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ERIC Number: EJ1166994
Record Type: Journal
Publication Date: 2018-Jan
Pages: 5
Abstractor: As Provided
ISSN: ISSN-0021-9584
Experimental Determination of Activation Energy of Nucleophilic Aromatic Substitution on Porphyrins
Rizvi, Waqar; Khwaja, Emaad; Siddiqui, Saim; Bhupathiraju, N. V. S. Dinesh K.; Drain, Charles Michael
Journal of Chemical Education, v95 n1 p164-168 Jan 2018
A physical organic chemistry experiment is described for second-year college students. Students performed nucleophilic aromatic substitution (NAS) reactions on 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrin (TPPF[subscript 20]) using three different nucleophiles. Substitution occurs preferentially at the 4-position ("para") because it is thermodynamically favored, and the 2- and 6- ("ortho") positions are kinetically disfavored because of steric interactions with the porphyrin ring. The activation energy depends heavily on the nucleophile. Open-source software (ImageJ from NIH) was used to quantify relative intensities of spots on a TLC plate obtained from different times and varying temperatures. These data were used to generate Arrhenius plots allowing students to determine relative activation energies for three different primary nucleophiles. The experiment was developed by 5 undergraduates and evaluated by 40 organic chemistry II students and 8 students in a physical chemistry laboratory. Students gained a deeper understanding of the relationships between the NAS mechanism, Arrhenius plots, and activation energy.
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: National Science Foundation (NSF); National Institute on Minority Health and Health Disparities (NIMHD) (DHHS/NIH)
Authoring Institution: N/A
Grant or Contract Numbers: CHE1610755; 8G12MD007599