Nitric Acid In Acetic Anhydride Research Articles

An Addition Reaction of Indane with Nitric Acid in Acetic Anhydride

cis- and trans-5-Acetoxy-7a-nitro-5,7-dihydroindane are formed as well as the 4- and 5-nitroindanes when indane is reacted with nitric acid and acetic anhydride. These adducts both decompose on standing by loss of nitrous acid forming 5-acetoxyindane. The cis isomer is obtained in greater amount and it undergoes elimination less readily than the trans.

The nitration of bibenzyl. Part II. Comparison of the products from nitrations by nitric acid in acetic anhydride and by nitronium salts in organic solvents

The nitration of bibenzyl (in excess) with a solution of nitric acid in acetic anhydride gives very little dinitration, in marked contrast to the nitration of bibenzyl (in excess) with solutions of nitronium salts in organic solvents. For the reactions with preformed nitronium ions, the isomeric composition of the dinitro-fraction and the product composition in the nitration of mixtures of bibenzyl and mononitrobibenzyls support the earlier conclusion that the dinitration arises mainly from reaction during the mixing of the reactant solutions. For dinitration, there is no evidence of a significant contribution from the addition of a nitronium ion to the first nitro-group followed by an intramolecular NO2–transfer to the second ring.

Aromatic reactivity. Part LI. Nitrosodesilylation as a route to nitrodesilylation products from aryltrimethylsilanes and nitric acid in acetic anhydride

A detailed study of the reaction between p-tolyltrimethylsilane and nitric acid in acetic anhydride has shown that the formation of the nitrodesilylation product, p-nitrotoluene, takes place predominantly, and possibly exclusively, via nitrosodesilylation. Thus, (i) when the mixture of nitric acid and acetic anhydride was heated briefly to 100° then used at 15°, the ratio of nitrodesilylation to nitration product (2-nitro-4-trimethylsilyltoluene) was 90, (ii) when the mixture was made up and used at 15° the ratio was 0·64, (iii) when the mixture was made up and used at 15° but with urea present, the ratio was 0·14, and (iv) when the mixture was made up at 15° and nitrous fumes were dissolved in it before use at 15° the ratio was 4·8. With a solution of nitrous fumes in acetic acid–acetic anhydride, only the nitrodesilylation product was formed. The p-nitrotoluene formed in the reaction with solutions of acetyl nitrate or dinitrogen pentoxide also seems to be produced predominantly and exclusively through nitrosodesilylation.

Syntheses of Nitrogen-containing Heterocyclic Compounds. XIX. Nitration of 2-Anilinopyridine

Nitration of 2-anilinopyridine (II) with a mixed acid afforded 2-(2-nitroanilino)pyridine (III), 2-(4'-nitroanilino)pyridine (V), and 2-(2', 4'-dinitroanilino)pyridine (VI), in a poor yield, but that with excess nitric acid gave VI alone in a high yield. Nitration of II with acetyl nitrate gave VI, 2-(2', 4'-dinitroanilino)-5-nitropyridine (IX), and 2-(2', 4'-dinitroanilino)-3, 5-dinitropyridine (X). II showed different reactivity in nitration with a strong acidic medium and a mild medium like nitric acid in acetic anhydride. In order to elucidate the reactivity of II in each case, it was assumed that II takes an anilinopyridinium ion form in a strongly acidic medium and a neutral anilinopyridine form in the mild acidic medium.

Aromatic detritiation. Part IV. 1,3,5-Triphenylbenzene: a possible example of steric hindrance to hydrogen exchange

Rates of protiodetritiation of 1,3,5-triphenylbenzene have been measured in anhydrous trifluoroacetic acid at temperatures between 70 and 130 °C and lead to the following partial rate factors: 72,600 (2-position); 88 (4′-position); 29 (2′-position). This quantitative determination of the electrophilic reactivity of the molecule shows that the isomer distributions obtained in all previous electrophilic substitutions of it are affected by steric hindrance to 2- and 2′-substitution, and further, by comparison with detritiation data for biphenyl, that even in hydrogen exchange the 2- and 2′-positions are probably slightly hindered; this being so, it constitutes the first example of steric hindrance to acid-catalysed hydrogen exchange. The data for nitration of triphenylbenzene by nitric acid in acetic anhydride is at variance with the prediction of the hydrogen exchange reaction indicating the nitration pattern to be anomalous as is that for nitration of biphenyl under these conditions.

Ipso-Nitration at an aromatic methoxy-group

The major product from reaction of 5-acetoxy-or 5-methoxy-1,2,3-trimethoxybenzene with nitric acid in acetic anhydride is 2,6-dimethoxyquinone, via the moderately stable 3,4,5-trimethoxy-4-nitrocyclohexa-2,5-dienone as common intermediate.

Nitropyrroles—III : The nitration of acylpyrroles

The products and isomer distributions have been determined for the action of nitric acid in acetic anhydride at −15°. Under these conditions the substitution pattern was insensitive to the nature of the acyl group. From 1-acyl- and 2-acyl-pyrroles the products were mixtures containing equimolar amounts of α- and β-nitro derivatives; from 3-acylpyrroles only 4-acyl-2-nitropyrroles were obtained. Structures of the products were conveniently confirmed by their NMR spectra. The relative reactivities of the acylpyrroles are discussed on the basis of a simple HMO treatment, which appears to provide a satisfactory qualitative description if allowance is made for proximity and solvent effects. Oxidation of 2-acetyl-4-and -5-nitropyrroles with dilute nitric acid gave the corresponding furoxans; from 4-acetyl-2-nitropyrrole (2- nitro-4- pyrrolyl) glyoxalic acid was obtained.

Electrophilic substitution on the thiophen ring. Part IV. Kinetics and mechanism of the nitration of thiophen

The kinetics of the nitration of thiophen and some substituted thiophens in sulphuric and perchloric acid have been studied. There is a linear relationship between log k2(obs) and –(HR+ log aW)(where w = H2O) and the mechanism of reaction appears to be the same as that for benzene compounds. However, it is not a suitable preparative procedure owing to the high reactivity of thiophen. Nitration of thiophen, with a solution of nitric acid in acetic acid, proceeds with explosive violence owing to the easy nitrosation of thiophen in an autocatalytic reaction, leading to a variety of unidentified products. If nitrous acid is removed by addition of urea, nitration of thiophen at low concentration is of the first order in thiophen and nitrothiophen is obtained in high yield. However, at high thiophen concentration nitrosation again becomes the predominant reaction. The reason for this is discussed. As has been known for some time, the most successful reagent for the nitration of thiophen is nitric acid in acetic anhydride. Acetic anhydride does not greatly increase the rate of nitration but appears to remove complications due to nitrosation.

The acetoxylation of arenes. Part VI. Formation of 4-nitrocyclohexa-2,5-dienones in the nitration of bromo-, acetoxy- and methoxy-arenes

Reaction of 5-substituted-hemimellitenes (1,2,3-trimethylbenzenes)(3a—c) and 4-substituted-o-xylenes (3d—f) with nitric acid–acetic anhydride gives 4-nitrocyclohexa-2,5-dienones (5a) and (5b) in addition to normal substitution products.

Diene intermediates in the acetoxylation of o-xylene

The intermediates in the acetoxylation of o-xylene by nitric acid in acetic anhydride are moderately stable acetoxynitrodimethylcyclohexadienes.

Enzymic deacylation of esterified mono- and disaccharides. 3. The location of acetylated positions in partially acetylated sugars

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Enzymic deacylation of esterified mono- and disaccharides. 3. The location of acetylated positions in partially acetylated sugars

The nitrate ester, formed by reaction with fuming nitric acid in acetic anhydride at 0 °C, was suitable to block free hydroxyl groups in partially acetylated sugars without acetyl migration. This allowed the acetylated positions in partially acetylated mono- and disaccharides to be located by the reaction sequence: nitration, deacetylation, methylation, de-nitration, disaccharide hydrolysis and methyl glycosylation (initial product identification by paper partition chromatography), acetylation, and analysis of the products by gas-liquid partition chromatography. D-Glucose, penta-O-acetyl-D-glucopyranose, and 2,3-di-O-acetyl-β-D-glucopyranose were used as test compounds in the evaluation of this scheme.

Ground states of σ-bonded molecules—VIII : MINDO Calculations for species involved in nitration by acetyl nitrate

It is shown that the MINDO semiempirical SCF MO method gives good values for heats of formation of inorganic species and ions as well as neutral molecules. Calculations are reported for the various species that could be involved in nitrations by nitric acid in acetic anhydride; it is concluded that the active agent is protonatedacetyl nitr acetyl nitrate protonated at the ether-type oxygen.

Nitration of Thenyl Derivatives. II. Preparation of Three Isomeric Mononitro Derivatives of 2-Thenyl Chloride and 2-Thenyl Acetate

Abstract In connection with the investigation of the products of the nitration of 2-thenyl chloride (I) and 2-thenyl acetate (II), three isomeric mononitro derivatives of I and II were prepared, and it was shown by NMR spectral study that, as in the case of I, the product obtained in the nitration of II by nitric acid in acetic anhydride consisted of all three isomeric mononitro derivatives. The isomer distribution of the mononitro derivatives of II, as determined by infrared spectroscopy, indicated 77% of the 5-, 9% of the 4-, and 14% of the 3-nitro isomer.

Benzocyclo-octatetraenes. Part II. Nitro derivatives

The nitration of biphenylene with nitric acid in acetic anhydride gives 3-acetoxy-8-nitrobenzocyclo-octatetraene as the principal product. Addition reactions of biphenylene with nitrosyl chloride and formate lead to analogous products. Some facile rearrangement reactions of these compounds are described.

The additivity principle. Nitration and acetoxylation of some methylbenzenes

Product distributions resulting from nitration of various methylbenzenes in three nitrating systems have been determined by gas chromatography. The additivity principle does not predict successfully the experimental product ratios. A value of ρ for acetoxylation in nitric acid–acetic anhydride mixtures is obtained.

The ortho: para ratio in the nitration of biphenyl

The ortho: para ratio in the nitration of biphenyl has been accurately determined under various conditions by means of vapour phase chromatography. The low ratio (ca. 0·6) commonly observed in nitric acid–sulphuric acid is found to be due predominantly to a homogeneous reaction, rather than to a heterogeneous reaction as has been previously suggested; under suitable conditions a predominantly heterogeneous reaction can be obtained which by contrast gives a high ratio (ca. 1·5). A previous theory attributing variable ratios in biphenyl nitration to the degree of homogeneity of the reaction mixture is accordingly modified, and it is shown that nitric acid in acetic anhydride and dinitrogen pentoxide in acetonitrile do give uniquely high and closely similar ratios as in the nitration of anilides and ethers, so that a common explanation is necessary. It is proposed that nitration with preformed nitronium ions gives rise to normal ortho: para ratios, whereas nitration with all species of the type NO2X (some of which are positively charged) gives enhanced ratios due to an additional mode of ortho-substitution involving, in the case of biphenyl, nucleophilic displacement of X (or X–) by the π-electrons of the unsubstituted ring to give a π-complex involving NO2+. This π-complex goes over to the most accessible σ-complex which is, because of the nonplanarity of the phenyl rings, that formed at the ortho-position in the other ring.Nitration by nitric acid–acetic acid produced widely varying ratios according to the technique employed, and this is attributed to different nitrating species being present under the different conditions. Nitration under free-radical conditions gave up to 40% of meta-product in the mononitrobiphenyls, but overall yields were extremely low because of side reactions.Conditions for the optimum yield of ortho- and of para-nitrobiphenyl are given.

Syntheses from 4,5-dibromo-2-furaldehyde

1. The nitration of 4,5-dibromo-2-furaldehyde with nitric acid in acetic anhydride goes with the replacement of the bromine atom in the α-position of the furan nucleus by a nitro group, and 4-bromo-5-nitro-2-furanmethanediol diacetate is formed. 2. In the reaction of butyllithium with 4,5-dibromo-2-furaldehyde acetal the bromide in the α-position of the furan nucleus is replaced by lithium. 3. It was shown that from 4,5-dibromo-2-furaldehyde it is possible to prepare some new difficultly accessible furan compounds with three substituants in the nucleus.

REACTIONS OF PHENYL-SUBSTITUTED HETEROCYCLIC COMPOUNDS: V. NITRATIONS OF 1,3- AND 1,5-DIPHENYLPYRAZOLES

Dinitration of 1,3- or 1,5-diphenylpyrazole in sulphuric acid yields the corresponding di(p-nitrophenyl) compounds, while nitric acid–acetic anhydride yields the 4-nitro-1-p-nitrophenyl compounds.Mononitration at the 4-position occurs when the diphenylpyrazoles and several other 1-phenylpyrazoles are nitrated at 0° by nitric acid–acetic anhydride.Possible explanations of the dependence of orientation on the nature of the nitrating agent-are discussed.Nuclear magnetic resonance (n.m.r.) spectroscopy was used in demonstrating the structures of many of the nitration products, and a general discussion of the n.m.r. spectra of substituted 1-phenylpyrazoles is given.

New heteroaromatic compounds—IV : The nitration and chlorination of 10-methyl-10:9- borazarophenanthrene

10-Methyl- and 10-hydroxy-10:9-borazarophenanthrene have been nitrated with nitric acid in acetic anhydride, and the former compound has been chlorinated with chlorine in acetic acid; the products have been oriented and the proportions of isomers determined quantitatively. The results are shown to be in general agreement with the predictions of MO theory, attack taking place in the 6- and 8-positions. A method for degrading such boron compounds is described, and also the synthesis of 2-, 6-, and 8-chloro-10-methyl-10:9-borazarophenanthrenes as reference compounds. The 6- and 8-amino derivatives of 10-methyl and 10-hydroxy-10:9-borazarophenanthrene have been prepared by reduction of the corresponding nitro derivatives.