Concentrated sulfuric acio increases the rate of the reaction by increasing the concentration of the electrophile-the nitronium ion (NO2) Step 1 H-o-N+ HOSO3H H——-o—NO2+HSO4 Lewis base Lewis acid 质子化硝酸 step2H-9—No2+n250 NO2+ H3O HSO4 Nitronium ion 硝基正离子
Concentrated sulfuric acid increases the rate of the reaction by increasing the concentration of the electrophile-the nitronium ion (NO2 + ) Step 1 H O N O O + HOSO3H H O H NO2 + HSO4 - + Lewis base Lewis acid 质 子 化 硝 酸 Step 2 H O H NO2 + + H2 SO4 + NO2 + H3O + + HSO4 - Nitronium ion 硝 基 正 离 子
The nitronium ion reacts with benzene by attacking the Tr cloud and forming an arenium Ion H Step 3 Slow NO NO 2 Nitronium ion 硝基正离子 Arenium Step 4 NO2 fast no. +HSO4— H2sO4 Nitrobenzene
The nitronium ion reacts with benzene by attacking the π cloud and forming an arenium ion Step 3 + NO2 Nitronium ion 硝 基 正 离 子 + Slow H NO2 + Arenium Step 4 + HSO4 - H NO2 + NO2 + H2 SO4 fast Nitrobenzene
15.5 Sulfonation of benzene 苯的磺化 Benzene reacts with fuming sulfuric acid at room temperature to produce benzene sulfonic acid Fuming sulfuric acid is sulfuric acid that contains added sulfur trioxide ( so3 concd H,so s—oH 25°C Sulfur trioxide Benzenesulfonic acid 苯磺酸 (56%
15.5 Sulfonation of benzene 苯的磺化 Benzene reacts with fuming sulfuric acid at room temperature to produce benzene sulfonic acid. Fuming sulfuric acid is sulfuric acid that contains added sulfur trioxide (SO3 ) + O S O O Sulfur trioxide concd H2 SO4 25 o C S O O OH Benzenesulfonic acid 苯 磺 酸 (56%)
The mechanism of sulfonation Step 1 2 H2S04 SO3 H3O HSO4 Slow SO Step 2 Sulfur trioxide So. Step 3 SO HSO Fast t soA SO SO3H Step 4 H3o 0 Benzenesulfonic acid
The mechanism of sulfonation Step 1 2 H2 SO4 SO3 + H3O + + HSO4 - O S O O Sulfur trioxide Step 2 + H SO3 - + Slow H SO3 - + HSO4 - SO3 - Fast Step 3 + H2 SO4 Benzenesulfonic acid Step 4 SO3 - + H3O + SO3H fast + H2O
We may remove the sulfonic acid group by desulfonation SO3H +H20 h2SO4 Benzenesulfonic acid We shall see later that sulfonation and desulfonation reactions are often used in synthetic work
We may remove the sulfonic acid group by desulfonation Benzenesulfonic acid SO3H + H2O + H2 SO4 We shall see later that sulfonation and desulfonation reactions are often used in synthetic work