San‐ichiro Mizushima

Normal Vibrations of N‐Methylacetamide

The in‐plane normal vibrations of N‐methylacetamide and its deuterated compound were calculated as a six‐body problem. The force constants were transferred from diformylhydrazine and other molecules with similar structures. The normal modes as well as the distributions of the potential energy among symmetry coordinates were also calculated. The result of these calculations allows quantitative discussions concerning the nature of the amide I, II, II′, III, III′, and IV vibrations and other normal vibrations of N‐methylacetamide.

Characteristic Infrared Bands of Monosubstituted Amides

Infrared spectra of various monosubstituted amides and the corresponding deuterated compounds have been measured in the gaseous, liquid, and crystalline states and in solutions. From the experimental results, the bands characteristic of the amide structure have been determined. Furthermore, from the comparison with the spectra of related substances and by the application of the product rule, the assignments of these characteristic bands have been made. The observed change of frequencies of these characteristic bands with change of state confirms this assignment.

On the Helical Configuration of a Polymer Chain

A mathematical expression for the helical configuration of a polymer chain has been derived as a function of the bond lengths, bond angles, and internal rotation angles. The result of the calculation has been applied to the determination of stable configurations of several polymer chains.

Assignments of the vibrational frequencies of glycine

Abstract Infra-red spectra of α-glycine, α-glycine-D3, glycine-hydrochloride, glycine-hydro-chloride-D3, Na-glycinate, and Na-monochloroacetate have been compared in the NaCl region. Infra-red spectra of α- and γ-glycine and α- and γ-glycine-D3 have been observed in the KBr region. A dichroic measurement has been made on the single crystal of γ-glycine, in which all the glycine molecules are arranged almost in the same direction. Based on the results a complete assignment has been made of the fundamental vibrational frequencies of glycine observed in the 1800–400 cm−1 region.

Normal vibrations of urea and urea-d4

Abstract Infra-red absorption spectra of urea and urea- d 4 have been measured. Infra-red dichroic measurement and Raman measurement have been made for urea in the crystalline state. The normal vibrations of the planar C 2 v model have been calculated as an eight-body problem and the assignment of the observed frequencies has been made.

Rotational Isomerism in Chloroacetone

Raman spectra of chloroacetone were measured in the liquid and solid states and in solutions. Infrared absorption spectra of this substance were measured in the gaseous, liquid, and solid states and in solutions. The temperature dependence of the intensity of the Raman lines and of the absorption bands were measured in the liquid state. From the experimental results together with the dipole data it was concluded that chloroacetone exists in two molecular forms in the liquid and gaseous states and in one form in the solid state. The less stable form in the liquid state becomes much more abundant than the other form in the gaseous state. Some considerations on the nature of hindering potential of internal rotation have been made.

The Configurations of Rotational Isomers and Their Normal Frequencies

Normal frequencies of molecular configurations of different azimuthal angles of internal rotation have been calculated for various molecules showing rotational isomerism. It has been shown that one can tell fairly accurately the value of azimuthal angle by comparing the observed frequencies (especially the skeletal deformation frequencies) with those calculated for different configurations. The sum rule for the rotational isomers similar to that for isotopic molecules has been derived and has been shown to be very useful in assigning the observed frequencies. The product rule for rotational isomers derived in our previous paper has also been applied to this problem and has been shown to be useful in determining the azimuthal angles of rotational isomers.

Rotational Isomers of Chloroacetyl Chloride, Bromoacetyl Chloride, and Bromoacetyl Bromide

The Raman spectra of chloroacetyl chloride, bromoacetyl chloride, and bromoacetyl bromide have been measured in the solid and liquid states. The infrared absorption spectra of these substances have also been measured in the liquid and the gaseous states. From the experimental results it has been concluded that there are two rotational isomers in the liquid and gaseous states and only one of them persists in the solid state. The temperature dependence of the intensity of the infrared absorption in the gaseous state has also been studied, and the energy difference between these two isomers has been found as 1.0±0.1 kcal/mol for bromoacetyl chloride and 1.9±0.3 kcal/mol for bromoacetyl bromide.The calculation of the normal vibrations and of the product rule has been made for various configurations of rotational isomers, and it has been shown that the more stable form is the trans form (or nearly this one) with regard to the two halogen atoms. The less stable form is considered to have an azimuthal angle betw...

The internal rotation in anilides about the peptide bond as axis

Abstract Observation of near-infra-red absorption spectra and measurement of apparent dipole moments were made of formanilide, acetanilide, thioformanilide and thioacetanilide, dissolved in carbon tetrachloride at various concentrations. The results showed that formanilide and thioacetanilide exist in two forms- trans - and cis -forms, in the former of which the CO bond and the N-H bond are hi the trans -poeition with respect to each other in the internal rotation about the C-N axis, and in the latter the two bonds are in the cis -position. Acetanilide was shown to exist mostly in the trans -form, while thioformanilide mostly in the cis -form. The energy difference between the trans - and cis -forms was determined for each of formanilide, thioformanilide and thioacetanilide, by observing the temperature effect on the intensity ratio of the two free NH bands—one due to the trans -form and the other due to the cis - form. The observed relative stabilities of the trans - and cis -forms of these anilides can be explained on the basis of the steric repulsion between the groups at both ends of the C-N bond in each anilide.

The Constant Frequency Raman Lines of N‐Paraffins

Assuming the Urey‐Bradley field for the intramolecular potential, we have calculated the normal frequencies of long chain molecules in the extended form. Especially the vibration type of the frequencies remaining almost constant throughout the homologous series has been discussed. The result has been applied to the assignment of Raman lines of N‐paraffins and of the infra‐red absorption lines of polyethylene.