制药工程专业英语第6单元

1、PART 2 BIOCHEMICAL PHARMACEUTICALSUnit 6 Isolation of Caffeine from TeaIn this experiment，Caffeine will be isolated from tea leaves. The major problem of theisolation is that caffeine does not occur alone in tea leaves，but is accompanied by other natural substances from which it must be separated. T

2、he major component of tea leaves is cellulose，which is the major structural material of all plant cells. Cellulose is a polymer of glucose. Since cellulose is virtually insoluble in water，it presents no problems in the isolation procedure. Caffeine，on the other hand，is water soluble and is one of th

3、e major substances extracted into the solution called "tea.”Caffeine comprises as much as 5 percent by weight of the leaf material in tea plants. Tannins also dissolve in the hot water used to extract tea leaves. The term tannin does not refer to a single homogeneous compound，or even to substan

4、ces which have similar chemical structure. It refers to a class of compounds which have certain properties in common. Tannins are phenolic compounds having molecular weights between 500 and 3000. They are widely used to "tan”leather. They precipitate alkaloids'z and proteins from aqueous so

5、lutions. Tannins are usually divided into two classes: those which can be hydrolyzed and those which cannot. Tannins of the first type which are found in tea generally yield glucose and gallic acid when they are hydrolyzed. These tannins are esters of gallic acid and glucose. They represent structur

6、es in which some of the hydroxyl groups in glucose have been esterified by digalloyl groups. The non-hydrolyzable tannins found in tea are condensation polymers of catechin. These polymers are not uniform in structure，but catechin molecules are usually linked together at ring positions 4 and 8. When

7、 tannins are extracted into hot water，the hydrolyzable ones are partially hydrolyzed，meaning that free gallic acid is also found in tea. The tannins，by virtue of their phenolic groups，and gallic acid by virtue of its carboxyl groups，are both acidic. If calcium carbonate，a base，is added to tea water，

8、the calcium salts of these acids are formed. Caffeine can be extracted from the basic tea solution with chloroform，but the calcium salts of gallic acid and the tannins are not chloroform soluble and remain behind in the aqueous solution.The brown color of a tea solution is due to flavonoid pigments

9、and chlorophylls，as well as their respective oxidation products. Although chlorophylls are somewhat chloroform soluble，most of the other substances in tea are not. Thus，the chloroform extraction of the basic tea solution removes nearly pure caffeine. The chloroform is easily removed by distillation(

10、by 61'C)to leave the crude caffeine. The caffeine may be purified by recrystallization or by sublimation. 68 Catechin Gallic Acid In a second part of this experiment，Caffeine will be converted to a derivative. A derivative of a compound is a second compound，of known melting point，formed from the

11、 original compound by a simple chemical reaction. In trying to make a positive identification of an organic compound，it is often customary to convert it into a derivative. If the first compound，Caffeine in this case，and its derivative both have melting points which match those reported in the chemic

12、al literature (e. g.，a handbook)，it is assumed that there is no coincidence and that the identity of the first compound，Caffeine，has been definitely established.Caffeine is a base and will react with an acid to give a salt. Using salicylic acid，a derivative salt of Caffeine，Caffeine salicylate，will

13、be made in order to establish the identity of the Caffeine isolated from tea leaves. Special Instructions Be careful when handling chloroform. It is a toxic solvent，and you should not breathe it excessively or spill it on yourself. When discarding spent tea leaves，do not put them in the sink because

14、 they will clog the drain. Dispose of them in a waste container. Procedure Place 25g of dry tea leaves，25g of calcium carbonate powder，and 250ml of water in a 500ml three neck round bottom flask equipped with a condenser for reflux. Stopper the unused openings in the flask and heat the mixture under

15、 reflux for about 20 minutes. Use a Bunsen burner to heat. While the solution is still hot，filter it by gravity through a fluted filter using a fast filter paper such as E&D No. 617 or S&S No. 595. You may need to change the filter paper if it clogs.Cool the filtrate (filtered liquid)to room

16、 temperature and，using a separatory funnel， extract it twice with 25ml portions of chloroform. Combine the two portions of chloroform in a 100ml round bottom flask，Assemble an apparatus for simple distillation and remove the chloroform by distillation. Use a steam bath to heat. The residue in the di

17、stillation flask contains the caffeine and is purified as described below (crystallization). Save the chloroform that was distilled. You will use some of it in the next step. The remainder should be placed in a collection container. 69 Crystallization(Purification)Dissolve the residue obtained from

18、the chloroform extraction of the tea solution in about 10m1 of the chloroform that you saved from the distillation. It may be necessary to heat the mixture on a steam bath. Transfer the solution to a 50ml beaker. Rinse the flask with an additional 5m1 of chloroform and combine this in the beaker. Ev

19、aporate the now light-green solution to dryness by heating it on a steam bath in the hood. The residue obtained on evaporation of the chloroform is next crystallized by the mixed solvent method. Dissolve it in a small quantity (about 2 to 4ml) of hot benzene and add just enough highboiling (60'C

20、 to 90'C)petroleum ether (or ligroin) to turn the solution faintly cloudy. Alternatively，acetone may be used for simple crystallization without a second solvent. Cool the solution and collect the crystalline product by vacuum filtration using a Hirsch funnel. Crystallize the product the same way

21、 a second time if necessary，and allow the product to dry by allowing it to stand in the suction funnel for a while. Weigh the product. Calculate the weighty percentage yield based on tea and determine the melting point. If desired，the product may be further purified by sublimation as described in th

22、e next experiment. The Derivative Dissolve 0. 20g of Caffeine and 0. 15g of salicylic acid in 15ml of benzene in a small beaker by warming the mixture on a steam bath. Add about 5ml of high boiling (60C to 90'C)petroleum ether and allow the mixture to cool and crystallize. It may be necessary to

23、 cool the beaker in an ice water bath or to add a small amount of extra petroleum ether to induce crystallization. Collect the crystalline product by vacuum filtration using a Hirsch funnel. Dry the product by allowing it to stand in the air，and determine its melting point. Check the value against t

24、hat in the literature. Submit the sample to the instructor in a labeled vial.Selected from Pavia Donald L. Introduction to Organtc Laboratory Techniques: a ContemporaryApproach. W. B. Saunders Company, 1976.Exercises1. Answer the following questions: (1)Can you list several plants that contain caffe

25、ine?(2) What kind of method can be used to isolate caffeine from tea? (3) How does man use caffeine in the daily life?2. Competing the following paragraph. Choose Not More Than Three Words from the passage for each answer. The active ingredient that makes tea and coffee valuable to man is _ .Caffein

26、e is an _ ，a class of naturally occurring compounds containing nitrogen and having the properties of an organic amine base. Tea and coffee are not the only plant sources of caffeine. Others include:kola nuts，mate leaves，guarana seeds，and in smaall amount，cocoa beans.Place 35g of ground coffee a boil

27、ing stone and 125ml of water into a 500ml _ round bottom flask equipped with a _ for reflux. _ the unused openings in the flask and heat the mixture under _ for about 20 minutes.Use ato heat. During the heating period，assemble a vacuum filtrationapparatus. When boiling action has stopped and the cof

28、fee grounds have settled somewhat，but while the solution is still hot，filter the solution through a _ by vacuum filtration.3. Put the following into Chinese: cellulose glucose chloroform beaker crystallization purification apparatus filter paper hydroxyl group carboxyl group benzene acetone evaporat

29、ion insoluble condensation residue第2部分生化制药 6单元的分离从茶叶中的咖啡因 在这个实验中，咖啡因会被孤立于茶叶。在的主要问题： 隔离是，咖啡因不会出现在茶叶单，而是由其他的，它必须伴随着分离的天然物质。对茶叶的主要成分是纤维素，这是所有植物细胞的主要结构材料。纤维素是葡萄糖的聚合物。由于纤维素几乎不溶于水，它提出了在隔离程序没有问题。咖啡因，另一方面，易溶于水，是提取到解决方案的主要物质之一，被称为“茶”。咖啡因包括高达5通过在茶树叶片材料的重量百分比。鞣质也溶于热水用于提取茶叶。单宁一词不是指为一个单一的化合物，甚至有相似

30、的化学物质的结构。它是指一种化合物具有某些共同属性的类。单宁分子量之间有酚类化合物500和3000。它们被广泛用于“晒黑”皮革。他们从水溶液中沉淀alkaloids'z和蛋白质。单宁通常分为两类：那些可以水解，哪些不能。第一种类型的单宁是茶中通常会产生葡萄糖和没食子酸水解时，。这些单宁是没食子酸和葡萄糖酯。它们代表，其中在一些葡萄糖的羟基被酯化digalloyl群体结构。非水解性单宁是茶中的儿茶素缩合聚合物。这些聚合物的结构不统一，但儿茶素分子在环通常与位置4和8在一起。     当单宁分为热水提取，部分水解水解的是，这意味着自由没食子

31、酸也发现茶叶中。凭借他们的酚羟基，单宁酸，没食子酸的羧基凭借其，都是酸性的。如果碳酸钙，一个基地，被添加到茶水，这些酸的钙盐的形成。咖啡因可以用氯仿提取茶叶基本解决方案，但没食子酸的钙盐和单宁酸不溶于氯仿，并保持在水溶液中落后。 一个茶解褐色是由于黄酮类色素，叶绿素，以及他们各自的氧化产物。叶绿素虽然有点溶于氯仿，茶叶中的其它物质大多数都不是。因此，基本解决氯仿萃取去除茶几乎纯咖啡因。氯仿很容易去除蒸馏（由61'C）离开原油咖啡因。咖啡因可能是重结晶纯化或升华。 68        &#

32、160;                                    儿茶素没食子酸     在本次实验的第二部分，咖啡因会被转换为衍生工具。衍生的一种化合物是第二个化合物，已知熔

33、点，从一个简单的化学反应形成的原始化合物。在努力做一个积极的鉴定一种有机化合物，它往往是习惯性地转换成一个派生它。如果第一个化合物，咖啡因在这种情况下，它的衍生物都有匹配熔点在化学文献（例如，一本手册），这是假设是没有巧合，报道的第一个化合物，咖啡因身份已绝对成立。 咖啡因是一种基础，并将与酸反应，让盐。使用水杨酸，盐衍生物的咖啡因，咖啡因水杨酸，将在以确定身份的咖啡因从茶叶孤立。 特别说明时要小心处理氯仿。它是一种有毒溶剂，你不应该过分或吸到它洒在自己身上。当丢弃花茶叶，不要放在水槽里，因为他们会阻塞排水管。他们掷入垃圾容器。    

34、; 程序放在一个500毫升三颈圆底与一个装有回流冷凝器的烧瓶干茶叶25克，25克碳酸钙粉，水250毫升。塞烧瓶中加热回流20分钟左右的混合物未使用的开口。使用本生灯加热。虽然解决办法仍然是热的，它靠重力过滤槽过滤器通过使用快速滤纸，如ED第617和SS的第595号。您可能需要更改滤纸如果木屐。 冷却过滤（过滤液体）到室温，用分液漏斗中，用25毫升氯仿提取部分两次。结合氯仿中的两个100毫升的圆底烧瓶部分，组建一个简单的蒸馏设备和蒸馏除去氯仿。使用热蒸汽浴室。蒸馏烧瓶中的残留物含有咖啡因和被提纯如下（结晶）中所述。这是保存蒸馏氯仿。您将在下一步中使用了一些。其余应放置在一个集合容器。  69     结晶（净化）解散的茶溶液对氯仿，您从氯仿萃取蒸馏保存10m1取得的残留物。它可能需要加热的混合物上的蒸气浴。转移到一个50毫升的烧杯的解决方案。冲洗用一个额外的5m1瓶氯仿，并结合在烧杯这一点。蒸发现在浅绿色溶液加热罩在它干燥蒸气浴。     对氯仿蒸发残渣是未来获得的结晶的混合溶剂法。溶解在少量的热苯（约2至4毫升），并添加刚够highboiling（60'C至90'C）石油