芳香族硝基化合物的常见合成方法实例
芳烃的直接硝化是合成芳香族硝基化合物最重要的方法。可使芳烃硝化的试剂很多，最常用的硝酸及其盐、以及硝酸酯等。
HNO3 作为硝化试剂反应示例
硝酸是最常用的硝化试剂之一，它能使许多芳香族化合物发生硝化，普通硝酸和发烟硝酸都能用于硝化。
A wide-mouth 1-L flask is supported inside a water bath. The flask is fitted with a moderate-speed stainless-steel propeller-type stirrer,and nitric acid (sp. gr. 1.4, 350mL.) at 20° is poured into it. Veratraldehyde (70 g, 0.42 mole) is crushed atleast as fine as rice grains and is slowly added in small portions to the acid. The rate of addition should be such thatit requires about 1 hour to add all the aldehyde. The internal temperature is checked from timeto time and should be held between 18° and 22°. The mixture is stirred for 10minutes after the addition of the last of the aldehyde.
Themixture is then poured into 4 Lof vigorously agitated cold water. From this point onward the protection of theproduct from light is extremely important. The stirring is continued for a fewminutes; then the batch is filtered through Büchnerfunnel. The filter cake is recrystallized from 95% ethanol to give 55–60 g of pure material, melting at 132–133°.
HNO3 /H2SO4作为硝化试剂反应示例
硝酸与硫酸组成的混酸是比硝酸更强的硝化剂，根据底物活性的高低可以使用普通的硝酸或发烟硝酸，这个方法可以顺利地得到多硝基取代的产物。
A 5-L three-necked flask fitted with an all-glass addition funnel and two condensersis charged with 770 mL of concentrated sulfuric acid and 1.3 L of 90% fuming nitric acid. The solution is heated under gentle reflux,and a solution of (73 g, 0.4 mol) of 9-fluorenone in 840 mL ofconcentrated sulfuric acid is added from thedropping funnel over a 1-hour period. After the fluorenoneaddition is complete, a solution of 950 mL of fuming nitric acid in 1120 mL ofconcentrated sulfuric acid is added dropwiseduring 8.5 hours to the gently refluxing reaction mixture. The heating jacket is turned off and thesolution is allowed to stand for 10 hours. The reaction mixture is poured into5 gallons of water in two 5-gal Crocks. The light yellow precipitate is washed withwater, twice by decantation, filtered, washed several times with water andsucked dry, and finally is dried in a vacuum ovenat 80° for 10 hours. The yield of crude 2,4,5,7-tetranitrofluorenone, mp 249–253°,is 105–117 g(72–80%). This solid is recrystallized from 1.6 L of acetic acid containing 100 mL of acetic anhydride.The hot solution is filtered through a fluted filterand cooled rapidly to yield 80–86 g (51–54%) of 2,4,5,7-tetranitrofluorenone, mp 253.0–254.5°.
硝酸盐/H2SO4作为硝化试剂反应示例
硝酸盐/H2SO4是硝化常用的试剂，通常使用的硝酸盐是硝酸钾，反应条件温和，操作方便，反应迅速，通常在0oC进行，缺点是选择性不好。
4-bromo-2-tert-butylphenylmethyl carbonate (470 g,1.67 mol) is dissolved in conc. H2SO4 (1000 mL) at 0 ℃. KNO3 (253 g, 2.5 mol) was added in portions over 90 minutesto the above solution and the reaction mixture is sequentially stirred for 2 hoursat 0 ℃. The mixture is poured into 20 L ice-water. The resulting precipitate is collected andwashed with water thoroughly, dried and recrystallized from ether to give thepure product (332 g,yield 60%)。