Vibration Spectra and Rotational Isomerism of Chain Molecules. V. 2,5-Dioxahexane, 2,5-Dithiahexane, and 2-Oxa-5-thiahexane

Abstract

The Raman and infrared spectra of 2,5-dioxahexane CH3OCH2CH2OCH3, 2,5-dithiahexane CH3SCH2CH2SCH3 and 2-oxa-5-thiahexane CH3OCH2CH2SCH3 were measured for the gaseous, liquid, glassy and crystalline states and were correlated with the normal-vibration calculations. The rotational isomerism was studied and the following conclusions were obtained. (1) The molecular form existing in the crystalline state is a non-extended form, in contrast with the cases of the unbranched ethers or sulfides containing one oxygen or sulfur atom which take the extended all-trans form. (2) Many forms coexist in the gaseous, liquid and glassy states. (3) The form existing in the crystalline state is the most stable in the liquid state. It was found that the repulsive force between non-bonded hydrogen atoms is one of the important factors influencing the conformational stabilities and for 2,5-dioxahexane the dipole-dipole interaction is another important factor. The stable conformations of these molecules were correlated with those of the polyether and polythioether chains. The stable isomers of 2-oxa-5-thiahexane could be explained on the basis of the knowledge of the conformational stabilities of the unbranched ethers and sulfides. The force constants of the ethers and sulfides were satisfactorily transferred to 2-oxa-5-thiahexane.

Conformational spectroscopy of flexible chain molecules near the folding limit

“…However, the previous carrier gas series showed no signs of clustering for the tgg' conformation either. Earlier studies investigating the aggregation of monoglyme in the liquid and solid phases found strong preferences for the tgt conformation [11,116,117,147], which is in line with the observed cluster formation of tgt in the jet expansion.…”

“…The first IR spectrum of liquid and solid monoglyme was reported in 1967 by Snyder and Zerbi which concluded that crystalline monoglyme consists of tgt chains [115]. A shift in the conformational preferences with dominant tgt contributions in the liquid and solid phases found through a comparison of gaseous, liquid and solid Raman and IR spectra of monoglyme [116] strengthened this conclusion. Additionally, molecular dynamics simulations confirmed dominant tgt contributions in the liquid and solid phase while three conformers (ttt, tgt, tgg') were found to be very close in energy in the gas phase [117].…”

Intramolecular fluorescence quenching in porphyrin-bearing [2]catenates

“…The rate constants for quenching k q1 and k q2 (Table 5) While k q1 is within experimental error independent of the temperature, a decrease of k q2 upon decreasing the temperature is observed for [2] [39]. The activation energies and preexponential factor are also of the correct order of magnitude for a conformational change around a (saturated)carbonoxygen bond [40][41][42][43][44] in open-chain molecules. Hence, it is [45,46].…”

Reaction of rhodium trichloride and dirhodium(II) acetate with trans-4,4′-bis(diethoxyphosphoryl)biphenyl-18-crown-6

“…Their frequency varies at the coordination within rather a wide limit depending on the torsion angle and the type of the chemical bond [26,28,29]. Therefore, changes of the bands of the conformation-sensitive vibrations ν as (COC) are due to the conformational rearrangement of the polyethylene glycol chains of the ligand at the complexation and are an indication of the complex formation.…”

“…Therefore, changes of the bands of the conformation-sensitive vibrations ν as (COC) are due to the conformational rearrangement of the polyethylene glycol chains of the ligand at the complexation and are an indication of the complex formation. The main analytical bands in the IR spectrum of the ligand L are the absorption bands associated with vibrations of the phosphoryl group and its surrounding [10,[22][23][24][25], as well as the absorption band of ethylene glycol groups of the crown ether ring [26][27][28]. The shift of the vibration frequency of ethylene glycol group of crown ethers in the IR spectra is known to indicate the formation of a complex [26,29].…”