View: PDF | PDF w/ Links. Related Content. Related Content: The Systematic Identification of Organic Compounds, 8th Edition By R. Shriner, C. Hermann. Request PDF on ResearchGate | The Systematic identification of organic compounds: a laboratory manual / Ralph L. Shriner, Reynold C. Fuson, David Y. Curtin. The Systematic Identifiation of Organic Compounds. 4th ed. By Ralph L. Shriner, Reynold C. Fuson, and David Y. Curtin. John Wiley & Sons,. Inc., New York.
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The title of the book was changed, in the fourth edition, to "The Systematic Identification of Organic Compounds." Infrared spec troscopy was added, with. The systematic identification of organic compounds. 4th ed. By Ralph L. Shriner, Reynold C. Fuson, and David Y. Curtin. John Wiley & Sons, Inc., New York. View: PDF | PDF w/ Links The Systematic Identification of Organic Compounds, 8th Edition By R. Shriner, C. Hermann, T. Morrill, D. Curtin, and R. Fuson.
In subsequent determinations the observed value. Fuse the drawn tube at one end Figure 3. The first Sections 3. The compound 2-bromobutane is a simple example of a chiral compound. Chapter 4 on separations should be consulted. Thus curve IV.
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Article Tools. Nature menu. Nature Research menu. Search Article search Search. The theory of odor is certainly dependent upon stereochemistry. Many nitro compounds. Thus aldehydes are different from ketones. Other compound classes have distinguishable but less pronounced odors. Phenols also have unique odors. Thiols or mercaptans and organic sulfides thioethers are easily detected by their rotten egg smell. Esters usually have pleasant smells that are often characterized as fruity.
Some amines have common or trivial names that suggest odors. If an unknown compound is a stable. If the substance is flammable. Heat the sample until ignition has occurred. A few simple tests will often determine the nature of the metal present.
Although liqUids are very often easily analyzed by gas chromatography Section 4. Add a drop of distilled water. Note whether a gas evolves. Perform a flame test. Physical Properties. Preliminary Examination. The control samples cited earlier containing metal sodium. As the oxygen content of the compound increases. Heat the sample gently over a low flame. The Merck Index can also be consulted for more information. If an inorganic residue l is left after ignition.
Test the solution with litmus paper. AliphatiC hydrocarbons burn with flames that are yellow but much less sooty. If various tests in this section indicate that the compound is very impure. This test also shows whether the melting point of a solid should be taken and indicates whether the solid is explosive.
Discussion Many liqUids burn with a characteristic flame that assists in determining the nature of the compound. All labs must provide MSD sheets describing the toxicity of any organic compound used in that laboratory. Will it fuse? If a residue is left. A residue is more than a small streak of blackened remains. If a melting point determination by Procedure A indicates definite decomposition or transition from one crystalline state to another.
Thus the procedure of determining melting points of mixtures described below is strongly recommended. Procedure B is recommended. Since this process is frequently accompanied by decomposition. Melting points for a large number of compounds and their derivatives are listed in this book. The capillary tube should contain mm of sample. Regulate the temperature. Place the cover glasses in the depression of the aluminum block. These tubes are typically 1. Use the capillary tube in melting point apparatuses such as the Thomas-Hoover melting point apparatus Figure 3.
One end is sealed. Use a new melting point capillary tube for each melting point. Place a small amount of the sample. If necessary. Figure 3. Another type of melting point apparatus is the Fisher-Johns apparatus Figure 3.
Hold the capillary tube vertically. Place the sample between two mm microscope cover glasses. Used with pennission. The observed melting point of the standard compound is plotted against the corrected value. It is often timesaving to run a preliminary melting point determination. Prepare a calibration curve for the instrument by reference to known compounds as described below. Use a fresh sample of the compound for each melting point determination.
After the approximate melting point is known. HippuriC acid Isatin Anthracene 1. N' -Diacetylbenzidine. As soon as crystals begin to form. Make small piles of apprOximately equal sizes of the two components A and B being examined. In subsequent determinations the observed value. Some organic compounds. Stir the liquid vigorously. Such a calibration curve includes corrections for inaccuracies in the thermometer and stem correction. Fasten the tube in a slightly larger test tube by means of a cork and cool them in an ice or ice-salt bath or an acetone-dry ice bath Figure 3.
The melting points of all three mixtures may be measured at the same time by any of the preceding procedures. The thermometer should be calibrated by observing the melting points of several pure compounds. A few pairs of substances when mixed show no melting point depression.
The freeZing points of most organic liquids are only approximate due to the relatively large amount of sample. Continue the vigorous stirring and read the temperature on the thermometer. Mixture Melting Points The "mixed melting point" method provides a means of testing for the identity of two solids which should. The temperature of the cooling bath should not be too far below the freezing point of the compound.
This colligative property is discussed.
The presence of impurities in the sample can lead to a freezing point depression. Freezing Points Place mL of the liquid in an ordinary test tube fitted with a thermometer and a wire stirrer made of copper.
If the melting point range or decomposition range is wide. It is important to record the melting point range ofan unknown compound. A large majority of pure organic compounds melt within a range of 0. To the first add the remainder of component A. Although the use of mixed melting points is valuable at certain points of the identification procedure. Curtis and A. In general.
Mix one-half of pile A with one-half of pile B. Insert the thermometer so that the top of the mercury bulb is just below the side arm. Sand has been used to fill in the well. Add a few bOiling chips and 10 mL of the unknown liquid. Heat the liquid to bailing using a sand bath illustrated in Figure 3. Procedure A Set up a simple distillation as illustrated in Figure 3.
Water Qut Heating mantle Figure 3. The bOiling point determined by the distillation of a small amount of liquid as described above is frequently in error. Distill the liquid at as uniform a rate as possible. Collect the next mL in a dry receiver. Place an inverted sealed capillary tube inside the. Use a 5-cm test tube for the outer tube. Slowly heat the liquid to boiling so that the thermometer bulb is immersed in the vapor. The second fraction collected above should be used for a more accurate boiling point determination by Procedure B below.
Add two drops of the unknown liquid. Portions of the main fraction should also be used for the detennination. Great care should be exercised against overrelying upon bOiling point as a criterion of purity or a basis for identity.
Generally the first few milliliters of distillate will contain any water or more volatile impurities. Change the receiver. Procedure B Place a thermometer For liquids with low boiling points. This value is the bOiling point of the liqUid. If the bOiling point range is large. Unless special care is taken. Allow the temperature to remain at a constant value for 30 sec. Many organic liquids are hygroscopic. Procedure C Set up a micro bOiling point tube Figure 3. Use a purchased glass bell or prepare one by heating 3-mm 0.
Remove the heat and allow the Thiele tube to cool. This procedure may be repeated on the same sample.
LL syringe. These corrections are applied in the following equation: Adjust the heat so that the temperature drops. Record this temperature as the boiling point of the liquid. Note the temperature at the instant bubbles cease to come out of the capillary and immediately before the liquid enters it. Place the micro bOiling point tube in a Thiele tube Figure 3.
Record the boiling point at the point when the last bubble collapses. Fuse the drawn tube at one end Figure 3. Inject the melting point capillary tube with J. Table 3. Place the entire unit in a standard melting point apparatus. Insert the glass bell. For a nonassociated liquid. The corrections are obtained by distilling a number of different types of compounds with different bOiling points. Azeotropes In some cases. An example is provided in Appendix I. Chapter 3. Use Appendix The vapor of the azeotrope has the same composition as the boiling liqUid.
Using the pressure-temperature nomograph in Appendix I. It is evident that small deviations in pressure from mm. In order to give an idea of the change in bOiling point with pressure.
TABLE 3. These mixtures are examples of azeotropes. Water boiling at the University of Colorado ca. Nomographs for boiling point versus pressure data of organic compounds have been devised. Evans in Colorado. This effect is especially pronounced in the alcohols Figure 3. Correlations of Boiling Point with Structure The bOiling points of the members of a given homologous series increase as the series is ascended. If a hydrogen atom of a saturated hydrocarbon alkane is replaced by another atom or group.
The bOiling points rise in a uniform manner. The data indicate that. Thus alkyl halides. As more hydroxyl groups are introduced. If the group introduced is of such a nature that it promotes association. If the hydroxyl groups are converted to ether linkages.
The following series illustrates this effect: The thiol RSH compounds are associated only slightly and hence boil lower than their oxygen analogs. The saturated aliphatic alcohols Table 3. Just as with solubility relationships Chapter 5. A knowledge of the bOiling points of some simple compounds is frequently of value in excluding certain types of compounds.
The follOwing simple generalizations are helpful. This follows from the fact that the simplest of aryl halides. Among isomeric alcohols. A comparison of the boiling points of isomeric primary. Other bromo and iodo compounds may be either aliphatic or aromatic. If comparisons are made of alcohols of the same type. Specific gravity may be determined by means of a small pycnometer. Procedure If a small pycnometer with a capacity of mL is not available.
Remove the flask from the water bath. Determine the weight of the empty flask. After 10 min. Such densities are available from standard chemistry handbooks. Recall that specific gravity sp gr. Make a small scratch on the other vertical piece at the same height as the tip of the capillary.
Bend a piece of capillary tubing to an V-shape Figure 3. Remove the pycnometer from the water bath. Adjust the level of the water with a pipet. A commercial1. Suspend the pycnometer with a fine Nichrome.
Calculate the specific gravity of the unknown liquid using the equation shown below: The rather limited data on the alkyl fluorides are shown by curve V.
Curves VI and VII show that the specific gravities of the primary alkyl bromides and iodides are greater than 1. As a given homologous series of hydrocarbons is ascended. Thus curve IV.
The slopes of curves IV. The data in Table 3. Give the name and structure of the compound. A36 The replacement of one atom by another of higher atomic weight usually increases the density. Hydrocarbons are usually lighter than water.
Curves I. This may be done by means of the factor 0. Moving the double bond nearer the middle of the molecule causes an increase in the specific gravity. Discussion The specific gravity of a liquid may often be used to exclude certain compounds from the list of possibilities. In a I-mL pycnometer. It varies with the composition as well as the structure of the compound. The position the unsaturated linkage occupies also influences the density.
Similar relationships are exhibited by secondary and tertiary chlorides, bromides, and iodides. The specific gravities of aryl halides also arrange themselves in order of increasing weight of the substituent Table 3. An increase in the number of halogen atoms present in the molecule increases the specific gravity.
Compounds containing two or more chlorine atoms or one chlorine. Compound Benzyl chloride Bem. Compound Carbon tetrachloride Ethylene chlorohydrin Chloroacetone Methyl chloroacetate.
The introduction of functional groups containing oxygen causes an increase in the specific gravity. The curves in Figure 3. The ethers curve VIII are the lightest of all the organic oxygen compounds.
The aliphatic alcohols curve IX are heavier than the ethers but lighter than water. The specific gravity of the alcohols becomes greater than 1. The dip in curve IX is due to the fact that methanol is more highly associated than ethanol. The amines curve X are not as dense as the alcohols and are less associated.
Introduction of the aromatic ring may also cause esters to be heavier than water. Examples of esters of these types that are heavier than water are phenyl acetate, methyl benzoate, benzyl acetate, ethyl salicylate, butyl oxalate, triacetin, isopropyl tartrate, and ethyl citrate.
In general, compounds containing several functional groups-especially those groups that promote association-will have a specific gravity greater than 1. This is of considerable value in the case of neutral liquids. If the compound is heavier than water, it is probably polyfunctional. Index of Refraction of Liquids The refractive index of a liquid is equal to the ratio of the sine of the angle of incidence of a ray of light in air to the sine of the angle of refraction in the liquid Figure 3.
The Abbe-3L benchtop refractometer,6 illustrated in Figure 3. A schematic drawing of the Leica Auto Abbe refractometer is illustrated in Figure 3. Procedure Place a drop of the sample on the prism. Close the cover. While looking through the eyepiece, rotate the adjustment knob until the dividing line between the light and dark halves coincides with the center of the crosshairs Figure 3.
Record the refractive index and the temperature. At other temperatures, a correction factor is added, with "obs refractive index" as the observed refractive index and "obs temp" as the observed temperature:.
Calculate the corrected refractive index of a liquid that has an observed refractive index of 1. Clean the prisms with a cotton swab that has been dipped in toluene or petroleum ether for water-insoluble compounds. Do not use acetone. Use extreme care so that the prisms are not scratched.
Avoid metal or glass applicators, and use only clean, absorbent, dust-free cotton to clean the prisms. Discussion The values for denSity and refractive index are useful in excluding certain compounds from consideration in the identification of an unknown. Care must be taken, however, that the sample is pure. It is best to determine these phYSical constants on a middle cut from distillation or a gas chromatography collection.
This constant can also serve as a final check on an unknown after its identity and structure have been established. This checking is accomplished by comparing the observed refractive index to the literature value. A molecular structure that does not possess an internal mirror plane is called chiral possesses "handedness". A chiral compound has the potential of being optically active.
The compound 2-bromobutane is a simple example of a chiral compound. Its structure reveals one stereocenter a carbon center bearing four different substituents at C Thus 2-bromobutane can exist in two different forms called enantiomers: Intersection of mirror plane I. The R and 5 forms of 2-bromobutane have identical IR spectra, NMR spectra, boiling points, densities, and chromatographic retention times. They differ only in their abilities to rotate plane-polarized light and thus only in their optical rotations, or optical activity.
The terms R and 5 refer to the three-dimensional absolute configurations of the two forms of 2-bromobutane as defined by the Cahn-Ingold-Prelog notation this is described in detail in organic lecture texts. These two forms of 2-bromobutane thus have optical activity that is measurable on a polarimeter as described below. Configuration R or 5 does not necessarily correspond to a particular rotation.
The optical rotation is determined only if the list of possible compounds contains optically active substances. Preparation of the Solution Procedure Accurately weigh 0. The commonly used solvents are water, ethanol, and chloroform. The solution should be clear, with no suspended particles of dust or filter paper. Discard the first 25 mL of the filtrate; use the last 25 mL in the polarimeter. Filling the Polarimeter Tube Procedure Screw the cap on the end of the polarimeter tube. Hold the tube vertically and pour in the solution until the tube is full and the rounded meniscus extends above the end of the tube.
Slide the glass plate over the end of the tube so that no air bubbles are caught. Screw on the brass cap. Precautions 1. Place a rubber washer between the glass plate and the brass cap.
Do not place any washers between the glass end plate and the glass tube. Do not screw on the ends too tightly. Screw on the ends enough to make a firm, leak-proof joint. If the ends are screwed on too tightly, the glass end plates will be strained and a rotation will be observed with nothing in the tube at all. For substances with low readings, loosen the caps and tighten them again between readings.
A schematic is shown in Figure 3. Analyzer Servo motor. Functional principle of a PerkinElmer polarimeter. Procedure Select the desired wavelength for the sample. Place the filled polarimeter tube into the sample tube holder. On the manual polarimeter, adjust the analyzer until the maximum amount of light is transmitted. This adjustment is done automatically on the electronic polarimeter. Read the observed rotation. The sodium or mercury light passes through the polarizer.
The polarizer allows only one plane of polarized light to be emitted. The light passes through the sample cell. If an optical active compound is present, then the plane of polarized light is rotated. After the sample cell, the light passes through the analyzer. The analyzing filter is adjusted. The difference, in degrees, between the polarizer and the analyzer is the observed rotation of the sample.
Expression of Results The specific rotation of a substance is calculated by one of the following formulas:. It should be noted that the specific rotation may be quite sensitive to the nature of the solvent and, in certain cases, even to the concentration of the substance being examined. The wavelength of the light used for measurement can also affect not only the magnitude but also the sign of rotation. Attention should be paid, therefore, to the exact conditions under which a rotation reported in the literature was measured.
The follOwing is the correct way to report specific rotation: It is necessary to determine the observed rotation, a, at two different concentrations. In the Simplest cases, observed rotations will be decreased by the same factor as the concentration decrease; for example, a. Thus in such a case the [a] determined from all three experiments will be the same, and one has in hand a value of [a] that can be safely compared to literature values of [a] determined at other concentrations.
In this way the value of [a] in such Simple cases can be used to confirm the identity of the compound of interest.
If the value of [a] has been determined upon a liquid sample using no solvent, the specific rotation should be reported as follows: Calculate the speCific rotation. Give the name of the carbohydrate. As described earlier, the existence of a single stereocenter also called chiral or asymmetric center in a compound such as 2-bromobutane can cause optical activity.
Other commonly encountered organic compounds with one stereocenter include H. The L designation used above for alanine refers to its absolute configuration here the L form has the S configuration. The enantiomer of L-alanine would be D-alanine the 0 and L notation for absolute configuration is frequently encountered for amino acids and carbohydrates, and is less general than R and S notation.
In like manner, 0 absolute configuration is not the same as d rotation. In fact it is not uncommon to find that a 0 stereoisomer has 1, or - , rotation! Chiral compounds with more than one stereocenter are common. Glucose, for example, has four stereocenters when acyclic and five when cyclic. Intersection of mirror plane. The meso form shows no optical activity; although it has two stereocenters, the effects of these two centers cancel, resulting in an optically inactive or achiral compound.
The lack of activity is not surprising in view of the fact that this compound bears a meso plane the intersection of which is illustrated by the dotted line. Since this meso plane is an internal mirror plane, this compound by definition is achiral and thus optically inactive.
Optical Purity In introducing optically active compounds above, we have discussed compounds that are one enantiomer e. The speCific rotations should be carried out at the same temperature and concentration and in the same solvent. The resulting enantiomeric excess can be related to the solution composition as follows: Recrystallization procedures can be quite complex.
Standard laboratory textbooks for organic chemistry usually have exercises to introduce these procedures. Even if the correct solvent or solvent pair cannot be found in Table 3. For example, if a phenylurethane derivative does not recrystallize from petroleum ether, then petroleum ether-toluene might work.
Procedure for a Single Solvent Select a solvent so that the sample is five times as soluble in the hot solvent as in the cold solvent. Place the solid, oil, or semisolid sample in a small amount of solvent. Add one or two boiling chips. Heat the solution on a hot plate until the sample dissolves completely. If necessary, add more solvent, a little at a time, to completely dissolve the sample. Use the minimum amount of solvent needed to dissolve the sample. The undissolved solid remains in the filter paper or in the.
Hydrocarbons Water Water, toluene, hydrocarbons Acetone, alcohols, dioxane, acetonitrile Ether, ethyl acetate, hydrocarbons Water, ether, hydrocarbons Water, hydrocarbons, ethyl acetate See line 4. Acetone, hydrocarbons, ethyl acetate, toluene, methylene chloride Ethyl alcohol, hydrocarbons See line 9; bromo compounds See line 7.
Gordon and R. Remember that many of these solvents, of which benzene Is an important. Methylene chloride is also a possible alternative for chloroform. Methanol; ethanol Methanol; ethanol Methanol-water; ethanol Methanol; ethanol Methanol-water; ethanol Acetone-alcohol; methanol; ethanol Methanol; ethanol Petroleum ether-toluene Ethyl acetate; methanol; ethanol Methanol-water; ethanol Petroleum ether Methanol-water; ethanol Methanol; ethanol; acetone-alcohol Petroleum ether-toluene Acetone-alcohol Petroleum ether Toluene; ethanol; methanol-water Ethyl acetate; isopropyl ether Ethanol; methanol-water Methanol-water; ethanol Chloroform; methylene chloride Methanol; ethanol Dioxane-water.
Allow the solution to cool to room temperature. In the "ideal" case, uniform crystals slowly appear. When the solution becomes cloudy or a few crystals appear, chill the solution in an ice bath. Wait until there is a transparent layer of liquid above the layer of crystals before isolating the crystals. Depending on the amount of crystals, isolate the crystals by filtering the solution through a Hirsch funnel or a Buchner funnel.
Procedure for a Solvent Pair Dissolve the sample in a minimum amount of hot solvent in which the sample is more soluble. After the solution becomes cloudy or a few crystals appear, chill the solution in an ice bath. Isolate the crystals by fIltering the solution through a Hirsch funnel or a Buchner funnel. Check the crystals for purity. Check with your instructor to see if the color is due to impurities.
To remove a highly colored impurity, dissolve the sample in a hot solvent in which it is readily. Add a small amount of decolorizing charcoal so that the solution turns black.
Pour the bOiling solution through filter paper into another flask. Remove the solvent, by bOiling or evaporation, and proceed with the directions for either a single solvent or solvent pair.
Oil Fonnation Frequently, recrystallization attempts will result in oil formation rather than the desired solid. An oil is recognized by the formation of a second layer. The formation of an oil may be due to the fact that the sample is impure.
Additional Suggestions Oils may persist, even after repeated pUrifications. This may be due to the fact that the sample is inherently difficult to crystallize or that the last traces of impurity must be removed by recrystallization.
Shake the flask several times. Sometimes this gives enough momentum to start the formation of crystals. Provide a site for crystal nucleation to initiate the recrystallization process. Add a small seed of pure sample during recrystallization. Lower the temperature to decrease the solubility of the sample, not to freeze the solvent or sample.
See Appendix I for additional chilling solutions. Room temperature Refrigeration Ice-water bath Refrigerator freezer or salted ice bath Dry ice-acetone Liquid nitrogen Be careful not to confuse frozen solvent or frozen amorphous oils with crystals; frozen oils will melt and form oils at room temperature.
This stirring can be done in contact with the mother liquor. Seeding can also be used. In some cases, a long period of stirring is needed to induce crystallization. List a solvent or solvent combination that can be used to recrystallize an acid anhydride. List a solvent or solvent combination that can be used to recrystallize a benzoate.
The detection of these elements, by means of chemical tests, is usually straightforward. Many of these chemical tests are quite sensitive, so all aqueous solutions should be carefully prepared using only distilled or deionized water. Compounds that are known to react explosively with molten sodium are nitroalkanes, organic azides, diazo esters, diazonium salts, and some aliphatic polyhalides such as chloroform or carbon tetrachloride.
Safety glasses, with side shields, must be wom at all times when any procedure or experiment is being conducted. The safety of other members of the class must be taken into account and therefore care must be taken so that reaction flasks are not pointed toward others in the lab.
A sample of 4-bromobenzenesulfonamide is recommended as a control. It may even be advantageous to run a control on a compound that is known not to contain the element of interest; observations associated with this control allow one to draw conclusions about tests yielding negative results or about the purity of the reagents involved.
Knowledge of the elemental composition of an organic compound being studied is essential for the follOwing reasons. Additionally, NMR spectra Chapter 6 , IR spectra Chapter 7 , and mass spectra Chapter 8 can be interpreted so that the structure of the unknown is determined.
In this text we will, however, be concerned with detection of only a few of the elements more commonly found in organic compounds; detection of the other elements is a subject that is discussed in other courses, such as one on instrumental analysis that covers atomic absorption and other instrumental procedures.
A few of the most common salts, such as those containing Na, K, and Ca, might also be included. The filtrate is then used for determination of the presence of sulfur, nitrogen, and halogen. A compound such as. Heat the test tube until the bottom is a glOwing red. Do not heat the test tube or its contents to redness.
Break up the test tube with a stirring rod. Add a few drops of ethanol. During the heating. Heat the test tube to a dull red again and. Repeat until no further bubbles of hydrogen gas are evolved.
Vinson and W. Prior to placing the sodium in the test tube. Allow the glOwing and charred residue to cool to room temperature. Rinse the knife. With a knife. Add 10K. The mixture of the unknown and powdered sugar provides a charring and redUcing action so that compounds containing nitrogen. Filter the solution. It is imperative that the preparation of the sodium fusion filtrate be done in the hood.
Procedure AlO Support a small test tube approximately X 13 mm made of soft glass not Pyrex or Kimax in a vertical position with a clamp from which the rubber has been removed. Use the filtrate. The first time that the student prepares the sodium fusion filtrate. Heat and filter the solution. Heat the test tube with a flame until sodium vapors rise in the tube.
Campbell and B. Use the fIltrate. Sulfur compounds. Add 2 mL of water to this solution. Add the mixture and heat the test tube for a second and third time. Cool the test tube. Heat the bottom of the tube to a dull red. Heat the lower part of the test tube until the sodium melts and sodium vapors rise in the test tube. One method 13 involves the formation of a calcium oxide-zinc fusion. Guthrie and I. A black precipitate of lead sulfide indicates the presence of sulfur in the unknown.
If a sharp explosion occurs when the initial portion of the unknown is heated with the sodium. The oxygen flask method l yields a liquid that can be used for elemental analysis. Allow the test tube to cool to room temperature. Del Valle. Cleaning Up Place the sodium fusion solutions from Procedures A. Combine these filtrates together and use them for the specific tests described below. Filter the reaction mixture while still warm.
Sulfur Use either of the follOwing procedures to test for the presence of sulfur. Additional methods have been published to form the fusion solution. Do not heat too strongly. Remove the flame until the reaction ceases. A deep blue-violet color indicates the presence of sulfur.
Procedure a for Sulfur Acidify 1 mL of the sodium fusion nItrate with acetic acid. Specific Tests for Elements Use the sodium fusion nItrate.. Rinse the test tube with 2 mL of water and filter the rinsings. Add 0. Place the hexane washings.
Add 3 mL of water and heat the test tube gently for 2 min. Kramer and G. The use of these elemental tests. Such classification tests include the treatment of the unknown with sodium hydroxide. Place the solutions from both tests for sulfur in the aqueous solution Nitrogen The presence of nitrogen can be detected using any of the procedures below.
Cleaning Up container. Acidification of the solution of the purple dianion results in a yellow solution of 2-nitrophenylhydroxylamine an acid-base indicator. Guilbault and D. This test for nitrogen is more sensitive than the Prussian blue test described in the fifth or earlier editions of this text. The products of the above reactions provide the explanation as to why this test is especially sensitive.
The deep-purple compound is due to a dianion produced when sodium cyanide. A positive test for nitrogen is the appearance of a deep-blue-purple compound. Procedure a for Nitrogen 17 In a small test tube. Add two drops of the sodium fusion filtrate. The appearance of the characteristic precipitate of Prussian blue indicates the presence of nitrogen.
Boil gently for 30 sec. For this test. Controls Test these procedures with benzenesulfonamide positive test and toluene negative test. A green flame indicates halogen and is not sustained for very long. Use the data from these tests. Unless otherwise stated. The solution is acidic when the litmus paper turns red and basic when the litmus paper turns blue. Cleaning Up Place all solutions in the aqueous solution container. The presence of a red color indicates that nitrogen was present in the original unknown.
Procedure a for Presence of a Halogen Beilstein's test is a very general test to see if any halogen is present. Isolate and wash the precipitate on white filter paper to better observe the color. Some inorganic compounds also give green flames. If no precipitate is observed but a blue or greenish-blue solution is obtained. Halogens Use the tests listed below to check for the presence and identity of halogens. Cool the wire.
Dip the loop in a little of the original unknown compound and heat it in the edge of the flame. A purple color indicates the presence of iodine. Add 25 mg of oxalic acid to barely decolorize the solution. If the methylene chloride layer is colorless.
Add three drops of 0. Boil gently for a few minutes to expel any hydrogen cyanide or hydrogen sulfide that might be present due to nitrogen or sulfur contained in the original compound.
Silver iodide does not undergo reaction with the ammonium hydroxide and thus remains insoluble. Isolate the precipitate by filtration. New York. An immediate heavy formation of a solid indicates the presence of chlorine. Add 1 mL of methylene chloride. Silver chloride is white. Add 1 mL of methylene chloride and again shake the mixture. If any precipitation occurs at this point. Cool the solution to room temperature.
A brown color indicates that bromine is present. The production of a purple color in the bottom methylene chloride layer indicates the presence of iodine. Add 10 drops of a 1. Since silver fluoride is soluble in water. Silver chlOride. If only a faint turbidity is produced. Isolate the solid. Boil to expel any hydrogen cyanide and hydrogen sulfide that might be present. The chlorine does not produce a color when in solution in methylene chloride.
The purple will gradually disappear and be replaced by a reddish-brown color if bromine is present. If iodine is present. One of the procedures listed below should be used to confirm the presence of chlorine. This treatment results in the reaction of any silver thiocyanate that may be present. A purple color indicates iodine. Procedure f for Bromine To 3 mL of the sodium fusion filtrate in a test tube.
The formation of a yellow solid. Chlorides and cyanides do not interfere with this test. If bromide is present in the solution. To 1 mL of this solution. Cool the mixture. Boil the precipitate of silver halides with 4 mL of 0. Awhite precipitate indicates the presence of chlorine. A white precipitate indicates chlorine.
Cool the solution.
Procedure h for Chlorine in the Presence of Nitrogen. Iodides produce a brown color. A brown color indicates the presence of bromine. Place a piece of filter paper.
Boil the solution for a few minutes. Dilute the resulting mixture to 6 mL of distilled water and filter. Dilute the remaining 9 mL of the acidified solution to 60 mL with water. Cleaning Up Filter off the Silver. The entire system is then evacuated with a vacuum pump. Place one drop of the solution on a piece of zirconium-alizarin test paper. The sample can also be placed in a small vial with a high-quality laboratory tissue held around the mouth of the container with a rubber band.
Neutralize the aqueous layers with sodium bicarbonate. Baron Consulting. Heat the solution to boiling. Procedure j for Fluorine Acidify 4 mL of the stock solution with acetic acid. For removal of water. The unknown can be dried to remove residual solvents in an Abderhalden drying pistol Figure 3. The drying bulb of the drying pistol is charged with fresh.
The speed at which the sample loses the solvent may be increased by allowing toluene or xylene to reflux up from the lower flask. Such microanalyses are usually determined by commercial firms 20 equipped with combustion or other appropriate analytical equipment. HulTman Laboratories. If fluorine is present. The container is then placed in the horizontal portion of the drying pistol.
Add four drops of saturated calcium chloride solution. A yellow color on the red paper indicates the presence of fluorine. Controls Test these procedures with chlorobenzene positive test for chlorine.