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Description:
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The structure , potential energy functions and vibrational spectra of several cyclic
and bicyclic molecules have been investigated using several spectroscopic techniques
and high -level ab initio and density functional theory (DFT ) calculations . Laser induced
fluorescence and Raman spectroscopies were used to study the conformation of 2 -
indanol in the electronic ground and excited states . These , along with detailed ab initio
calculations , confirmed the existence of four different stable conformations with the one
undergoing an intermolecular hydrogen bonding being the most stable . A theoretical
two -dimensional surface in terms of the ring -puckering and the hydroxyl group internal
rotation vibrations was constructed . This work was extended to obtain preliminary
insights on the conformations and ring -puckering frequencies of 3 -cyclopenten -1 -ol
using ab initio and DFT calculations .
Infrared and Raman spectra were also utilized to study the structures and
vibrational spectra of -crotonolactone and 2 ,3 -cyclopentenopyridine (pyrindan ) . Ab initio results showed that -crotonolactone is rigidly planar in the electronic ground state
and has a nearly harmonic ring -puckering potential function . The calculated vibrational
levels were shown to be in very good agreement with the experimental ring -puckering
frequency from vapor -phase Raman observations .
The structures , vibrational spectra , and potential energy functions of several
cyclic molecules were reinvestigated using high -level ab initio computations , and
detailed vibrational analyses based on DFT -B3LYP calculated frequencies were also
carried out . A number of new insights were presented by re -evaluating the available
experimental data for several cyclopentenes , silacyclobutanes and silacyclopentenes . It
was found that the vibrational spectra of some deuterated cyclopentenes possess
extensive coupling between several ring modes and other low -frequency modes .
Reassignments of these spectra have been proposed . Frequencies from DFT -B3LYP
calculations showed very good agreement with the experimental values for
silacyclobutane and its derivatives . The presence of silicon and halogen atoms did not
affect the accuracy of the DFT calculations . In addition , the ring -puckering potential
energy function for silacyclopent -2 -ene was studied and alternative assignments of the
far -infrared results were proposed . The new assignments are in good agreement with
computational results . Silacyclopent -2 -ene and its -1 ,1 -d2 isotopomer were shown to be
slightly puckered with barriers of less than 50 cm -1 . |