1、有机化学实验有机化学实验Experimental Organic ChemistrySteam distillation1.Purpose1.1 Study the principle and methods of Steam Distillation used for purifing organic liquids.1.2 Grasp the techniques of steam distillation.2.PrinciplelSteam distillation,one of the immiscible（不溶的）（不溶的）phases being water,is one of t
2、he most commonly used methods of separating and purifying liquids.lIn this method steam is passed into the immiscible and volatile liquid in the distillation flask,and then the water and organic compound co-distill（共沸）（共沸）,condense in the condenser,and are collected in the normal way.lAccording to t
3、he law of partial pressure,the total vapor pressure（蒸气压）（蒸气压）above the mixture is the sum of the partial pressures of the pure individual components.BOH2ppptotal?BpIs the vapor pressure of the immiscible organic compound.In the distillate（馏出液）,the weight ration of organic compound mB and mH2O can be
4、 expressed as in equation:0HB2mmOHOHBB22MpMp=lSteam distillation is applicable to the following situations:A high boiling-point organic compound which decompose at its boiling point.A mixture containing in organic salts or other organic solids,not suitable for distillation,filtraion and extraction.A
5、 mixture containg large amounts of resin-like nearly intractable substances or nonvolatile impurities which is hard to isolate or purify in any other way.lIn order for steam distillation to be feasible,the substances to be purified should have these characteristics:Insoluble or immiscible in water.N
6、o reaction with water when co-boiling.Having a certain vapor pressure at 100,665Pa3.ProcedureFigure1 Typical Apparatus for steam distillation 图图1 水蒸气蒸馏装置水蒸气蒸馏装置Boing chipsOne third NOTESlIn order to avoid filling with condensed water in the three-neck flask during distillation,heat the flask with a
7、small flame to make the on-going distillation proceed more quickly.lBefore end the steam distillation,open the T tube clamp first,then remove the heat source,disassemble the apparatus,in turn.Avoid letting the liquid form the flask back up into the steam line.0.16(4)2.8(75)6.6(98)2.6Solubility 水中溶解度
8、水中溶解度/g/100g258（分解）（分解）131.5b.p.沸点沸点/0.11531.8vapour pressure at 100 100时蒸气压时蒸气压/kPasalicylic acid水杨酸水杨酸isopentanol异戊醇异戊醇Organic compound 有机物名称有机物名称uSeparate isopentanol(异戊醇)and salicylic acid(水杨酸)mixture Isopentanol insoluble or immiscible in water.Isopentanol(异戊醇)and salicylic acid(水杨酸)no reaction
9、 with water when coboiling.Isopentanol insoluble having a certain vapour pressure at 100 The principle of isopentanol(异戊醇)and salicylic acid(水杨酸)mixture can be separate by steam distillation:production test 产品检验产品检验:salicylic acid test水杨酸的检验水杨酸的检验 10d 0.1 FeCl3Observable phenomena!10d solution isope
10、ntanol test异戊醇的检验异戊醇的检验 10d solution10d 5 K2Cr2O75d 16H2SO4Observable phenomena!Solvent extraction and solution washing1.Purpose1.2 Learn how to choose suitable solvent.2.Principle1.1 Study the principle and methods of Solvent extraction and solution washing.lSolvent extraction is a technique freque
11、ntly used in the organic chemistry laboratory to separate or isolate a desired species from a mixture of compounds or from impurities.Substances for extraction usually are solid or liquid.lSolution washing is the reverse process of solvent extraction.Usually it is performed in the case of impurities
12、 in a solution that can be extracted by another immiscible solvent,which has a small solubility to the desired substance.lThe apparatus for extraction and solution washing from liquid is called separatory funnel,and its use is one of the essential operations for organic chemistry experiments.Figure1
13、 Separatory funnel（分液漏斗）（分液漏斗）There a three kinds of separatory funnel-spherical(球形）球形）,subulate（锥形的）（锥形的）and pear（梨形）（梨形）forms.In organic experiments,a separatory funnel is mainly applied to this areas:Separate two kinds of liquid which are immiscible and do not react with each other.Extract a cera
14、tin component from a solutiom.Wash a liquid product or the solution of a solid product with water,aqueous alkaline or acidic solution.Add dropwise a certain reagent(used as a dripping funnle)pSeparatory funnels are very expensive and borken easily.Never prop The funnel on its stem,but support it on
15、a ring,a funnel support,or some other stable support.Figure2 Venting separatory funnel（分液漏斗的振摇与放气）（分液漏斗的振摇与放气）The extraction principle can be illustrated by the following calculation.)()(21BBKThe concentration ration of x in solvent 1 and 2 is a constant at a given temperature,and the ratio is also
16、called the distribution coefficient,expressed as K.KVmmVms101sVKVKVmm01KVmmVms2122012ssVKVKVmVKVKVmmnsnVKVKVmm0First extractionSecond extractionMultiple(n)extractionsVKVKV1Based on the above calculations,it is known that the multiple extracions are more efficicent than a single extraction with the s
17、ame volume of extracion solvent.An aqueous solution containing 4g of butanoic acid in 100 ml of water is exracted at 15 with 100ml benzene.The K value(participation coefficient of butanoic acid between benzene and water)is 1/3.after once extcration with 100ml of benzene,the remained amount of butano
18、ic acid in water is:If the 100ml of benzene is divided into three portions,the remained amount of butanoic acid in water after the third extration is:gm0.1100100311003141%75%100414 gm5.01001003110031433The extraction efficiency:The extraction efficiency:%5.87%10045.043 Procedure The extraction of acetic acid（乙酸）from an aqueous solution by diethyl ether（乙醚）.Single extractionTriple extractioncNaOH=0.2000Mol/L乙酸的密度：乙酸的密度：1.049g/cm3
