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The Chemical Educator
ISSN: 1430-4171 (electronic version)
Abstract Volume 23
(2018) pp 133-136
Applying Intermolecular Hydrogen Bonding Interactions of
Phenol Derivatives to the Harmonic Oscillator Using Infrared Spectroscopy
Anna M. Fedor* and Megan J. Toda
Misericordia University 301 Lake St. Dallas, PA 18612, afedor@misericordia.edu
Received May 28, 2018. Accepted June 25, 2018.
Published: 17 July 2018
Abstract. A
physical chemistry laboratory experiment was designed to connect the theory of
infrared spectroscopy to prior knowledge learned in organic chemistry. The
infrared spectra of phenol, p-cresol, 4-isopropylphenol, and 4-fluorophenol
were studied in 2.0 M solutions of dichloromethane to analyze their ability to
form hydrogen bonds. Geometry optimizations and vibrational frequency
calculations of the monomer, dimer, and trimer of these systems were completed
using density functional theory [(B3LYP/6-311++G(d,p)]. Computational software
was used to calculate frequencies, assign the peaks in the IR spectra, and
visualize their motions. Both experimental and computational evidence was used
to confirm that the electron donating and withdrawing nature of these
substituents resulted in varying degrees of hydrogen bonding. The highest
degree of hydrogen bonding was observed for 4-isopropylphenol followed by
p-cresol, phenol, and 4-fluorophenol. It was concluded that the electron
donating nature of the isopropyl and methyl substituent encouraged hydrogen
bonding. By the end of the lab, students were able to explain the role of
hydrogen bonding and substituent effects using the harmonic oscillator model.
Key Words: Laboratories and Demonstrations; physical chemistry; infrared spectroscopy
(*) Corresponding author. (E-mail: afedor@misericordia.edu)
Article in PDF format (517 KB) HTML format
Supporting Materials:
There is an additional document provided for instructor and student use. This detailed laboratory experiment handout includes notes on the experimental and computational methods necessary to complete the laboratory experiment and background information. (371 KB)
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