J. 1. Valentine,' J. B. Entrikin ond M. W. Hanson Centenary College of Louisiono Shreveport
A Test for the Subclasses of Aliphatic Amines
T h e compound 3,3',5,5'-tetrabromophenolphthalein ethyl ester,%-' also named bromophthalein magenta E, has been mentioned as having possibilities as a reagent for the qualitative detection of amines using nonaqueous ~olvents.5.~ Investigation of this reagent dissolved separately in 10 organic solvents with amines has led to the conclusion that it is a very useful reagent for subclassifying aliphatic arnines. No reliable procedure was found for aromatic amines. The following procedure was developed after testing more than 30 aliphatic amines in various concentrations and in several solvents. The compound to be tested should be known to be an amine since other functional groups may produce analagous colors with the reagent. It is vital that all apparatus used be dry, since water does produce a color change in the reagent. The reagent must be protected from laboratory fumes because it is extremely sensitive to acidic or basic vapors. Procedure. Prepare a 1.5 X lo-' M solution of 3,3',5,5'tetrabromophenolphthalein ethyl ester in carbon tetrachloride. Keep the reagent bottle tightly stoppered to prevent contamination. Pour 3 ml of the reagent into a dry 4in. test tube, add one drop of the aliphatic &mine, insert s. clean cork in the tube, and shake the contents vigorously. Immediately observe the color change, if any, from the initial yellow color of the reagent.
Primary aliphatic amines normally produce a purple color; secondary amines, a blue color; and tertiary amines, a red color. Aromatic amines do not affect the yellow color of the reagent in carbon tetrachloride. Consistent results were obtained with use of Ca, C I , and Cs aliphatic amines. Known exceptions and comments follow. Certain aliphatic amines which are not secondary aliphatic arnines may produce a blue color with the reagent. Several compounds have been noted which follow this pattern. These are benzylamine, ethylamine, and 2,2',2r-trihydroxytriethylamine. This apparent discrepancy may be circumvented by the use
of a 1.5 X lo-' M solution of 3,3',5,5'-tetrabromophenolphthalein ethyl ester in isopropyl ether. Thus, whenever the blue color is observed in the carbon tetrachloride reagent, one drop of the amine must also be added to 3 ml of the isopropyl ether reagent. In this particular reagent secondary aliphatic amines produce a pink-rose color, whereas other subclasses of aliphatic and aromatic arnines produce various shades of blue. This study has also shown that the subclasses of aliphatic amines may be identified spectrophotometrically. Using the same concentration of reagent and amine specified above, it was found that primary aliphatic amines show a minimum traasmittance between 530-540 mp; secondary aliphatic amines, between 570-580 mp; and tertiary aliphatic amines, between 520-530 mp. A limited number of aromatic amiues were tested with 3,3',5,5'-tetrabromophenolphthalein ethyl ester in the following solvents: isopropyl ether, dimethylforamide, and acetone. For example, with dimethylforamide as a solvent, 3-nitroanaline gives no color change from the initial blue color, while 2-nitroamline and 4-nitroanaline change the reagent to a green color. While no general classification was indicated, certain observations suggest the possibility for specific structures which might be developed by further study. Presented a t the Southwest Regional Meeting of the ACS, Houston, Texas, December 1963. 'Present addreas: Dept. of Pharmaceutical Chemistry, University of Mississippi, University, Mississippi. E., Ber. deut. chem. Ges., 'NIETZKI, R., AND BURCKHARDT, 30,175 (1897). a THIEL,A., A N D DIEHL,R., Sitzbw.Ges. Reforder. Ges. Natunu. Marburg., 62,472(1927). RAMART-LUCAS, P., Bull. soe. ehim., 8,865 (1941). 5 DAVIS, MARION M., A N D SCHUHMANN, PRI~CILLA J., J . Re8. Nat. BUT.Std.,39,231 (1947). ' DAVIS,MARIONM., A N D HETZER,HANNAH B., J. Res. Nal. BUT.Std.,46,406 (1951); 48,381 (1952).
Vacuum Filtration System At times there is need to operate a suction atration apparatus over extended periods. We have found that the use of a large reservoir volume in a simple vacuum system is superior to having an aspirator ruaniog for a long time. We use several gallon jugs connected together and to a mercury manometer. An aspirator will evacuate the system relatively quickly; the manometer allows the vacuum to be monitored. It is possible to accomplirih slow filtrations through efficient finepore paper completely unattended if the system is leak free. The system will draw until the filter NUS dry. BROTHER WILLIAM SCHUBMEHL, C.S.C. ST.EDWARD HIGHSCHOOL CLEVELAND, OHIO Volume 4 1 , Number 10, October 1964
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