Obtinere
~~~~~~~~
Se foloseste : - 1 parte glicerina
- 2,05 parti Acid azotic
- 3,19 parti Acid sulfuric
*Raporturile se refera la masa reactantilor
Se amesteca acidul azotic cu acidul sulfuric cu mare atentie deoarece
se degaja caldura, concomitent se raceste amestecul respectiv intr-o baie de
gheata.
Se adauga glicerina in proportii mici, agitinduse usor continutul. In
tot acest timp se continua racirea cu gheata.
Dupa dizolvarea glicerinei se asteapta citeva minute ÷ 15 dupa care se
toarna un volum dublu de apa racita cu gheata, peste amestecul din reactia
anterioara (Apa se va adauga prin prelingere).
La sfirsit se va agita usor amestecul, astfel, pe fundul vasului va
ramine nitroglicerina, sub forma unei substante uleioase.
Nota:
~~~~~
- Pe tot timpul desfasurarii reactiei, temperatura amestecului
trebuie sa aiba in jur de 10øC, dar in nici un caz sa nu depaseasca 30øC.
- Surplusul de apa se va elimina, raminind nitroglicerina pura.
- Acidul sulfuric se adauga peste cel azotic, prin agitare continua
si racire permanenta.
Reactia:
CH2 - O - NO2 HONO2 CH2 - O - NO2
| |
CH - O - NO2 + HONO2 ----> CH - O - NO2 + 3H2O
| |
CH2 - O - NO2 HONO2 CH2 - O - NO2
(glicerina) (Acid (Trinitrat de
Azotic) glicerina)
Trinitratul de glicerina este un ester, si nu un nitroderivat, grupa
-NO2 nefiind legata direct de atomul de C, ci prin intermediul unui atom de O.
Explodeaza usor prin zdruncinare sau lovire, fiind una din substantele
explozive cele mai puternice. Nestabilitatea se explica prin faptul ca in
molecula sa se gaseste o cantitate suficienta de atomi de oxigen cu care sa se
transforme cu atomi de Carbon in CO2 si cei de H in apa. Atomii de azot
prezinta o bariera intre cei de O si C insa la o usoara zdruncinare se
regrupeaza atomii, forminduse:
CO2, H2O, N si o mare cantitate de caldura.
Conditia minima de explozie este satisfacuta de reactia in lant generata de o
singura regrupare.
ENG: Nitroglycerin.
Nitroglycerin (NG), also known as nitroglycerine, trinitroglycerin, and glyceryl trinitrate, is a chemical compound. It is a heavy, colorless, oily, explosive liquid obtained by nitrating glycerol. It is used in the manufacture of explosives, specifically dynamite, and as such is employed in the construction and demolition industries, and as a plasticizer in some solid propellants. It is also used medically as a vasodilator to treat heart conditions.
Preparation:
Nitroglycerin is prepared by nitration of glycerol (also known as glycerin). In the process, glycerin is slowly tipped into a mix of full concentration nitric acid and sulfuric acid (about 50% sulfuric acid, 40% nitric acid, and 5-10% glycerin). The mixed acid must be cooled to approximately room temperature before the glycerin is added because they will exotherm (heat up) greatly when combined. The solution is slowly stirred. A few seconds after mixing, the vessel must be immersed in a jacket of ice water to prevent the exothermic reaction from overheating it, causing nitric acid decomposition or even an explosion. The temperature should never exceed 10 °C (50 °F), but the chemicals must not be cooled by the ice water before mixing, or the nitrating reaction will not take place. If the reaction is successful, the nitroglycerin will form a slightly yellow or straw colored liquid which will float to the top of the acid mix. The mix is then carefully poured into a large container of water. The nitroglycerin will settle to the bottom (it is water insoluble) and should be neutralized with sodium carbonate and water mix until its pH becomes neutral. Another method of producing nitroglycerin is to mix the glycerin and sulfuric acid first, which produces heat, but at this stage is not dangerous. After cooling, the Nitric acid can be added reasonably quickly to the mix, but it can still cause uncontrolled nitration. It can also cause the acid to spurt back at you. Therefore it should be avoided and the nitration mixture should be added very slowly to the glycerol. The then nitrated glycerin and acid solution has to be left for the nitroglycerin to float to the top, as this method can sometimes produce the nitroglycerin in fine quantities. The waiting period is a day or less, but the prolonged exposure to the acids may cause the decomposition or even the explosion of the nitroglycerin, although the latter will only occur in large batches. If a milky colour is seen, it is only because of water in the mix, and not to be worried about. From this point, continue as above. This method was used in the time of Nobel, although it was not his own.
