Nitrobenzene chlorination

Dichloroisoviolanthrone is prepared by chlorination of isoviolanthrone with sulfuryl chloride in nitrobenzene. Chlorine substitution occurs in positions 6 and 15. 

The action of chlorine on phenothiazine-6,5-dioxide in acetic acid or in nitrobenzene at room temperature yields 1,3,7-trichloro-phenothiazine-5,5-dioxide. The lowering of the reactivity in electrophilic substitutions by oxidation at the sulfur bridge is also shown by the fact that 1,3,7,9-tetrachlorophenothiazine-5,5-dioxide is the final product of chlorination even in nitrobenzene at 100°. Direct chlorination was also used with some substituted phenothia-zines. Bromophenothiazines are chlorinated in nitrobenzene to octahalophenazathionium perhalides, as mentioned in Section IV,H,2. There are also reports on the chlorination of some nitro-phenothiazines. Thus, if chlorine is bubbled through the reaction mixture prepared on treating phenothiazine with nitric acid, chloronitrophenothiazine-5-oxides of unknown orientation were obtained. When chlorination of nitrophenothiazines is carried out in nitrobenzene, chlorine replaces the nitrogroups e.g., 3-nitro-lO-methylphenothiazine was converted into octachlorophenothiazine. b. Bromination with Elementary Bromine. The formation of phenazathionium perbromide (66) by the action of bromine on... 

In studying the mechanism of action of bisquatemary ammonium compounds upon mediator exchange in the vegetative nerve system, most attention has been concentrated on the part played by thiamine and panthothenic acid. The results obtained from these studies have shown that thiamine and calcium pantheonate as antidotes exert a certain positive effect in acute poisonings by one of the bisquatemary ammonium compounds, such as hexamethylen-bis-(4-nitrobenzene) chlorine ammonium. Calcium pantheonate has shown a high antidote activity. 

Class 1 Aniline, EDC, dioxane, phenol, nitrobenzene, chlorinated methanes (except MDC)... 

Phosphorus pentachloride Aluminum, chlorine, chlorine dioxide, chlorine trioxide, fluorine, magnesium oxide, nitrobenzene, diphosphorus trioxide, potassium, sodium, urea, water... 

Aluminum chloride dissolves readily in chlorinated solvents such as chloroform, methylene chloride, and carbon tetrachloride. In polar aprotic solvents, such as acetonitrile, ethyl ether, anisole, nitromethane, and nitrobenzene, it dissolves forming a complex with the solvent. The catalytic activity of aluminum chloride is moderated by these complexes. Anhydrous aluminum chloride reacts vigorously with most protic solvents, such as water and alcohols. The ability to catalyze alkylation reactions is lost by complexing aluminum chloride with these protic solvents. However, small amounts of these "procatalysts" can promote the formation of catalyticaHy active aluminum chloride complexes. 

Nitration of benzene yields nitrobenzene, which is reduced to aniline, an important intermediate for dyes and pharmaceuticals. Benzene is chlorinated to produce chlorobenzene, which finds use in the preparation of pesticides, solvents, and dyes. 

It is also interesting to note that quatemization of a chloropyrimi-dine at the nitrogen atom adjacent to the chloro group with methyl iodide results in the easy replacement of the chlorine by iodine, whereas similar salt formation on the remote nitrogen either leaves the chlorine unaffected or replacement occurs only at higher temperatures. A similar reaction occurs between 2-amino-6-chloro-4-methylpyrimidine and dimethyl sulfate in nitrobenzene to give the salt 45 and betaine 46. ... 

The usual order found with halogenonitrobenzenes is F > Cl Br I, the order of Cl and Br being variable, just as in heteroaromatic reactivity. The position of fluorine is of interest the available data indicate that it is usually the same as for nitrobenzene derivatives. Thus, in acid hydrolysis the order F > Cl for 2-halogeno-quinolines can be deduced beyond doubt since the fluoro derivative appears to react in the non-protonated form and the chloro derivative to resist hydrolytic attack even in the protonated form under appropriate conditions (Section II,D, l,d). Furthermore, in the benzo-thiazole ring, fluorine is displaced by the CHgO reagent at a rate 10 times that for chlorine. ... 

Similar to the alkylation and the chlorination of benzene, the nitration reaction is an electrophilic substitution of a benzene hydrogen (a proton) with a nitronium ion (NO ). The liquid-phase reaction occurs in presence of both concentrated nitric and sulfuric acids at approximately 50°C. Concentrated sulfuric acid has two functions it reacts with nitric acid to form the nitronium ion, and it absorbs the water formed during the reaction, which shifts the equilibrium to the formation of nitrobenzene ... 

P pentachloride causes ignition on contact with Al powder (Ref 2), while contact with a mixt of chlorine and chlorine dioxide usually results in expln, possibly due to formation of the more sensitive chlorine monoxide (Ref 5). Interaction with diphosphorus trioxide is rather violent at ambient temp (Ref 3) treatment with fluorine causes the entire mass to become incandescent (Ref 1). Ignition occurs when hydroxylamine is mixed with P pentachloride (Ref 6), while mixts with Mg oxide react with brilliant incandescence (Ref 7). The residue from interaction of P pentachloride and anilide in benz and removal of solvent and phosphoryl chloride in vacuo expld violently on admission of air (Ref 12). A soln of P pentachloride in nitrobenzene is stable at 110°, but begins to de-... 

Generally, higher catalyst concentration leads to side reactions. An efficient approach to minimize the side reactions is to use the minimum amounts of Friedel-Crafts catalyst (e.g., FeCl3, 0.1-4 wt%). The reaction can be performed either in bulk or in solution using, for example, nitrobenzene, dimethyl sulfone, or chlorinated biphenyls as the reaction media. 

There are certain formal analogies here to m- attack on nitrobenzene (cf. p. 152), but pyridine is very much more difficult to substitute than the former. Thus nitration, chlorination, bromination and Friedel-Crafts reactions cannot really be made to take place usefully, and sulphonation only occurs on heating with oleum for 24 hours at 230°, with an Hg2 catalyst. This difficulty of attack is due partly to the fact that pyridine has an available electron pair on nitrogen, and can thus protonate (66), or interact with an electrophile (67) ... 

Nitrobenzene can be chlorinated at 40-50° by the use of 1 per cent of iron with 0.1 per cent of iodine as a combined catalyst. Fierz-David, Naturwiss. 17, 13 (1929). 

Chloroethyl)-4-nitrobenzene, ketone deoxygenative chlorination, 134 Chromium complexes ... 

The following quaternary ammonium salts are used as phase transfer catalyst tetra-K-butylammonium chloride (TBAC), tetra-n-butylammonium bromide (TBAB), benzyltriethylammonium chloride (BTEAC), and benzyltriethylammo-nium bromide (BTEAB). Chlorinated hydrocarbons, such as dichloromethane (DCM), chloroform (CF), tetrachloromethane (TCM), 1,2-dichloromethane (DCE), and nitrobenzene (NB) are used as solvents. The effects of phase-transfer catalyst and solvent on the yield and reduced viscosity are summarized in Table 9.1. 

Other high-boiling solvents such as nitrobenzene and 2-nitrotoluene can also be used in the solvent process, but 4-nitrobiphenyl, a listed carcinogen, is produced when nitrobenzene is employed. One way to avoid the formation of substituted biphenyls is to employ a polysubstituted toluene as solvent, the substituents being chlorine or alkyl groups, mainly propyl. These are difficult to prepare but they have been patented by Toyo Inks. 

Explanation Chlorine combined originally to chlorobutol is being converted by hydrolysis in the presence of sodium hydroxide to ionic chloride that may be estimated quantitatively by Volhard s method in the presence of nitrobenzene. 

The efficiency of nitrobenzene photoreduction may be increased remarkably in 2-propanol/hydrochloric acid mixtures. In 50% 2-propanol/water containing 6 moles l i HCl, acetone and a complex mixture of chlorinated reduction products are formed i ). Both HCl and 2-propanol (as hydrogen source) are needed. When sulfuric acid is substituted for HCl, enhanced photoreduction does not occtu . When using mixtures of HCl and LiCl to maintain a constant chloride concentration (6 M) and vary [H+], a constant disappearance quantum yield 366 =0.15 is found within the [H+]-range 0.05—6 moles l i. This strongly suggests that chloride ions play an essential role, probably via electron transfer to 3(n, tt )-nitrobenzene i > [Eq. (1)], but it is also evident from the data presented that the presence of add is probably important in subsequent steps, [Eq. (3)]. 

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