Rotational isomerism and barriers to internal rotation in hydroxyacetonitrile from microwave spectroscopy

Abstract

The microwave spectra of HOCHzCN and DOCHzCN show that the molecule exists as the gauche rotamer in the gas phase. A large number of intense lines converging to a band head near 16 800 MHz for DOCHzCN and 110 700 MHz for HOCHzCN are attributed to the ZI = l+O transitions of the hydroxyl torsion. The rotational constants indicate that cce, the angle between the HOC and OCC planes at the potential minima is approximately 123" from the trans position. Potential functions which reproduce the observed ZI = 140 torsional frequencies have been obtained for 106" <a,< 116" and show there is a barrier of 270k 50 cm-l at the cis position and one of 570-L 200 cm-' at the trans position. The rotational constants calculated from a molecular model and the potential functions indicate that is probably closer to 116" than 106".

Microwave Spectrum and Intramolecular Hydrogen Bonding of 2-Isocyanoethanol (HOCH2CH2N≡C)

“…5 Examples of alkynes with intramolecular hydrogen bonds investigated by MW spectroscopy include propargyl alcohol (HOCH 2 CCH), 6 3-butyn-2-ol (H 3 CCH(OH)CCH), 7 3-butyn-1-ol (HOCH 2 CH 2 CCH), 8 − 12 4-pentyn-1-ol (HOCH 2 CH 2 CH 2 CCH), 13 propargyl thiol (HSCH 2 C CH), 14 3-butyne-1-thiol (HSCH 2 CH 2 CCH), 15 propargyl s e l e n o l ( H S e C H 2 C  C H ) , 1 6 3 -b u t y n e -1 -s e l e n o l (HSeCH 2 CH 2 CCH), 17 propargyl amine (H 2 NCH 2 C CH), 18 N-methylpropargyl amine (H 3 C(NH)CH 2 CCH), 19 and 1-amino-3-butyne (H 2 NCH 2 CH 2 CCH). 20 Similarly, intramolecular hydrogen bonding has been reported for a number of nitriles comprising hydroxyacetonitrile (HOCH 2 CN), 21 lactonitrile (H 3 CCH(OH)CN), 22 3-hydroxypropanenitrile (HOCH 2 CH 2 CN), 23 3-mercaptopropionitrile (HSCH 2 CH 2 CN), 24 Z-3-mercapto-2-propenenitrile (HSCHCHCN), 25 aminoacetonitrile (H 2 NCH 2 C N), 26,27 3-aminopropionitrile (H 2 NCH 2 CH 2 CN), 28 (Nmethylamino)ethanenitrile (H 3 C−NH−CH 2 CN), 29 2-aminopropionitrile (H 3 C(NH 2 )CHCN), 30 Z-3-amino-2-propenenitrile (H 2 NCHCHCN), 31 and 3-phosphinopropionitrile (H 2 PCH 2 CH 2 CN). 32 In contrast to these many investigations of internal hydrogen bonding with the π-electrons of the triple bonds in alkynes and nitriles, no gas-phase studies of this interaction have been reported for isonitriles (R−NC), the third functional group possessing a triple bond.…”

Submillimeter spectra of 2-hydroxyacetonitrile (glycolonitrile; HOCH2CN) and its searches in GBT PRIMOS observations of Sgr B2(N)

“…3b of Mehringer et al 1993). For the purposes of this study, we assume these same source sizes for warm molecular material and cold molecular material and explicitly calculate Cazzoli et al (1973). the spatial overlap of these regions with the GBT beam as its size varies across the frequency coverage.…”

“…Some less perturbed levels were found above 400 GHz, and an assignment and fit was possible by treating the two sublevels separately for K a values up to 2 in the 400-500 GHz range, improving the values of the rotational and the centrifugal distortion constants. The two sublevels were then merged in a unique fit, using the energy difference between the 0 − and 0 + levels determined by Cazzoli et al (1973) as the starting point. We note that this value, 110 700 MHz, is close to the one we determined, 112 672.5526(30) MHz.…”

“…The component along the c-axis of the dipole moment is linked to torsional motion, giving rise to transitions between the two torsional substates 0 − and 0 + . An initial prediction of the spectra was made for the two substates 0 − and 0 + separately with Watson's Hamiltonian in the I r representation using the rotational parameters from Cazzoli et al (1973) and the quartic centrifugal distortion constants obtained from the harmonic force field at the MP2/aug-ccpVTZ level of theory. We first assign the A-type, R-branch transitions, which are the brightest in our spectra.…”

“…The gas-phase, infrared spectrum of HOCH 2 CN has been recently reinvestigated (Chrostowska et al 2015), while the microwave spectrum of HOCH 2 CN has not been treated since it was first observed by Cazzoli et al (1973) from 8-40 GHz. The gauche rotamer has been observed.…”