Benzylidene Amine Research Articles

Intramolecular resonance-assisted hydrogen bonds: A theoretical description by means of atomic charges and charge fluxes

The characterization of intramolecular H-bonds in terms of atomic charges and charge fluxes (at the B3LYP/cc-pVTZ level of theory) has been extended to the case of the so called resonance-assisted (RA) H-bonds. A quadratic correlation between the charge fluxes ϕH and the molecular IR absorption coefficients E that includes the entire family of the studied systems (31 of them) containing both intra- and intermolecular hydrogen bonds (O–H⋯O/N) confirmed the critical importance of the charge fluxes on the IR intensity enhancements. Since they reflect changing of the atomic charge distribution during the normal modes of vibrations, the dynamic nature of hydrogen bonding properties has been re-emphasized. The changes of the charge flux of the hydroxyl hydrogen in an RA intramolecular H-bond are between those for “free” OH bonds and the values calculated for intermolecular H-bonds. The transition “free”→intramolecular→intermolecular is gradual and therefore the hydrogen charge flux can be considered as practically sufficient to give quantitative measure to the intuitively obvious statement that “intramolecular H-bonding is somehow in between no H-bonding situation and intermolecular H-bonding” and thus provide a quantitative and yet simple parameterization of H-bond strength. In strictly planar molecules, the difference of the sums of charges of atoms participating in the 6-membered H-bond ring ΔΣ can serve as a measure of the charge delocalization after the H-bond is formed. The electronic charge is withdrawn from the group of six atoms when the H-bond is formed in nitrophenol (ΔΣ=−0.07), while the opposite is true (ΔΣ=+0.03) for 2-hydroxy benzylidene amine. The corresponding values of the geometrical resonance parameter Δ are 0.39 and 0.37, respectively, similar to those found for 2-hydroxy acetophenone and 2-hydroxy benzaldehyde. The extent of the π-electron delocalization as measured by the resonance parameter Δ does not follow the strength of H-bond as measured by the charge flux ϕH.

Synthesis and Mesomorphic Properties of Three-Benzene-Ring Containing Bent-Core Liquid Crystal 1,3-Phenylene-bis[4-(nonylcarboyloxyl) benzylideneamine

A bent-core compound with three benzene-ring cores 1,3-phenylene-bis [4-(nonylcarboyloxyl)benzyl ideneamine] was synthesized. Its mesomorphic properties were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. This kind of bent-core compound exhibited mesophases in the temperature range of 155-185oC for the first cooling but cyclic heating and cooling could lower the phase transition temperatures for this bent-core liquid crystal. Our results demonstrated that bent-core molecules with three benzene-ring cores can also form mesophases as those five benzene-ring containing bent-core molecules do.

Solvent and Substitution Influence on the Character of Tautomers Resulting from Proton Transfer Reaction in Some Phenol Derivatives

The work verifies the application of a “resonance model” in description of the structure of tautomers in the so-called resonance-assisted hydrogen bonds. The results of B3LYP/6-31G + G(d,p) calculations are presented for N-methyl-2-hydroxy benzylidene amine and its 2,- and 2,4-chloroderivatives (Schiff bases) as well as for related Mannich bases. The influence of surrounding permittivity and the phenol acidity on the structure is discussed. It is demonstrated that enhancement of both the factors leads to the increase of the content of keto resonance forms in Mannich bases. In the case of Schiff bases, a decrease of the content of such forms with surrounding permittivity increase has been found. The differences in dipole moments of particular forms explain such tendencies.

Intermolecular triplet-sensitized photolysis of alkyl azides: Trapping of triplet alkyl nitrenes

We report the first observation that the intermolecular triplet sensitization of alkyl azides leads to bimolecular reactivity, by forming triplet alkyl nitrenes. The intermolecular triplet-sensitized photolysis of 1-azidoadamantane with acetone, acetophenone and benzophenone leads to the formation of di-(adamantan-1-yl)-1,2-diazene as the major product via dimerization of triplet adamantan-1-yl nitrene. The triplet alkyl nitrene also abstracts a H-atom from the solvent to form adamantan-1-yl amine, adamantan-1-yl-benzyl amine and adamantan-1-yl benzylidene amine. The rates of the energy transfer from acetophenone and benzophenone to 1-azidodamantane are 1×10 8 and 5×10 6 M −1 s −1, respectively. Triplet-sensitized photolysis of benzyl azide with acetophenone gave methylene phenyl amine, dibenzyl amine and tribenzyl amine as the major products. Thus triplet benzyl nitrene abstracts a H-atom from the solvent to form dibenzyl amine and tribenzyl amine and rearranges to form methylene phenyl amine. The energy transfer rate between acetophenone and benzyl azide is diffusion controlled, or 2×10 9 M −1 s −1. Sensitized photolysis of benzyl azide with benzophenone yielded only benzylideneamine. Presumably, benzophenone abstracts a H-atom from benzyl azide and the resulting radical rearranges into benzylideneamine. The rate of the chemical quenching of benzophenone with benzyl azide is 5×10 7 M −1 s −1.

1H1H and 1H19F coupling constants of some styrene, benzaldehyde and benzylidene amine derivatives

AbstractFive para‐fluorobenzene derivatives having a CHCR2 or a CHNR group were prepared and their 1H and 19F NMR spectra in acetone‐d6 were analysed. The 6J(Hα,F) and 4J(Hα,H) couplings of the nitrogen derivatives fall between those of the carbon and oxygen derivatives: the electronegativity of the side‐chain β‐atom seems to have a prominent role in the spin information transmission. The 6J(Hα,F) and 4(Hα,H) couplings indicate that the nitrogen derivatives are rigidly planar whereas the carbon derivatives are non‐planar.

MOLECULAR REARRANGEMENTS. VI. THERMOLYSIS OF α-(N-ARYL)BENZYL ARYL SULFIDES

Abstract In view of the significance of studying the effect of heat on organic compounds especially those containing nitrogen and/or sulfur, six substituted α-(N-aryl) benzyl aryl sulfides (4–9) were prepared and subjected to thermolysis at 200°C. Surveying of the reaction products showed the formation of amines, benzylidene amines, sulfides, disulfides, dibenzyl, stilbene, benzthiazole, benzimidazole, tetraphenyl thiophene as principle products in variable ratios according to the type of the starting sulfide. A mechanism involving the homolytic cleavage of the C[sbnd]S and the C[sbnd]N bond is suggested to rationalize the thermolysis products.

Solid Fluorescence Properties and Electronic Absorption Spectra of Solution of Salicylidene Amines and Benzylidene Amines

サリチリデンアミン22種およびベンジリデンアミン4種の岡体螢光スペクトル,螢光量子収率ならびにエタノール溶液の吸収スペクトルを測定した。螢光量子収率は同一測定条件下におけるアントラセン固体の螢光強度と試料のそれを比較することにより求めた。なおアントラセンの螢光量子収率としてはWrightによってあたえられた0.94を用いた。サリチリデンアミンはホトトロピーを示すものをのぞいて,すべて紫外線照射下で螢光を発する。これに対してベンジリデンアミンは無螢光性であるか,極微弱な螢光しか発しなかった。このことからサリチリデンアミンの螢光発光能には分子内水素結合が関与するものと考えられる。サリチリデンアミンの溶液吸収スペクトルは450m,u近傍に弱い吸収帯を有していることを見いだした。ベンジリデンアミンにはこのような吸収帯は見いだされなかった。またこの吸収帯は固体螢光帯と鏡像関係を示すとともに,置換基,共範結合の長さなどの諸影響に対して,螢光帯と類似の挙動を示した。four benzylidene