US3488397A - Nitration of alkyl benzenes with nitric and phosphoric acids - Google Patents

Nitration of alkyl benzenes with nitric and phosphoric acids Download PDF

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Publication number
US3488397A
US3488397A US676607A US3488397DA US3488397A US 3488397 A US3488397 A US 3488397A US 676607 A US676607 A US 676607A US 3488397D A US3488397D A US 3488397DA US 3488397 A US3488397 A US 3488397A
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acid
nitration
nitric
content
dnt
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Christer Lennart Hakansson
Arne Arvid Arvidsson
Ingar Loken
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Saab Bofors AB
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Bofors AB
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C201/00Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
    • C07C201/06Preparation of nitro compounds
    • C07C201/08Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups

Definitions

  • the method of nitrating alkyl-substituted aromatic compounds, particularly toluene, in such a way that a greater portion of p-isomer is obtained than when earlier methods are used, is characterized according to the present invention in that the nitration is carried out with nitric acid in the presence of phosphoric acid, the concentration and quantity of which is chosen in such a way that after the reaction the P 0 content of the phosphoric acid to not more than 82%.
  • the phosphoric acid should particularly be chosen so that the P 0 content after the reaction does not exceed 76%, and it can appropriately amount to between 62 and 76%. It can also be appropriate that the acid mixture used for the nitration also contains sulphuric acid, and the quantity of sulphuric acid should then amount to not more than 80% of the quantity of phosphoric acid.
  • Example 1 In Example 1, to 5.65 g. of toluene there was added during the course of 15 minutes and with intensive stirring, 41.5 g. of nitration acid, consisting of 4 g. of 99% nitric acid and 37.5 g. of phosphoric acid containing 73% P 0 The stirring was thereafter continued for 40 minutes, and during the whole of the experiment the temperature was kept at 30i1 C. The reaction mixture was thereafter poured out on 400 g. of ice, after which extraction with 3 X 20 ml. of chloroform took place. The chloroform phase was thereafter washed with water and analyzed with gas chromatography.
  • 41.5 g. of nitration acid consisting of 4 g. of 99% nitric acid and 37.5 g. of phosphoric acid containing 73% P 0
  • the stirring was thereafter continued for 40 minutes, and during the whole of the experiment the temperature was kept at 30i1 C.
  • the reaction mixture was thereafter poured out on 400 g. of ice, after which
  • Example 1 a molar excess of approximately 2% of nitric acid in relation to the toluene was used, while for experiments 2-7, nitric acid with approximately 6% deficit was used.
  • Example 1 As will be noted from the table, at Example 1, a considerably greater portion of p-isomer was obtained than at the conventional nitration with nitric acid and sulphur acid, in which the ratio p-nitrotoluene (PNT) to o-nitrotoluene (ONT) is approximately 0.63, while said ratio in Example 1 amounted to 1.11.
  • PNT p-nitrotoluene
  • ONT o-nitrotoluene
  • Example 2 the P content of spent acid is 62.7, and even at this low concentration, there is a noticeable improvement as regards the increased yield of p-isomer.
  • Example 3 the P 0 content in the spent acid has been increased to 69.0%, and thereby also a considerable improvement of the yield of p-isomer has been obtained in relation to Example 2.
  • Example 4 the increase of the P 0 content in the spent acid (to 76.6) has increased the portion of p-isomer in the end product, but at the same time a certain, although comparatively small, quantity of dinitrotoluene (DNT) has been formed.
  • DNT dinitrotoluene
  • Example 5 If, as in Example 5, the P 0 content in the spent acid is allowed to amount to 82.0%, the quantity of dinitrotoluene will increase quite considerably, and therefore the P 0 content must not be allowed to exceed 82%. In Example 5, the quantity of p-nitrotoluene in relation to the quantity of o-nitrotoluene has further increased, but this is associated with the fact that at the dinitration, which is not desired, it is particularly the o-nitrotoluene which is consumed.
  • Example 6 shows an experiment in which the reaction temperature has been reduced to 10 C., which does not seem to have had any noticeable effect on the relaiton between the quantities of pand o-isomers.
  • Example 7 finally, the reaction temperature has been increased to 70 C., and a comparison with Example 3 shows that the decrease in the relation of p-isomer to o-isomer is comparatively insignificant.
  • the P 0 content in the spent acid should amount to not more than 82%, but should appropriately not be more than 76%, in order that the desired increase of the quantity of p-nitrotoluene may be obtained without altogether too great dinitration. It will also be noted from the table that the influence of the reaction temperature is insignificant when this is varied within reasonable limits. Nor does a slight excess or deficit of nitric acid seem to have any noticeable influence on the result.
  • Example 8 To 7.1 g. of ethylbenzene was added during the course of minutes, with intensive stirring, 53 g. of nitration acid consisting of 4 g. of nitric acid and 49 g. of phosphoric acid with 76.7% P 0 This involves that the molar ratio between the nitric acid and the ethylbenzene shows as deficit of nitric acid of approximately 5%.
  • the stirring was continued for 40 minutes, and during this time, as well as during the entire experiment, the temperature was kept at 30 C.
  • the reaction mixture was thereafter poured out on ice and extracted with chloroform, after which the chloroform phase was washed with water and analyzed with gas chromatography. This analysis gave the following results:
  • the P 0 content in the spent acid amounted to 75.0%.
  • Example 9 To 7.1 g. of isopropylbenzene was added during the course of 45 minutes and with intensive stirring 53 g. of nitration acid with the same composition as per example 8, after which the stirring was continued for 10 minutes at 3540 C. During the actual addition of the ingredients, the temperature was approximately 50 C. In this case, the gas chromatography gave a ratio between p/o-isomer of 3.03, which is considerably higher than the same value 2.08 for the corresponding conventional nitration with nitric acid and sulphuric acid.
  • Example 10 To 0.2 g. of toluene was added during the course of 15 minutes with intensive stirring 53 g. of nitration acid consisting of 4 g. of nitric acid and 49 g. of phosphoric acid with 82% P 0 This addition of ingredients involves that to each mole of toluene is added approximately 29 moles of nitric acid. After the addition of the ingredients, the stirring was continued for 1 hour, and during the whole experiment the temperature was kept at 30 C. The P 0 content in the spent acid was 81.45%. Through gas chromatography, the following composition of the product was obtained:
  • Example 11 To 5 g. of o-nitrotoluene was added during the course of 15 minutes and with intensive stirring 53.6 g. of nitration acid consisting of 4.6 g. of nitric acid and 49 g. of phosphoric acid with 82.2% P 0 This addition of ingredients involves that to each mole of o-nitrotoluene is added 2 moles of nitric acid. After the addition of the ingredients, the stirring was continued for 1 hour, and during the whole of the experiment the temperature was kept at 30 C. This P 0 content in the spent acid was 81%. The analysis with gas chromatography gave the following results:
  • compositions of the two products are compared, it will be clearly noted that the content of 3,4-DNT increased at the expense of the 2,3-DNT.
  • the content of P in the spent acid was 81.0%.
  • Example 13 To 12 g. of toluene was added during the course of 15 minutes and with intensive stirring 57.9 g. of nitration acid consisting of 4 g. of nitric acid, 49 g. of phosphoric acid with 78.4% P 0 and 4.9 g. of sulphuric acid (96.5 This addition of ingredients involves that approximately 0.5 mole of nitric acid corresponded to each mole of toluene. After the addition of the ingredients, the stirring was continued for 40 minutes. During the whole of the experiment that temperature was kept at 30 C. Through gas chromatography the composition of the products was fixed at:
  • Nitration according to the invention can take place advantageously with a continuous procedure, and it has proven possible, for instance, for continuous mononitration of the toluene, to use apparatus which has originally been designed for conventional nitration with nitric acid and sulphuric acid.
  • Recovery of the phosphoric acid in the spent acid can, in principle, take place in the same way as for sulphuric acid, i.e. by heating and distilling 011 the water.
  • a process for nitrating an alkyl-substituted aromatic compound in such a way that the p-isomer yield is optirnized comprising the step of carrying out the nitration with nitric acid in the presence of phosphoric acid and sulphuric acid, with the concentration and quantity of the phosphoric acid chosen in such a way that after the reaction the P 0 content thereof is not more than 82%.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
US676607A 1966-10-20 1967-10-19 Nitration of alkyl benzenes with nitric and phosphoric acids Expired - Lifetime US3488397A (en)

Applications Claiming Priority (1)

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SE14264/66A SE305862B (cs) 1966-10-20 1966-10-20

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US3488397A true US3488397A (en) 1970-01-06

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US (1) US3488397A (cs)
CH (1) CH485643A (cs)
DE (1) DE1643600C3 (cs)
GB (1) GB1207384A (cs)
SE (1) SE305862B (cs)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4996376A (en) * 1988-10-24 1991-02-26 Rhone-Poulenc Chimie Preparation of dinitrotoluenes
US6768032B2 (en) 2001-04-06 2004-07-27 Bayer Chemicals Ag Continuous isothermal process for preparing mononitrotoluenes in the presence of phosphoric acid

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4996376A (en) * 1988-10-24 1991-02-26 Rhone-Poulenc Chimie Preparation of dinitrotoluenes
US6768032B2 (en) 2001-04-06 2004-07-27 Bayer Chemicals Ag Continuous isothermal process for preparing mononitrotoluenes in the presence of phosphoric acid

Also Published As

Publication number Publication date
CH485643A (de) 1970-02-15
DE1643600C3 (de) 1973-12-20
DE1643600A1 (de) 1971-07-01
SE305862B (cs) 1968-11-11
DE1643600B2 (de) 1973-05-24
GB1207384A (en) 1970-09-30

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