综合实验讲义[1]

从红辣椒中分离红色素

一、实验目的

1、学习用薄层层析和柱层析分离提取红色素。

2、掌握用薄层层析鉴定红色素、记录红色素的红外和紫外光谱。

二、实验原理

红辣椒中含有几种色素，因其极性不同，可用薄层层析和柱层析分离出来。

三、仪器与试剂

1、仪器

硅胶G薄层广口瓶层析柱

2、试剂

碾细的红辣椒1g，300ml二氯甲烷, 10g硅胶

四、实验步骤

1、在25ml圆底烧瓶中加入1g红辣椒和几粒沸石，加入10m二氯甲烷，装

上回流管回流20分钟，将烧瓶冷至室温，过滤除去固体，得粗色素溶液。

2、用广口瓶作为层析槽，以二氯甲烷作为展开剂，在硅胶G薄板上点样后，

在层析槽中进行层析。观察每一点的颜色，计算Rf值，用柱层析分离

Rf＝0.6的主要红色素。

3、在层析柱的底部垫一团脱脂棉花并压紧它，加入洗脱剂二氯甲烷至层析

柱的3/4高度，打开活塞，放出少许溶剂，用玻璃压脱脂棉中的气泡，再

将30ml二氯甲烷与7.5g硅胶调成糊状加入层析柱中，使吸咐剂装填致密，然后在吸附剂上层覆盖一层石英砂。

4、打开活塞，使二氯甲烷洗脱剂液面降至覆盖硅胶的滤纸上表面，关闭活

塞。将色素的粗混合物溶液（约2ml）小心的转移至层析柱面上（用滴管

转移）。再打开活塞，待红色素溶液液面与滤纸齐平时，缓缓注入二氯甲

烷至高出石英砂2cm即可，以保持层析柱中的固定相不干，当再加入洗

脱剂不再带有色素颜色时，可将洗脱剂加至层析柱最上端。在层析柱下

端用试管分段收集各种颜色的馏分，当红色素洗脱后停止层析。

5、蒸除收集到的红色素馏分中的二氯甲烷，得红色素纯品。

五、实验结果与处理

用紫外光谱鉴别红色素，记录λmax。

Diels-Alder 反应

一、实验目的：

1.通过环戊二烯与对苯醌或马来酸酐的加成验证环加成反应；

2.熟练处理固体产物的操作。

二、实验原理： O O

+

O

O H H +C

O

C

O C C O H H

+C O C O H C C H H ONa ONa O +C

O

C O O O O O O O KO KO 22O

三、实验步骤：

1. 环戊二烯与对苯醌的加成

在100ml 烧杯中，加入1.8g(0.017mol)对苯醌和7ml 乙醇，使成悬浮液，将此烧杯置于冰浴中冷却至0-5℃。将新蒸馏的环戊二烯1.3g(1.5ml,0.018mol)迅速加入到上述悬浮液中，略加摇匀后即置于冰浴中，15min 后除去冰浴，在室温放置45min 。然后在冷却状态下抽滤，得淡黄色固体1.3g(产率为44%)。

2. 环戊二烯与马来酸酐加成

在125ml 三角烧瓶中加入6g(0.061mol)马来酸酐，用20ml 乙酸乙酯在水浴上加热使之溶解，再加入20ml 石油醚(沸程60-90℃)，稍冷后（不能析出结晶），往此混合液中加入 4.8g(6ml,0.073mol)新蒸馏的环戊二烯。振荡反应瓶，直到放热反应完成。加成物为一白色固体，mp 为164-165℃，产量7.2g （产率72%）。此加成产物还保留有双键，能使高锰酸钾溶液或溴的四氯化碳溶液褪色。

3. 蒽和马来酸酐加成

在50ml 圆底烧瓶中加入2g 纯蒽、1g 马来酸酐和25ml 无水的二甲苯，连接回流冷凝管，加热回流25min 。将液面的边缘上述析出的晶体振荡下去，再继续加热

5min，停止加热。当不回流时趁热经一预热过的布氏漏斗过滤，滤液放冷，抽滤分出固体产物，在真空干燥器内干燥，产品的mp为262-263℃（分解），产率约2g。

synthesize of iodobenzene

PhNH22

N Cl PhI + N2 + KCl

HCl

Dissolve 20 g (19.6 ml, 0.215 mol) of aniline in a mixture of 55 ml of concentrated hydrochloric acid (1)and 55 ml of water contained in a 500-ml round-bottomed flask. Place a thermometer in the solution and immerse the flask in a bath of crushed ice (2); cool until the temperature of the stirred solution falls below 5℃. Dissolve 16 g (0.23 mol) of sodium nitrite in 75 ml of water and chill the solution by immersion in the ice bath; add the sodium nitrite solution (3)in small volumes (2-3 ml at a time) to the cold aniline hydrochloride solution, and keep the latter well shaken, Heat is evolved by the reaction. The temperature should not be allowed to rise above 10℃(add a few grams of ice to the reaction mixture if necessary) otherwise appreciable decomposition of the diazonium compound and of nitrous acid will occur. Add the last 5 percent of the sodium nitrite solution more slowly (say, about 1 ml at a time) and, after shaking for 3-4 minutes, test a drop of the solution diluted with 3-4 drops of water with potassium iodide-starch paper (4); if no immediate blue colour is obtained at the point of contact with the paper, add a further 1 ml of the nitrite solution and test again after 3-4 minutes. Continue until a slight excess of nitrous acid is present.

To the solution of benzenediazonium chloride add a solution of 36 g (0.216 mol) of potassium iodide in 40 ml of water slowly and with shaking. Nitrogen is evolved. Allow the mixture to stand for a few hours. Fit the flask with an air condenser and heat it cautiously in a boiling water bath until evolution of gas ceases. Allow to cool. Decant as much as possible of the upper aqueous layer and render the residual aqueous and organic layers alkaline by the cautious addition of 10 percent sodium hydroxide solution, i.e. until a drop of the well-shaken mixture withdrawn on a glass rod imparts a blue colour to red litmus paper. The alkali converts any phenol present into sodium phenoxide, which, unlike phenol itself, is not volatile in steam. Steam distil until no more oily drops pass over. Transfer the distillate to a separatory funnel and run off the lower layer of iodobenzene into a small conical flask. The crude iodobenzene should have a pale yellow colour; if it is dark in colour, return it to the separatory funnel and shake it with a little sodium metabisulphite solution until a pale yellow colour is obtained, then remove the heavy layer as before. Dry with about 1 g of anhydrous calcium chloride or magnesium sulphate: filter through a fluted filter paper into a small distilling flask equipped with a short air condenser. Distil using an air bath and collect the fraction, b.p. 185-190℃(5). The yield of iodobenzene (an almost colourless liquid) is 33 g (75%); the compound gradually develops a yellow colour upon exposure to light.