formic acid

The simplest fatty acid

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Formic acid is an organic substance with the chemical formula of HCOOH, molecular weight of 46.03, commonly known as formic acid, which is the simplest carboxylic acid 。 It is a colorless and pungent liquid. Formic acid belongs to Weak electrolyte However, its aqueous solution is weak acidic and corrosive, which can stimulate skin blistering. It usually exists in the secretion of bees, some ants and caterpillars. It is an organic chemical raw material and also used as disinfectant and preservative 。^[1]

Chinese name: formic acid^[11]
Foreign name: Formic acid^[11]
Alias: Formic acid
chemical formula: CH two O two
molecular weight: forty-six point zero three
CAS login number: 64-18-6
EINECS login number: 200-001-8
Melting point: 8.2 to 8.4 ℃
Boiling point: 100.6 ℃
Density: 1.22 g/cm³
Appearance: Colorless transparent fuming liquid with strong pungent smell

Flash point: 69 ℃
Security description: S45；S26；S23；S36/37/39
Hazard description: R35
Refractive index: one point three seven one four
MDL No: MFCD00003297
RTECS No: LQ4900000
BRN No: one million two hundred and nine thousand two hundred and forty-six
PubChem No: twenty-four million eight hundred and seventy-three thousand two hundred and forty-three
InChI: 1S/CH2O2/c2-1-3/h1H,(H,2,3)
Solubility: Soluble in water, ethanol, ether, benzene and other organic solvents^[1]
Structural: HCOOH

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A brief history of research

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Formic acid was first introduced by J- 50. For Gai Lvsak oxalate It is made by decomposition. From 1855 to 1856, M. Beiteluo used sodium hydroxide And carbon monoxide Directly made Sodium formate , T. Goldschmidt was the first to obtain formic acid from sodium formate by hydrolysis. This method was used for industrial production in Europe in 1896, and it is still used for small batch production today. In 1980, American Scientific Design Corporation, Bethlehem Steel Corporation and Leonard Corporation successfully developed methanol Carbonylation The method of producing formic acid has been put into operation in a factory with an annual output of 20 thousand tons of formic acid. In addition, formic acid can also be Light oil Oxidation acetic acid It is recovered from the by-product of.^[2]

Physical and chemical properties

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physical property

Solubility	It can be freely miscible with water, ethanol, ether and glycerin, and is miscible with most polar organic solvents. It also has a certain solubility in hydrocarbons.
solid state	Formic acid solution with high concentration is easy to freeze in winter.^[1]
Relative density (20 ℃, 4 ℃)	one point two two zero
Refractive index	one point three seven one four
Heat of combustion	254.4 kJ/mol
critical temperature	306.8 ℃
critical pressure	8.63 MPa^[11]
flash point	68.9 ℃ (open cup)
density	1.22 g/cm three
Saturated vapor pressure (24 ℃)	5.33 kPa^[11]
Viscosity (mPa · s, 25 º C)	one point nine six six^[11]
Viscosity (mPa · s, 30 º C)	one point four four three^[11]
Evaporation heat (kJ/mol, 25 º C)	nineteen point nine zero^[11]
Heat of evaporation (kJ/mol, b.p.)	twenty-three point one nine^[11]
Melting heat (kJ/mol)	twelve point six nine^[11]
Heat of generation (kJ/mol, 25 º C, liquid)	-425.04^[11]
Specific heat capacity (kJ/(kg · K), 26.68 º C, constant pressure)	two point one five^[11]
Thermal conductivity (W/(m · K), 15 º C)	thirteen point nine one four eight^[11]
Thermal conductivity (W/(m · K), 30 º C)	thirteen point eight four five six^[11]
Thermal conductivity (W/(m · K), 60 º C)	thirteen point seven seven four four^[11]
Thermal conductivity (W/(m · K), 90 º C)	thirteen point six zero three three^[11]
Octanol /Logarithm of water partition coefficient	-0.54^[11]
Upper explosive limit（ V / V ）	57%^[11]
Lower explosive limit（ V / V ）	18%
Molar refractive index	eight point four zero^[11]
Molar volume (cm three /mol）	thirty-nine point eight^[11]
Isotonic specific volume (90.2 K)	ninety-seven point five^[11]
Surface tension (dyne/cm)	thirty-five point eight^[11]
Polarization (10 -24 cm three ）	three point three three^[4]

In hydrocarbon and gaseous state, formic acid appears as dimer through hydrogen bond. In the gaseous state, hydrogen bonding causes formic acid gas to interact with Ideal gas equation of state There is a large deviation between them. Liquid and solid formic acid consists of formic acid molecules that are continuously bonded by hydrogen bonds. Because of the special structure of formic acid, one of its hydrogen atoms is directly connected with the carboxyl group. It can also be regarded as a hydroxy formaldehyde.^[5]

chemical property

1. Acidity of formic acid

Formic acid is the only fatty acid with hydrogen atom attached to the carboxyl group. The electron repulsion force of the hydrogen atom is far less than that of the hydrocarbon group, which makes the electron density of the carbon atom of the carboxyl group lower than that of other carboxylic acids. Because of the conjugation effect and the electron on the oxygen atom of the carboxyl group is more carbon oriented, the acidity of formic acid is stronger than that of other carboxylic acids in the same series. Formic acid has carboxylic acid With the same properties, formic acid will not be generated under normal circumstances Acyl chloride perhaps Acid anhydride 。 Formic acid is a weak monoacid in aqueous solution, Acidity coefficient (pKa)=3.75 (at 20 ℃) The pH value of 1% formic acid solution is 2.2.^[2]

The following are the properties of formic acid:

Reaction with alkali

Formic acid has the property of acid, so it can neutralize with alkali to generate formate and water.

Reaction of formic acid and ammonia: HCOOH+NH three ·H two O = =HCOONH four +H two O

Formic acid and sodium hydroxide: HCOOH+NaOH=HCOONa+H two O

Formic acid and copper hydroxide: 2HCOOH+Cu (OH) two = Cu(HCOO) two +2H two O

Formic acid and calcium hydroxide: 2HCOOH+Ca (OH) two = Ca(HCOO) two +2H two O

Reaction with salt

Formic acid can also react with some salts.

Formic acid and sodium carbonate: 2HCOOH+Na two CO three = 2HCOONa+H two O+CO two ↑

Formic acid and calcium carbonate: 2HCOOH+CaCO three = Ca(HCOO) two +H two O+CO two ↑

React with metal

Due to the nature of weak acid, formic acid is corrosive to many metals, such as magnesium and zinc, which react to generate hydrogen and metal formate.

Formic acid reacts with sodium: 2HCOOH+2Na=2HCOONa+H two ↑

Reaction of formic acid and zinc: 2HCOOH+Zn=Zn (COOH) two +H two ↑

Formic acid reacts with magnesium: 2HCOOH+Mg=Mg (COOH) two +H two ↑^[5]

2. Fade potassium permanganate

Formic acid has similar reducibility to aldehyde, while acidic potassium permanganate has strong oxidization, so they can undergo redox reaction to fade potassium permanganate solution.^[5]

3. Decomposition reaction

Formic acid in concentrated sulfuric acid Of Catalysis Lower heating decomposition into CO and H two O。^[5]

4. Silver mirror reaction

Formic acid is a strong reducing agent, which can Silver mirror reaction , the silver ion in the silver ammonia complex ion is reduced to metallic silver, and is oxidized to carbon dioxide And water.^[5]

5. Addition reaction

Formic acid is the only carboxylic acid capable of addition reaction with olefins. Formic acid is affected by acid (such as sulphuric acid ， hydrofluoric acid ）, and olefin Rapid reaction to form formate. However, side reactions similar to Koch reaction can also occur, and the products are higher carboxylic acid 。^[5]

6. Esterification reaction

Formic acid and alcohols can undergo esterification reaction under the action of concentrated sulfuric acid and heating. If formic acid and methanol are catalyzed by concentrated sulfuric acid and heated, esterification reaction can occur to generate Methyl formate 。^[5]

7. Reduction reaction

Formic acid can be reduced to formaldehyde 。^[5]

8. Complete combustion of formic acid

High purity formic acid can be completely burned under oxygen, which will generate carbon dioxide and water.^[9]

Preparation method

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Laboratory method

Without water Glycerol Medium heating oxalate , rear steam Distillation.

Or on hydrochloric acid Hydrolysis of isobutyronitrile under action yields:^[5]

Industrial process

1、 Sodium formate method: carbon monoxide reacts with sodium hydroxide solution at 160-200 ℃ and 2 MPa pressure to produce sodium formate, and then the finished product is obtained through sulfuric acid hydrolysis and distillation.^[5]

2、 Methanol carbonyl synthesis method (also known as methyl formate method): methanol and carbon monoxide react in the presence of catalyst sodium methoxide to generate methyl formate, and then hydrolyze to generate formic acid and methanol. Methanol can be recycled into methyl formate reactor, and formic acid can be rectified to obtain products of different specifications.

3、 Formamide method: carbon monoxide reacts with ammonia in methanol solution to produce formamide, which is then hydrolyzed in the presence of sulfuric acid to obtain formic acid, and ammonium sulfate is also by-product. Raw material consumption quota: methanol 31 kg/t, carbon monoxide 702 kg/t, ammonia 314 kg/t, sulfuric acid 1010 kg/t.

4、 The industrial grade formic acid is prepared by the reaction of sodium formate and concentrated sulfuric acid, and then can be used activated carbon adsorption After vacuum distillation, the pure product is obtained.

5、 Carbon dioxide method: under the catalysis of palladium complex Triethylamine In aqueous solution, carbon dioxide reacts with hydrogen at 140~160 ℃.^[4]

Refining method

1. Anhydrous formic acid can be directly fractionated under reduced pressure. During fractionation, it is cooled and condensed with ice water. For aqueous formic acid, anhydrous copper sulfate can be used as desiccant. Available for 88% reagent grade formic acid Phthalic anhydride Remove the water by distillation after refluxing for 6 hours. Further purification can be achieved by fractional crystallization. When formic acid and acetic acid are mixed together, aliphatic hydrocarbon can be added for azeotropic distillation separation.

2. Mix formic acid with Phosphorus pentoxide Mix, conduct vacuum distillation, and repeat 5-10 times to obtain anhydrous formic acid, but the amount is low and takes a long time, which will cause some decomposition. The distillation of formic acid and boric acid alcohol is simple and effective. The boric acid is dehydrated at high temperature until no bubbles are generated. The resulting molten material is poured onto the iron sheet, cooled in a dryer, and then ground into powder. Add boric acid phenol fine powder to formic acid, place it for several days to form a hard block, separate clear liquid for vacuum distillation, and collect 22-25 ℃/12-18 mm fraction as the product. The distiller shall be fully ground joint and protected by drying tube.^[4]

application area

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Formic acid is one of the basic organic chemical raw materials, which is widely used in pesticide, leather, dye, medicine, rubber and other industries. Formic acid can be directly used in fabric processing, tanning, textile printing and dyeing, and storage of green fodder, as well as Metal surface treatment agent 、 Rubber additive and Industrial solvent 。 stay Organic synthesis It is used in the synthesis of various formate esters, acridine dyes and formamide series of pharmaceutical intermediates. The specific classification is as follows:

1. Pharmaceutical industry: can be used for caffeine 、 Analgin 、 Aminopyrine 、 aminophylline 、 Theobromine borneol 、 Vitamin B1 、 metronidazole 、 Mebendazole Processing of.

2. Pesticide industry: can be used for Triadimefon 、 Triadimefon 、 Tricyclazole 、 Triazole 、 Triazophos 、 Paclobutrazol 、 Uniconazole 、 Insecticidal ether 、 Dicofol Processing of.

3. Chemical industry: manufacturing various formates Formamide 、 Pentaerythritol 、 Neopentyl glycol 、 Epoxidized soybean oil 、 Epoxy octyl soybean oleate 、 Pivaloyl chloride 、 Paint remover 、 phenolic resin Raw materials.

4. Leather industry: used as tanning agent, deliming agent and neutralizer for leather.

5. Rubber industry: used for processing natural rubber coagulant and manufacturing rubber antioxidant.

6. CO is produced in the laboratory. Chemical reaction formula:

8. Determination of cerium, rhenium and tungsten. Test aromatic primary amine, secondary amine and methoxy group. The relative molecular weight and crystalline solvent methoxy group were determined. Used as fixative in microscopic analysis.

9. Formic acid and its aqueous solution can dissolve many metals, metal oxides, hydroxides and salts. The generated formate can be dissolved in water, so it can be used as a chemical cleaning agent. Formic acid does not contain chloride ion and can be used for cleaning equipment containing stainless steel materials.^[2]

10. It is used to mix apple, papaya, jackfruit, bread, cheese, cheese, cream and other edible essences as well as essences for whisky and rum. The concentration in the final flavored food is about 1~18 mg/kg^[3] 。

11. Others: It can also manufacture printing and dyeing mordant, dyeing agent, treatment agent, plasticizer, food preservation, animal feed additive and reducing agent for fiber and paper.

Calculate chemical data

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Drainage parameter calculation reference value (XlogP)	-0.2
Number of hydrogen bond donors	one
Number of hydrogen bond receptors	two
Number of rotatable chemical bonds	zero
Number of tautomers	zero
Topological molecular polar surface area (TPSA)	thirty-seven point three
Number of heavy atoms	three
surface charge	zero
Complexity	ten point three
Number of isotope atoms	zero
Determine the number of atomic geometric centers	zero
Number of atomic geometric centers in uncertainty	zero
Determine the number of chemical bond stereocenters	zero
Number of uncertain chemical bond stereocenters	zero
Number of covalent bond units	one^[4]

Safety measures

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Health hazards

It mainly causes irritation of skin and mucous membrane. Contact may cause conjunctivitis, eyelid edema, rhinitis, bronchitis, or even acute chemical pneumonia. After oral administration, concentrated formic acid can corrode oral and digestive tract mucosa, causing vomiting, diarrhea, gastrointestinal bleeding, and even death due to acute renal failure or respiratory failure. Skin contact can cause inflammation and ulcers. Allergic reaction occasionally.^[10]

First aid measures

Exposure	First aid measures
inhalation	Quickly leave the site to fresh air. Keep the respiratory tract unobstructed. If breathing is difficult, give oxygen. If breathing stops, perform artificial respiration immediately. Get medical attention.
Misingestion	Rinse with water and drink milk or egg white. Get medical attention.
Skin contact	Take off the contaminated clothes immediately and wash them with plenty of flowing water for at least 15 minutes. Get medical attention.
Eye contact	Immediately lift the eyelid, and thoroughly flush it with a large amount of flowing water or physiological saline for at least 15 minutes. Get medical attention.^[10]

Leakage treatment

Evacuate the personnel in the leakage contaminated area to a safe area quickly, isolate them, and strictly restrict access. Cut off the ignition source. It is recommended that emergency treatment personnel wear self-contained positive pressure respirators and acid and alkali resistant work clothes. Do not touch the leakage directly. Cut off the leakage source as much as possible. Prevent from flowing into restricted spaces such as sewers and flood discharge ditches.

Small amount of leakage: absorb or absorb with sand or other incombustible materials. The floor can also be sprinkled with soda ash, and then washed with a large amount of water, which will be diluted and put into the waste water system.

Large amount of leakage: build a dike or dig a pit to receive. Cover with foam to reduce steam disaster. Spray water cooling and dilution steam. Transfer to tank car or special collector with pump, and recycle or transport to waste disposal site for disposal.^[10]

Protective measures

Protective parts	Protective measures
engineering control	The production process is closed and ventilation is strengthened. Provide safety shower and eyewash equipment.
respiratory system protection	In case of possible contact with its vapor, you must wear a self-priming filtering gas mask (full face mask) or a self-priming long tube mask. In case of emergency rescue or evacuation, it is recommended to wear an air respirator.
Eye protection	The respiratory system has been protected.
Body protection	Wear rubber acid and alkali resistant clothes.
Hand protection	Wear rubber acid and alkali resistant gloves.
Other protection	Smoking, eating and drinking are prohibited at the work site. After work, take a shower and change clothes. Pay attention to personal hygiene.

Fire fighting measures

Hazard characteristics: combustible; Its vapor and air can form explosive mixture, which can cause combustion and explosion when encountering open fire and high heat. Chemical reaction may occur in contact with strong oxidant. It is highly corrosive.

Hazardous combustion products: carbon monoxide

Extinguishing agent: insoluble foam, dry powder, carbon dioxide.

Precautions for fire extinguishing: firefighters must wear full body protective clothing and oxygen respirators to extinguish the fire. Use water to keep the fire site container cool, and spray water to protect the personnel who are plugging.^[10]

environmental effect

Ecotoxicity: LC fifty : 175 mg/L (24 h) (bluegill sunfish); 46 mg/L (96 h) (goldfish); 122 mg/L (48 h) (golden round bellied yala, static); 34 mg/L (48 h) (Daphnia).

Biodegradability: MITI-I test, the initial concentration is 100 ppm, the sludge concentration is 30 ppm, and the degradation is 100% after 2 weeks.

Non biodegradable: in the air, when the concentration of hydroxyl radical is 5.00 × 10 five Pcs/cm three The half-life of degradation is 36 d (theoretical)^[4] 。

security information

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Safety instructions	S23: Do not breathe vapor.
	S26: In case of contact with eyes, immediately flush with plenty of water and send to a doctor for treatment.
	S45: In case of accident or discomfort, go to the doctor immediately for help (it is better to bring the product container label).
	S36/37/39: Wear appropriate protective clothing, gloves and eye/face protection^[4] 。
Hazard Category Code	R35: Causes serious burns.

Toxicological data

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acute toxicity	LD fifty : 1100 mg/kg (rat oral)
acute toxicity	LC fifty ：15000 mg/m three (Inhalation of rats, 15 min)
thrill	Rabbit percutaneous: 610 mg, mild stimulation (open stimulation test).
thrill	Rabbit eye: 122 mg, severe irritation.
Subacute and chronic toxicity	The drinking water of mice contains 0.01%~0.25% free formic acid. If there is no effect of 0.5% within 2~4 months, it will affect appetite and slow growth. Mice inhaled 10 g/m three They died after 1-4 days.
Mutagenicity	Microbial mutagenicity: Escherichia coli 70 ppm (3 h).
	Sister chromatid exchange: human lymphocytes 10 mmol/L.
	Cytogenetic analysis: hamster ovary 10 mmol/L.

Storage and transportation

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Storage method

Store in a cool and ventilated warehouse. Keep away from kindling and heat sources. The storage temperature shall not exceed 30 ℃, and the relative humidity shall not exceed 85%. Keep container sealed. It shall be stored separately from oxidant, alkali and active metal powder, and mixed storage is strictly prohibited. Equip with corresponding types and quantities of fire-fighting equipment. The storage area shall be equipped with leakage emergency treatment equipment and appropriate materials.^[4]

Transport method

The railway transportation shall be carried out in strict accordance with the dangerous goods loading table in the Dangerous Goods Transportation Rules of the Ministry of Railways. The package shall be complete and the loading shall be stable when the goods are shipped. During transportation, the container shall not leak, collapse, fall or be damaged. It is strictly prohibited to mix with oxidants, alkalis, active metal powders, edible chemicals, etc. During transportation, the transportation vehicles shall be equipped with corresponding types and quantities of fire-fighting equipment and leakage emergency treatment equipment. During transportation, it shall be protected from sun exposure, rain and high temperature. Road transportation shall be carried out according to the specified route, and do not stay in residential areas and densely populated areas.^[4]

Executive standards

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GB/T 2093-2011 Formic Acid for Industrial Use^[6]

Formic acid content: use phenolphthalein as indicator and titrate with sodium hydroxide solution.

Chloride: in the nitric acid acid solution, the chloride ion in the sample and silver nitrate generate silver chloride, which is turbid with the standard turbidimetric solution.

Sulfate: add sodium carbonate in the sample to make sulfate radical in formic acid generate sulfate, and add barium chloride solution in the presence of hydrochloric acid to generate barium sulfate , turbidimetric with standard turbidimetric solution.^[8]

Iron (Fe 2+ ）: According to GB/T 3049-2006.^[7]

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