Dimethyl sulfate is a liquid with a boiling point of 188.5 ° C and almost no odor. Both gaseous and liquid dimethyl sulfate are highly toxic and should be used in fume hoods and rubber gloves. Inhalation of gaseous dimethyl sulfate can cause dizziness and even poisoning, and liquid dimethyl sulfate can penetrate the skin and cause poisoning. If liquid dimethyl sulfate is accidentally spilled on your hands, immediately rinse it with concentrated ammonia water, decompose it before it penetrates the skin, and then gently wipe it with a cotton pad soaked in ammonia.
The toxicity of diethyl sulfate is weaker than that of dimethyl sulfate, but the same precautions should be taken during use and handling. All operations should be carried out with rubber gloves in a fume hood. If diethyl sulfate is black, it should be washed in ice separator with a separatory funnel and then washed with sodium bicarbonate until it is not acidic. Finally, it is dried with calcium oxide and fractionated to collect a fraction of 93 ° C / 1.7 kPa .
27 . Chlorine gas
Chlorine is a highly irritating irritating gas that must be handled and used in a well ventilated fume hood. For the use of large amounts of chlorine, commercially available cylinder chlorine can be used. The gas can be dried by two gas cylinders filled with concentrated sulfuric acid and then passed through a glass wool-filled gas cylinder to remove the acid mist. A small amount of chlorine can be obtained by the reaction of potassium permanganate and concentrated hydrochloric acid in the apparatus shown in Figure 2. The amount of potassium permanganate (about 0.9 g of KMnO4 for 1 g of Cl2 ) was calculated based on the mass of chlorine required and added to a round bottom flask. A slight excess of concentrated hydrochloric acid was placed in a constant pressure dropping funnel ( 1 g of KMnO 4 required 6.2 mL of concentrated hydrochloric acid) and then the constant pressure funnel was stoppered and the piston was fitted with a rubber band. The chlorine is passed through a water-filled gas cylinder to remove HCl , and then dried by another gas cylinder containing concentrated sulfuric acid, preferably a safety bottle is placed between the reactor and the drying device. Hydrochloric acid should be slowly added dropwise to the permanganate crystals and the flask was continually shaken. When the acid is added in half, the volatilization rate of the gas is gradually lowered. At this time, the flask should be slightly heated, and after the acid is added, the mixture is heated to a slight boiling to completely evaporate the chlorine.
Figure 2 chlorine gas preparation device
28 . Chloroform
Chloroform has a boiling point of 61.2 °C and a density of d = 1.4916 . It is insoluble in water and easily decomposes into Cl2 , HCl , CO2 and phosgene (very toxic) in sunlight. It should be stored in a brown bottle. The chloroform supplied on the market is 1% more . Ethanol to eliminate phosgene, ethanol in chloroform can be tested by iodoform, free hydrogen chloride can be used to test the alcohol solution of AgNO3 .
Purification of chloroform: first remove the ethanol with concentrated sulfuric acid, then dry with anhydrous calcium chloride, and finally carry out distillation. Chloroform will explode in the presence of sodium metal and cannot be dried with sodium metal.
29 . Chlorosulfonic acid ( ClSO3H )
Care must be taken when handling chlorosulfonic acid, which is highly corrosive to skin and clothing and reacts violently with water. If impure reagent, distillation can be performed in all-glass apparatus, the fraction boiling at 148 ~ 150 ℃ / 100kPa, the fraction moistureproof measure to deal with.
30 . Stannous chloride
Anhydrous stannous chloride is easily soluble in acetone and 1 -pentanol, soluble in anhydrous methanol and absolute ethanol; insoluble in benzene, toluene, xylene and chloroform. As long as there is a trace amount of water, it immediately hydrolyzes to form a milky precipitate.
The crystalline stannous chloride ( SnCl2?2H2O ) is heated in an oil bath at 195 to 200 °C for 1 hour, and the melt is cooled to become a powder. It can be stored in a desiccator or a stoppered bottle. The obtained product is in many experiments. Can meet the requirements.
Use the following procedure to obtain a better anhydrous stannous chloride: Add 102 g ( 89.5 mL , 1 mol ) of freshly distilled acetic anhydride to a 400 mL beaker, 123 g of analytically pure SnCl2?2H2O ( 0.5 mol ) The crystals are immediately dehydrated, exothermic, and the acetic anhydride boils. After 1 hour, anhydrous stannous chloride was filtered through a Buchner funnel or a fritted glass funnel, washed with two portions of 30 mL of anhydrous ether to remove acetic anhydride, and then dried overnight in a desiccator. Can be stored in a desiccator or in a stoppered bottle.
31 . Cuprous chloride
35 g ( 0.14 mol ) of ketone pentahydrate and 9.2 g ( 0.175 mol ) of pure sodium chloride were dissolved in 125 mL of water and dissolved warmly. Add 8.4 g ( 0.044 mol ) of sodium thiosulfate dissolved in 90 mL of water for 5 min , vortex continuously, cool to room temperature (if necessary, use an ice bath), separate the upper liquid from the white cuprous chloride. The precipitate was washed twice with water in which a small amount of sulfur dioxide was dissolved (sulfur dioxide was used to prevent oxidation of the product). The moist cuprous chloride is dissolved in 60 mL of concentrated hydrochloric acid, which must be used within 24 hours after preparation because it is easily oxidized. If not used immediately, store the solution in a tightly closed bottle. If the use of dry cuprous chloride, sulfur dioxide may be washed cuprous chloride aqueous wet solid was then filtered using a Buchner funnel, washed several times with a small amount of acetic acid, and then to 100 ~ 120 ℃ baked in an oven Dry until there is no longer a smell of glacial acetic acid. The pure white cuprous chloride was obtained and stored in a stoppered bottle, and the yield was almost quantitative.
32 . Hydrogen chloride
Production Method 1 : Prepared from concentrated sulfuric acid and molten ammonium chloride. Hydrogen chloride is produced by reacting concentrated sulfuric acid with molten bulk ammonium chloride in a chirp generator. The gas is dried by a gas cylinder containing concentrated sulfuric acid. The dry bottle should be connected to a safety bottle to prevent back suction.
Preparation Method 2 : Prepared from concentrated sulfuric acid and concentrated hydrochloric acid. The device is shown in Figure 3. The upper funnel has a volume of 100 mL and a large enough glass tube is inserted into the outlet. The following dropping funnel has a volume of 500 mL . The gas bottle A is filled with concentrated sulfuric acid, and the other gas bottle is used as a safety bottle. All the devices must be installed on a stable iron stand.
Approximately 150 mL of concentrated sulfuric acid was placed in the lower funnel. The upper separatory funnel was filled with 100 mL of concentrated hydrochloric acid. The long neck of the funnel was near the bottom of the funnel below. Lift the small funnel up until the glass tube is on the surface of the sulfuric acid solution, carefully inject concentrated hydrochloric acid into the glass tube, and then insert the funnel into the joint. At this time, the evaporation rate of hydrogen chloride is determined by the dropping speed of concentrated hydrochloric acid, and the reaction can be diluted. The sulfuric acid is released and the device is re-installed. The production of hydrogen chloride is 31 to 33 g/100 mL of concentrated hydrochloric acid. The funnel below can also be replaced by a flask, which is better with electromagnetic stirring.
Figure 3 Hydrogen chloride generator
33 . sodium
Care must be taken when handling sodium. Under any conditions, it should not be in contact with water. Sodium should be stored in kerosene or paraffin. Do not touch metal sodium by hand. Unused sodium should be placed in a container filled with kerosene or paraffin. Do not throw it in a sink or trash can. If the small sodium block is to be disposed of, the small sodium block can be put into a large amount of industrial alcohol in batches. The surface of the sodium is always covered with a non-metallic layer. It is scraped off with a knife in an inert solvent (such as diethyl ether, xylene) before use, but it is quite wasteful; the sodium block can also be immersed in xylene. In a large conical flask, carefully heat and gently agitate until the sodium melts and separates from the oxide layer on the surface. The conical flask is removed from the hot plate and cooled. The molten sodium solidifies into a small spherical shape, which is then taken out with a spatula and immersed in a freshly prepared inert solvent. The residue layer washed with xylene can be safely decomposed by immersion in industrial alcohol.
Sodium sand was prepared by adding 23 g of clean sodium and 150 to 200 mL of dry xylene in a 1 L three-necked flask equipped with a reflux condenser (with a soda lime drying tube), a sealed stirring and a dropping funnel. Heat to a slight reflux, start stirring until the sodium is granular, the flask is cooled to room temperature, stirring is stopped, xylene is decanted, and the sodium sand is washed with 2 parts of 100 mL of dry diethyl ether to remove residual xylene. A large amount of sodium sand is obtained.
34 . hydrogen
Commercially available cylinders of hydrogen are used in the laboratory, and the high purity hydrogen content can reach 99.99% . It can also be prepared by reacting an active metal with a dilute acid. Ordinary hydrogen contains a small amount of nitrogen, oxygen, water and hydrocarbons. To remove oxygen from hydrogen, deaerator can be removed with Fieser 's solution (see Section 8 Nitrogen in this section), then passed to a wash bottle containing concentrated sulfuric acid, and A small amount of silver sulfide is added to the bottle, and the silver sulfide removes the hydrogen sulfide decomposed from the Fieser's solution.
35 . Hydroiodic acid
Hydroiodic acid is an aqueous azeotrope containing 55 to 57% hydrogen iodide, boiling point 122.5 to 126.5 °C , relative density d = 1.07 (including HI 0.936 to 0.99 g/mL ), and concentrations of 45% and 67. % of hydriodic acid. The addition of 67% hydriodic acid to 0.03% hypophosphorous acid is more stable. If the bottle is left open for a few days, the hydriodic acid solution will deteriorate and should be sealed and filled with nitrogen before sealing.
The preparation method of hydriodic acid is as follows: 480 g of iodine and 600 mL of water are added to a 1.5 L three-necked flask in a fume hood, the middle bottle is filled with mechanical stirring, and the other bottle is introduced into a tube to introduce hydrogen sulfide gas into the bottle. Under the surface of the liquid. The outlet tube was connected to an inverted funnel which was extended to the surface of a 5% NaOH solution. The reactant was stirred vigorously, and hydrogen sulfide gas was introduced as quickly as possible according to the absorption rate of hydrogen sulfide. Hydrogen sulphide gas can be generated by a QF generator. After a few hours, the solution turns yellow (sometimes almost no color), and most of the generated sulphur is condensed into a hard block. It is filtered with a frosted glass funnel or a glass wool funnel. The remaining sulfur blocks can be added to the flask with concentrated nitric acid in a fume hood and heated to boiling to remove. The filtrate was boiled until no hydrogen sulfide gas was detected with lead acetate test paper. If necessary, it can be filtered again, then distilling hydroiodic acid in a 500 mL flask, collecting 125.5 ~ 126.5 °C / 100kPa fraction, can obtain a concentration of 57% constant boiling hydriodic acid 785 g , yield 90% .
H2S + I2 === 2 HI + S
pharmacological action
Oxytetracycline has broad-spectrum antiviral effect on microorganisms. It is a rapid bacteriostatic agent. It has bactericidal effect on some bacteria at high concentration. Its mechanism is that the drug can specifically bind to the a position of ribosomal 30S subunit and prevent the connection of aminoacyl tRNA at this position, so as to inhibit the growth of peptide chain and affect the protein synthesis of bacteria or other pathogenic microorganisms. Oxytetracycline has strong antibacterial activity against Staphylococcus aureus, pneumococcus, Streptococcus pyogenes, Neisseria gonorrhoeae, meningococci, Escherichia coli, aerogenic bacteria, Shigella, Yersinia and Listeria monocytogenes; In addition, oxytetracycline also has strong effects on Rickettsia, mycoplasma, chlamydia and actinomycetes. [3]
Pharmacokinetics
The oral absorption of oxytetracycline hydrochloride is incomplete (about 30% - 58%), and the distribution volume is about 0.9-1.9l/kg. After a single dose of 1g, the peak blood concentration was about 3.9mg/l. After absorption, the drug is widely distributed, which can penetrate into pleural effusion and peritoneal effusion, or enter fetal blood circulation through placental barrier, but it is not easy to pass through blood cerebrospinal fluid barrier, so the drug concentration in cerebrospinal fluid is low. Oxytetracycline can also be distributed in liver, spleen, bone marrow, bone, dentin and enamel, and the drug can also reach a high concentration in milk. The binding rate of oxytetracycline protein is about 20% - 35%. The half-life of patients with normal renal function is 6-10h, the half-life of patients with renal insufficiency is prolonged, and the half-life of patients without urine can reach 47-66h. Drugs are mainly excreted through glomerular filtration, 70% of the dosage can be excreted within 24 hours of administration, and a small amount of drugs are excreted through bile and feces. Hemodialysis can remove 10% - 15% of drugs. [4]
indication
1. Oxytetracycline can be used as an optional drug for the treatment of the following diseases:
(1) Rickettsia disease, including epidemic typhus, endemic typhus and tsutsugamushi disease; [3]
(2) Mycoplasma pneumoniae infection; [3]
(3) Chlamydia infection, including psittacosis, inguinal granuloma (venereal lymphogranuloma), nonspecific urethritis, salpingitis and trachoma; (4) Regressive fever; [3]
(5) Brucellosis (in combination with aminoglycosides); [3]
(6) Cholera; [3]
(7) plague (combined with aminoglycoside drugs); [3]
(8) Rabbit fever. [3]
2. Oxytetracycline can be used to treat tetanus, gas gangrene, Yasi, syphilis, gonorrhea and leptospirosis allergic to penicillin antibiotics.
3. Oxytetracycline can also be used to treat respiratory tract, biliary tract, urinary tract, skin and soft tissue infections caused by sensitive bacteria. [3]
4. Oxytetracycline can also be used in the treatment of acne. [3]
contraindication
Allergic to oxytetracycline or other tetracyclines. [3]
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