PART 2 BIOCHEMICAL PHARMACEUTICALS
生化制药
Unit 6 Isolation of Caffeine from Tea
从茶叶中分离
In this experiment, Caffeine will be isolated from tea leaves.
在这个实验中，会从茶叶中分离出来。
The major problem of the isolation is that caffeine does not occur alone in tea leaves, but is accompanied by other natural substances from which it must be separated.
分离过程中的主要问题就是，茶叶中不仅仅只有，还伴随着需要被分离除去的其他天然物质。
航天员在太空怎么上厕所The major component of tea leaves is cellulose，which is the major structural material of all plant cells.
茶叶中的主要成分是所有植物细胞中的主要结构材料——纤维素。
Cellulose is a polymer of glucose.
纤维素是葡萄糖的聚合物。
Since cellulose is virtually insoluble in water, it presents no problems in the isolation procedure.
然而纤维素实际上是不溶于水的，所以在隔离的程序上不用考虑去除纤维素。
Caffeine, on the other hand, is water soluble and is one of the major substances extracted into the solution called "tea”.
另一方面，是水溶性的，也是萃取到溶液（也就是茶）里的主要物质之一。
Caffeine comprise读书小故事s as much as 5 percent by weight of the leaf material in tea plants.
包含了茶树叶片材料总重的5%之多。
Tannins also dissolve in the hot water used to extract tea leaves.
丹宁（鞣酸）也溶解于用于萃取茶叶的热水中。
The term tannin does not refer to a single homogeneous compound, or even to substances which have similar chemical structure.
丹宁一词不是指单个均一的化合物，也不是具有相似化学结构的物质。蒜烧小黄鱼是哪个地方的菜
It refers to a class of compounds which have certain properties in common.
它是指某些具有共同属性的化合物的种类。
Tannins are phenolic compounds having molecular weights去丽江需要多少钱 between 500 and 3000.
丹宁是一类分子质量在500到3000的含酚的化合物。原来心疼是种惩罚
They are widely used to "tan” leather.
它们被广泛用于鞣革。
They precipitate alkaloids and proteins from aqueous solutions.
它们从水溶液中沉淀出生物碱和蛋白质
Tannins are usually divided into two classes: those which can be hydrolyzed and those which cannot.
丹宁通常被分为两类：可水解和不可水解。
Tannins of the first type which are found in tea generally yield glucose and gallic acid when they are hydrolyzed.
在茶中，第一类丹宁水解后通常产生葡萄糖和五倍子酸。
These tannins are esters of gallic acid and glucose.
这些丹宁是五倍子酸和葡萄糖的酯类。
They represent structures in which some of the hydroxyl groups in glucose have been esterified by digalloyl groups.
它们代表着葡萄糖中的一些羟基被酯化为鞣酰基的结构。
The non-hydrolyzable tannins found in tea are condensation polymers of catechin.
茶中的不可水解的丹宁是儿茶酚的缩合聚合物。
These polymers are not uniform in structure, but catechin molecules are usually linked together at ring positions 4 and 8.
这些聚合物在结构上是不一致的，但儿茶酚分子通常在环的4号和8号位是相连的。
When tannins are extracted into hot water, the hydrolyzable ones are partially hydrolyzed, meaning that free gallic acid is also found in tea.
当丹宁被萃取到热水中，可水解的部分水解掉了，意味着茶中还有多余的五倍子酸。
The tannins, by virtue of their phenolic groups, and gallic acid by virtue of its carboxyl groups, are both acidic.
由于丹宁中含有酚，五倍子酸中含有羧基，所以它们都是酸性的。
If calcium carbonate, a base, is added to tea water, the calcium salts of these acids are formed.
如果茶水中加入碳酸钙，这些酸的钙盐就会形成。
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.
可以被茶的氯仿溶液萃取，但五倍子酸和丹宁的钙盐是不溶于氯仿的，所以它们会留在水溶液中。
The brown color of a tea solution is due to flavonoid pigments and chlorophylls马来西亚天气, as well as their respective oxidation products.
茶水呈现出褐是由于黄酮类素和叶绿素，以及它们各自的氧化物。
Although chlorophylls are somewhat chloroform soluble, most of the other substances in tea are not.
虽然叶绿素是微溶于氯仿的，但茶叶中的其他大多数物质不是如此。
Thus, the chloroform extraction of the basic tea solution removes nearly pure caffeine.
因此，碱性茶水的氯仿提取去除了几乎无杂质的。
The chloroform is easily removed by distillation (by 61'C) to leave the crude caffeine.
氯仿在61℃蒸馏中易被去除，从而分离出的粗产物。
The caffeine may be purified by recrystallization or by sublimation.
可以通过结晶或升华来纯化。
In a second part of this experiment, Caffeine will be converted to a derivative.
本次实验的第二个部分，会被转化为衍生物。
A derivative of a compound is a second compound, of known melting point, formed from the original compound by a simple chemical reaction.
一个化合物的衍生物是一个已知熔点的第二化合物，是由原来的化合物通过简单化学反应生成的。
In trying to make a positive identification of an organic compound, it is often customary to convert it into a derivative.
为了试图鉴定原始化合物，我们通常习惯将它转化成衍生物。
If the first compound, Caffeine in this case, and its derivative both have melting points which match those reported in the chemical 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.
版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。
发表评论