Microwave and Quantum-Chemical Study of Conformational Properties and Intramolecular Hydrogen Bonding of 2-Hydroxy-3-Butynenitrile (HC≡CCH(OH)C≡N)

Abstract

The microwave spectra of 2-hydroxy-3-butynenitrile, HC≡CCH(OH)C≡N, and a deuterated species, HC≡CCH(OD)C≡N, have been investigated in the 38-120 GHz spectral region. Three rotameric forms, each stabilized by intramolecular hydrogen bonds, are possible for this compound. The hydrogen atom of the hydroxyl group is hydrogen-bonded to the π electrons of the alkynyl group in one of these conformers, to the π electrons of the cyano group in the second rotamer, and to both of these groups simultaneously in the third conformer. The microwave spectra of the parent and deuterated species of last-mentioned form have been assigned, and accurate values of the rotational and quartic centrifugal distortion constants of these species have been determined. The spectra of two vibrational excited states of this conformer have also been assigned, and their frequencies have been determined by relative intensity measurements. Quantum-chemical calculations at the MP2/cc-pVTZ and CCSD/cc-pVQZ levels were performed to assist the microwave work. The theoretical predictions were generally found to be in good agreement with observations.

Microwave and Quantum Chemical Study of the Hydrazino Group as Proton Donor in Intramolecular Hydrogen Bonding of (2-Fluoroethyl)hydrazine (FCH2CH2NHNH2)

“…Much of our work has focused on weak proton donor groups. Recently, we reported gas-phase studies of alcohols, − carboxylic acids, thiols, − thiolcarboxylic acids, selenols, − amines, − amides, , and phosphines, − where the said groups are proton donors in internal H bonds with acceptors such as the fluorine atom, ,,, the chlorine atom, ,,, π-electrons of triple bonds, − ,,,, π-electrons of double bonds, ,,,, and Walsh pseudo-π electrons. ,, References of many of our earlier works are found in the cited literature as well as in reviews. − …”

The Electronic Structure of Some Cyanohydrins—A Spectroscopically Under‐Investigated Family of Compounds

“…In fact, such studies are difficult to perform because the vapor pressure is very low and the decomposition on heating into hydrogen cyanide andt he corresponding aldehydeo ccurs at relativelyl ow temperature. [9] Up to date, the microwave spectra of hydroxyacetonitrile and lactonitrile [10] have been only partially recorded and, very recently,t he spectrumo ft he kinetically unstable 2-hydroxybut-3-ynenitrile [11] has been reported, in spite of an important decomposition in the cell of the spectrometerd uring the recording of the spectrum. Attempts by some of us to record the microwave spectrum of 2-hydroxybut-3-enenitrile have been unsuccessful until now.C yanohydrins are particularly interesting compounds because of the interactions between hydroxyl and cyanide groups, which can be comparedt ot hose between aminoa nd cyanideg roups in the extensively studied alkylated a-aminonitriles.…”