The microwave spectrum of formamide–water and formamide–methanol complexes

Abstract

The microwave spectra of the formamide–water and formamide–methanol complexes have been investigated with a pulsed beam Fabry–Perot cavity Fourier transform microwave spectrometer. The observed hyperfine structure due to the 14N nuclear quadrupole interaction was used to assign the rotational transitions for both species. For formamide–water the rotational analysis of ten transitions provides the constants: A=11 227.931(1) MHz, B=4586.9628(10) MHz, C=3258.8278(7) MHz, eQqaa =1.332(3) MHz, and eQqbb =2.037(3) MHz. The formamide–methanol spectrum exhibits an additional splitting from internal rotation of the methyl group. Eighteen observed transitions from the A and E symmetry states have been assigned and fitted with the rotational constants: A=10 186.594(6) MHz, B=2090.36(59) MHz, and C=1762.80(56) MHz with hyperfine constants close to those of formamide–water. By assuming a methyl top moment of inertia Iα =3.206 uÅ2, the barrier to internal rotation V3=231.01(17) cm−1 is obtained. This barrier height is about 36% smaller than that of methanol. The structures determined for these complexes agree well with prior ab initio calculations which indicate essentially planar, double hydrogen bonded structures for both species.

Site- and sequence-selective ultrafast hydration of DNA

“…The variation in time constants most probably is due to selective interactions. Formamide is able to form dimers with water molecules through double hydrogen-bonding (24) as evidenced by microwave spectroscopy (25). The hydrogen-bond breakage of the network also alters the diffusional relaxation (slow component) (26).…”

Hydrogen‐Bond Cooperativity in Formamide2–Water: A Model for Water‐Mediated Interactions

“…Different examples of investigations on isolated hydrated amide clusters done in supersonic jets by microwave spectroscopy can be found in the literature. [20,[24][25][26][27][28][29][30] These works, in particular the detailed investigation of the structures of formamide-(H2O)n [25] (see Figure 1) (n=1,2), have led to interesting pieces of information. The observation of the conformers build from the different docking sites of formamide led to conclude that the dominant interaction results to be the HB of water with the amide carbonyl group as found in globular proteins.…”

Study of the formamide–methanol dimer with ab initio and density functional theory methods

“…T he characterization of the hydrogen bonding interactions between methanol and formamide has been of considerable interest to experimentalists and theoreticians [1][2][3][4][5]. This interest stems from the fact that formamide may be viewed as the simplest molecule containing a peptide linkage.…”