- Effect of Hydroxide Ion on the Cis-Trans Thermal Isomerization of Azobenzene Derivatives
-
Azobenzenes can be photochemically transformed from the trans (E) form, which is thermodynamically more stable, to the cis (Z) form.In the dark, the latter reverts to the former.We report here a kinetic study of the thermal isomerization of methyl orange (1), 4-(dimethylamino)-4'-methoxyazobenzene (2), and naphthalene-1-azo-(4'-(dimethylamino)benzene) (3) in water or in water/cosolvent solution measured at different hydroxide ion concentrations.It was found that the reaction is strongly dependent on the hydroxide ion concentration.The observed rate constant for 2 changes from 1.43E-2 s-1 at NaOH (1.0E-3 M) to 7.7E-4 s-1 at NaOH (0.10 M).These results can be interpreted in terms of the isomerization rate constant of the protonated substrates which is at least 1E8 times faster than that of the neutral compound.
- Sanchez, Ana M.,Rossi, Rita H. de
-
-
Read Online
- Supramolecular motifs in s-block metal-bound sulfonated monoazo dyes, part 1: Structural class controlled by cation type and modulated by sulfonate aryl ring position
-
The solid-state structures of 43 Li, Na, K, Rb, Mg, Ca and Ba salts of para- and meta-sulfonated azo dyes have been examined and can be categorised into three structural classes. All form alternating organic and inorganic layers, however, the nature of th
- Kennedy, Alan R.,Kirkhouse, Jennifer B. A.,McCarney, Karen M.,Puissegur, Olivier,Smith, W. Ewen,Staunton, Edward,Teat, Simon J.,Cherryman, Julian C.,James, Rachel
-
-
Read Online
- Synthesis of methyl orange using ionic liquids
-
Two ionic liquids were synthesized, each system consisting of the 1-hexyl-3-methylimidazolium ion ([hmim]+) as the cation and either hexafluorophosphate ([PF6]-), or perchlorate ([ClO4]-) as the anions. This study involves
- Astolfi, Danette L.,Mayville, Francis C.
-
p. 9223 - 9224
(2007/10/03)
-
- Molecular recognition studies on supramolecular systems. 32. Molecular recognition of dyes by organoselenium-bridged bis(β-cyclodextrin)s
-
A series of novel bis(β-cyclodextrin)s tethered with organoselenium linkers, i.e., 6,6′-(o-phenylenediseleno)-bridged bis(β-cyclodextrin) (2), 6,6′-[2,2′-diselenobis(benzoyloxy)]-bridged bis(β-cyclodextrin) (3), and 6,6′-[2,2′-diselenobis[2-(benzoylamino)ethylamino]]-bridged bis(β-cyclodextrin) (4), were synthesized from β-cyclodextrin (1). The inclusion complexation behavior of 1-4 with some dyes, such as 8-anilinonaphthalenesulfonate (ANS), Brilliant Green, Crystal Violet, Tropaeolin OO, Auramine O, and Methyl Orange, was investigated in aqueous phosphate buffer solution (pH 7.20) at 25 °C by UV-vis, fluorescence, and circular dichroism spectrometry, as well as fluorescence lifetime measurements. The complex stability constants (KS) and Gibbs free energy changes (δG°) for the stoichiometric 1:1 inclusion complexation of 1-4 with the dyes were obtained by the spectrophotometric or spectropolarimetric titrations. The bis(β-cyclodextrin)s 2-4 showed much higher affinities toward these guest dyes than native β-cyclodextrin I with fairly good molecular selectivities. The cooperative binding abilities of these bis(β-cyclodextrin)s are discussed from the viewpoints of size/shape-fit interaction, induced-fit concept, and multiple recognition mechanism.
- Liu,Li,You,Wada,Inoue
-
p. 225 - 232
(2007/10/03)
-
- On the mechanism of the acid/base-catalyzed thermal cis-trans isomerization of methyl orange
-
The thermal cis-trans isomerization of methyl orange (i.e., sodium 4-[4′-(dimethylammo)phenylazo]-benzenesulfonate) in acidic aqueous solutions has been investigated by means of laser-flash photolysis techniques. The thermal cis-trans isomerization is fou
- Sanchez, Ana M.,Barra, Monica,De Rossi, Rita H.
-
p. 1604 - 1609
(2007/10/03)
-