Aromatic pentoxid

Saturated and aromatic hydrocarbons Ethers Anhydrous calcium chloride anhydrous calcium sulphate metallic sodium phosphorus pentoxide. 

By dehydration of aromatic amides with phosphorus pentoxide, for example ... 

Kinetic studies of nitration using dilute solutions of dinitrogen pentoxide in organic solvents, chiefly carbon tetrachloride, have provided evidence for the operation, under certain circumstances of the molecular species as the electrophile. The reactions of benzene and toluene were inconveniently fast, and therefore a series of halogenobenzenes and aromatic esters was examined. 

Nitrations in acetic anhydride, or in solutions containing benzoyl nitrate ( 5.2) or dinitrogen pentoxide ( 4.2.3) have long been associated with the formation from some aromatics of higher proportions of o-nitro-compounds than are formed under other conditions. 

Expt. 27. A solution of dinitrogen pentoxide (0-005 tnol) in acetonitrile (0-4 ml) was added slowly to the aromatic compound (o-oi mol) in acetonitrile (i ml). 

In earlier chapters we have been concerned with the identification of the effective electrophile in nitrations carried out under various conditions. We have seen that very commonly the nitronium ion is the electrophile, though dinitrogen pentoxide seems capable of assuming this role. We now consider how the electrophile, specifically the nitronium ion, reacts with the aromatic compound to cause nitration. 

Dinitrogen tetroxide is an effective Eriedel-Crafts nitrating agent (152) for aromatics in the presence of aluminum chloride, ferric chloride, or sulfuric acid (153). Dinitrogen pentoxide is a powerhil nitrating agent, even in the absence of catalysts, preferably in sulfuric acid solution (154). SoHd dinitrogen pentoxide is known to be the nitronium nitrate, (N02) (N02). The use of BE as catalyst has been reported (155). 

Sulfonic acids may be subjected to a variety of transformation conditions, as shown in Figure 2. Sulfonic acids can be used to produce sulfonic anhydrides by treatment with a dehydrating agent, such as thionyl chloride [7719-09-7J. This transformation is also accomphshed using phosphoms pentoxide [1314-56-3J. Sulfonic anhydrides, particulady aromatic sulfonic anhydrides, are often produced in situ during sulfonation with sulfur trioxide. Under dehydrating conditions, sulfonic acids react with substituted aromatic compounds to give sulfone derivatives. 

Polycyclic aromatic hydrocarbons (PAH) Apply sample solution and dry. Place TLX2 plate for 20 min in a twin-trough chamber containing phosphorus pentoxide to which 2 to 3 ml cone, nitric acid have been added. PAH nitrated by nitrous fumes. [20]... 

Tetrahydroharman, m.p. 179-80°, has been prepared by a number of workers by a modification of this reaction, viz., by the interaction of tryptamine (3-)5-aminoethylindole) with acetaldehyde or paraldehyde and Hahn et al. have obtained a series of derivatives of tetrahydronorharman by the use of other aldehydes and a-ketonic acids under biological conditions of pH and temperature, while Asahina and Osada, by the action of aromatic acid chlorides on the same amine, have prepared a series of amides from which the corresponding substituted dihydronorharmans have been made by effecting ring closure with phosphorus pentoxide in xylene solution. 

Trifluoromethanesulfonic (triflic) anhydride is commercially available or can be prepared easily by the reaction of triflic acid with phosphorus pentoxide [66] This moderately hygroscopic colorless liquid is a useful reagent for the preparation of various organic derivatives of triflic acid A large variety of organic ionic triflates can be prepared from triflic anhydride A recent example is the preparation of unusual oxo-bridged dicatiomc salts of different types [SS, 89, 90, 91, 92, 93] (equations 38-44) Stabilized dication ether salts of the Huckel aromatic system and some other systems (equations 38 and 39) can be prepared in one step by the... 

Dinitrogen pentoxide (prepared by the oxidation of N204 with 03) in nitric acid is a potent nitration system. It can be used for nitrating aromatic compounds at lower temperatures than conventional system. It is also convenient for preparing explosives that are unstable in nitrating media containing sulfuric acid (Eq. 2.7).20... 

A powerful and efficient method for the preparation of poly(ketone)s is the direct polycondensation of dicarboxylic acids with aromatic compounds or of aromatic carboxylic acids using phosphorus pentoxide/methanesulfonic acid (PPMA)16 or polyphosphoric acid (PPA)17 as the condensing agent and solvent. By applying both of these reagents to the synthesis of hexafluoroisopropylidene-unit-containing aromatic poly(ketone)s, various types of poly(ketone)s such as poly(ether ketone) (11), poly(ketone) (12), poly(sulfide ketone) (13), and poly-... 

The nitration reagents (NO2 Y) for electrophilic aromatic nitration span a wide range and contain anions Y such as nitric acid (Y = OH-), acetyl nitrate (Y = OAc-), dinitrogen pentoxide (Y = NO3-), nitryl chloride (Y = Cl-), TV-nitropyridinium (Y = pyridine) and tetranitromethane [Y = C(N02)3-]. All reagents contain electron-deficient species which can serve as effective electron acceptors and form electron donor-acceptor (EDA) complexes with electron-rich donors including aromatic hydrocarbons107 (ArH, equation 86). Excitation of the EDA complexes by irradiation of the charge-transfer (CT) absorption band results in full electron transfer (equation 87) to form radical ion... 

Dinitrogen pentoxide has also been used to synthesize aryldinitromethanes from arylal-doximes in yields between 20 % and 60 Aromatic ring nitration can also occur during these reactions.Dinitrogen pentoxide in chloroform converts a-chlorooximes to the corresponding Q -chloro-Q, Q -dinitro compounds. 

The first use of dinitrogen pentoxide as an A-nitrating agent appears to have been for the conversion of aromatic amines to arylnitramines. Difficulties in preparing pure dinitrogen pentoxide meant that reactions with aliphatic amines were not properly examined for another 60 years. 

Solutions of dinitrogen pentoxide in methylene chloride or chloroform have been used for the V-nitration of the sodium salts of some V-alkylsulfamides. " Sulfonamide substrates with both alkyl and aryl substituents are V-nitrated in excellent yields with this reagent. Aromatic ring nitration occurs when aryl substituents are present. 

Dinitrogen pentoxide has been used for aromatic nitration in other media and some are notable. While a solution of dinitrogen pentoxide in carbon tetrachloride will not convert 1,3-dinitrobenzene to 1,3,5-trinitrobenzene, a solution in concentrated sulfuric acid at 160 °C will effect this conversion. In this medium dinitrogen pentoxide is fully ionized to nitronium and nitrate ions. Solutions of dinitrogen pentoxide in liquid sulfur trioxide have been used for the nitration of some deactivated pyridines. ... 

The complex formed between dinitrogen pentoxide and boron Uifluoride is a powerful nitrating agent and has been used in organic solvents like carbon tetrachloride, nitromethane and sulfolane for the nitration of deactivated aromatic substrates, including the conversion of benzoic acid to 1,3-dinitrobenzoic acid in 70% yield. Olah and co-workers" studied aromatic nitrations with dinitrogen pentoxide in the presence of other Lewis acids. 

Vanadium pentoxide (V203)-based catalysts, for example, are extensively used in industry for a number of catalytic processes including the selective oxidation of aromatic hydrocarbons and transformation of SOj into SO3 [14,15]. The vanadium pentoxide catalysts are usually prepared in supported form on a proper... 

This method is very useful for the construction of 1-substituted 3,4-dihydroisoquinolines, which if necessary can be oxidized to isoquinolines. A P-phenylethylamine (l-amino-2-phenylethane) is the starting material, and this is usually preformed by reacting an aromatic aldehyde with nitromethane in the presence of sodium methoxide, and allowing the adduct to eliminate methanol and give a P-nitrostyrene (l-nitro-2-phenylethene) (Scheme 3.17). This product is then reduced to the p-phenylethylamine, commonly by the action of lithium aluminium hydride. Once prepared, the p-phenylethylamine is reacted with an acyl chloride and a base to give the corresponding amide (R = H) and then this is cyclized to a 3,4-dihydro-isoquinoline by treatment with either phosphorus pentoxide or phosphorus oxychloride (Scheme 3.18). Finally, aromatization is accomplished by heating the 3,4-dihydroisoquinoline over palladium on charcoal. 

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