Benzaldehyde Moieties Research Articles

Design of donor–acceptor geometry for tuning excited-state polarization: fluorescence solvatochromism of push–pull biphenyls with various torsional restrictions on their aryl–aryl bonds

In this work, push–pull biphenyl analogs (4-(N,N-dimethylamino)-4′-formylbiphenyl) with a modulated dihedral angle of the aryl–aryl bond, using a bridged structure or methyl groups, were synthesized. Photophysical measurements of the synthesized compounds revealed the effect of the torsion between N,N-dimethylaniline (donor) and benzaldehyde moieties (acceptor) on their solvatochromic properties. Our data showed that the sensitivity of the fluorescence maxima to solvent polarity gradually increases as the biphenyl chromophore was restricted to a twisted conformation. This finding indicates that changing the torsional restrictions on the donor–acceptor system can be a factor to take into account for the development of novel solvatochromic dyes.

Kinetic investigation of oxidation of aromatic anils by magnesium monoperoxyphthalate in aqueous acidic medium

Abstract The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by magnesium monoperoxyphthalate (MMPP) has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that ionic strength of the reaction has no significant effect on rate. The added acrylonitrile has no effect on the reaction rate indicating the absence of free radical mechanism. The added Mn(II) decreases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative ΔS# values indicate a structured transition state. The deviation of Hammett plot is noted and a non-linear concave downward curve is obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus σ is attributed to the transition state whereas the non-linear concave upward curve is observed for the substituents in the benzaldehyde moiety and a non-linear concacve upward curve is observed for the substituents in the combination of aniline and benzaldehyde moiety and a suitable mechanism is proposed

Kinetic Investigation of Oxidation of Aromatic Anils by Potassium Peroxymonosulfate in Aqueous Acidic Medium

The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that the variation in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization was not observed when acrylonitrile was added to the reaction mixture. This observation rules out the formation of any free radical in the reaction. The added Mn(II) increases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative ∆S# values indicate a structured transition state. The deviation of the Hammett plot was noted, and a concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus σ is attributed to the transition state whereas the concave upward curve was observed for the substituents in the benzaldehyde moiety and in the combination of aniline and benzaldehyde moieties, and a suitable mechanism was proposed.

Synthesis and solvatochromism of heterocyclic bichromophoric dyes derived from 2‐aminothiazole

PurposeThe purpose of this paper is to investigate some novel bis‐hetaryl dyes containing both azo and azo methine chromophores on their molecular structures: two series of different molecular structures of these dyes were synthesised. The spectral characteristics and the relationships between colour and constitution of these dyes in solvents with different polarities were systematically investigated and discussed.Design/methodology/approachA series of novel bichromophoric dyes containing azo and azomethine chromophores were synthesized using two kinds of reaction routes. 2‐amino‐4‐(p‐substituted) phenyl‐thiazole derivatives, which are coupling components, were subjected to diazotisation with aniline derivatives and then to condensation with benzaldehyde derivatives. By exchanging the synthesis route, two series of bichromophoric dyes could be obtained.FindingsThe maximum absorption wavelengths of the obtained dyes would be attributed to the higher bathochromic shift in basic organic solvent with high polarity, such as dimethylformamide, as compared with the solvent with low polarity, such as chloroform.Research limitations/implicationsIn the present study, a series of novel bichromophoric dyes were synthesized by means of two‐step pathway. In addition, the effects of substituent on the primary aromatic amine and on benzaldehyde moieties will also be discussed.Practical implicationsThis novel synthesis method of the thiazole ring would lead to the formation of 2‐amino‐4‐(p‐substituted)phenyl‐thiazole with heteroaromatic coupling component position at C‐5, and consequently would produce the heteroaromatic diazo component at C‐2 for the preparation of the heteroaryl diazo dyes.Originality/valueIn this paper, the bichromophoric dyes obtained by different synthesis routes would indicate that the effect of solvent polarity should be responsible for the bathochromic shifts of the dyes.

Efficient conjugation of oligonucleotides through aromatic oxime formation

The present work reports on the preparation of oligonucleotide conjugates via the formation of aromatic oxime linkage. The conjugation consists in the reaction between the oligonucleotide derivatized at 5′-extremity with a benzaldehyde moiety and an aminooxy reporter group. The conjugation was found highly efficient and was extended for the conjugation of phosphorothioate oligonucleotide. In addition, the stability of the so-formed oxime conjugate was investigated.

Mechanistic investigation of oxidation of aromatic anils by isonicotinium dichromate in acidic medium. A kinetic study

Under identical experimental conditions the kinetics of oxidation of aromatic anils to benzaldehyde and nitrosobenzene, by isonicotinium dichromate, has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. Ionic strength has no significant effect on the conversion. The added Mn(II) decreases the rate of the reaction. The added acrylonitrile has no effect on the reaction rate indicating the absence of free radical mechanism. Highly negative ΔS # values indicate a structured transition state. The deviation of Hammett plot is noted and a concave downward curve is obtained for the anils with substituents in the aniline moiety. The observed break in the log k obs versus σ is attributed to the change in the transition state whereas the linear plot is observed for the substituents in the benzaldehyde moiety. A suitable mechanism has been proposed. Mechanistic investigation of oxidation of aromatic anils by isonicotinium dichromate in acidic medium. A kinetic study. $${\hbox{Ph-CH=N-Ph}\dynrightarrow{\hbox{Cr(VI)}} {\hbox{H}^{+}}\hbox{PhCHO}+\hbox{Ph}-\hbox{N}= \hbox{O}+\hbox{Cr}(\hbox{III})}$$

Crystal Structures of Two Calix[4]arene Isomers with Benzaldehyde Moiety and Their Photophysical Properties with Terbium(III) Ions

AbstractTwo calix[4]arene isomers with benzaldehyde moieties, i.e., 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[2‐(o‐formyl‐phenoxy)ethoxy]‐26,28‐dihydroxycalix[4]arene (3) and 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[2‐(p‐formylphenoxy)‐ ethoxy]‐26,28‐dihydroxycalix[4]arene (4), were synthesized according to a newly designed route in high yields, and their crystal structures have been determined by X‐ray crystallographic study. The photophysical behavior on com‐plexation of calix[4]arene derivatives 3 and 4 with terbium(III) nitrate was investigated in anhydrous acetonitrile at 25°C by UV‐Vis and fluorescence spectroscopies. The crystallographic structure of 3 indicated that the eight oxygen atoms formed a preorganized ionophoric cavity due to intramolecular π‐π stacking, which could encapsulate lanthanide ions tightly. In sharp contrast, the compound 4 formed a linear array by intermolecular π‐π stacking, hence the oxygen atoms of pendant arms could not coordinate with metal ions, giving a poor binding ability to Tb3+. The absorption spectra of 3 with Tb3+ showed clearly a new broad intense absorption at 385 nm. Interestingly, the narrow emission line spectrum has also been observed for compound 3 with Tb3+, and the results obtained were discussed from the viewpoint of energy transfer mechanism between host structures and the properties of lanthanide ions.

Unsymmetrical salen-type ligands: high yield synthesis of salen-type Schiff bases containing two different benzaldehyde moieties

Salen-type Schiff base ligands incorporating two different benzylidene moieties and a diamine backbone were synthesized in high yield (80–90%) under mild conditions via a stepwise approach. In the first step, anhydrous hydrochloric acid was used to selectively protect one amino group of the vicinal diamine backbone. The resulting ammonium salt was added to a substituted benzaldehyde providing access to a mono-imine product. This compound reacted with an equivalent of a different benzaldehyde in the presence of triethylamine to afford an unsymmetrical salen-type ligand. This synthetic method allows facile access to a plethora of salen-type Schiff base ligands with easily tunable steric and electronic properties.

Study of interactive free-energy relationships on ruthenium(III) catalyzed oxidation of phenyl styryl ketone and its substituted analogues by V(V) in acid medium

Kinetics of Ru(III) catalyzed oxidation of phenyl styryl ketone (PSK) and its substituted analogues by V(V) has been investigated in aqueous acetic acid-sulphuric acid medium in the temperature range 298–313 K. First-order dependence each on [V(V)], [PSK], [Ru(III)] was observed. Inverse first-order dependence was observed for [V(IV)]. The rate decreased with the increase in dielectric constant (D) of the medium. The rates were enhanced by electron-donating substituents in both the phenyl rings and decreased by electron-withdrawing substituents. Linear Hammett's plots were obtained for various substituents in benzaldehyde moiety of PSK for a given substituent in acetophenone moiety and vice versa. The mechanism proposed envisages formation of Ru(IV) from V(V) + Ru(III) reaction followed by the attack on by Ru(IV). Applicability of interactive free-energy relationship has been tested. The cross-interaction constants qx and qy have been determined at different temperatures and possible interpretations discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 581–588, 2000

Separation of Ring Polar and Resonance Effects on the Rate and Equilibrium Constants for Methoxide Ion-Promoted Addition of Methanol to N-Benzylideneanilines Substituted at the Benzylidene Moiety

Rate and equilibrium constants for the title reaction (α-amino ether formation) at 25 o C in methanol are reported for (16) N-benzylideneani- lines (BAs) substituted at the benzaldehyde moiety. In contrast to a previous report dealing with BAs substituted at the aniline residue, it is shown that an uncatalyzed pathway competes with the methoxide ion- catalyzed reaction, these two processes corresponding to rate-limiting attachment of the lyate ion to the C=N bond of iminium ion and free imine, respectively. For the latter reaction pathway, the lifetimes of the amide-ion intermediates are long enough to allow a stepwise mecha- nism

Aldol‐group‐transfer polymerization of 2‐phenyl‐1,3,2‐dioxaborole. Preparation of graft and comb‐like polymers

AbstractThe aldol‐group‐transfer polymerization of 2‐phenyl‐1,3,2‐dioxaborole is described. By initiation with aldehydes the molecualr weights of the polymers can be controlled through the mole ratio of initiator to monomer, ranging between 700–130000. The phenylboronic ester groups can be removed from the polymer, yielding polymers carrying a hydroxyl group at each carbon atom of the chain. It was also possible to prepare polymerizable macromonomers by initiation with 4‐vinylbenzaldehyde. Polymerization of the macromonomers by radical initiation yields comb‐like arrangements. Similar polymers can be obtained by grafting phenyl‐1,3,2‐dioxaborole onto a polymer containing benzaldehyde moieties in the side chains.

1-Alkoxyamino-1-deoxy alditols, useful u.v.-absorbing derivatives of neutral and acidic oligosaccharides

The feasibility of using 1-alkoxyamino-1-deoxy alditol derivatives to facilitate the purification and structural characterization of oligosaccharides was examined. 1-Benzyloxyamino-1-deoxy, 1-deoxy-1- p-nitrobenzyloxyamino, and 1-deoxy-1-[4-( p-nitrophenyl)butoxyamino] alditol derivatives of mono- and oligo-saccharides were prepared by reduction of the corresponding O-substituted oximes with sodium cyanoborohydride. The 1-alkoxyamino-1-deoxy alditol derivatives were separated by h.p.l.c. and characterized by 1H-n.m.r. spectroscopy and f.a.b.-m.s. Per- O-methylation of the 1-benzyloxyamino-1-deoxy and 1-deoxy-1- p-nitrobenzyloxyamino alditol derivatives resulted in the elimination of a benzaldehyde moiety and formation of a quaternary ammonium salt. The positive mode f.a.b. mass spectra of these cationic per- O-methylated derivatives of oligosaccharides included very intense molecular ion signals, suggesting the possibility of a significant reduction in the amount of per- O-methylated oligosaccharide required for f.a.b.-m.s. analysis. Because the ionic nature of the derivatives hinders their analysis by g.c.-m.s. a new reagent, 4-( p-nitrophenyl)butoxyamine, was synthesized and used to prepare the 1-deoxy-1-[4-( p-nitrophenyl)butoxyamino] alditol derivatives of several mono- and oligo-saccharides. These could be separated by h.p.l.c., with detection by u.v. absorption, and they were stable under O-methylation conditions. The per- O-methylated derivatives of oligosaccharides can be analyzed by e.i.-m.s. as well as f.a.b.-m.s. O-Methylated 1-deoxy-1-[4-( p-nitrophenyl)butoxyamino] alditol derivatives of monosaccharides are amenable to processing by g.c.—m.s., allowing standard methylation analysis of derivatized oligosaccharides to be performed. Thus, the separation and structural analysis of oligosaccharides are facilitated by the physical and chemical properties (u.v. absorption, ease of separation by h.p.l.c., stability to methylation and hydrolysis conditions, and ease of analysis by g.c.—m.s. and f.a.b.-m.s.) imparted to oligosaccharides by forming the 1-deoxy-1-[4-( p-nitrophenyl)butoxyamino] alditol derivatives.

Azomethine proton chemical shift of Schiff bases

Abstract The azomethine proton chemical shift of thirteen para-substituted neutral Schiff bases, XC 6 H 4 CHNC 6 H 4 Y, has been determined in DMSO. Excellent correlation of the chemical shifts of azomethine group with Hammet σ p constants was obtained for substituents in the benzaldehyde moiety. The lack of correlation for substituents in the aniline ring was attributed to the non-planar structure of the benzalaniline derivatives.