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This paper, the first of a series of papers, examines equilibrium properties of N2O4⇌NO2 in liquid state by classical molecular dynamics simulations of liquid NO2. An ab initio MO calculation has been carried out to elucidate NO2–NO2 potential, and an orientation-sensitive pairwise potential (OSPP), which can reproduce highly anisotropic character of covalent bonding between N–N, has been formulated. The OSPP potential is parameterized by the well depth De and by two anisotropy factors: Aθ (0⩽Aθ⩽1) the anisotropy factor for the rocking angle between NN bond and ONO direction, and Aτ (0⩽Aτ⩽1) for torsional angle of the two NO2 about NN bond. The reactive liquid N2O4 is modeled as liquid NO2 which interacts with the OSPP potential between N–N atoms and Lennard-Jones potentials between N–O and O–O atoms. Equilibrium properties were found to be very sensitive to the well depth De and anisotropy factors of OSPP. The population of more than the NO2 dimer (3-mer, 4-mer,…) is considerable when anisotropy factors ...

Infrared absorption spectrum of formamide for the matrix isolated species has been simulated using the extended molecular mechanics method employing a force field which includes equilibrium bond charges and charge fluxes as coulomb potential parameters. The features of the simulated spectra are generally in good agreement with the observed spectra. The vibrational frequencies of several deuterated isotopomers of formamide have been calculated in satisfactory agreement with the experimental frequencies. The thermodynamic quantities, dipole moment and its orientation and equilibrium structure of formamide have also been successfully computed.

Molecular dynamics simulations were performed for the dissociation and association (D/A) reactions N 2 O 4 2NO 2 in the gas and liquid phases. The transition state of the D/A reactions was identified as the phase space surface E T =0, where E T is the sum of the potential and kinetic energies of the interfragment motion. The dissociation reaction in liquid N 2 O 4 is found to occur by two steps: first, a reactant is activated by intermolecular energy transfer from solvent to reactant, and second, the dissociation occurs by energy transfer from intrafragment vibrational and rotational modes to interfragment translational mode. The association reaction proceeds by two steps: interfragment translational energy of an encounter NO 2 pair is transferred to intrafragment modes and then the associated N 2 O 4 is deactivated by intermolecular energy transfer from product to solvent.

In order to explain the large permittivity of liquid cyanogen consisting of centrosymmetric molecules, a molecular dynamics simulation which includes all degrees of freedom of vibration, rotation, and translation has been performed. The intramolecular potential energy is expressed in terms of the internal coordinates with quadratic, cubic, and quartic force constants. The intermolecular potential consists of an atom–atom pair potential with Coulombic and Buckingham terms. The simulation has given an adequate value of self‐diffusion coefficient and a typical form of radial distribution function for the liquid state. The simulation has reproduced well the large value of the permittivity observed in experiments, suggesting that the value results from the extraordinarily large atomic polarization brought by the intramolecular bending motion in an antisymmetric mode. The simulation has also suggested that the nitrogen atoms collide with each other more frequently than with carbon atoms and the collision shifts the normal frequencies related to the N≡C bond to higher frequency. The infrared and Raman spectra together with the real and imaginary parts of the refractive index have also been calculated.

Vibrational spectra of benzene and benzene-d6 in the gas and liquid phase have been simulated by a molecular mechanics method including the calculation of equilibrium structures, thermodynamic quantities, normal frequencies and vibrational transition probabilities. The potential parameters have been estimated by referring to the observed frequencies of benzene, benzene-d6 and 1,3,5-benzene-d3 and also to results of ab initio calculations. Four and ten independent parameters are required, respectively, for elucidating the infrared absorption and Raman intensities of these compounds in the gas and liquid phase. The infrared absorption spectrum of benzene-d1 is reproduced well by using the potential and the intensity parameters estimated for benzene and benzene-d6. The change of relative band intensities on the phase change has been elucidated in terms of the change of various intensity parameters.

Polarized infrared spectra of well-oriented crystalline thin films of dodecylbutyldimethylammonum bromide monohydrate (DBDM·H 2 O) were recorded in the region 5400-250 cm −1 . From the results of the polychroism measurements and the X-ray analysis, water bands were divided into three symmetry species ( A 1 , B 1 , and B 2 ). With the aid of frequencies and isotopic frequency ratios, the water bands were assigned to the three fundamental vibrations, two librations, and their overtones and combinations. In the crystalline environment, we have observed the doublets for each of the vibrationally isolated OH and OD stretching bands of HOD in isotopically diluted monohydrates DBDM·HOD. This spectral feature suggests the presence of two distinct configurations of the water molecule, one forming a strong and linear O 1 H ⋯ Br 1 hydrogen bond and the other forming a weak and slightly bent O 1 H ⋯ Br 2 hydrogen bond. The results in this work are discussed in connection with previous work. The OH stretcing bands in DBDM·H 2 O appear at higher frequency than in dodecylpropyldimethylammonium bromide (DPDM)·H 2 O or in DPDM· 1 2 H 2 O, while the HOH scissoring, rocking, and wagging modes occur at lower frequency. These are consistent with the weaker hydrogen bond of the water molecule and the longer O ⋯ Br hydrogen bond distance in DBDM·H 2 O than in the DPDM hydrates. Correlation between ν(OD) and the O ⋯ Br distance is also argued.

Molecular dynamics simulations were performed for the dissociation and association (D/A) reactions N2O4■2 NO2 in the gas phase and in liquid N2O4. The trajectory was initialized from an equilibrium distribution of all variables in liquid N2O4, except the reactive mode, the NN distance of a reactant NO2 pair, was excited above the dissociation limit of the Morse‐like potential between NO2 fragments, and the dynamics were calculated for 500 fs both forward and backward in time. Characteristics of the translational and vibrational energy relaxations of the reactant were studied in detail. Energy ERT, which is defined to be the sum of the potential and kinetic energies of interfragment motion, is found to play a key role in the D/A dynamics; a reactant pair is associated when ERT

In order to study the cation dependence of the ionic dynamics in molten nitrates, molecular dynamics simulations including vibrational degrees of freedom were carried out for molten LiNO3, NaNO3, and RbNO3. Coulomb pair potential with Born‐type repulsion was adopted for the interionic interaction. The simulated diffusion coefficient was smaller for a larger cation, and that of nitrate ions did not change with changing cation species. The mean squared charge displacements showed that the static conductivity decreased considerably as the cation size increased from Li+ to Rb+. The simulated orientational correlation function of nitrate ions decayed more quickly as the cation size increased. Far infrared absorption spectrum simulated from the time evolution of the dipole moment (or the current) of the system showed that the peak shifted to the low energy side and the intensity decreased as the cation size increased. Results of the simulation were compared with the experimental diffusion constants, static and ...

An extended molecular mechanics calculation of thermodynamic quantities, structure parameters, infrared absorption spectra, and Raman spectra of normal fatty acids was carried out on the basis of t...

To study the microdynamics of translational, orientational and vibrational motions in liquid N2O4, molecular dynamics simulations, including all degrees of freedom of vibrating N2O4 molecules, were carried out. Atom-atom Lennard-Jones potentials with and without Coulomb potentials (LJ + C and LJ, respectively), were adopted in the simulation. When Coulomb interaction between atoms was included, mean-squared force and torque increased, the velocity and angular momentum correlation functions decayed faster to more evident negative parts, and both the translational and orientational diffusion slowed down. Simulated rotational correlation functions for LJ + C agreed reasonably with those derived from Raman spectroscopy, while those for LJ were found to decay too fast. Vibrational correlation functions for the NN stretching v 3 mode were calculated and the vibrational spectra were obtained from their Fourier transforms. Two simulations for the harmonic and the anharmonic intramolecular potentials, where anharm...

The molecular mechanics simulation of the infrared absorption and Raman spectra of acetic acid in the solution or liquid phase has been carried out by using an empirically estimated force field which includes the equilibrium charges and the charge fluxes as the Coulomb potential parameters. The variation of the observed band widths among different normal modes has been taken into account by introducing the half band width parameters empirically assigned to individual internal coordinates. The half widths of more than 20 bands observed in the infrared absorption and the Raman spectra are well reproduced in terms of five half band width parameters. The thermodynamic properties and the structures of acetic acid monomer and dimer are successfully simulated. The overall features of the simulated spectra of acetic acid are in good agreement with the observed ones.

Molecular dynamics simulation has been used to investigate the infrared spectra of ordered and disordered benzoic acid crystals consisting of various proportions of the A and B configurations, whose C–O and C=O bonds are approximately parallel to the a axis, respectively. The simulation reproduced well the splitting and the temperature dependence in intensity for the C=O stretching bands observed. The absorption coefficient of the lower frequency band was simulated as several times larger than that of the higher frequency band in accord with the observed. To interpret this peculiar result of the molecular dynamics simulation, a simple calculation of the band splitting has been made in terms of the transition dipole–transition dipole interaction. It has been shown that the interaction is an essential factor to produce the large difference in intensity and the splitting for the C=O stretching bands. The higher and lower bands are interpreted as due to the A configuration reduced in intensity by the B form, and due to the B form enhanced in intensity by the A form, respectively. Compression effect in the O⋅⋅⋅O distance of the hydrogen bond is also studied in comparison with the observed value.

The integrated infrared absorption intensities of sodium acetate and its deuterated derivative have been measured. The absorption band shapes were succesfully simulated by using Lorentzian functions with the band areas calculated in terms of the equilibrium atomic charges and their first-order fluxes. The relative Raman intensities were also simulated by using non-cylindrical electro-optical parameters. For a quantitative description of the contribution of each internal symmetry coordinate to the vibrational intensities of a normal mode, new quantities designated the infrared and Raman intensity distributions are defined in analogy with the potential energy distributions conventionally used for describing the contribution to the vibrational frequency.

The shifts caused by nickel and hydrogen isotopic substitutions indicate that three bands at 342, 297 and 222 cm −1 are Ni-ligand stretching vibrations complicatedly coupled with Ni-O and Ni-N stretching vibrations. The conformational differences between gauche-anti and anti-gauche serinates in metallo-serinate complexes are characterized by the COO deformation vibrations. A normal coordinate analysis on the basis of a complete molecular conformation of Ni(L-ser) 2 •2H 2 O and an intermolecular force field reproduced well the observed frequencies and isotope shifts

The title tetrapeptide, Leu-Arg-Pro-Gly-NH2, forms a complex with trypsin in a novel orthorhombic crystal form with low molecular packing density. The complex formation was directly evidenced by X-ray crystallography. The crystal structure at 1.8 A resolution was refined to an R-factor of 20.5% for 13,923 reflection data, which were measured with synchrotron radiation. The tetrapeptide is bound to trypsin at the active site, and the binding mode is very similar to that of a bovine pancreatic trypsin inhibitor (BPTI):trypsin complex. The tetrapeptide:trypsin complex is the first observation that a peptide forms a stable complex with trypsin.

Relative band intensities in the polarized Raman spectra of a sodium formate single crystal have been measured. Electrooptical parameters (EOPs) of formate anion are calculated based on the oriented gas model. The valence EOPs of the Co − 2 group are treated as non-cylindrical. To select the correct sign combinations of the components of the derived polarizability tensors, all the equilibrium EOPs and the valence EOPs of the CH bond are assumed to be cylindrical and the band intensities of polycrystalline sodium formate are compared with those of its deuterated derivative. The depolarization ratios observed for their aqueous solutions are also utilized. Two plausible sets of EOPs are obtained. The valence EOPs associated with the CO − 2 symmetric stretching and the bending mode show one order differences between the in- and the out-of-plane components.

The crystal structures of the three title compounds have been determined by the X-ray structure analysis. The molecule of (E)-O-hexanoyl phenyl 2-pyridyl ketone oxime1 has an anti form at the N-O-C-C ester linkage, while the molecules of (E)-O-octanoyl phenyl 2-pyridyl ketone oxime2 and (E)-O-myristoyl phenyl 2-pyridyl ketone oxime 3 each have a syn form. Compounds2 and3 are crystallized in isomorphic bilayer structures, in which alkyl chains are packed in an antiparallel arrangement.

The x-ray diffraction study of the C-terminally unprotected tripeptide benzyloxy-carbonyl-L-alanyl-alpha-aminoisobutyl-alpha- aminoisobutylic acid (Z-L-Ala-Aib-Aib-OH) has shown that the molecule adopts a consecutive type III beta-turn, which characterizes a right-handed 3(10) helix. A very weak 4----1 intramolecular hydrogen bond with the long N...O distance of 3.32 A, and a unique "oxy analogue" of the 4----1 hydrogen bond wih the O...O distance of 2.77 A, were observed. The stability of the observed conformation with the asymmetric Aib residues was theoretically evaluated by a conformation-energy calculation. The stereochemical characteristics of Aib and Ala residues were made clear by a comparison of the conformations of the short peptides containing both Aib and Ala residues.

In order to study the effect of the potential well on the single ion dynamics and the charge transport in molten LiNO3, a molecular dynamics simulation, which included all degrees of freedom of vibrating nitrate ions, was carried out. Simple Coulomb pair potential with Born‐type repulsion was adopted as a standard, and a potential well of varying depth between Li+ and O of NO−3 was added to the standard potential. As the well depth increased, both the translational and orientational diffusion were found to slow down, leading to solid like dynamics. The potential dependence of the ionic dynamics was studied from the translational, orientational, and current correlation functions. Results of the simulation were compared with the experimental diffusion constants, static conductivity, and rotational behavior revealed by Raman spectroscopy. Using the relation between the infrared absorption spectrum and the autocorrelation function of the dipole moment (or the current) of the system, we carried out the first s...

The atomic force microscope has been developed and used to image arrays of molecules at the (001) and (100) faces of aspirin crystals in water and in air. Lattice spacings composed of methyl groups and the part of the phenyl groups on the surface of the (001) in water, are consistent with X-ray diffraction data. The surface of (100) face which shows most perfect cleavage in bulk, is more difficult to image. This initial success in imaging at drug crystal surfaces clarified the different structural behavior at the submolecular level for three crystal faces, and the close relationship to the differences in the dissolution velocity.

The crystal of bovine trypsin complexed with a potent inhibitor, 4-[4-(N,N- dimethylcarbamoylmethoxycarbonylmethyl)phenoxycarbonylphenyl ]guanidinium (FOY-305) in the novel orthorhombic from with a low molecular packing density was studied by the X-ray diffraction method. Using synchrotron radiation, the intensity data were collected to 1.8 A resolution. The structure was solved by molecular replacement methods, and refined to an R-factor = 18.0% for 14364 reflections by the restrained least-squares method. The final difference Fourier maps revealed that hydrolyzed inhibitor fragments bind with the protein at multiple sites around the active center of trypsin. The structural feature in the crystalline state probably corresponds to a statistical average of several complexes which would be formed between the inhibitor and trypsin during the binding and releasing process in solution.

The 600 MHz 1H-nuclear magnetic resonance spectra of a mixed aqueous solution of typsin and a synthesized trypsin inhibitor, 4-[4-(N, N-dimethylcarbamoylmethoxycarbonylmethyl)phenoxycarbonylphenyl]-guanidinium methanesulfonate(FOY-305) were measured. Signals assigned to the inhibitor protons indicated that the hydrated fragment of the inhibitor formed a complex with trypsin. The signal change during 4 h of incubation at 37°C was interpreted as reflecting a successive process of the partial release of the fragment and its weak recombination with the enzyme around the active site. The result is consistent with the disorder of the fragment in the crystal structure of the inhibitor : trypsin complex.

The inhibition of biphenylcarboxylic acid analogs on glyceride synthesis was studied in association with conformation of the chemicals. Chemicals used were benzoic acid substituted with phenyl, benzoyl and phenoxy groups, phenylphenyloxyacetic acid and p-phenylacetic acid. Twist angles were calculated by a molecular orbital method. Following oral administration of p-phenylbenzoic acid to the rats for 7 days, the decrease of the triglyceride synthesized from [14C]oleic acid was observed in the adipose tissue. The in vitro inhibitions on the formation of fatty acyl-CoA thioester were examined from the influence on the hippuric acid formation from [14C]benzoic acid using the rat liver slices. In the homologous series, high inhibition was observed in para and meta substituents. None, or low inhibitions of ortho-substituted chemicals were related to the steric hindrance of the phenyl ring against carboxyl groups. This hinderance was associated with conformation and with the geometrical relationship between substituted phenyl rings and carbon atoms of carboxylic acid. In the in vitro inhibition on overall formation of diglyceride and triglyceride from [14C]glycerol, o-phenylbenzoic acid showing no inhibition on hippuric acid formation did not show inhibition. However, other ortho-substituted chemicals showed higher inhibition in comparison with the inhibition on hippuric acid formation. The inhibition of para- and meta-substituted chemicals were higher than the corresponding values of ortho substituted compounds.

The atomic force microscope was developed in order to image arrays of molecules on the (001), (100) and (011) faces of aspirin crystals in water. Lattice spacings and symmetries of methyl groups and the part of the phenyl groups on the (001) face in water are consistent with X-ray diffraction data. Surfaces of the (100) face that show the best-developed cleavage, in general, are difficult to image. Although the lattice constant derived from (100) image is consistent with the X-ray diffraction data, the c-glide plane symmetry is lost and diffused spots are observed that are 1.8-3.1 times more elongated than (001) spots. It is not possible to image the (011) surface. This initial success in imaging the molecular crystal surfaces of drug compounds has clarified the different submolecular structures of the three different crystal faces, and the close relationship between the imaging difficulties and the differences in the dissolution process in water.

The resonance Raman intensities of methyl orange and brilliant blue FCF in aqueous solutions were measured by using a rotating divided Raman cell which provides an external intensity standard. The logarithms of the apparent intensities of the sample bands revealed a good linear dependence on the light path length. The relative Raman scattering coefficients of the samples with respect to a common reference band were determined from the intercepts. The effects of the excitation wavelength and the presence of surfactant on the apparent Raman intensities and the relative Raman scattering coefficients are discussed.

Relative intensities of the resonance Raman bands of four azo and two phthalein dyes and two colourless aromatic compounds in the solid state have been evaluated by recording the addition Raman spectra using the divided KBr disc method. The 984 cm−1 band of potassium sulphate was used as the intensity standard. From the relationship between the relative intensity and the sample concentration, the scattering coefficients for representative resonance Raman bands and the sum of the absorption coefficients at the wavelengths of the excitation and the Raman lines were estimated simultaneously for each dye.

Resonance Raman spectra of p-hydroxyazobenzene (HAB) and its three ring deuterated derivatives have been measured in the strongly acidic solution. The observed Raman bands have been assigned by referring to the spectra of related compounds and the deuteration effect. The NN stretching band of HAB in the solution of 20% hydrochloric acid undergoes a high frequency shift by about 60 cm−1 on changing the solvent to 20% deuterochloric acid. In the strongly acidic solution HAB has been confirmed to exist as a resonance hybrid between the azo and the hydrazone forms, of which the former is predominant. A normal coordinate analysis of a simplified model, CNHNC6H4pOH, has been carried out to give a good agreement between the calculated and the observed frequencies.

The polarized i.r. spectra and the Raman spectra of N,N-dimethylsulfamide and its C,C′-and N,N-deuterated compounds in the solid state have been measured. Vibrational assignments have been made by referring to the isotopic frequency shifts and the i.r. dichroism. A normal coordinate analysis based on the molecular symmetry of Cs has been carried out by using the modified Urey-Bradley force field. The Cs model reproduced well the observed fundamental frequencies of the four isotopic molecules.

The infrared and Raman spectra of dimethylaminosulfonyl chloride and its C-deuterated derivative have been recorded in the liquid state. The fundamental frequencies have been assigned by referring to the band intensities, Raman depolarization ratios and isotopic frequency shifts. A normal coordinate analysis based on a planar Cs molecular model has been carried out by using a simple Urey-Bradley force field for stretching and bending coordinates and a valence force field for torsional coordinates. The calculated frequencies based on a refined set of force constants agree well with the observed ones.

The anharmonic force constants governing the NH-stretching vibrations of a variety of substituted anilines were determined by the least-squares method combined with the perturbation calculation. The fundamental, the first overtone and the binary combination frequencies were calculated in good agreement with the observed values. The force field of the meta- and the para-substituted anilines could be expressed in terms of only one parameter, the quadratic diagonal constant, from which the other parameters were estimated by empirical linear relations. Based on this one-parameter calculation, the Hammett's reaction constant ρ for the dissociation of the NH bond was calculated to be −3.9 at 25°C. The appearance of the combination band in the middle of the two overtone bands of strongly hydrogen-bonded ortho-substituted anilines is explained from the asymmetry of the force field around the two NH bonds.

Resonance Raman spectra of 2-(4′-hydroxyphenylazo)-benzoic acid have been recorded for aqueous and ethanolic solutions. The change of pH of the aqueous solution gives four types of spectra corresponding to the stages of protonation and deprotonation processes. On addition of bovine serum albumin or cetyltrimethylammonium bromide to the neutral solution, the spectrum shows a little change which can be elucidated based on the shift of equilibrium between the azo- and the hydrazone-forms. The spectrum of the ethanolic solution shows a marked concentration dependence.

Resonance Raman spectra of p -hydroxyazobenzene, HO( p )C 6 H 4 NNC 6 H 5 , and its three ring-deuterated derivatives containing ( p )C 6 D 4 and/or C 6 D 5 have been recorded in the neutral and the alkaline pH regions. Based on the observed isotopic frequency shifts, the bands due to the p -disubstituted and monosubstituted rings have been distinguished clearly from each other. The spectral change on alkalifying the neutral solution shows that the contribution of the hydrazone structure in the resonance hybridization increases on the dissociation of a proton from the hydroxyl group.

Resonance Raman spectra of methyl orange and its ring-deuterated and azo-15N-substituted derivatives have been recorded in neutral aqueous solution and in solutions in 0.1 M hydrochloric and deuteriochloric acids. Band assignments have been given by referring to the isotope shifts, and on that basis the structures of the base and the acid forms of the dye molecule in the lowest electronic excited state are discussed.

Infrared and Raman spectra of acetylurea its C - and NN ′-deuterated derivatives have been recorded in the crystalline state and vibrational assignments have been made by referring to the isotopic frequency shifts and the spectra of related compounds. Normal coordinate analysis of the four isotopic molecules has been carried out for both the trans—cis and the trans—trans models of acetylurea. The trans—cis model reproduced the observed fundamental frequencies very well, while the trans—trans model led to an unacceptable set of force constants.

Polarized Raman spectra of DL-alanine and N-deuterated DL-alanine single crystals have been recorded. A normal coordinate analysis has been made for the optical active intra- and intermolecular vibrations of DL-alanine crystal. As in the case of L-alanine crystal, large factor group splittings were observed for the CH3 asymmetric deformation mode. The magnitudes of the observed splittings are elucidated well by the empirical potential function of the exp-6 type for the non-bonded atom-atom interaction. The differences in the NH3 rocking and the CH3 rocking frequencies between L- and DL-alanine crystals are ascribed to the differences in the intermolecular potential and the molecular geometry, respectively. A good agreement was obtained between the observed and the calculated lattice frequencies.

A crystal of 1,3-dimethyl-5-fluorouracil can be used to solve large amounts of 1,3-dimethyluracil as a solid–solution crystal. The crystal structure has been determined by an X-ray method. The planar molecules are arranged in a parallel sheet, and the molecules within the same sheet interact with each other through short CH···O and CH···F contacts. The short intermolecular C···F distance is 2.999(6) A. The stability of a mixed crystal could be explained in terms of intermolecular interactions around the fluorine atom.

Comparison of the 1H and 13C chemical shift data of bryonolic acid (D : C-friedoolean-8-en-3β-ol-29-oic acid) and its derivatives (13 species) revealed that the conformational features of these compounds in CDCl3 solution depend on whether the functional groups at C-29 are trigonal, such as COOCH3, or tetrahedral, such as CH2OH. In order to study the conformational features of these two groups of compounds, vicinal coupling constants between the protons on the E rings of the methyl ester of D : C-friedoolean-8-en-29-oic acid, D : C-friedoolean-8-en-29-oic and its acetate were measured. Comparison of the results with the steric geometries to be expected from the molecular mechanics calculation for the E-ring moieties of these derivatives in the S form (D-E rings: boat-boat form) and the F form (D-E rings: chair-chair form) led to the conclusion that the compounds having a trigonal functional group at C-29 mainly adopt the S form, and those having a tetrahedral functional group at C-29 are present as mixtures of the S and F form in equilibrium in the solutions.

The near-infrared spectra of formamide and its N- and C-deuterated compounds in chloroform solutions were investigated and a perturbation calculation of the vibrational levels of these isotopic formamides was carried out. The trans -interaction constant and the cubic cross-term constants between the NH stretching and the CNH bending coordinates were found to be necessary to reproduce observed frequencies. The stretching potentials of the trans - and the cis -NH bonds show close correspondence with those of the free and the bonded NH bonds of o -bromoaniline. The correlation between the compliance constants and the change of the CH, CO, and NH bond lengths on the dissociation of the CN bond is discussed.

Etude des spectres IR des composes cites et de leurs derives isotopiques pour le metal et les hydrogenes

Infrared and Raman spectra of nitrobenzene-p-d and -d5 have been recorded in the liquid state and sixty-seven of the seventy-two fundamental frequencies of the two isotopes have been assigned by referring to the isotopic frequency shifts, the Raman depolarization ratios and the assignments of sodium benzoate-p-d and -d5. A normal coordinate analysis has been carried out for the five isotopic nitrobenzenes, -d0, -p-d, -d5, -18O2 and -15N. The force constants have been refined by the method of least squares and a good fit between the observed and the calculated frequencies has been obtained.

Polarized Raman spectra of l -alanine and N-deuterated l -alanine single crystals have been measured. A normal coordinate analysis has been made for the optical active intra- and intermolecular vibrations of l -alanine crystal. The large factor group splittings observed for the CH3 asymmetric deformation and the CH3 torsional modes were elucidated well by using the potential including only the non-bonded atom—atom repulsion interaction. A good agreement was obtained between the observed and the calculated lattice vibrational frequencies on addition of the terms due to the hydrogen bond stretching and long range Coulomb interaction to the intermolecular potential.

Infrared and Raman spectra of sodium benzoate, benzoate- p - d and benzoate- d 5 have been recorded in the solid state and in the saturated aqueous solution. Sixty-seven of the seventy-two fundamental frequencies of benzoate- p - d and benzoate- d 5 ions have been assigned by referring to the Raman depolarization ratios and isotopic frequency shifts. A normal coordinate analysis of the three isotopic benzoate ions has been carried out by assuming the C v 2 symmetry and a valence force field. The force constants have been refined by the method of least squares and a good fit between the observed and the calculated frequencies has been obtained.

The pure rotational spectra of three deuterated ethylenes, CH2CD2, CH2CHD, and cis-CHDCHD, were observed by microwave spectroscopy, and the rotational and centrifugal distortion constants were determined precisely. The dipole moment of CH2CD2 was calculated from the Stark effects to be 0.0091 ± 0.0004 D. From the observed rotational constants the average structure was calculated to be r z (CC) = 1.3391 ± 0.0013 A , r z (CH) = 1.0869 ± 0.0013 A , θz(CCH) = 121.28 ± 0.10°, and r z (CH) - r z (CD) = 0.00137 ± 0.00037 A , where the errors include one standard deviation in the fitting and errors due to an uncertainty (±0.03°) in θz(CCH) - θz(CCD).

Raman spectra of 14 monosubstituted benzenes and eight p -deuterated derivatives have been recorded in the region between 2000 and 1600 cm −1 , and the observed bands have been assigned to overtones of the CH out-of-plane deformation vibrations. The results have been utilized to investigate the correlation between the CH out-of-plane deformation frequencies and the electronic properties of the substituent. For the substituents with no lone pair electrons at the α-atom, the frequencies of the in-phase CH out-of-plane deformation vibration are nearly proportional to Taft's resonance parameter σ 0 R of the substituent. The change of the out-of-plane force constants giving rise to the observed variations of the out-of-plane fundamentals have been studied.

Band intensities in the polarized Raman spectra have been measured for the CO2− stretching, the CH2 stretching and the CH2 bending modes of α-glycine crystal and the CO2− stretching and the CH3 symmetric deformation modes of L- and DL-alanine crystals. Variations in the relative band intensities on the change of the scattering geometry have been elucidated by applying the oriented gas model to the local groups, –CH2, –CH3 and –CO2−, of these amino acid crystals. The calculated values of the components of the derived polarizability tensors are consistent with the geometry of the groups. The depolarization ratios estimated from the calculated anisotropy of the polarizability tensors have been compared with those observed for aqueous solutions.