Sulfuric add fuming

Note Nitrous fumes can also be generated in a twin trough chamber eg. by pouring 50<% nitric acid [12], hydrochloric acid (c = 2 mol/L) [11] or sulfuric add onto sodium nitrite... 

The polycrystalline platinum electrode was mounted in Kel>F resin and polished with a scries of alumina powders down to 0.05, resulting mirror finish. The apparent surface area was 1.85 cm. The electrode was washed with fuming sulfuric add and rinsed with ultra pure water prior to each measurement. 

For monosulfonation of PPh3 the reaction mixture can be heated for a limited time [1-3] while multiple sulfonation is achieved hy letting the solution stand at room temperature for a few days [4-10], In this simplest way of the preparation several problems may arise. Under the harsh conditions of sulfonation there is always some oxidation of the phosphine into phosphine oxide and phosphine sulfides are formed, too. Furthermore, selective preparation of TPPMS (1) or TPPDS (2) requires optimum reaction temperature and time and is best achieved by constantly monitoring the reaction by NMR [10] or HPLC [7]. Even then, the product can be contaminated with unreacted starting material. However, 1 can be freed of both the non-sulfonated and the multiply sulfonated contaminants by simple methods, and in the preparation of TPPTS (3) contamination with PPh3, 1 or 2 is usually not the case. Direct sulfonation with fuming sulfuric add was also used for the preparation of the chelating diphosphines 34-38, 51, 52. 

Sulfur Trioxide Sulfuric Acid (fuming 98%) Sulfuric Add (hot, cone.) Sulfuric Acid (cold, cone.) Sulfuric Acid (75-95%)... 

The first industrial preparation of sulfuric add from green vitriol (ferrous sulfate), according to Hermann Kopp, was by Johann Christian Bernhardt in 1755 (9,10). A fuming sulfuric acid known as Nordhausen oil of vitriol was manufactured at Nordhausen, Thuringia, from partially dehydrated green vitriol (11). 

Methyl m-nitrobenzoate has been prepared by the esterification of m-nitrobenzoic acid 1 this method is, however, obviously much less satisfactory than nitration of methyl benzoate. Nitration by means of fuming nitric acid has also been applied to methyl benzoate,2 but the use of the ordinary nitration mixture of concentrated sulfuric add and concentrated nitric acid is more satisfactory. 

LIGHT SULFUR IN BOTTLE CAP. LOWER BURNING SULFUR INTO JAR. WHEN JAR IS FULL OF FUMES, REMOVE SULFUR. ADD A FEW ml WA TER. SHAKE. AS S02 DISSOLVES IN WATER IT FORMS A WEAK ACID— SULFUROUS ACID, HjSO,. TEST FOR ACID WITH BLUE LITMUS PAPER. 

OLEUM. The Latin word for oil, applied to fuming sulfuric add. (Sulfuric acid was onginally called oil of vttnol.)... 

Step 14. Take up the residue in 5 mL of concentrated HN03. Add 0.5 mL of concentrated H2S04 and evaporate until the nitric acid has been volatilized and fumes of sulfuric acid appear. Nitric acid fumes are fluffy white. Sulfuric acid fumes are dense white. Remove from hot plate. Allow the sample to cool and add 3 mL of deionized water, swirling to mix. 

Transfer the filter paper and precipitate into a tared platinum crucible, char, and ignite at 900° to constant weight. Moisten the residue with a few drops of water, add 15 mL of hydrofluoric acid and 8 drops of sulfuric acid, and heat on a hot plate in a hood until white fumes of sulfur trioxide evolve. Cool add 5 mL of water, 10 mL of hydrofluoric acid, and 3 drops of sulfuric acid and evaporate to dryness on the hot plate. Heat cautiously over an open flame until sulfur trioxide fumes cease to evolve, and ignite at 900° to constant weight. The weight loss after the addition of hydrofluoric acid represents the weight of Si02 in the sample taken. 

OB to CO +27.5%. Wh syrupy mass sol in ale, eth 8c acet. Can be prepd by nitrating D-arabitol with fuming nitric acid at -5°, followed by addn of concxl sulfuric add. Its expl poops were not investigated... 

Bromopyrazoles (298) react with fuming nitric acid in 80% sulfuric add to give 4-nitropyrazoles ipso nitration Section 4.04.2.3.7). When R was an alkyl group, nitration took place at C-3 giving (299) (a small amount of the dinitro derivative (300) was also obtained) (79AJC1727). Nitrodebromination proceeds from the protonated pyrazolium ion whereas 3-and 5-nitration were expected to involve the free base. 

Sulfonation. Most aromatic compounds can be sulfonated by the action of concentrated or fuming sulfuric add to form sulfonic acids. The reaction may be represented as ... 

Sulfur trioxide produces iU smoke effect by the formation of fine dn>plcts of sulfurous and sulfuric acids that remain suspended in the air for some time beraxine of their minute Hise, and then are not volatilised because of the low vapor prejssure of thetie acids. As the SO fumes combine with moisture in the air, concentrated sulfuric add is formed, which attracts more moisture and tends to become diluted, until finally an equilibrium is efltabltNhed btdween the moisture in the air and the sulfuric acid droplets, the latter being concentrati d in proportion to the humidity of the air. Sulfuric acid is not so hygroscopic as the phosphoric acid formed by burning phosphorus, and the formation of its droplets stops Kooner, so that sulfur trioxide smoke is less stable than phosphorus smoke. 

Aromatic rings can be sulfonated reaction with fuming sulfuric add, mixture ofH2S04 and SO ,. The reactive electrophile is either HSOs or neutral SO3, dependii on reaction conditions. Substitution occurs by the si two-step mechanism seen previously for bromination and nitration (Figun 16.7). Note, however, that the sulfonation reaction is readily reversible can occur either forward or backward, depending on the reaction conditiom... 

Sulfonation is effected (1) with ordinary concentrated sulfuric add (66°B6) (2) with 100 per cent sulfuric acid (3) with fuming sulfuric add (oleum), with the concentration of SO3 varying from 5 to 70 per cent (4) widi chlorosulfonic acid, with or without diluent or (5) by baking (dry heating) the acid sulfate of an amine, often in vacuum. 

Another very common method to keep the amount of water in the mix to a minimum is to add a substance which will soak up water in the reaction mixture. The most favored chemical for this purpose is concentrated sulfuric acid. This material has a great thirst for water, and performs its task admirably. It is usually added to a batch of nitro to the extent of one part nitric acid, two parts sulfuric acid. Fuming sulfuric acid works even better, but is expensive. This topic will be covered in more detail in the sulfuric acid section. 

The compound nitralin (SD 11831, 11) was first described by Soloway and Zwahlen (1966). Its synthesis starts with 4-chiorophenyl methyl sulfone, which is nitrated with a fuming sulfuric acid-fuming nitric add mixture to the dinitro compound. This then reacts with dipropylamine to give nitralin ... 

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