Nitro compounds nitroparaffins

Aliphatic nitro compounds nitroparaffins (e.g. nitromethane, nitroethane, etc.). 

Some nitro-compounds are themselves coloured and can be used as dyestuffs, e.g. picric acid. In this case the nitro-group can be considered to be the chromophore. For aliphatic nitro-compounds see nitroparaffins. 

A nitro alcohol is formed when an ahphatic nitro compound with a hydrogen atom on the nitro-bearing carbon atom reacts with an aldehyde in the presence of a base. Many such compounds have been synthesized, but only those formed by the condensation of formaldehyde (qv) and the lower nitroparaffins (qv) are marketed commercially. The condensation may occur one to three times, depending on the number of hydrogen atoms on the nitro-substituted carbon (R and R = H or alkyl), and yield nitro alcohols with one to three hydroxyl groups. 

Ttinitroparaffins can be prepared from 1,1-dinitroparaffins by electrolytic nitration, ie, electrolysis in aqueous caustic sodium nitrate solution (57). Secondary nitroparaffins dimerize on electrolytic oxidation (58) for example, 2-nitropropane yields 2,3-dimethyl-2,3-dinitrobutane, as well as some 2,2-dinitropropane. Addition of sodium nitrate to the anolyte favors formation of the former. The oxidation of salts of i7k-2-nitropropane with either cationic or anionic oxidants generally gives both 2,2-dinitropropane and acetone (59) with ammonium peroxysulfate, for example, these products are formed in 53 and 14% yields, respectively. Ozone oxidation of nitroso groups gives nitro compounds 2-nitroso-2-nitropropane [5275-46-7] (propylpseudonitrole), for example, yields 2,2-dinitropropane (60). 

Nitrating propane produces a complex mixture of nitro compounds ranging from nitromethane to nitropropanes. The presence of lower nitroparaffins is attributed to carbon-carbon bond fission occurring at the temperature used. Temperatures and pressures are in the range of 390°-440°C and 100-125 psig, respectively. Increasing the mole ratio of propane to nitric acid increases the yield of nitropropanes. Typical product composition for 25 1 propane/acid ratio is ... 

Almost without exception the numerous transformations which primary and secondary nitroparaffins undergo involve the aci-iorm, i.e. they take place under conditions in which the salt of the oci-form is produced. Qualitatively the nitroparaffins greatly resemble ketones in their mode of action, although the much greater reaction velocity of the nitro-compounds brings about a quantitative difference. 

Strong centres, forming anion radical even from nitrobenzene molecule are poisoned irreversibly, however, their presence is not necessity for the preservation of catalytic activity. Taking into consideration that regenerated MgO which is not able to ionize nitrobenzene molecule is still active in its reduction by hydrogen transfer and that only a few from reduced nitro compounds form ion radicals on catalyst surface one can ascertain that ion radicals formation is not necessary step in nitroarenes (or nitroparaffins) activation. Probably, one-electron donor sites take part only in activation of alcohol what was demonstrated by us earlier. 

Excellent comprehensive reviews10 of the chemistry of the nitroparaffins are available elsewhere and it is intended to discuss here only those reactions of aliphatic nitro compounds which have found application in the chemistry of the carbohydrates. 

At 300°C the yield of a mixture of nitro compounds was 24-42% by weight. 27-39% of this mixture was composed of lower nitroparaffins (nitromethane,... 

In the case of simplest nitro compounds the absorption band produced by this group corresponds to the following values. For aliphatic nitro compounds, for example nitromethane, nitroethane, 1- and 2-nitropropanes, they are 260-270 mu at extinctions s = 40-120. (According to Ungnade said Smiley [1] the values for higher nitroparaffins are 274-278 mp, s = 24-41.) For aromatic nitro compounds, such as nitrobenzene the bands are 250-260 mp at extinctions s = 9000-10,000. When a primary or secondary nitro group takes an aci-form, the maximum disappears, as shown by earlier research work of Hantzsch and Voigt [2]. 

The chemical properties of primary and secondary nitro compounds differ considerably from those of tertiary nitro compounds. This is due to the presence of active hydrogen atoms in the first two. The difference appears most clearly when nitro compounds are treated with alkalis. As long ago as 1872 Meyer [48,48a] observed that certain nitroparaffins were soluble in sodium hydroxide solutions. In 1888 Michael [49], and later Nef [50], suggested that the salt formed in the... 

The pale yellow colour of nitrobenzene or p- nitrotoluene turns more intense when the compound is dissolved in sulphuric acid, while solutions of nitromethane and other nitroparaffins are colourless. The yellow colour of the aromatic nitro compounds is due presumably to an ionic structure containing a quinonoid ring. 

In a variation of the Michael condensation, nitroparaffins having active methylene groups add to reactive olefinic compounds including ot,/3-unsaturated esters (method 301), a.,y6-unsaturated cyanides (method 388), and a-nitro olefins. Interaction of primary or secondary aliphatic nitro compounds with the unsaturated nitro compounds in the presence of sodium ethoxide in alcohol yields 1,3-dinitroparaffins. The reaction is general, but the yields vary, depending on the degree of polymerization that the nitro olefin undergoes and the amount of addition of alcohol to it as well as on the reactivity of the product toward further condensation. 

Olefin synthesis. Komblum et at.1 have described a new synthesis of tetrasubsti-tuted olefins from vicinal dinitro compounds. There are several methods for conversion of aliphatic and alicyclic nitro compounds into p/V-dinitro compounds, the most useful of which is a procedure of Seigle and Hass.2 A nitroparaffin is converted into the lithium salt (1) by treatment with lithium methoxide and this is then treated with bromine to form a bromonitro compound (2). Reaction of (2) with a second equivalent of the nitro-... 

CALCIUM HYDROXIDE (1305-62-0) Contact with maleic anhydride may cause explosive decomposition. Contact with phosphorus, nitroethane, nitro-methane, nitroparaffins, or nitropropane may form explosive compounds or cause explosion. Attacks some metals and coatings. 

The nitroparaffins differ from the ketones in that they are sufficiently strong acids (pK = 8-10) to be completely neutralized by aqueous solutions of sodium hydroxide. It is well known that this neutralization takes place at a measurable rate (Hantzsch and Yeit, 51), and Hantzsch and others have supposed that the nitro compound is first converted slowly into the aci form, which then reacts rapidly with hydroxyl ions. However, according to modern views, the aci form cannot be produced without the intermediate formation of the anion, and the slow process must therefore be... 

Nitroparaffins. Shake the compound (3 drops) with a solution of 0 1 g of sodium nitrite in 1 ml of 30% aqueous sodiimi hydroxide. Primary and secondary nitroparaffins dissolve. Dilute the solution with 3 ml of water and add dropwise 2N sulphuric add. Primary nitroparaffins give a red colour which is destroyed by excess of acid, secondary nitro-compounds a blue or green colour soluble in chloroform, whereas tertiary nitro-compounds (RR R"CN02) do not react. 

Reaction With Carbonyl Compounds. Primary and secondary nitroparaffins undergo aldol-type reactions with a variety of aldehydes and ketones to give nitro alcohols (11). Those derived from the lower nitroparaffins and formaldehyde are available commercially (see Nitro alcohols). Nitro alcohols can be reduced to the corresponding amino alcohols (see Alkanolamines). 

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

Most nitroparaffins do not react with ketones, but ia the presence of alkoxide catalysts, nitromethane and lower aUphatic ketones give nitro alcohols ia the presence of amine catalysts dinitro compounds are obtained. 

One of the most extensively investigated groups of 1,3-oxazine derivatives is the 5-nitro derivatives of tetrahydro-l,3-oxazine. They were first prepared from 1-nitropropane, aqueous formaldehyde, and ammonia by Hirst et and independently by Senkus from other primary nitroparaffins, formaldehyde, and primary amines. Numerous compounds of the general formula (6) were later prepared from primary nitroparaffins. " ... 

Nitroparaffins. Nitro-organics as a class of compounds are of greater interest in solid than liquid propellants. However, some nitroparaffins have been utilized in liquid systems. Nitromethane has been used as a monopropellant, while tetranitromethane, hexanitroethane, nitroform, and nitroform salts have been considered as oxidizing components in bipropellant systems. The high melting points of the latter and their sensitivity restrict their use to solutes in lower freezing, insensitive liquids. A solution of 70 wt. % C(N02)4 in N204 is an example of such a system and has been proposed as an oxidizer (3). 

Mixtures of hydrazine and other compounds form liquid explosives which have been described. A study of the detonability of binary and ternary mixtures of nitro me thane—hydrazine—methanol showed that N2H4 sensitizes nitromethane and nitromethane-methanol mixtures to detonation (Ref 29). From 2-10% N2H4 and 90-98% lower molecular weight nitroparaffins are claimed to be a water insoluble liquid explosive (Ref 22). Mixtures of hydrazine, ammonium nitrate and aluminum have been patented as explosive compositions with high air blast effects (Ref 32). 

The yields of nitro alcohols from simple nitroparaffins and aliphatic aldehydes or benzaldehyde are usually above 60%. The condensations are generally carried out with aqueous ethanolic sodium hydroxide, although weaker bases are sometimes desirable to prevent polymerization of the aldehyde. Sodium bisulfite addition compounds of the aldehydes are sometimes used. Better results are obtained with sodium methoxide than with alkali hydroxides in the condensation of nitroethane with formaldehyde. Sodium alkoxides are also used to effect the condensation of nitroethane with acetone and cyclohexanone. Condensation proceeds to the nitroalkanediol stage in certain cases with both nitromethane and with formaldehyde. ... 

The nitroparaffins are condensed with aldehydes to yield nitro alcohols (70-80%), which on acetylation and treatment with an aqueous methanolic solution of sodium bicarbonate are converted to nitroolefins (80-84%). These compounds are reduced to the corresponding ketoximes by zinc and acetic acid (50-60%). Reduction with iron and dilute hydrochloric acid gives good yields of either ketones or ketoximes, depending upon the amount of hydrochloric acid used. The ketoximes can be hydrolyzed to ketones by refluxing with dilute sulfuric acid in the presence of formalin, which acts as a hydroxylamine acceptor (80%). The over-all yields from the nitroolefins are 40-60%. In this manner, certain otherwise difficultly obtainable ketones are prepared. Semicarbazones have been converted to ketones by treatment with sodium nitrite in glacial acetic acid, with aqueous oxalic acid, or with phthalic anhydride. ... 

Other complex metal hydrides can only rarely be applied to reduction of C=C bonds. Sodium borohydride, which can be used in aqueous-alcoholic solution, seems not normally to attack ethylenic bonds. A few cases only of partial reduction of cyclic iminum salts96 and of selective reduction of unusually activated ethylenic bonds97 have been reported. However, some polynitro aromatic compounds, e.g., 1,3,5-trinitrobenzene, can be converted in high yield with saturation of the aromatic system into nitrocyclohexanes or nitro-cyclohexenes.98 Sodium hydridotrimethoxyborate has proved valuable as a mild reducing agent for preparation of a series of nitroparaffins from nitro-alkenes."... 

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