Akio Kuwae

A comparative vibrational and NMR study of cis-cinnamic acid polymorphs and trans-cinnamic acid.

The IR and Raman spectra of the two polymorphic forms (58 degree- and 68 degree-forms) of cis-cinnamic acid were measured, and the spectral differences discussed on the basis of the crystal structures of the two forms. The IR bands related to the COOH group differ in the frequencies and band shape, reflecting differences in the hydrogen bonding between the two modifications. These spectra were compared with those of trans-cinnamic acid. The IR, Raman, and NMR spectra of the isotopic compounds, including the deuterated and 13C analogs of the cis and trans acids, were also recorded in the solid state and in solution to confirm the spectral assignments.

Characterization of microbial poly (ε-l-lysine) by FT-IR, Raman and solid state 13C NMR spectroscopies

Abstract The molecular structure and conformation of microbial poly(e- l -lysine) (M-e-PL) produced by a variant of Streptomyces albulus were studied by means of FT-IR, FT-Raman and solid-state 13C NMR spectroscopies. Vibrational results indicate that M-e-PL assumes a β-sheet conformation in the solid state. Solid state 13C NMR spectra of the crystalline and the amorphous components were observed separately and the degree of crystallinity was estimated to be 63%. A plausible conformation model was proposed.

Molecular structure and vibrational spectra of phenolphthalein and its dianion

Infrared (IR) and Raman spectra of phenolphthalein (PP) and its dianion form (sodium and potassium salts) were studied both in the solid state and in aqueous solution. Band assignments were carried out on the basis of the isotope shifts of the ring deuterated and 13C-substituted derivatives. Spectral analyses reveal that the PP dianion exists as mixtures of the benzenoid form (colorless) and the quinonoid form (colored) in the solid state and in aqueous solution, while the neutral PP solely takes the gamma-lactone form. This work provides the first vibrational spectroscopic evidence for the coexistence of the two species in the PP dianions.

Vibrational and NMR spectra of phenylpyruvic acid and its salts in aqueous solution

Abstract The IR, Raman and NMR spectra of phenylpyruvic acid and its sodium and lithium salts were recorded in aqueous solution. The spectral data indicate that the acid exists mostly in the hydrated keto form (gem-diol form) in acidic solution and that the sodium and lithium salt hydrates take predominantly the normal keto form in aqueous solution in contrast with those in the solid state. Also the solution of the acid and the salts contain a small amount of the enol form. A solvent isotope effect, i.e. the enol content differs between the H2O and D2O solutions of the sodium salt, was found.

Resonance raman spectra and structure of p-aminoazobenzene dyes in diprotonated form

Abstract Resonance Raman spectra of methyl orange and its three ring deuterated and three 15N-azo derivatives have been measured in solutions in concentrated sulfuric acid and sulfuric acid-d2. From the isotope shifts of the observed Raman bands, methylorange is confirmed to take the dicationic azo form protonated at the dimethylamino and the α-azo nitrogen atoms. The resonance Raman spectrum of tropaeolin OO is entirely different from that of methyl orange in concentrated sulfuric acid and is well elucidated on the basis of the protonated hydrazone-form, -NH-N+H =.

Crystal structures and conformations of 5-benzyl-2-thiohydantoin and its 1-acetylated derivative

ABSTRACT The crystal structures of 5-benzyl-2-thiohydantoin (5-BTH) and 1-acetyl-5-benzyl-2-thiohydantoin (1-Ac-5-BTH) have been determined by X-ray diffraction. In the 5-BTH crystals, the enantiomeric (R)- and (S)-5-BTH molecules are connected to form cyclic dimers via the hydrogen bonds of the thioamide and the amide moieties. On the other hand, the intermolecular hydrogen bonds in 1-Ac-5-BTH crystals form an infinite chain. These differences in the hydrogen bond pattern are also discussed in the IR and Raman spectra. The ab initio molecular orbital calculations (Gaussian 03) with 6-31G(d,p) basis set were carried out for 5-BTH and 1-Ac-5-BTH to get the preferred conformation.

Polymorphism of phenylpyruvic acid studied by IR, Raman and solid state 13C NMR spectroscopy

Abstract Polymorphs I and II of phenylpyruvic acid are obtained as mixtures of both crystal forms or relatively pure crystals, from different solvents. Polymorph I is more stable than polymorph II at room temperature. Spectral characteristics of these polymorphs are discussed on the basis of IR, Raman and solid state 13 C NMR spectra. Also, the assignment of the IR features observed in the 1600–1700 cm −1 region is re-investigated by referring to the spectra of heavy-atom substituted derivatives. It is suggested that the CO stretching band is split by the crystal field for both polymorphs.

Vibrational spectra of β-lactams—III. potassium 2-azetidinone-1-sulfonate and its isotopic compounds

Abstract The IR and Raman spectra of potassium 2-azetidinone-1-sulfonate and its three deuterated and two 15N-substituted compounds have been recorded, and the observed bands have been assigned on the basis of the isotope effects and the normal coordinate analysis. Comparison of the force constants for the amide group among 2-azetidinone, 1-methyl-2-azetidinone and potassium 2-azetidinone-1-sulfonate indicates that there is a correlation between these constants and the ease of hydrolysis which was determined by NMR spectroscopy, depending on the amide resonance.

Molecular Structure and Dimerization of d-Cycloserine in the Solid State

Abstract d-cycloserine (CS) is transformed into cis-3, 6-bis(aminooxymethyl)-2, 5-piperazinedione (CS-dimer) in the solid state under a humid atmosphere. This dimerization process was followed by measuring the IR bands characteristic of CS and CS-dimer. The reaction was accelerated by the presence of increased water vapor. The X-ray analysis of CS monohydrate (CS · H2O) revealed that the CS molecules exist as a zwitter ion where the α-amino N atom is protonated and the amide N atom is deprotonated in the crystal. Participation of water molecules was suggested in the dimerization of CS.

Solid state structures of phenylpyruvates as studied by high resolution 13C NMR spectroscopy

Abstract High resolution solid state 13 C NMR measurements were made on phenylpyruvic acid and its sodium, lithium and calcium salts, using the total suppression of spinning side bands and the dipolar diphasing technique. The spectra of their 2- 13 C enriched analogs were also recorded. The NMR data were discussed by reference to the solution spectra, and the following definitive evidence was obtained: the acid, the hydrated sodium and lithium salts and the dehydrated sodium salt take the enol, the diol and the keto form, respectively, but the hydrated calcium salt exists in the keto form. The 13 C NMR signal of the gem -diol carbon was found to appear at 98 ppm. The calcium salt has two doublets at 166 and 134 ppm which originate from the carbons C(1) and C(4); this splitting suggests that the carboxylate group and/or the phenyl ring in the phenylpyruvate anion are oriented in two different ways.