
(10% or more after about 60 days storage at room temperature);
Methylparaben should be stored in a well-closed container in a cool, dry place.
Fractionally crystallise the ester from its melt, and recrystallise it from *benzene, then from *benzene/MeOH and dry it over CaCl2 in a vacuum desiccator. [Beilstein 10 IV 360.]
The antimicrobial activity of methylparaben and other parabens is
considerably reduced in the presence of nonionic surfactants, such
as polysorbate 80, as a result of micellization.However,
propylene glycol (10%) has been shown to potentiate the
antimicrobial activity of the parabens in the presence of nonionic
surfactants and prevents the interaction between methylparaben
and polysorbate 80.
Incompatibilities with other substances, such as bentonite, magnesium trisilicate,talc,tragacanth,sodium alginate, essential oils,sorbitol,and atropine,have been reported. It also reacts with various sugars and related sugar alcohols. Absorption of methylparaben by plastics has also been reported; the amount absorbed is dependent upon the type of plastic and the vehicle. It has been claimed that low-density and high-density polyethylene bottles do not absorb methylparaben.
Methylparaben is discolored in the presence of iron and is subject to hydrolysis by weak alkalis and strong acids.
Methylparaben and propylparaben are affirmed GRAS Direct Food
Substances in the USA at levels up to 0.1%. All esters except the
benzyl ester are allowed for injection in Japan. In cosmetics, the EU
and Brazil allow use of each paraben at 0.4%, but the total of all
parabens may not exceed 0.8%. The upper limit in Japan is 1.0%.
Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (IM, IV, and SC injections; inhalation preparations; ophthalmic preparations; oral capsules, tablets, solutions and suspensions; otic, rectal, topical, and vaginal preparations). Included in medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
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