The N−H stretching frequencies and molecular configurations of some aromatic amines

The infra-red spectra of N-benzylaniline and a number of its substituted derivatives have been examined in the N−H stretching region. A comparison of the solid- and solution-state spectra supports previous suggestions that rotational isomerism occurs in N-benzylaniline. The N−H stretching frequencies are discussed in relation to possible rotational isomers present. A comparison of the infra-red spectra of secondary aromatic amines with ortho or para nitro-substituents indicate that intramolecular hydrogen bonding occurs in the former. A brief study of the N−H stretching frequencies of monodeuteroamines has been interpreted on the basis of cis-trans isomerism of the NHD group. It is suggested that this provides a sensitive method for the detection of non-equivalent N−H bonds in compounds containing the NH₂ group.     

Profile analysis of infrared absorption of NH stretching band

The shape of the infrared NH stretching band of N-methyl aniline in different solvents has been studied. Carbon tetrachloride, tetrachloroethylene, carbon disulfide, benzene, anisole, chloroform, dioxane and di-n-butyl ether were used as solvents. Band shapes observed show self-association of N-methyl aniline in dioxane, di-n-butyl ether and chloroform solutions.Moments analysis and time autocorrelation function calculations have been performed. The frequencies of the band maximum are more sensible to the solvent than the half band width and the band shape. Moments values depend strongly on the integration interval. The correlation function shows non-exponential decays in a short time range (0–0.16 ps) for any solutions, and this indicates that the molecular motions do not obey a simple rotational diffusion model. Exponential decays show at times longer than 0.16 ps. Relaxation times are linearly related with the solvents viscosity.     

Vibrational spectroscopy of D—Glucose: the CH stretching region

We recorded the infrared and Raman spectra of α- and β-D-Glucose and five deuterated derivatives, in the solid. A rule is proposed for the interpretation of the behaviour of the principal force constants of the CH bonds in the various positions, taking into account the interaction of each CH with the vicinal oxygen atom.     

Pyrrole studies—VI. The NH stretching frequencies of substituted pyrroles: methyl and carbethoxy substituents

The infrared spectra of a number of substituted pyrroles have been examined in the NH stretching region under high resolution in carbon tetrachloride. In all cases two concentration independent bands were observed. For compounds with a carbethoxy group in the α-position, this is attributed to rotational isomerism. In other cases, the evidence suggests that the second band arises from interaction with the out of plane deformation vibration of the NH group, producing a hot band.An analysis of the data for pyrroles containing methyl and carbethoxy substituents shows that the effect of each group on the NH stretching frequency is independent of other substituents and additive. The frequencies can therefore be represented by a single equation, ν_NH = 3496 - 9n_αCH₃ + 2n_βCH₃ - 13n_βCO₂Et - ¹⁴₃₁n_αCO₂Et where n_α and n_β are the number of substituents in the α and β positions respectively.     

Characterization of NH overtone and combination bands in the near-infrared absorption spectra of simple cyclic imides

Bands due to overtone and combination vibrational modes attributable to the imide grouping have been elucidated in the near-IR absorption spectra of small-ring cyclic imides, in which the grouping is in a cis, cis conformation. The spectra closely parallel the spectra of cis lactams except that two combination modes involving the carbonyl stretching fundamental, [ν(NH) + ν(CO)] and [2ν(C=O) + imide III], occur at higher wavenumbers in the imide spectra, reflecting the higher frequency at which this fundamental absorbs. This same factor results in a reversal in the wavenumber positions of the [2ν(CO) + imide III] and [ν(NH) + imide III] combination bands in the imide spectra relative to those in the lactam spectra. In addition, in-phase and out-of-phase vibrational coupling between the two carbonyl groups in the imides may compound the band due to the [ν(NH) + ν(CO)] combination mode. These three spectral characteristics serve to distinguish the imides from the lactams in the near-IR.     

Derivative analysis of Raman spectra of liquid water in the OH (D) stretching region

Second derivative analysis of Raman spectra of H₂O, D₂O and HOD in liquid phase at room temperature for parallel and perpendicular polarized modes in the OH and OD stretching regions is reported. Five components obtained at approximately 3215, 3375, 3455, 3535 and 3640 cm⁻¹ for the second derivative plots of Raman spectra of liquid water are explained as due to the presence of three types of associated water species with (i) both OH bonds involved in moderately strong hydrogen bonds (SS), (ii) both OH bonds involved in weak hydrogen bonds (WW), and (iii) one OH bond involved in strong and one in weak hydrogen bonds (SW) respectively. The derivative plots obtained for Raman spectra of D₂O and HOD also contain features expected to be present on the basis of this model.     

Infrared-Spectral investigation of steric effects on hydrogen bond formation in esters of 3-benzoylaminopropionic acids—I. NH stretching region

The NH stretching frequencies of series of tert. butyl and ethyl esters of 3-benzoylaminopropionic acids and suitably substituted N-benzoyldiphenylmethylamines in various solvents have been studied. The data for the influence of the solvents on the NH stretching vibration were treated according to the Bellamy—Hallam—Williams plot. Steric effects of the substituents and the ester groups on the formation of the intramolecular NH … OC (ester) hydrogen bond were discussed.     

Vibrational spectra in the CH stretching region for potassium n-hexanoate and its specifically deuterated derivatives

Infrared and Raman spectra in the solid state for potassium n-hexanoate, CH₃(CH₂)₄CO₂K, and its six kinds of specifically deuterated derivatives have been measured in the CH stretching region. Complete vibrational assignments of the CH stretching vibrations have been made. Characteristic vibrational bands for the specifically deuterated position of the carbon atom have been discussed.     

The frequency of the HOH bending fundamental in solids and liquids

A survey has been made of HOH bending frequencies in water-containing solids and liquids, using data from the literature and from the author's laboratory. After the effects of hydrogen bonding and dynamic coupling have been allowed for, HOH bending frequencies are found to be lowered by cation—water interactions. This frequency lowering increases statistically with increasing cation charge and with decreasing cation size.     

Infra-red studies with sulphoxidesPart I The SO stretching absorptions of some simple sulphoxides

The frequencies, half-band widths and apparent molecular extinction coefficients of the sulphoxide stretching absorption of eight simple sulphoxides in various solvents are recorded. The results are discussed in terms of Fermi resonance and solvent effects.     

Solvent effect on SiH stretching bands of substituted silanes

Infrared frequencies of SiH stretching vibration bands of dimethyl naphthoxy silane and dimethyl quinoxy silane have been measured in a number of solvents. The results have been used to examine the importance of the bulk dielectric effect and specific solute—solvent interactions. The deviation from the Kirkwood—Bauer—Magat relationship produced by polar, as well as by non-polar, solvents is analysed in terms of the formation of molecular complexes.     

Acidities of some fluorine substituted CH acids

Acidities of some fluorinated hydrocarbons, R_FH, have been estimated by polarographic method. Polarographic data on electrochemical reduction of (R_F)₂Hg have been correlated with rate constants of hydrogen isotopic exchange in R_FH in methanol.     

Solvent effects in infra-red spectra. OE and SH stretching vibrations

The intensities, band widths and frequencies of the OH stretching vibrations of methanol, tert.-butanol and phenol, and of the SH stretching vibrations of tert.-butyl mercaptan and thiophenol in a range of solvents are reported and discussed in terms of current solvent effect theories. Similar solvent dependences were found for the hydroxyl and thiol solutes in the more strongly bonding solvents suggesting that hydrogen bond forces were operative in both cases. For the hydroxyl compounds, the frequency shifts were found to be related to the electron densities at centres of negative charge on the solvent molecules.