Nitration of naphthalene to dinitronaphthalene

The direct nitration of naphthalene to dinitronaphthalene by the method applied at I. G. Ludwigshafen is carried out in the following way  

A cast or wrought iron jacketed nitrator (of 3.4 m3 capacityX equipped with a propeller stirrer (25-26 r. p. m), is charged with the following quantities of acids  

As heat is generated during stirring the temperature of the mixture rises to 30°C. Then 295 kg of naphthalene is introduced through a screw metering tank at a rate of 14.75-11.8 kg/hr. The naphthalene is added in the following way  

After adding all the naphthalene, the temperature is raised during a period of 4 hr up to 80°C and the nitrator contents are kept at this temperature for another hour. 

The spent acid, containing 30% of H2SC 4 (sp. gr. 1.220) is disposed to a drain. The product on the filter is washed with 6 m3 of cold, then with 12-14 m3 of warm water. 

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Indeed Pascal [83] found that in the waste acid from the nitration of naphthalene to dinitronaphthalene, the NH3 content amounted to 0.001-0.002%, based on the naphthalene used for nitration. 

The nitration of naphthalene to dinitronaphthalene (after Pascal [20a]) is effected in a nitrator essentially of die sane type as that used for the nitration of naphthalene to nitronaphthalene by the French method (Fig. 108, p. 441), the only difference being in the outlet which is wider at the bottom - 8 cm in diameter - since the nitration product is solid. 

The two-stage nitration of naphthalene to dinitronaphthalene requires more complex plant and is more labour consuming nevertheless it is more economic than single stage nitration, since the product obtained is of higher purity, more easily freed from acid, and the consumption of nitric acid is lower. 

Nitronaphthalene. 1-Nitronaphthalene is manufactured by nitrating naphthalene with nitric and sulfuric acids at ca 40—50°C (37). The product is obtained in very high yield and contains ca 3—10 wt % 2-nitronaphthalene and traces of dinitronaphthalene the product can be purified by distillation or by recrystaUization from alcohol. 1-Nitronaphthalene is important for the manufacture of 1-naphthalenearnine. Photochemical nitration of naphthalene by tetranitromethane in dichioromethane and acetonitrile to give 1-nitronaphthalene has been described (38). 

Donaldson [2] gives an example. In 1,8-dinitronaphthalene the 3- and 6-positions are the least deactivated and nitration leads to 1,3,6,8-tetranitronaphthalene. Where two positions remain open the a- position shows a greater activity because of the nature of the naphthalene ring. An anomalous and important case is that of 1,5 dinitronaphthalene, in which only positions 3 and 7 are not deactivated. The main product of nitration of 1,5-dinitronaphthalene is 1,4,5-trinitronaphthalene and not 1,3,5- as would be expected. This led Hodgson and Ward [3] to conclude that the predominant hybrid in 1,5-dinitronaphthalene is... 

Nitration of naphthalene gives 1-nitronaphthalene (12). Further substitution does not occur in the same ring and the main products of dinitration are 1,5- (13) and 1,8-dinitronaphthalenes (14). The initial nitro group deactivates that ring to further electrophilic substitution and attack at the a-positions of the other ring therefore takes place. 

The potential of microreaction processes to influence isomeric product distributions was demonstrated by Loebbecke et cd. [20], They reported on the nitration of naphthalene at moderate temperatures in different types of microreactors to ensure isothermal processing and precise control of residence time (Scheme 4.8). A deliberate synthesis of either mono- or dinitro-substituted naphthalene with high selectivities was achieved, in contrast to a broad product spectrum obtained rmder macroscopic batch conditions. In particular, isomeric ratios of 1- to 2-mononitro-naphthalene and also 1,5- to 1,8-dinitronaphthalene could be significantly increased compared with batch processes. 

Dinitronaphthalene ( Gamma-dinitronaph-thalene, 1,3-DNN), Bright yel needles from aq pyridine, mp 144°, bp subl (Refs 1 32) CA Registry No 606-37-1. It is prepd by the action of nitric ac/sulfuric ac on naphthalene at low temps (Refs 14 33) by the nitration of 1-MNN with a mixt of 17.3% nitric ac, 61.2% sulfuric ac, and 21.5% w, temp 59-75°, time 90min (Ref 52) by the action of powd Cu (Ref 18) or hydrazine (Ref 22) on l-chioro-2,4-dinitro-naphthalene by the diazotization of 2,4-dinitro-1-naphthylamine followed by redn of the dia-zonium salt with EtOH (Ref 25) or by the action of Br on 5,7-dinitro-l,2,3,4-tetrahydro-naphthalene followed by dehydrobromination (Ref 13). It is used to prep more highly nitrated naphthalenes... 

Naphthalene nitrates more readily than benzene, the first nitro group taking the a-position which is ortho on one nucleus to the side chain which the other nucleus constitutes. The second nitro group takes one or another of the expected positions, either the position meta to the nitro group already present or one of the a-positions of the unsubstituted nucleus. The dinitration of naphthalene in actual practice thus produces a mixture which consists almost entirely of three isomers. Ten different isomeric dinitronaphthalenes are possible, seven of which are derived from a-nitronaphthalene, seven from /3-nitronaphthalene, and four... 

As for naphthalene, Pictet [56] found that nitration at temperatures from -50 to -60°C mostly resulted in the formation of 1,5-dinitronaphthalene with a certain amount of the 1,3-isomer, while at a temperature higher than room temperature 1,5-dinitronaphthalene is formed along with 1,8-isomer. 

The mixture is prepared from 600 kg of the spent acid from the dinitronaph-thalene manufacture and 550 kg of the spent acid from mononitration, which has been re-used for washing dinitronaphthalene. In consequence the spent acid contains some of the HN03 adsorbed by dinitronaphthalene. The composition and the quantity of the mixture should be so calculated as to contain 128 kg of HN03, required for complete nitration of 300 kg of naphthalene. 

Dinitronaphthalene (2,3-DNN). Yel needles from MeOH, mp 170.5—1.0° (Refs 8 23) CA Registry No 1875-63-4. It is prepd by bromination of 5,6-dinitro-l,2,3,4-tetrahydro-naphthalene followed by dehydrohalogenation (Ref 23) or by nitration of a naphthalene-hexachlorocyclopentadiene adduct (Diels-Alder), followed by pyrolysis to regenerate the 2,3-DNN (Ref 58)... 

The naphthalene ring activation with the NMe2 groups is so high that the nitration of l,8-bis(dimethylamino)-3,6-dinitronaphthalene (43) proceeds further, enabling one to isolate the hexanitro proton sponge 168 in a good yield (equation 14)37. The second... 

None of the nitrated naphthalenes is very sensitive to shock. a-Nitronaphthalene is not an explosive at all and cannot be detonated. Dinitronaphthalene begins to show a feeble capacity for explosion, and trinitronaphthalene stands between dinitrobenzene and dinitrotoluene in its explosive power. Tetranitro-naphthalene is about as powerful as TNT, and distinctly less sensitive to impact than that explosive. Vennin and Chesneau report that the nitrated naphthalenes, charged in a manometric bomb at a density of loading of 0.3, gave on firing the pressures indicated below.46... 

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