An experiment designed for organic chemistry students at the sophomore level is presented. The experiment, which involves no special equipment and which employs only inexpensive reagents, demonstrates the conversion of anthranilic acid to o-fluorobenzoic acid via the modified Schiemann Reaction

Setliff, Frank L.

English

UARK (University of Arkansas )

Journal of the Arkansas Academy of Science Volume 25 Article 6 1971 Preparation of o-Fluorobenzoic Acid. An Elementary Organic Laboratory Experiment Frank L. Setliff University of Arkansas at Little Rock Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the Organic Chemistry Commons Recommended Citation Setliff, Frank L. (1971) "Preparation of o-Fluorobenzoic Acid. An Elementary Organic Laboratory Experiment," Journal of the Arkansas Academy of Science: Vol. 25 , Article 6. Available at: https://scholarworks.uark.edu/jaas/vol25/iss1/6 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. .•Arkansas Academy of Science Proceedings, Vol. XXV,197112Frank L. SetliffThe Preparation of o-Fluorobenzoic Acid.An Elementary Organic Laboratory ExperimentFrank L. SetliffDepartment of ChemistryUniversity of Arkansas at Little RockLittle Rock, Arkansas 72204ABSTRACTEAn experiment designed for organic chemistry students at the sophomore level is presented. The experiment,ich involves no special equipment and which employs only inexpensive reagents, demonstrates the conversion ofhranilic acid to o-fluorobenzoic acid via the modified Schiemann Reaction.Although most elementary organic texts illustrate thentroduction of fluorine into aromatic systems by theSchiemann Reaction, 1 2 (equation 1) no experiments aregenerally available for the student laboratory applicationof this recct on.NaNU © <s> HBF © <=> lieat ,ArNH i-» ArN Cl *-* ArN BF ? ArF + N, + BF (1)'HC1.O0 2' "Rutherford and co-workers 11 observed that replace-ment of fluoboric acid (HBF.,,) with hexafluorophosphoricacid (HPF6) in the above reaction resulted in improvedoverall yields of aromatic fluorides. The most outstand-ng yield increase (-j-52%) was in the case of the con-version of anthranilic acid to o-fluorobenzoic acid.We have found that the general procedure employedby Rutherford is, with some modification, suitable for thepreparation of o-fluorobenzoic acid in the elementaryorganic laboratory. The overall reaction scheme is il-ustrated by equation 2.+ N2 + PP 5The experiment is conveniently performed in two laboratory periods. Diazotization of anthranilic acid and subsequent isolation of the o-carboxybenzenediazonium hexafluorophosphate is performed in the first period, and thesecond preiod is utilized for the thermal decompositionof the diazonium salt. The decomposition step proceedssmoothly, and students find it an interesting chemicatransformation to observe. 4ExperimentalTo a solution of anthranilic acid (10.3 g, 0.75 mole)dissolved in water (53 ml) and cone HC1 (7.5 ml) ina 400 ml beaker cooled to -5° (a ppt of the hydrochlorideresults) is added NaN0 2 (6.1 g in 20 ml H2O dropwisefrom a separatory funnel) over a 30 min period withmanual stirring. Hexafluorophosphoric acid 5 (25 ml of65%) is added in one portion from a polyethylene gradu-ate cylinder to the cold, now gelatinous, diazotized mix-ture. After allowing the resulting slurry to stand at icebath temperature for i/2 hr, the white solid is suctionfiltered, washed on the filter pad with ice water (150 ml),sucked dry, and air dried until the next laboratoryperiod (mp. 125-129°, dec; yield 13-15 g).Decomposition is carried out in a standard taper500 ml, round-bottomed, one-necked flask containing200 ml xylene and equipped with a condenser and inverted funnel gas trap6 leading to a beaker of diluteNaOH solution. The mixture is heated with a small flameand with manual agitation until decomposition of thesalt begins (evolution of white phosphorus pentafluoridefumes. WARNING: PF S is intensely irritating to skin,eyes and mucous membranes. Inhalation may cause pul-monary edema. Students should be thoroughly warnedof this danger, each apparatus individually inspected bythe instructor and the decomposition performed in aneffecient fume hood). As decomposition ceases, thexylene is heated to boiling for 5 min to expel the excessgases. The reaction mixture is cooled to room tempera-ture, extracted with three 50-ml portions of 5% NaOH12Journal of the Arkansas Academy of Science, Vol. 25 [1971], Art. 6Published by Arkansas Academy of Science, 1971iArkansas Academy of Science Proceedings, Vol. XXV, 1971 13solution, and the aqueous extracts are poured with stir-ring into a slush of ice (100 g) and cone HC1 (100 ml).the precipitated acid is suction filtered, washed on thefilter with ice water (150 ml), dried, and recrystallizedfrom methylcyclohexane (15 ml/g) using a steam cone.The yield of light yellow solid is 4-5 g, (40-50% fromanthranilic acid), mp 120-122° (lit3 mp 124-125°).References1. Balz, G., and Schiemann, G., Chem. Ber., 60, 1186(1927).2. Roe, A. in "Organic Reactions," Vol. V, J. Wileyand Sons, Inc., New York, 1949, p. 193.3. Rutherford, K., Redmond, W., and Rigamonti, J.,J. Org. Chem., 26, 5149 (1961).4. Unlike some aromatic diazonium salts which havebeen reported to be shock sensitive, diazoniumfluoborates and hexafluorophosphates have beenfound to be remarkably stable in this respectFurthermore, the success of their use in synthesisis based upon their stability and ability to be smoothly decomposed.5. Obtainable from the Ozark Mahoning Co., TulsaOklahoma. This reagent will etch glass on prolonged contact. However, we have observed noglassware damage if students thoroughly wash alglassware in previous contact with the acid.6. c. f Dannley, R. and Crum, J., "Experimental Or-ganic Chemistry." The Macmillan Co., New York,1968, p. 29.Physics And Environmental StudiesJoe M. GuenterThe Physical Science DepartmentUniversity of Arkansas at Monticello 71655ABSTRACTTo further implement the course curriculum for the Earth Science major and to constructively channel the cur-rent interest and concern with the environmental problems, the Department of Physical Science at the Universityof Arkansas at Monticello introduced a course entitled Environmental Studies this past spring.As it was necessary to offer both a general education Elementary Physics course in addition to the new course,it was decided to combine the two courses and use an approach similar to that of Edwin Marston, Queens College,Flushing, New York.Problems of conservation, pollution, and environmental quality were considered by the class whose rank rangedfrom freshman to senior with widely diverse backgrounds. Physics with minimal math was incorporated sporadicallyas needed.The basic structure of class organization allowed students of the Environmental Studies class to present paneldiscussions for the other students to participate in through comments, questions, and answers.The process of implementing the planned EarthScience major curriculum began two years ago at Ar-(ansas A&M College, now the University of Arkansas atMonticello. The program, which is one of the offeringsof the Department of Physical Science, gained severalmajors and minors and matured rapidly.This past fall it was realized that the single persondevoted to the earth science and geology area could notoffer all of the general and advanced courses currentlyneeded. As finances would not permit the addition ofanother faculty member at that time and as there wasone member on leave for the academic yer, faculty timewas at a premium.A general education physics course was to be of-fered and an additional upper level course for thosemajoring or minoring in Earth Science was needed forthe fall semester. It was, therefore, decided to intro-duce one of the previously formulated courses, Environ-mental Studies, at this time. It was further agreed thatthe two courses, Elements of Physics and EnvironmentalStudies, would be combined and taught together. Thetemporary combining of these two courses was the ap-parent solution to the situation previously indicated.This approach was not altogether unique as Dr.Edwin Martson, Queens College, Flushing, New York,had described an innovative course in an article in the13Journal of the Arkansas Academy of Science, Vol. 25 [1971], Art. 6https://scholarworks.uark.edu/jaas/vol25/iss1/6

Preparation of o-Fluorobenzoic Acid.  An Elementary Organic Laboratory Experiment

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Journal of the Arkansas Academy of ScienceVolume 25 Article 61971Preparation of o-Fluorobenzoic Acid. AnElementary Organic Laboratory ExperimentFrank L. SetliffUniversity of Arkansas at Little RockFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Organic Chemistry CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationSetliff, Frank L. (1971) "Preparation of o-Fluorobenzoic Acid. An Elementary Organic Laboratory Experiment," Journal of theArkansas Academy of Science: Vol. 25 , Article 6.Available at: http://scholarworks.uark.edu/jaas/vol25/iss1/6.•Arkansas Academy of Science Proceedings, Vol. XXV,197112Frank L. SetliffThe Preparation of o-Fluorobenzoic Acid.An Elementary Organic Laboratory ExperimentFrank L. SetliffDepartment of ChemistryUniversity of Arkansas at Little RockLittle Rock, Arkansas 72204ABSTRACTEAn experiment designed for organic chemistry students at the sophomore level is presented. The experiment,ich involves no special equipment and which employs only inexpensive reagents, demonstrates the conversion ofhranilic acid to o-fluorobenzoic acid via the modified Schiemann Reaction.Although most elementary organic texts illustrate thentroduction of fluorine into aromatic systems by theSchiemann Reaction, 1 2 (equation 1) no experiments aregenerally available for the student laboratory applicationof this recct on.NaNU © <s> HBF © <=> lieat ,ArNH i-» ArN Cl *-* ArN BF ? ArF + N, + BF (1)'HC1.O 0 2' "Rutherford and co-workers 11 observed that replace-ment of fluoboric acid (HBF.,,) with hexafluorophosphoricacid (HPF6) in the above reaction resulted in improvedoverall yields of aromatic fluorides. The most outstand-ng yield increase (-j-52%) was in the case of the con-version of anthranilic acid to o-fluorobenzoic acid.We have found that the general procedure employedby Rutherford is, with some modification, suitable for thepreparation of o-fluorobenzoic acid in the elementaryorganic laboratory. The overall reaction scheme is il-ustrated by equation 2.+ N2 + PP 5The experiment is conveniently performed in two laboratory periods. Diazotization of anthranilic acid and subsequent isolation of the o-carboxybenzenediazonium hexafluorophosphate is performed in the first period, and thesecond preiod is utilized for the thermal decompositionof the diazonium salt. The decomposition step proceedssmoothly, and students find it an interesting chemicatransformation to observe. 4ExperimentalTo a solution of anthranilic acid (10.3 g, 0.75 mole)dissolved in water (53 ml) and cone HC1 (7.5 ml) ina 400 ml beaker cooled to -5° (a ppt of the hydrochlorideresults) is added NaN0 2 (6.1 g in 20 ml H2O dropwisefrom a separatory funnel) over a 30 min period withmanual stirring. Hexafluorophosphoric acid 5 (25 ml of65%) is added in one portion from a polyethylene gradu-ate cylinder to the cold, now gelatinous, diazotized mix-ture. After allowing the resulting slurry to stand at icebath temperature for i/2 hr, the white solid is suctionfiltered, washed on the filter pad with ice water (150 ml),sucked dry, and air dried until the next laboratoryperiod (mp. 125-129°, dec; yield 13-15 g).Decomposition is carried out in a standard taper500 ml, round-bottomed, one-necked flask containing200 ml xylene and equipped with a condenser and inverted funnel gas trap6 leading to a beaker of diluteNaOH solution. The mixture is heated with a small flameand with manual agitation until decomposition of thesalt begins (evolution of white phosphorus pentafluoridefumes. WARNING: PF S is intensely irritating to skin,eyes and mucous membranes. Inhalation may cause pul-monary edema. Students should be thoroughly warnedof this danger, each apparatus individually inspected bythe instructor and the decomposition performed in aneffecient fume hood). As decomposition ceases, thexylene is heated to boiling for 5 min to expel the excessgases. The reaction mixture is cooled to room tempera-ture, extracted with three 50-ml portions of 5% NaOH12Journal of the Arkansas Academy of Science, Vol. 25 [1971], Art. 6Published by Arkansas Academy of Science, 1971iArkansas Academy of Science Proceedings, Vol. XXV, 1971 13solution, and the aqueous extracts are poured with stir-ring into a slush of ice (100 g) and cone HC1 (100 ml).the precipitated acid is suction filtered, washed on thefilter with ice water (150 ml), dried, and recrystallizedfrom methylcyclohexane (15 ml/g) using a steam cone.The yield of light yellow solid is 4-5 g, (40-50% fromanthranilic acid), mp 120-122° (lit3 mp 124-125°).References1. Balz, G., and Schiemann, G., Chem. Ber., 60, 1186(1927).2. Roe, A. in "Organic Reactions," Vol. V, J. Wileyand Sons, Inc., New York, 1949, p. 193.3. Rutherford, K., Redmond, W., and Rigamonti, J.,J. Org. Chem., 26, 5149 (1961).4. Unlike some aromatic diazonium salts which havebeen reported to be shock sensitive, diazoniumfluoborates and hexafluorophosphates have beenfound to be remarkably stable in this respectFurthermore, the success of their use in synthesisis based upon their stability and ability to be smoothly decomposed.5. Obtainable from the Ozark Mahoning Co., TulsaOklahoma. This reagent will etch glass on prolonged contact. However, we have observed noglassware damage if students thoroughly wash alglassware in previous contact with the acid.6. c. f Dannley, R. and Crum, J., "Experimental Or-ganic Chemistry." The Macmillan Co., New York,1968, p. 29.Physics And Environmental StudiesJoe M. GuenterThe Physical Science DepartmentUniversity of Arkansas at Monticello 71655ABSTRACTTo further implement the course curriculum for the Earth Science major and to constructively channel the cur-rent interest and concern with the environmental problems, the Department of Physical Science at the Universityof Arkansas at Monticello introduced a course entitled Environmental Studies this past spring.As it was necessary to offer both a general education Elementary Physics course in addition to the new course,it was decided to combine the two courses and use an approach similar to that of Edwin Marston, Queens College,Flushing, New York.Problems of conservation, pollution, and environmental quality were considered by the class whose rank rangedfrom freshman to senior with widely diverse backgrounds. Physics with minimal math was incorporated sporadicallyas needed.The basic structure of class organization allowed students of the Environmental Studies class to present paneldiscussions for the other students to participate in through comments, questions, and answers.The process of implementing the planned EarthScience major curriculum began two years ago at Ar-(ansas A&M College, now the University of Arkansas atMonticello. The program, which is one of the offeringsof the Department of Physical Science, gained severalmajors and minors and matured rapidly.This past fall it was realized that the single persondevoted to the earth science and geology area could notoffer all of the general and advanced courses currentlyneeded. As finances would not permit the addition ofanother faculty member at that time and as there wasone member on leave for the academic yer, faculty timewas at a premium.A general education physics course was to be of-fered and an additional upper level course for thosemajoring or minoring in Earth Science was needed forthe fall semester. It was, therefore, decided to intro-duce one of the previously formulated courses, Environ-mental Studies, at this time. It was further agreed thatthe two courses, Elements of Physics and EnvironmentalStudies, would be combined and taught together. Thetemporary combining of these two courses was the ap-parent solution to the situation previously indicated.This approach was not altogether unique as Dr.Edwin Martson, Queens College, Flushing, New York,had described an innovative course in an article in the13Journal of the Arkansas Academy of Science, Vol. 25 [1971], Art. 6http://scholarworks.uark.edu/jaas/vol25/iss1/6

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Preparation of o-Fluorobenzoic Acid. An Elementary Organic Laboratory Experiment

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