Pogranicza
Potrzebuje przepisu na synteze nitrometanu,
podobno reakcja: kwas chlorooctowy z NaN02 daje nitrometan...
tylko czy ktos to juz kiedys robil? chcialbym miec pewnosc ze nie bedzie zadnych niemilych niespodzianek ;D jak z wydajnoscia?
pozdro
Neok
có¿, mam przepis w preparatyce, ale tam wydajno¶æ ledwo 30%, ja nie niestety nie próbowa³em, poszukam przepisu na orgsynie jeszcze...
na orgsynie przepis jest taki:
1. Procedure
To a mixture of 500 g. (5.3 moles) of chloroacetic acid and 500 g. of cracked ice, is added, with stirring, just sufficient cold 40 per cent sodium hydroxide solution to make the solution faintly alkaline to phenolphthalein. About 360 cc. is required; the temperature should not rise above 20° (Note 1). The solution is then mixed with 365 g. (5.3 moles) of sodium nitrite dissolved in 500 cc. of water and heated in a 3-l. round-bottomed flask fitted with a two-holed stopper containing a bent tube of large diameter connecting with an efficient condenser (set downward for distillation) and a thermometer dipping into the liquid. The receiver should be so arranged that it can be cooled, if necessary, by a stream of water.
The solution is heated slowly until the first appearance of bubbles of carbon dioxide, which occurs when the temperature has reached about 80°. The flame is then removed and the reaction allowed to proceed by itself (Note 2). If no rise in temperature occurs, heat is very cautiously applied until the temperature rises to 85°, when the flame is again removed (Note 3). At this temperature the exothermic decomposition of the sodium nitroacetate becomes so rapid that the temperature rises almost to 100° without further application of external heat. If heat is applied after the temperature of the liquid reaches 85°, violent frothing will occur, with serious loss of nitromethane. If the reaction becomes too vigorous it may be checked by applying a wet towel to the flask. Nitromethane starts to distil over at about 90°. During the spontaneous heating, about 120 cc. of nitromethane distils over, accompanied by about 170 cc. of water (Note 4). This water is saved for redistillation.
When the mixture ceases to maintain its temperature spontaneously at 95–100°, heat is applied cautiously until the temperature reaches 110°. About 13 cc. of nitromethane and 200 cc. of water distil over. Further distillation gives water which contains too little nitromethane to pay for recovery. At this point enough sodium chloride and sodium carbonate have separated to cause serious bumping.
The water separated from the nitromethane distillates is mixed with one-fourth of its weight of salt, and redistilled, yielding 10–12 cc. of nitromethane and about 100 cc. of water. This water on distillation gives 3–4 cc. of nitromethane and about 45 cc. of water (Note 5).
The total yield of moist product is 125–135 g.; on drying with a little calcium chloride and distilling, 115–125 g. of pure nitromethane, boiling at 98–101°, is obtained (35–38 per cent of the theoretical amount). A small forerun distils over below 98°, and a little dark brown residue remains (Note 6).
2. Notes
1. In making the sodium chloroacetate, the use of sodium hydroxide with proper cooling is much more rapid than the use of sodium carbonate. In the case of sodium hydroxide it is essential to keep the solution cool in order to prevent the formation of sodium glycolate. If it is preferred to employ sodium carbonate, about 300 g. of the anhydrous material will be required to make the solution slightly alkaline.
2. The thermometer dipping in the liquid is absolutely necessary, as the success of the preparation depends on proper temperature control. The vital point of the whole preparation is to remove all external heat as soon as the reaction is well started. This is between 80 and 85°. No frothing ever occurs when this precaution is rigidly adhered to.
3. Several of these distilling sets can be set up and run by one operator, if each lot is started only when the preceding one has reached 85° and external heat has been removed. The corresponding water layers from different sets can be united and distilled at once.
4. It has been recommended1 that use be made of a gravity separator connected with the adapter in order to separate the nitromethane as fast as it condenses. It was found inadvisable to use such a separator, as the nitromethane is so little heavier than water that a rapid separation is not possible; drops of nitromethane remain suspended and pass over with the water. It is best to allow the distillates to stand in cylinders for at least one-half hour before separating the nitromethane by means of a separatory funnel. During this standing, as much as 2 per cent more of nitromethane sometimes settles out.
5. If the time consumed is an important consideration, it is well to note that the spontaneous heating from 85° to 100° gives three-fourths of all the nitromethane obtained in the preparation. This takes less than one hour. The further heating above 100° and the distillations of the water layers take over two hours, and give only one-fourth of the total yield.
6. It is suggested that improved yields are obtainable when 374 g. of crystalline boric acid is added subsequent to the sodium nitrite and prior to the heating. In this way, carbon dioxide together with some oxides of nitrogen are evolved at about 45°. The reason offered for the higher yields is the destruction of sodium bicarbonate by the boric acid, which thereby prevents alkaline hydrolysis of the sodium chloroacetate (C. L. Tseng, private communication; 2).
The yield is somewhat improved by using 625 g. of chloroacetic acid and about 450 cc. of 40 per cent sodium hydroxide solution instead of the 500 g. and 360 cc., respectively, now specified (H. Adkins, private communication; 2).
3. Discussion
Nitromethane can be prepared by the action of dimethyl sulfate on potassium nitrite,3 or of methyl p-toluenesulfonate4 or methyl chloride5 on sodium nitrite; and from potassium nitrite and potassium chloroacetate,2 or, preferably, the corresponding sodium salts.6 Nitromethane is now commercially available as a product of the vapor-phase nitration of the lower paraffin hydrocarbons.7
This preparation is referenced from:
* Org. Syn. Coll. Vol. 1, 413
References and notes:
1. Steinkopf, Ber. 42, 3438 (1909).
2. Kolbe, J. prakt. Chem. (2) 5, 427 (1872); Preibische, ibid. (2) 8, 316 (1874); Steinkopf, Ber. 41, 4457 (1908).
3. Walden, Ber. 40, 3216 (1907).
4. Rodionov, Alexeiv, and Carcanas, Bull. soc. chim. (4) 39, 324 (1926).
5. Great Western Electro-Chemical Co., U. S. pat. 2,105,581 [C. A. 32, 2148 (1938)].
6. Steinkopf and Kirchhoff, Ber. 42, 3438 (1909); Auger, Bull. soc. chim. (3) 23, 333 (1900); Wahl, ibid. (4) 5, 180 (1909); Pritzl and Adkins, J. Am. Chem. Soc. 53, 234 (1931); Hirano, J. Pharm. Soc. Japan 50, 869 (1930) [C. A. 25, 69 (1931)]; Wang and Tseng, Natl. Central Univ. Sci. Repts., Ser. A, Phys. Sci. 1, 27 (1930) [C. A. 25, 681 (1931)].
7. Haas, Hodge, and Vanderbilt, Ind. Eng. Chem. 28, 339 (1936); Hercules Powder Co., U. S. pat. 2,161,475 [C. A. 33, 7319 (1939)].
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jak widaæ z siarczanu dimetylu te¿ mo¿na próbowaæ, ale to bêdzie paskudna robota z paskudnym siarczanem dimetylu
a w reakcji bezwodnika octowego z HNO3 powstaje C(NO2)4
PS tak sie zastanawiam, czy nie da sie jako¶ wydajnie utleniæ CH3NH2, tyle ¿e niestety to jest gaz, tak samo CH3Cl, reakcja wygl±da fajnie, ale raczej w warunkach laboratoryjnych trudno to zrobiæ, chyba ¿eby wyj¶æ z jodku metylu, on jest ciek³y wiêc mo¿e w reakcji z azotynem
troche sporo z tym roboty....
czemu ten nitrometan taki drogi ;/
swoja droga ciekawe jakie by byly koszta jego produkcji we wlasnym zakresie...
mozna kiedys sprobowac ;D
dzieki za przepis
pozdro
Neok
nitrometan nie jest jakim¶ wybitnie drogim rozpuszczalniekiem, w du¿ych ilo¶ciach jest po kilka USD za litr, piêciolitrowy kanister kosztuje w granicach 180 pln, a czysto¶æ 99,95%
W laboratorium kosztu s± znacznie wy¿sze ni¿ w przemy¶le, bo w przemy¶le nitrometan jest produktem nitrowania propanu, nasz zwi±zek stanowi ok. 25% frakcji nitroalkanów tego procesu, wystarczy go destylacyjnie oddzieliæ od wy¿szych nitrowych (nitroetanu i nitropropanów)
Czy to prawda ¿e wszystkie substancje z przedrostkiem nitro- s± wybuchowe b±d¼ te¿ spalaj± siê gwa³townie?
w praktyce tak, im wiêcej jest grup NO2 tym zwi±zek bardziej niestabilny i sk³onny do wybuchowego rozk³adu, z tego powodu produktów reakcji nitrowania nigdy nie destuluje siê do koñca, bo pochodne dwu- czy nawet trójnitrowe zbieraj±ce siê w kolbie destylacyjnej jako najmniej lotne gro¿± wybuchem... A skrajnym przypadkiem jest kwas pikrynowy, który lubi wybuchaæ jak jest suchy (w handlu s± r-ry nasycone lub kwas o wilgotno¶ci >10%), szczego³nie niebezpieczne s± pikryniany metali ciê¿kich, kwas pikrynowy 2,4,6-trinitrofenol
Ale dosyæ ju¿ offtopowania
mowisz DM, ze bardziej sie oplaci kupic, niz produkowac wlasny? ;/
tak jest praktycznie z ka¿dym odczynnikiem, bardziej siê op³aca kupiæ, ni¿ samemu zrobiæ, chyba ¿e chcesz sobie zrobiæ kilkana¶cie gramów dla w³asnej satysfakcji (sztuka dla sztuki). policz, skora metod± laboratoryjn± wyjdzie ok 30%, to ile kwasu chlorooctowego zejdzie i NaNO2? sam koszt kwasu chlorooctowego jako surowca jest wyzszy o du¿o nic cena przemys³owego nitrometanu
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