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1、Structural Determination of Organic Compounds,34.1Introduction34.2Isolation and Purification of Organic Compounds34.3Tests for Purity34.4Qualitative Analysis of Elements in an Organic Compound34.5Determination of Empirical Formula and Molecular Formula from Analytical Data34.6Structural Information
2、from Physical Properties34.7Structural Information from Chemical Properties34.8Use of Infra-red Spectrocopy in the Identification of Functional Groups34.9Use of Mass Spectra to Obtain Structural Information,The general steps to determine the structure of an organic compound,Isolation and Purificatio
3、n of Organic Compounds,The mixture boils below 100C,If the substance is a solid,its purity can be checked by determining its melting pointIf it is a liquid,its purity can be checked by determining its boiling point,Tests for Purity,34.2 Isolation and Purification of Organic Compounds(SB p.78),Isolat
4、ion and Purification of Organic Compounds,The selection of a proper technique depends on the particular differences in physical properties of the substances present in the mixture,34.2 Isolation and Purification of Organic Compounds(SB p.78),Filtration,To separate an insoluble solid from a liquid pa
5、rticularly when the solid is suspended throughout the liquid The solid/liquid mixture is called a suspension,34.2 Isolation and Purification of Organic Compounds(SB p.78),Filtration,The laboratory set-up of filtration,34.2 Isolation and Purification of Organic Compounds(SB p.78),Filtration,There are
6、 many small holes in the filter paperallow very small particles of solvent and dissolved solutes to pass through as filtrateLarger insoluble particles are retained on the filter paper as residue,34.2 Isolation and Purification of Organic Compounds(SB p.79),Centrifugation,When there is only a small a
7、mount of suspension,or when much faster separation is requiredCentrifugation is often used instead of filtration,34.2 Isolation and Purification of Organic Compounds(SB p.79),Centrifugation,The liquid containing undissolved solids is put in a centrifuge tubeThe tubes are then put into the tube holde
8、rs in a centrifuge,A centrifuge,34.2 Isolation and Purification of Organic Compounds(SB p.79),Centrifugation,The holders and tubes are spun around at a very high rate and are thrown outwardsThe denser solid is collected as a lump at the bottom of the tube with the clear liquid above,34.2 Isolation a
9、nd Purification of Organic Compounds(SB p.79),Crystallization,Crystals are solids that havea definite regular shapesmooth flat faces and straight edgesCrystallization is the process of forming crystals,34.2 Isolation and Purification of Organic Compounds(SB p.79),1.Crystallization by Cooling a Hot C
10、oncentrated Solution,To obtain crystals from an unsaturated aqueous solutionthe solution is gently heated to make it more concentratedAfter,the solution is allowed to cool at room conditions,34.2 Isolation and Purification of Organic Compounds(SB p.79),1.Crystallization by Cooling a Hot Concentrated
11、 Solution,The solubilities of most solids increase with temperatureWhen a hot concentrated solution is cooledthe solution cannot hold all of the dissolved solutesThe“excess”solute separates out as crystals,34.2 Isolation and Purification of Organic Compounds(SB p.79),1.Crystallization by Cooling a H
12、ot Concentrated Solution,Crystallization by cooling a hot concentrated solution,34.2 Isolation and Purification of Organic Compounds(SB p.80),2.Crystallization by Evaporating a Cold Solution at Room Temperature,As the solvent in a solution evaporates,the remaining solution becomes more and more conc
13、entratedeventually the solution becomes saturatedfurther evaporation causes crystallization to occur,34.2 Isolation and Purification of Organic Compounds(SB p.80),2.Crystallization by Evaporating a Cold Solution at Room Temperature,If a solution is allowed to stand at room temperature,evaporation wi
14、ll be slowIt may take days or even weeks for crystals to form,34.2 Isolation and Purification of Organic Compounds(SB p.80),2.Crystallization by Evaporating a Cold Solution at Room Temperature,Crystallization by slow evaporation of a solution(preferably saturated)at room temperature,34.2 Isolation a
15、nd Purification of Organic Compounds(SB p.80),Solvent Extraction,Involves extracting a component from a mixture with a suitable solventWater is the solvent used to extract salts from a mixture containing salts and sandNon-aqueous solvents(e.g.1,1,1-trichloroethane and diethyl ether)can be used to ex
16、tract organic products,34.2 Isolation and Purification of Organic Compounds(SB p.80),Solvent Extraction,Often involves the use of a separating funnelWhen an aqueous solution containing the organic product is shaken with diethyl ether in a separating funnel,the organic product dissolves into the ethe
17、r layer,34.2 Isolation and Purification of Organic Compounds(SB p.80),Solvent Extraction,The organic product in an aqueous solution can be extracted by solvent extraction using diethyl ether,34.2 Isolation and Purification of Organic Compounds(SB p.80),Solvent Extraction,The ether layer can be run o
18、ff from the separating funnel and savedAnother fresh portion of ether is shaken with the aqueous solution to extract any organic products remainingRepeated extraction will extract most of the organic product into the several portions of ether,34.2 Isolation and Purification of Organic Compounds(SB p
19、.80),Solvent Extraction,Conducting the extraction with several small portions of ether is more efficient than extracting in a single batch with the whole volume of etherThese several ether portions are combined and driedthe ether is distilled offleaving behind the organic product,34.2 Isolation and
20、Purification of Organic Compounds(SB p.81),Distillation,A method used to separate a solvent from a solution containing non-volatile solutesWhen a solution is boiled,only the solvent vaporizesthe hot vapour formed condenses to liquid again on a cold surfaceThe liquid collected is the distillate,34.2
21、Isolation and Purification of Organic Compounds(SB p.81),Distillation,The laboratory set-up of distillation,34.2 Isolation and Purification of Organic Compounds(SB p.81),Distillation,Before the solution is heated,several pieces of anti-bumping granules are added into the flaskprevent vigorous moveme
22、nt of the liquid called bumping to occur during heating make boiling smooth,34.2 Isolation and Purification of Organic Compounds(SB p.81),Distillation,If bumping occurs during distillation,some solution(not yet vaporized)may spurt out into the collecting vessel,34.2 Isolation and Purification of Org
23、anic Compounds(SB p.81),Fractional Distillation,A method used to separate a mixture of two or more miscible liquids,34.2 Isolation and Purification of Organic Compounds(SB p.82),Fractional Distillation,The laboratory set-up of fractional distillation,34.2 Isolation and Purification of Organic Compou
24、nds(SB p.82),Fractional Distillation,A fractionating column is attached vertically between the flask and the condensera column packed with glass beadsprovide a large surface area for the repeated condensation and vaporization of the mixture to occur,34.2 Isolation and Purification of Organic Compoun
25、ds(SB p.82),Fractional Distillation,The temperature of the escaping vapour is measured using a thermometerWhen the temperature reading becomes steady,the vapour with the lowest boiling point firstly comes out from the top of the column,34.2 Isolation and Purification of Organic Compounds(SB p.82),Fr
26、actional Distillation,When all of that liquid has distilled off,the temperature reading rises and becomes steady later onanother liquid with a higher boiling point distils outFractions with different boiling points can be collected separately,34.2 Isolation and Purification of Organic Compounds(SB p
27、.82),Sublimation,Sublimation is the direct change of a solid to vapour on heating,or a vapour to solid on coolingwithout going through the liquid state,34.2 Isolation and Purification of Organic Compounds(SB p.82),Sublimation,A mixture of two compounds is heated in an evaporating dishOne compound ch
28、anges from solid to vapour directlyThe vapour changes back to solid on a cold surfaceThe other compound is not affected by heating and remains in the evaporating dish,34.2 Isolation and Purification of Organic Compounds(SB p.83),Sublimation,A mixture of two compounds can be separated by sublimation,
29、34.2 Isolation and Purification of Organic Compounds(SB p.83),Chromatography,An effective method of separating a complex mixture of substancesPaper chromatography is a common type of chromatography,34.2 Isolation and Purification of Organic Compounds(SB p.83),Chromatography,The laboratory set-up of
30、paper chromatography,34.2 Isolation and Purification of Organic Compounds(SB p.83),Chromatography,A solution of the mixture is dropped at one end of the filter paper,34.2 Isolation and Purification of Organic Compounds(SB p.83),Chromatography,The thin film of water adhered onto the surface of the fi
31、lter paper forms the stationary phaseThe solvent is called the mobile phase or eluent,34.2 Isolation and Purification of Organic Compounds(SB p.83),Chromatography,When the solvent moves across the sample spot of the mixture,partition of the components between the stationary phase and the mobile phas
32、e occurs,34.2 Isolation and Purification of Organic Compounds(SB p.83),Chromatography,As the various components are being adsorbed or partitioned at different rates,they move upwards at different ratesThe ratio of the distance travelled by the substance to the distance travelled by the solventknown
33、as the Rf valuea characteristic of the substance,34.2 Isolation and Purification of Organic Compounds(SB p.84),A summary of different techniques of isolation and purification,34.2 Isolation and Purification of Organic Compounds(SB p.84),A summary of different techniques of isolation and purification
34、,Qualitative Analysis of Elements in an Organic Compound,34.4 Qualitative Analysis of Elements in an Organic Compound(SB p.86),Qualitative analysis of an organic compound isto determine what elements are present in the compound,Qualitative Analysis of an Organic Compound,34.4 Qualitative Analysis of
35、 Elements in an Organic Compound(SB p.86),Carbon and Hydrogen,Tests for carbon and hydrogen in an organic compound are usually unnecessaryan organic compound must contain carbon and hydrogen,34.4 Qualitative Analysis of Elements in an Organic Compound(SB p.86),Carbon and Hydrogen,Carbon and hydrogen
36、 can be detected by heating a small amount of the substance with copper(II)oxideCarbon and hydrogen would be oxidized to carbon dioxide and water respectivelyCarbon dioxide turns lime water milkyWater turns anhydrous cobalt(II)chloride paper pink,34.4 Qualitative Analysis of Elements in an Organic C
37、ompound(SB p.86),Halogens,Nitrogen and Sulphur,Halogens,nitrogen and sulphur in organic compounds can be detectedby performing the sodium fusion test,34.4 Qualitative Analysis of Elements in an Organic Compound(SB p.86),Halogens,Nitrogen and Sulphur,The compound under test isfused with a small piece
38、 of sodium metal in a small combustion tubeheated stronglyThe products of the test are extracted with water and then analyzed,34.4 Qualitative Analysis of Elements in an Organic Compound(SB p.86),Halogens,Nitrogen and Sulphur,During sodium fusion,halogens in the organic compound is converted to sodi
39、um halidesnitrogen in the organic compound is converted to sodium cyanidesulphur in the organic compound is converted to sodium sulphide,34.4 Qualitative Analysis of Elements in an Organic Compound(SB p.86),Results for halogens,nitrogen and sulphur in the sodium fusion test,34.4 Qualitative Analysis
40、 of Elements in an Organic Compound(SB p.86),Results for halogens,nitrogen and sulphur in the sodium fusion test,Determination of Empirical Formula and Molecular Formula from Analytical Data,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.87),After determining
41、 the constituent elements of a particular organic compoundperform quantitative analysis to find the percentage composition by mass of the compoundthe masses of different elements in an organic compound are determined,Quantitative Analysis of an Organic Compound,34.5 Determination of Empirical Formul
42、a and Molecular Formula from Analytical Data(SB p.87),1.Carbon and Hydrogen,The organic compound is burnt in excess oxygenThe carbon dioxide and water vapour formed are respectively absorbed by potassium hydroxide solution and anhydrous calcium chloride,34.5 Determination of Empirical Formula and Mo
43、lecular Formula from Analytical Data(SB p.87),1.Carbon and Hydrogen,The increases in mass in potassium hydroxide solution and calcium chloride representthe masses of carbon dioxide and water vapour formed respectively,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data
44、(SB p.87),2.Nitrogen,The organic compound is heated with excess copper(II)oxideThe nitrogen monoxide and nitrogen dioxide formed are passed over hot copperthe volume of nitrogen formed is measured,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.87),3.Halogens,
45、The organic compound is heated with fuming nitric(V)acid and excess silver nitrate solutionThe mixture is allowed to coolthen water is addedthe dry silver halide formed is weighed,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.87),4.Sulphur,The organic compou
46、nd is heated with fuming nitric(V)acidAfter cooling,barium nitrate solution is addedthe dry barium sulphate formed is weighed,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.87),Quantitative Analysis of an Organic Compound,After determining the percentage comp
47、osition by mass of a compound,the empirical formula of the compound can be calculated,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.87),Quantitative Analysis of an Organic Compound,The empirical formula of a compound is the formula which shows the simplest w
48、hole number ratio of the atoms present in the compound,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.87),Quantitative Analysis of an Organic Compound,When the relative molecular mass and the empirical formula of the compound are known,the molecular formula o
49、f the compound can be calculated,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.88),Quantitative Analysis of an Organic Compound,The molecular formula of a compound is the formula which shows the actual number of each kind of atoms present in a molecule of th
50、e compound,34.5 Determination of Empirical Formula and Molecular Formula from Analytical Data(SB p.88),Structural Information from Physical Properties,34.6 Structural Information from Physical Properties(SB p.89),The physical properties of a compound include its colour,odour,density,solubility,melti
