Microwave Spectrum for a Second Higher Energy Conformer of Cyclopropanecarboxylic Acid and Determination of the Gas Phase Structure of the Ground State

Aaron M. Pejlovas, Wei Lin, Stephen G Kukolich

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Microwave spectra for a higher-energy conformer of cyclopropanecarboxylic acid (CPCA) were measured using a Flygare-Balle-type pulsed-beam Fourier transform microwave spectrometer. The rotational constants (in megahertz) and centrifugal distortion constants (in kilohertz) for this higher-energy conformer are A = 7452.3132(57), B = 2789.8602(43), C = 2415.0725(40), DJ = 0.29(53), and DJK = 2.5(12). Differences between rotational constants for this excited-state conformation and the ground state are primarily due to the acidic OH bond moving from a position cis relative to the cyclopropyl group about the C1-C9 bond to the more stable trans conformation. Calculations indicate that the relative abundance of the higher-energy state should be 15% to 17% at room temperature, but the observed relative abundance for the supersonic expansion conditions is about 1%. The measurements of rotational transitions for the trans form of CPCA were extended to include all of the unique 13C singly substituted positions. These measurements, along with previously measured transitions of the parent and -OD isotopologues, were used to determine a best-fit gas-phase structure.

Original languageEnglish (US)
Pages (from-to)10016-10021
Number of pages6
JournalJournal of Physical Chemistry A
Volume119
Issue number39
DOIs
StatePublished - Oct 1 2015

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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