应用化学专业英语 Lesson 28 翻译.doc

Lesson 28 A Experiment Ease: Synthesis of Salicylic AcidFrom Oil of Wintergreen (Methyl Salicylate)overviewMethyl salicylate (水杨酸酯) (oil of wintergreen) and salicylic acid (水杨酸) are naturally occurring compounds with medicinal uses. You will try to prepare salicylic acid by boiling methyl salicylate with aqueous sodium hydroxide(lye碱液). You will also try to purify your product by recrystallization (再结晶) and characterize it by measuring its melting temperature.Time require:2 laboratory sessions.BackgroundMethyl salicylate and salicylic acid are naturally occurring compounds with medicinal uses. The procedure used here to convert methyl salicylate into salicylic acid is called saponification (皂化)。It is chemically related to the process used to convert natural fats into soap.Salicylic acid and aspirinMany plants produce salicylic acid naturally. Among these, willow trees (柳树) have been recognized since antiquity as a potent (有效) source of medicine. Hippocrates (一个希腊的名医) encouraged the pregnant women of ancient Greece to chew willow leaves and drink willow tea to alleviate (减轻) labor and birth pains. Chinese, Native Americans, and others also used willow.Salicylic acid is found mainly in the willows leaves and bark (树皮).The pure acid possesses several useful medicinal properties. It is an antipyretic (a fever reducer), an analgesic (a pain reducer), and an anti-inflammatory (a swelling reducer).Unfortunately, pure salicylic acid and even the concoctions (混合物) derived from willow, make for an extremely unpleasant medicine. The salicylic acid molecule contains two acidic functional groups, the phenol group (PhOH) and the carboxylic acid group (-COOH). These groups make salicylic acid an irritating (刺激性的) substance that burns the sensitive linings of the mouth, throat, esophagus (食道)， and stomach. Interestingly, salicylic acids ability to burn living tissue makes it useful for other applications. Salicylic acid is the active ingredient in Compound W, an over-the-counter (不需处方课合法出售的) wart (疣) remover.The best way to mitigate (减轻)salicylic acids harsh (令人生厌的) qualities is to replace the acidic hydrogens with less reactive groups of atoms. For example, replacing the phenolic hydrogen with an acetyl group, COCH3, gives acetylsalicylic acid or “aspirin”. salicylic acetylsalicylicacid acidAcetylsalicylic acid does not occur naturally. It contains only one acidic functional group, and bypass most of the digestive (消化的) system without causing burns. Eventually, acetylsalicylic acid reacts with water, mainly in the bloodstream to regenerate salicylic acid.Methyl salicylate Methyl salicylate, like salicylic acid, is produced by many plants. It was first isolated from wintergreen leaves, Gaultheria(白株树属) procumbens, and is often called oil of wintergreen. Methyl salicylate is similar to acetylsalicylic acid in that it masks one of the acidic hydrogens in salicylic acid. Methyl salicylate replaces the carboxylic acid hydrogen with a methyl group, CH3. The result is a relatively unreactive compound that does not liberate salicylic acid efficiently in the body. Consequently, methyl salicylate is not effective analgesic. Methyl salicylate has other uses, including its distinctive fragrance (香味)，and is added to many commercial products, including root beer (根汁汽水) and Ben-Gay ointment (油膏).Pre-lab preparationNotebook. This experiment involves a chemical preparation so you should set up your notebook according to the examples give in Padias and How-to Keep a Lab Notebook. Your chemical equation should not be a mechanism. Rather, show the material you will start with (methyl salicylate), important reagents (NaOH and H2O), important conditions (“reflux”), and the product that you expect to get (salicylic acid). Do not draw anything else. Dont forget to include a table of physical properties for the substances that might appear in this experiment. This includes all starting materials, reagents, and produce. A sample table with “?” indicating vital information is shown below.Safety Disposal. Wear gloves and goggles and carry out all operations in a fume hood. These are standard operating procedures, but they are especially important in this experiment. Any other hazards and warning about safe handling should be entered un your notebook. Disposal procedures should also be entered for each reagent. Salicylic acid will be collected in a special container.Pre-lab activity. Before you come to lab, download the activity sheet and complete it. We will discuss your answers at the start of lab.ReactionEquipment50ml round bottom flask lab jack + stirring motormagnetic stir bar ceramic heater +controllergraduated cylinderscrew clamps reflux condenser water hosesfunneldisposable pipettesIn your fume hood: place a stirring motor on top of a partially opened lab jack, then place a heater on top of the motor. Clamp the round bottom flask to the monkey bars (攀吊架) in your fume hood so that it rests in the heater. Plug the heater into the controller, but do not turn on the controller (never plug a heater directly into a wall socket). Transfer sufficient 6mol/L aqueous NaOH into a graduated cylinder so that you have 120mmol of NaOH, then transfer this liquid to the round bottom flask using a funnel. Record the volume of aqueous NaOH that you actually use. Rinse (漂洗) your funnel and graduated cylinder with water to remove all traces of the reagent, and remove any stray (零散的) drops of reagent from the ground-glass neck of your flask. Transfer about 21mmol of methyl salicylate to your graduated cylinder. Record the volume that you actually use and transfer this material to the round bottom flask using a funnel. You should see a white gummy(黏性的) material form in your flask. Equip the flask with a stir bar, reflux condenser, and water hoses. Slowly flow water though the reflux condenser and adjust the controller voltage to initiate reflux. Reflux the mixture for 30 minutes, while stirring as best you can (the gummy material prevent the stir bar from working at first, but the material soon dissolves). Turn off the controller and remove the lab jack, motor, and heater. Allow the mixture to cool temperature before contWorkupEquipment150ml beakerpH paper 400ml beaker(for ice water bath) 250ml filtering flask heavy-walled rubber hose Buchner funnel +neoprene adaptorFilter paper Pour the cooled mixture into a 150ml beaker. Add sufficient 3mol/L aqueous H2SO4 to precipitate (使沉淀) all of the salicylic acid. Place the beaker in an ice-water bath for several minutes, then collect your product by vacuum filtration. While still applying a vacuum, rinse the solids with a small amount of ice-cold water and let then air-dry for several minutes.RecrystallizationEquipmentTwo 250ml Erlenmeyer flasksBoiling chipsHot plate (stirring motor)Disposable pipers + rubber bulbsPlace your crude salicylic acid and 510ml of deionized water(去离子的水) in a 250ml.Erlenmeyer flask (“acid” flask). Place about 80120ml of deionized water in a second flask (“water” flask).Add 23 boiling chips to each flask. Place the “water” flask on a hot plate and bring the water to a boil. Next set the “acid” flask next to the “water” flask on the hot plate and bring the “acid” mixture to a boil as well. Transfer just enough boiling water form the “water” flask to the “acid” flask to dissolve all of the solids in the ”acid” flask. Remove the “acid” flask from the hot place and let solution cool slowly. Salicylic acid should crystallize spontaneously (自然地).After the solution has cooled sufficiently, recover the produce by vacuum filtration (use a clean filter flask and funnel). Set the product on a watch glass inside your laboratory cabinet to dry.Characterization (Week2)After your product has dried for at least 12 hours, record its weight and its melting temperature.ReportAll experiments in Chem 201/201 must be described by a lab report. The lab report must be turned in as a separate document that follow the technical writing conventions used by organic chemists (the appendix How to Write Lab Report provides complete instructions for preparing a technically sound lab report ). Because some of the writing conventions used in organic chemistry will seem strange the passive voice(被动态),the repetition of some information, but not all, etc., we have provided several sample reports for you to study and learn from. Assuming your experiment went according to plan, you can prepare your reports by plagiarizing(剽窃) our samples, but you are permitted to copy only the material that accurately describes your work. You will need to think carefully about each word, each number, and each symbol, in the sample report to make sure that these items accurately reflect your work. Do not trust (or copy) any numerical values that appear in the sample report. Do not trust (or copy) any of the literature references. ” Plagiarize” does not mean “stop thinking”. To make this a genuine learning experience, you must write your report “from scratch (乱写)”. If you can, neatly write your report by hand, but if you typing is easier, go ahead. If you choose to type do not copy-and-paste directly from this web page to your word processor. Do mot prepare an electronic file and share it with classmates. Etc. Etc. The standard operating procedures of Reed College (and scientific) ethics apply. You might enjoy reading a short essay that we have posted on the Honor Principle.Sample ReportSynthesis of Salicylic Acid from Methyl SalicylateC. DiverTues Lab, Box 007AbstractSalicylic acid was obtained from methyl salicylate in 78yield. The product was identified by its melting point. Results and DiscussionSalicylic acid was obtained in 78yield by refluxing methyl salicylate with aqueous NaOH. Recrystallization of the acid gave white needles, m.p.157158.5(lit.159). ExperimentalPreparation of salicylic acid. Methyl Salicylate (4ml, 31mmol) and 2mol/L ap. NaOH (10ml, 20mmol) were refluxed for 30min. The solution was acidified with 6 mol/L aq. H2SO4 (25ml) and filtered. The crude product was recrystallized from boiling ethanol and dried for three weeks to give green crystals of salicylic acid:3.33g (78 from methyl slicylate), m. p. 157158.5 (lit.159). References1. Kaplan, R., ed. “Bobs Big Book of Chemicals”, 1 st Ed., , XYZ P, New York, 1984.E-factorThis experiment used the following materials: methyl slicylate (3g), NaOH(3g), sulfuric acid (4g), ethanol (40g);total consumables (50g). The product (3.33g) does not count as waste; total disposables (46.7g). E-factor=14.Post-report question(Because this section does not involve copying phrases from the sample report, feel free to 1) type this section and 2) copy material from the Journal electronically). Please attach the title and abstract from a recently published article in the Journal of Organic Chemistry to your report (electronic copy-and-paste is perfectly acceptable here). The journal is available online though the synthesis of an organic molecule (the word “synthesis” will probably appear in the articles title). Cite the article so that I know which one you are looking at. Then provide brief answer to the following question:1) To what extent do the title and abstract comply with the standards set out by the Journal of Organic Chemistrys guidelines? (see How to Write Lab Reports for a short version of these guidelines), 2) In what ways does the information in the abstract supplement/extend the information found in the title? 3) In what way(s) does the information in the body of the article supplement/extend the information found in the abstract? Just pay attention to information that relates to the synthesis. Dont bother with other parts of the article.ExercisesTry to write a English chemical experiment report according to a laboratory text.28课 一个实验案例：从冬青油（水杨酸酯）中合成水杨酸概述水杨酸酯（冬青油）和水杨酸是常用于药物合成的天然物质。你可以尝试煮沸含有氢氧化钠水溶液（(lye碱液）的水杨酸酯制备水杨酸，你也可以通过重结晶提纯你的产品和通过测量它的熔解温度来描绘它的特性。 授课时数：2个实验课时背景水杨酸酯和水杨酸是常用于药物合成的天然物质。这里安吧水杨酸酯转化成水杨酸的过程叫做皂化。这是用化学方法和相关程序吧天然脂肪转化成肥皂。水杨酸和阿司匹林 许多植物都能产生天然的水杨酸。其中，柳树从古代就被认为是有效的药物资源。古希腊的名医希波克拉底鼓励孕妇咀嚼柳叶与和柳叶泡的茶来减轻分娩和生产时的痛苦。中国人，印第安人和其他人也使用柳树。水杨酸主要存在于柳树的叶子和树皮。这种纯酸占有几个重要的药物功能。它是一种退热药剂（一种退烧剂），一种镇痛剂（一种止痛药），一种抗炎药（一种消炎药）。不幸的是，高纯度的水杨酸和混合物同时从柳树中分离出来，用于药物中极其不乐观。水杨酸分子包括2个酸性官能团，酚组团（苯酚）和羧酸官能团（羧酸）。这些官能团使水杨酸成为对烧伤敏感的口腔、呼吸道、食道和胃有刺激性的物质。有趣的是，水杨酸可以燃烧活性组织的性能使它对其他应用很有帮助。水杨酸是合成一种有效治愈疣的消除剂W的有效组成部分。减轻水杨酸令人生厌的性质最好的办法是用酸性氢代替来减少反应的原子团。例如，用乙酰基COCH3,代替酚醛酸得到乙酰水杨酸或“阿司匹林”。水杨酸 乙酰水杨酸乙酰水杨酸不能天然生成。它只包含一个酸性官能团，不会导致烧伤地绕过大部分消化系统。乙酰水杨酸主要在流动的血液中与谁反应，最后还原成水杨酸。水杨酸酯 水杨酸酯和水杨酸一样可以冲许多植物中提炼。它第一次是从白株树属类的冬青树叶中分离得到的，所以常被叫做冬青油。水杨酸酯类似于乙酰水杨酸，是在于它掩盖了一个酸性氢水杨酸。水杨酸酯用一个甲基团CH3代替了羧酸氢，这使得一个相当难合成的反应无法在人体中有效释放出水杨酸。因此，水杨酸酯不是游戏的止痛剂。水杨酸酯还有其他用途，包括它的独特香味和许多其他贸易产品的添加剂，如根汁汽水和Ben-Gay油膏。实验前期准备笔记本。这个实验包含了一个化学制剂。所以你应该根据Padias和如何写实验笔记给出的案例来建立你的笔记本。你的化学反应式不应该仅有一个原理，而是更应该展示你一开始会使用的材料（水杨酸酯）、重要试剂（氢氧化钠和水），重要条件（“回流”），和你预期可得到的产物（水杨酸）。不需要引出其他物质。别忘了列一张有关可能出现在试验中的物质的物理性质的表格，这包括所有的原料、试剂和产物。一个带有“？”的示例表指示了至关重要的信息如下。合成物摩尔质量熔点沸点密度所需量水杨酸酯？ml6mol/L氢氧化钠？ml3mol/L硫酸水杨酸？安全处理。所有操作要在通风橱内执行并穿手套戴护目镜。这是标准的操作程序，但它们在这个实验中特别重要。其他任何关于安全处理的危险和警告都应该记录到你的笔记本里。程序处理也应该包括每种试剂，水杨酸应将被收集在一个特殊的容器中。准备实验活动。在你进入实验室前，下载活动表并填完它。实验开始前我们会讨论你的答案。反应设备50ml圆底烧瓶实验插孔+搅拌电机磁力搅拌器陶瓷加热器+控制器量筒螺丝钳夹回流冷凝器和软胶水管漏斗一次性吸量管 在你的通风橱里：把一个搅拌马达放在局部打开的使用插孔上，再把一个热器放在马达上。把圆底烧瓶固定在你通风橱内的攀吊架上，使它能紧贴着加热器。将插头接到控制器 上，但别打开控制器（千万别把加热器直接插入到墙上的电源插座里）。将足够的120mmol的6mol/L氢氧化钠溶液转移到量筒中，在用漏斗把它转移到圆底烧瓶里，记录你实际使用的氢氧化钠溶液。用谁漂洗你的漏斗和量筒以除去残留的试剂，并消除你烧瓶玻璃瓶颈上的热呵呵零散的试剂液滴。将约21mmol的水杨酸酯转移到量筒中，再用漏斗把原料转移到圆底烧瓶中，记录你实际使用的量。你应该会看到烧瓶中有一种白色物质。设备：带搅拌器的烧瓶、回流冷凝管及软胶水管。开始回流前，吧水缓缓通过冷凝管，校准电压控制器。让混合物回流30分钟，同时尽你最大的可能搅拌（搅拌开始时粘性物质会产生在搅拌器上，但会很快就熔解）。关掉控制器并分离开实验插孔、马达和加热器。在实验继续前让混合物先冷却至室温。临床检验设备150ml烧杯PH试纸400ml烧杯（水浴烧杯）250ml过滤瓶厚壁橡胶软布氏漏斗+氯丁橡胶适配器滤纸把冷却的混合液导入150ml烧杯中。加入足量的3mol/L硫酸溶液时所有的水杨酸沉淀。把烧杯放在冰水浴中冷却几分钟，然后通过真空抽气泵收集你的产物。使用真空抽气泵时用少量冰冷的水冲洗股日，然后再晾干几分钟。重结晶设备2个250ml的锥形瓶沸腾片热板（搅拌器）一次性吸量管+橡胶管将你未提纯的水杨酸和510ml的去离子水放在一个250ml锥形瓶中（“酸液”瓶）。把约80120ml的去离子水放在第二个烧瓶中（“水”溶液烧瓶）。每个烧瓶中加入23粒