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Synthesis of Nitrobenzene Pdf Synthesis of nitrobenzene pdf Continue Due to the need for benzene in this preparation, it cannot be performed in schools. The reason it is included in syllabuses as the example of electrophilic substitution is that the effect of substitutes already present on the aromatic ring need not be considered. Dangers: Benzene is flammable and carcinogenic; concentrated saltpeter and sulphuric acids are corrosive. Place 35 cm3 concentrated nitric acid in a 500 cm3 round bottom flask and slowly add 40 cm3 concentrated sulphuric acid, keeping the mixture cool during the addition by dipping the flask into cold water. Why does the mixture of acids heat up? The reaction between the acids is: HNO3 + 2H2SO4 → NO2+ + H3O+ + 2HSO4- The nitric acid contains about 30% water, and the hydration of the proton released by the sulphuric acid gives heat. Place a thermometer in this extraction mixture, then slowly add 29 cm3 benzene. This should be added about 3 cm3 at a time, and the contents of the flask thoroughly mixed after each addition. The temperature of the mixture must not exceed 50o C and should be controlled if necessary by immersing the flask in cold water. Why should the benzene be added slowly? The nitration is exothermic and the temperature should not rise too much. Explain the need to mix the ingredients thoroughly. The nitrating mixture and benzene are almost indispensable, so the mixture should be vigorously agitated so that the two phases are broken into small drops to maximize the surface of the two phases in contact. That's where reaction occurs. When all the benzene has been added, fit a reflux water condenser in the flask and place it in a water bath, which is then held at 60oC for 45 minutes. During this period, the flask must be removed from the bath from time to time and shaken vigorously to break the nitrobenzene layer that would otherwise float on the dense layer of acid underneath. Why is the mixture then heated for 45 minutes? This increases the yield by allowing time for the rather slow reaction to occur. After completion of the heating pour the contents of the flask into a large excess of cold water (about 300 cm3) in which the nitrobenzene sinks to the bottom. Stir the mixture as vigorously as possible. Decant as much of the supernatant aqueous layer as possible and transfer the residual fluid to a separation funnel. Run away and store the lower nitrobenzene layer and discard the top watery layer. Return the nitrobenzene to the funnel and shake it vigorously with an equal volume of cold water. Let the nitrobenzene separate and let it drain as before. Return it to the funnel and wash with an equal volume of diluted sodium carbonate solution, thus reducing the pressure Released. Repeat the wax with fresh sodium carbonate solution until there is no carbon dioxide. What is the function of the cold water? The acids are diluted and the reaction stopped. What is the reason for the powerful stirring? The acids are to some extent soluble in nitrobenzene, so vigorous stirring removes as much of these into the aqueous layer as possible. Why is the nitrobenzene washed with sodium carbonate solution? This reacts with and removes in the aqueous layer any residual acid dissolved in the nitrobenzene. Separate the nitrobenzene from the sodium carbonate solution completely as possible (see below), transfer it into a small flask and add some awash-free grain of calcium chloride. Shake until the liquid is completely clear. What is the function of the calcium chloride? It's a drying agent. What is the meaning of the liquid that becomes clear? The organic layer is then dry; wet organic compounds that are almost unserable with water look blurry. Filter the nitrobenzene directly into a 60cm3 distilling flask with an air condenser through a ribbed paper. Carefully distill the nitrobenzene and collect the fracture that boils between 207oC and 211oC. Why is a ribbed filter paper used? Ribbed papers allow faster filtering. What is an air condenser? A glass tube that is cooled by the surrounding air instead of by a watercoat. Why is such a condenser used? The boiling temperature of nitrobenzene is high enough to make an air capacitor efficient for condensing the vapor. Note: after washing with sodium carbonate solution it would be common to wash with water to remove any traces of sodium carbonate. However, Nitrobenzene tends to produce an emulsion when done, which takes a long time to separate, so the step is best omitted. Organic preparations index Chemistry contents Home Page © JRG Beavon 2001 Nitrobenzene Names Preferred IUPAC name Nitrobenzene Other names NitrobenzolOil of mirbane Identifiers CAS Number 98-95-3 Y 3D model (JSmol) Interactive image ChEBI CHEBI:27798 Y ChEMBL ChEMBL15750 Y ChemSpider 7138 Y ECHA InfoCard 100.002.469 KEGG C06813 Y PubChem CID 7416 RTECS number DA6475000 UNII E57JCN6SSY N CompTox Dashboard (EPA) DTXSID3020964 InChI InChI=1S/C6H5NO2/c8-7(9)6-4-2-1-3-5-6/h1-5H YKey: LQNUZADURLCDLV-UHFFFAOYSA-N YInChI=1/C6H5NO2/c8-7(9)6-4-2-1-3-5-6/h1-5HKey: LQNUZADURLCDLV-UHFFFAOYAA SMILES c1ccc(cc1)[N+](=O)[O-] Properties Chemical formula C6H5NO2 Molar mass 123.11 g/mol Appearance yellowish, oily liquid[1] Odor pungent, like paste shoe polish[1] Density 1.199 g/cm3 Melting point 5.7 °C (42.3 °F; 278.8 K) Boiling point 210.9 °C (411.6 °F; 484.0 K) Solubility in water 0.19 g/100 ml at 20 °C Vapor pressure 0.3 mmHg (25°C)[1] Magnetic susceptibility (χ) -61.80·10−6 cm3/mol Viscosity 1.8112 mPa·s[2] Hazards EU classification (outdated) T F N R phrases (out of date) R10, R23/24/25, R40.R48/23/24, R51/53, R62 S phrases S phrases (S1/2), S28, S36/37.S45, S61 NFPA 704 (fire diamond) 2 3 1 Flashpoint 88 °C (190°F; 361 K) Autoignitiontemperature 480 °C (896°F; 753 K) Explosive limit values 1,8%-? [1] Lethal dose or concentration (LD, LC): LD50 (median dose) 780 mg/kg (rat, oral)600 mg/kg (rat, oral)590 mg/kg (mouse, oral)[3] LDLo (lowest published) 750 mg/kg (dog, oral)[3] NIOSH (US health exposure limit): PEL (Permissible) TWA 1 ppm (5 mg/m3) [skin][1] REL (Recommended) TWA 1 ppm (5 mg/m3) m3) [skin][1] IDLH (Immediate danger) 200 ppm[1] Related compounds Related compounds Related compounds Related to compounds AnilineBenediazonium chloride Nitrosobenzene, unless otherwise stated, data are provided for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references Nitrobenzee is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like smell. It freezes to give green-yellow crystals. It is widely produced from benzene as a precursor to aniline. In the laboratory, it is occasionally used as a solvent, especially for electrophilic reagents. Nitrobenzene production is prepared by nitration of benzene with a mixture of concentrated sulphuric acid, water and nitric acid. This mixture is also called mixed acid. The production of nitrobenzene is one of the most dangerous processes carried out in the chemical industry due to the exothermity of the reaction (ΔH = −117 kJ/mol). [4] + H+ The world capacity for nitrobenzene in 1985 was approximately 1.7×106 tonnes. [4] The nitration process involves formation of nitronium ions (NO2+), followed by an electrophilic aromatic substitution reaction of it with benzene. The nitronium ion is generated by the reaction of nitric acid and an acidic dehydration agent, mostly sulphuric acid: HNO3 + H+ ⇌ NO2+ + H2O Used Approximately 95% of nitrobenze is consumed in the production of aniline:[4] C6H5NO2 + 3 H2 → C6H5NH2 + 2 H2O Aniline is a precursor to urethane polymers, rubber chemicals, pesticides, colourings (especially azo dyes), explosives and pharmaceuticals. Most aniline is consumed in the production of methylenedianiline, a precursor of polyurethane. Nitrobenzee's specialized applications are also used to mask unpleasant odours in shoe and floor wearers, leather bandages, paint solvents and other materials. Again, as oil of mirbane, nitrobenzene was used as a cheap perfume for soaps. It has been replaced by less toxic chemicals for this purpose. [5] An important buying market for nitrobenzene is its use in the production of analgesic paracetamol (also known as acetaminophen) (Mannsville 1991). [6] Nitrobenzene is also used Kerr cells, since it has an unusually large Kerr constant. Evidence suggests its use in agriculture as a plant growth/flowering stimulant. [7] Organic reactions Apart from the to aniline, nitrobenzene can be selectively reduced to azoxybenzene,[8] azoben sea,[9] nitrosobenzene,[10] hydrazoben sea,[11] and phenyldroxylamine. [12] It has been used as a mild oxidant in reactions such as skraup quinoline synthesis. [13] Safety Nitrobenzene is highly toxic (Threshold 5 mg/m3) and easily absorbed by the skin. Prolonged exposure can cause severe damage to the central nervous system, impair vision, liver or kidney damage, anemia and lung irritation. Inhalation of fumes can cause headache, nausea, fatigue, dizziness, cyanosis, weakness in the arms and legs, and in rare cases can be fatal. The oil is easily absorbed by the skin and can increase heart rate, cause convulsions or rarely death. Intake can also cause headaches, dizziness, nausea, vomiting and gastrointestinal irritation, loss of sensation/use in limbs and also causes internal bleeding. [10] Nitrobenzene is considered a probable human carcinogen by the United States Environmental Protection Agency,[14] and is classified by the IARC as a Group 2B carcinogen that may be carcinogenic to humans.
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