The vibrational spectra of maleimide and N-D maleimide

The infrared spectra of maleimide as a vapour (160°C), melt (100°C), oriented polycrystalline film, pellet and when dissolved in various solvents were recorded between 4000 and 400 cm^?1. Also certain spectra in the far infrared region 400-40 cm^?1 were obtained. Raman spectra of the crystalline solid, melt and as a saturated solution in acetonitrile were recorded and semiquantitative polarization measurements carried out. For N-D maleimide infrared and Raman spectra of the solid compound were recorded.The fundamental frequencies have been assigned in terms of C_2v, symmetry on the basis of infrared vapour contours and dichroism of the oriented film as well as on Raman polarization data. A force field was derived for maleimide, by initially transferring force constants from maleic anhydride and subsequent refinement of the force constants. The agreement between observed and calculated frequencies for the in-plane modes was satisfactory whereas certain large discrepancies remained for the out-of-plane vibrations.     

Vibrational and electronic absorption spectra of 4-chloro 2-methyl, 4-chloro 3-methyl and 6-chloro 3-methyl phenols

The infrared spectra of 4-Cl 2-Me, 4-Cl 3-Me and 6-Cl 3-Me phenols have been recorded. The vibrational spectrum has been analysed assuming that the molecules belong toC _s point group and a tentative assignment of the observed frequencies to various modes of vibration has been proposed. The near ultraviolet absorption spectrum of these compounds has also been recorded. Assuming the transition to be electronically allowed the strongest band on the longer wavelength side has been assigned as the (0, 0) band in each case. The spectrum has been analysed in terms of several excited state frequencies which have been correlated with the ground state frequencies observed in the infrared spectrum.     

Vibrational spectra and structure of some oxalic acid/substituted pyridine (methyl-, amino-, and dihalogeno-) complexes: Hydrogen bond features

The Raman and infrared spectra of some polycrystalline substituted pyridine/oxalic acid complexes have been investigated and assignments in terms of group frequencies are given. Various hydrogen bonds (NH?O, OH?O, OH?N) are distinguished and crystal structures are proposed. For the stronger bases (methyl- or aminopyridines with pk_a ≈ 6) proton transfer occurs. The 1/1 complex contains infinite chains of hydrogen oxalate ions linked by strong OH?O hydrogen bonds with vOH between 2000 and 800 cm⁻¹. R_OH?O distances are 2.47–2.62 Å). The substituted pyridinium cations are linked to the chain backbone by medium NH?O hydrogen bonds with NH?O lengths of 2.71–2.81 Å. The 3,5-dichloropyridine forms a 2/1 adduct without proton transfer, in accordance with its pk_a (0.6), and strong OH?N hydrogen bonds occur (vOH about 2000 cm⁻¹ and ). Finally, the 2,6-dihalogenopyridine derivatives do not form complex with oxalic acid, presumably because of steric hindrance.     

Spectroscopic study of the formation and structure of polyselenacyclobutane

Selenacyclobutane (trimethylene selenide) readily undergoes photochemical reaction to give polymeric products. Also, the material polymerizes rapidly when the polycrystalline solid film liquifies on a salt substrate in vacuum. Upon polymerization of the sample, infrared and Raman spectra exhibit profound changes which definitely establish ring cleavage. The Raman spectra of the polymer reveal strong C–Se stretching peaks but little or no scattering in the region of Se–Se stretching, strongly suggesting that the polymerization process proceeds in a regular head-to-tail fashion. An EPR study of the monomer exposed to ultraviolet radiation at ?180°C supports this fact, since the resulting spectrum is indicative of an intermediate radical species, (CH₂CH₂-CH₂Se)_n., where n is sufficiently large that the terminal electrons do not interact. No triplet spectra were observed. Molecular oxygen apparently plays an important role in the polymerization kinetics, since it is found that degassed samples of the substance, in contrast to those which have not been degassed, polymerize rapidly even under room illumination. Freezing-point depression measurements fix a lower limit to the average molecular weight of the polymer at 2700 (n = 23 monomer units).     

17O NMR spectra of equatorial and axial hydroxycyclohexanes and 5-hydroxy-1,3-dioxanes and their methyl ethers

¹⁷O chemical shifts of axial hydroxyl groups in cyclohexanols are upfield of those of corresponding equatorial groups, but in 5-hydroxy-1,3-dioxanes the opposite is observed: the axial OH resonates downfield of the equatorial OH. The situation is the same in the corresponding methyl ethers and is, thus, not a result of intramolecular hydrogen bonding in the axial 5-hydroxy-1,3-dioxane, but appears to parallel the effect on ¹³C and ¹⁹F shifts observed in corresponding equatorial and axial 5-methyl- and 5-fluoro-1,3-dioxanes, which has been attributed to an upfield shifting effect of the antiperiplanar γ-located heteroatoms. Surprisingly, the reciprocal effect is not seen in the ring ¹⁷O shifts of the 5-hydroxy-1,3-dioxanes. A δ compression shift is seen in the ¹⁷O spectrum of trans-3,3,5-trimethylcyclohexanol (syn-axial OH and CH₃), analogous to the effect earlier reported in ¹³C spectra. Conversion of four of the alcohols to methyl ethers produces a large upfield effect on the ¹⁷O shift, larger in the cyclohexanols than in the 1,3-dioxane-5-ols. Similar upfield shifts have been recorded in the literature; their extent depends on whether the alcohols are primary, secondary or tertiary.     

Neutron inelastic scattering spectra of strongly hydrogen bonded acid oxalates NaHC2O4, KHC2O4 and LiHC2O4

Neutron inelastic scattering spectra of NaHC₂O₄, KHC₂O₄ crystals at 80 K have been recorded in the 2200-200 cm^?1 range. The lithium acid salt was also studied at different temperatures. NIS spectra are compared to the corresponding infrared and Raman spectra and an assignment is proposed. Two strong bands near 1500 and 1100 cm^?1 are assigned to δ(OH) and γ(OH) vibrations, respectively, while five weak bands below 900 cm^?1 are associated with skeletal modes, mainly bending vibrations. The OH stretching vibration is not observed and is believed to be hidden by other bands; the peak intensity must be low because of its band width which is of the order of a few hundreds wavenumbers.     

Synthesis,infrared spectra and thermal investigation of gold(III) and zinc(II) urea complexes. A new procedure for the synthesis of basic zinc carbonate

Reaction of urea with sodium tetrachloroaurate(III) dihydrate and zinc(II) chloride has been investigated at room and elevated temperature (～90°C) producing three new compounds: [Au(urea)₄]Cl₃·2H₂O, [Au₂(NH₂)₂Cl₂(NCO)(OH)]·H₂O and 2ZnCO₃·3Zn(OH)₂. The infrared spectra were recorded and the observed bands were assigned. The binuclear gold complex and basic zinc carbonate basic were also investigated by thermal analysis, and general mechanisms describing their decompositions are suggested.     

Infrared and electronic absorption spectra of some trisubstituted benzenes

The electronic absorption spectra of 2,3-, 2,4-, 2,5-, 2,6- and 3,4-difluorobenzonitriles, 3,4-difluoroaniline and 3,4-difluoroanisole in the ultraviolet region in vapour phase have been recorded on medium quartz and Hilger large quartz spectrographs and on a Hitachi model 150-20 UV-VIS ratio recording spectrophotometer. All the molecules investigated have exhibited two π* ← π band systems corresponding to ¹B_2u ← ¹A_1g (λ2600 Å) and ¹B_1u ← ¹A_1g (λ2100 Å) systems of benzene. The infrared absorption spectra of all the molecules studied have also been recorded and analysed. These infrared data have been taken to help analyse the u.v. spectra of the molecules studied.     

Syntheses,crystal structures,and IR spectra of isonicotinamide-isonicotinamidium bis(isonicotinamide)-tetrakis(isothiocyanato)ferrate(III) and isonicotinamidium chloride

Reaction of iron(III) thiocyanate with isonicotinamide (inia) in ethanol leads to formation of a dark red, air stabile crystalline iron(III) compound of composition [iniaH·inia][Fe(inia)₂(NCS-N)₄]. Single-crystal X-ray diffraction analysis shows the triclinic P–1 space group with unit cell parameters: a?=?8.2440(4)?Å, b?=?9.5540(3)?Å, c?=?11.2590(5)?Å, α?=?93.945(4)°, β?=?95.554(4)°, γ?=?96.285(3)°, and Z?=?1. The iron compound contains [iniaH·inia]⁺ cations and [Fe(inia)₂(NCS-N)₄]^– anions, which are held together by ionic interactions and hydrogen bonding. The Fe(III) is octahedrally coordinated by six nitrogens, four from NCS^– in the equatorial plane and two from inia occupying axial positions. The [iniaH]Cl has been formed by reaction of inia with hydrochloric acid. [iniaH]Cl crystallized in the monoclinic C2/c space group with unit cell parameters: a?=?25.156(5)?Å, b?=?5.095(1)?Å, c?=?12.747(3)?Å, and Z?=?8. Both compounds have also been characterized by elemental analyses and infrared spectroscopy. Structural and infrared spectral data are compared with data of similar compounds in the literature.     

Radiation chemistry of poly(propylene oxide)

Atactic, isotactic, and optically active poly(propylene oxides), PPOx, were irradiated with both γ-rays and electron beams. Up to a dose of 37 Mrad no change could be detected in the optical activity. G values for hydrogen evolution decreased as compared to polypropylene in about the same ratio as G(H₂) of polyoxymethylene decreased as compared to polyethylene. G values for crosslinking and scission, estimated by means of gelation theories of Saito and Inokuti, were found to be greater for isotactic than for atactic PPOx. The behavior of transient infrared and ultraviolet absorption bands is discussed. Intrinsic viscosity data indicate a rapid initial chain degradation whereas CO gas and OH group production is linear with dose. Evidence for the conversion of one type of free radical to another on heating an irradiated sample from 77°K to room temperature is based on the behavior of transient infrared and ultraviolet absorption bands.     

IR spectra and structure of 2-aryl-3-hydroxypyridines

The IR spectra of methyl, chloro, and phenyl derivatives of 3-hydroxypyridines in CCl₄ solutions and in the crystalline state were studied. A comparison of the frequencies, half widths, and integral intensities of the bands of the stretching vibrations of the hydroxyl groups in the spectra of solutions of the 3-hydroxypyridine derivatives in CCl₄ with the characteristic OH bands in the spectra of phenols demonstrates that 3-hydroxypyridines exist practically completely in the hydroxy form in dilute CCl₄ solutions. The shift in the OH bands in the spectra of 2-phenyl-3-hydroxypyridine derivatives indicates that the OH group forms a -hydrogen bond with the phenyl ring. The presence also of a band of a free OH group is evidence for the existence of s-cis and s-trans conformers relative to the C-O bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–190, February, 1972.     

Synthesis,characterization and properties of a soluble polymer with a poly(phenylenevinylene) structure

Soluble poly(2,5-dialkoxy-1,4-phenylenevinylene) has been prepared via Stille coupling reaction between 2,5-dialkoxy-1,4-diiodobenzene and E-1,2-bis(tributylstannyl)-ethene in the presence of palladium complexes. Characterization of this material by means of ¹H and ¹³C nuclear magnetic resonance (NMR), ultraviolet/visible (UV/VIS) and infrared (IR) spectra is described. Molecular weights, determined by means of gelpermeation chromatography (GPC) analysis and referred to standard polystyrene, were in the range number-average molecular weights M _n = 2061–2544 and weight-average molecular weights M _w = 3347–3878. X-ray diffraction (XRD) analysis of the polymer showed semicrystalline structure. T_g = 57°C, transition to a stable smectic mesophase at 115°C and clearing point at 210°C were revealed by differential scanning calorimetry analysis, optical microscopy observation and XRD of the annealed polymer.     

The microwave and infrared spectra and structure of hydrothiophosphoryl difluoride

The microwave spectra of ³²SPHF₂, ³⁴SPHF₂ and ³²SPDF₂ have been analyzed. The structural parameters obtained from this analysis are: d(S-P) = 1.867±0.005Å, d(P-F) = 1.551 ±0.005Å, (P-H) = 1.392±0.005Å, ∠SPF = 117.4 ± 0.2 °, ∠SPH = 119.2±0.2 °, ∠FPF = 98.6±0.2 °. Centrifugal distortion coefficients were obtained for ³²SPHF₂. The spectra of two vibrational excited states of ³²SPHF₂ were observed. The two sets of rotational constants (A) 8336.72, 3726.70, 2807.56 MHz and (B) 8344.88, 3727.73, 2798.75 MHz were associated with the vibrational states with measured infrared frequencies 419 cm^?1 and 344 cm^?1 respectively. An analysis of the infrared spectrum is included. Dipole moment measurements yielded μ = 1.87±0.03 D for ³²SPHF₂ and μ = 1.86±0.03 D for ³²SPDF₂     

Vibrational spectra of ethyl iodedes

The infrared spectra of CH₃CH₂I, CD₃CH₂I, and CH₃CD₂I of the vapors and the solids at 170°C have been recorded from 4000-200 cm^?1. The Raman spectra of the liquids and vapors have also been recorded and depolarization values have been measured. Assignment of the eighteen fundamental vibrations has been based on depolarization values, band contours, group-frequency correlations, and normal coordinate calculations. A critical discussion of the CH stretching assignments in CH₃CH₂X molecules is presented.     

Mass spectra of alkenyl methyl ethers

Electron impact ionization mass spectra of numerous alkenyl methyl ethers C_nH_2n-1OCH₃ (n = 3–6) recorded under normal (4 kV, 70 eV, 175°C) and low-energy, low-temperature (8 kV, 12 eV, 75 °C) conditions are reported. The influence of the position and stereochemistry of the double bond on the dissociation of ionized alkenyl methyl ethers is discussed. The mechanisms by which these ethers fragment after ionization have been further investigated using extensive ²H-labelling experiments and by studying the energy dependence of the reactions. Ethers of allylic alcohols show spectra that are distinct from those of the isomeric species in which the double bond is separated by one or more sp³ carbon atoms from the carbon atom carrying the methoxy group. Three principal primary fragmentations are observed. The most common process, especially for ionized ethers of allylic alcohols, is loss of an alkyl group. This reaction often occurs by simple α-cleavage of radical-cations of the appropriate structure; however, alkyl groups attached to either end of the double bond are also readily lost. These formal β- and γ-cleavages are explained in terms of rearrangements via distonic ions and, at least in the case of γ-cleavages, ionized methoxycyclopropanes. Ionized homoallyl methyl ethers tend to eliminate an allylic radical, particularly at high internal energies, with formation of an oxonium ion (CH₃ ⁺O?CH₂ or CH₃ ⁺O?CHCH₃). The ethers of linear pentenols and hexenols show abundant [M - CH₃OH]⁺? ions in their spectra, especially when a terminal methoxy group is present Methanol loss also takes place from ionized ethers of allylic alcohols in which there is a Δ-hydrogen atom; this process is significantly favoured by cis, rather than trans, stereochemistry of the double bond.     

Protonization of purine, adenine, and guanine. NMR spectra and structure of mono, di, and tri cations

Proton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF₃COOH, FSO₃H and FSO₃H? SbF₅? SO₂ at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono-, di- and tri-cations are described and fully assigned.     

Gas phase structure and vibrational spectra of dimethoxysulfane (CH3O)2S

The vapor phase structure of (CH₃O)₂S [1] has been investigated by electron diffraction and ab initio MO calculations, which both result in a C₂ symmetry for the most stable geometry, the C_s conformer being less stable by about 12 kJ/mol. The torsional barrier for rotation about one SO bond was calculated as 37 kJ/mol (trans barrier). The geometrical parameters (electron diffraction) of the C₂ conformer are: d_SO = 162.5(2), d_CO = 142.6(3), d_CH = 110.5(7) pm angles OSO = 103(1)°, SOC = 115.9(4)°, HCH = 109(1)°, torsional angle COSO = 84(3)°. Geometrical data calculated with 6-31G^* basis set agree well with the diffraction data; calculated dipole moments 1.1 D (C₂) and 3.3 D (C_s). The infrared spectrum of gaseous (CH₃O)₂S and the Raman spectra of liquid and solid (CH₃O)₂S are reported and have been almost fully assigned to the 27 fundamental vibrations.     

Site of protonation in the chemical ionization mass spectra of olefinic methyl esters

The H₂ and CH₄ chemical ionization mass spectra of the olefinic esters methyl acrylate, methyl methacrylate, methyl crotonate, methyl 3-butenoate, methyl 2-methyl-2-butenoate, methyl 3-methyl-2-butenoate and methyl cinnamate have been determined. In addition to the expected loss of CH₃OH from [MH]⁺, in many cases the protonated molecules also show loss of CO or CH₂CO with methoxy group migration to the positive ion centre, indicative of protonation at the double bond. These rearrangement reactions, which have analogies in electron impact mass spectra, result in chemical ionization mass spectra of isomeric molecules which show more substantial differences than the electron impact mass spectra. In the case of methyl cinnamate, isotopic labelling experiments show considerable interchange of the added proton with the ortho and meta phenyl hydrogens prior to CH₃OH or CH₂CO loss, although the extent of interchange is not the same for both cases.     

Single‐microemulsion‐based Hydrothermal Approach to In(OH)3 and In2O3 Nanocubes

Well‐defined indium hydroxide [In(OH)₃] nanocubes have been successfully prepared through a facile single‐microemulsion‐mediated hydrothermal process at a relatively low temperature. Calcination of the In(OH)₃ precursor at 400°C in a furnace yielded In₂O₃ crystals with the same morphology. X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), and transmission electron microscopy (TEM) were used to characterize the samples. The effects of reaction parameters on the formation of nanostructures were also discussed, and the nucleation, aggregation and anisotropic growth mechanism was proposed. Room temperature photoluminescence (PL) spectra as well as the ultraviolet‐visible (UV‐vis) absorbance spectra were carried out on the In₂O₃ crystals to investigate their optical properties.     

Chemical ionization mass spectra of mononitroarenes

The H₂ and CH₄ chemical ionization mass spectra of a selection of substituted nitrobenzenes have been determined. It is shown that reduction of the nitro group to the amine is favoured by high source temperatures and the presence of water in the ion source. The H₂ chemical ionization mass spectra are much more useful for distinguishing between isomeric compounds than the CH₄ CI mass spectra because of the more extensive fragmentation. For ortho substituents bearing a labile hydrogen abundant [MH ? H₂O]⁺ fragments are observed. When the substituent is electron-releasing both ortho and para substituted nitrobenzenes show abundant [MH? OH]⁺ fragment ions while meta substituted compounds show abundant loss of NO and NO₂ from [MH]⁺. The latter fragmentation is interpreted in terms of protonation para to the substituent or ortho to the vitro function, while the first two fragmentation routes arise from protonation at the nitro group. When the substituent is electron-attracting the chemical ionization mass spectra of isomers are very similar except for the H₂O loss reaction for ortho compounds.