Host-Guest Complexation of Aromatic Carboxylic Acids and their Conjugate Bases by β-Cyclodextrins Monosubstituted at C 6 by Linear and Cyclic Alkyl Triamines in Aqueous Solution

1999 ◽  
Vol 52 (12) ◽  
pp. 1157 ◽  
Author(s):  
Suzanna D. Kean ◽  
Bruce L. May ◽  
Philip Clements ◽  
Christopher J. Easton ◽  
Stephen F. Lincoln
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Complex Stability ◽  
Guest Complex ◽  
Acid Complex ◽  
K Value ◽  
Host Guest Complex ◽  
Ph Range ◽  
Conjugate Bases ◽  
Significant Factors

A pH titrimetric study of the complexation of the guests benzoic acid, 4-methylbenzoic acid and (R)- and (S)-2-phenylpropanoic acids and their conjugate bases by the host 6A-[2-(2-aminoethylamino)ethylamino]-, 6A-[3-(3-aminopropylamino)propylamino]-, 6A-(1,4,7-triazacyclononan-1-yl)-, and 6A-(1,5,9-triazacyclododecan-1-yl)-6A-deoxy-β-cyclodextrins (βCDdien, βCDdipn, βCDtacn and βCDtacdo, respectively) is reported. Over the pH range 3.0–11.0, 49 host–guest complexes were detected. Their stability constants (K) range from 220±50 dm3 mol–1 for the βCDdienH22+ ·benzoate– complex to 48000±11000 dm3 mol–1 for the βCDdipnH22+·(S)-2-phenylpropanoic acid complex at 298.2 K and I = 0.10 mol dm–3 (NaClO4). The latter K value is among the highest reported for a complex of a simple carboxylic acid with a substituted β-cyclodextrin. The charge, hydrophobicity and stereochemistry of both host and guest appear to be significant factors in the variation of host–guest complex stability. 1H ROESY n.m.r. studies of some of the complexes formed are also reported.

Study on the Supramolecular Interaction of Dibenzoyl Peroxide(BPO) and ß-Cyclodextrin(ß-CD) by Spectrophtometry and its Analytical Application

2012 ◽  
Vol 554-556 ◽  
pp. 27-30
Author(s):  
Hui Xie ◽  
Yan Min Wang
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Benzoic Acid ◽  
Supramolecular Interaction ◽  
Guest Complex ◽  
Host Guest Complex ◽  
Molecule Recognition ◽  
Excellent Selectivity ◽  
Principal Advantage ◽  
Dibenzoyl Peroxide

The supramolecular interaction of BPO and ß-CD has been studied by spectrophtometry. The mechanism of the inclusion was studied. The results showed that ß-CD react with BPO to form a 2:1 or 1:1 host-guest complex.The ß-CD reacts with benzoic acid to form a 1:1 host-guest complex after the BPO was reduced by hydroxyl ammonium chloride.Based on the enhancement of the absorbance of BPO produced through complex formation, a spectrophotometric method for determination BPO in bulk aqueous solution in the presence of ß-CD was developed. A linear relationship between the absorbance and BPO concentration was obtained in the range of 0.2～50 μg.ml-1. The proposed method was used to determine the BPO in the flour with satisfactory results. The principal advantage of the proposed method is its excellent selectivity based on molecule recognition of ß-CD and simple.

scholarly journals Kinetics and Mechanism of the Decarboxylation of Pyrrole-2-carboxylic Acid in Aqueous Solution

1971 ◽  
Vol 49 (7) ◽  
pp. 1032-1035 ◽  
Author(s):  
G. E. Dunn ◽  
Gordon K. J . Lee
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Carboxylic Acid ◽  
Isotope Effect ◽  
Anthranilic Acid ◽  
Kinetic Isotope Effect ◽  
Pyrrole Ring ◽  
First Order ◽  
Kinetic Isotope ◽  
Ph Range

The decarboxylation of pyrrole-2-carboxylic acid in aqueous buffers at 50° and ionic strength 1.0 has been found to be first order with respect to substrate at a fixed pH. As the pH is decreased, the rate constant increases slightly in the pH range 3–1, then rises rapidly from pH 1 to 10 M HCl. The 13C-carboxyl kinetic isotope effect is 2.8% in 4 M HClO4 and negligible at pH ~ 3. These observations can be accounted for by a mechanism, previously proposed for the decarboxylation of anthranilic acid, in which the species undergoing decarboxylation is the carboxylate ion protonated at the 2-position of the pyrrole ring. This intermediate can be formed both by ring-protonation of the carboxylate anion and by ionization of the ring-protonated acid. At low acidities ring-protonation is rate determining, but at higher acidities the rate of protonation exceeds that of decarboxylation.

Cucurbit[7]uril host-guest complexes with cationic bis(4,5-dihydro-1H-imidazol-2-yl) guests in aqueous solution

2006 ◽  
Vol 84 (6) ◽  
pp. 905-914 ◽  
Author(s):  
D Saroja N Hettiarachchi ◽  
Donal H Macartney
Keyword(s):  
Mass Spectrometry ◽  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Stability Constants ◽  
Electrospray Mass Spectrometry ◽  
Hydrophobic Core ◽  
Guest Complex ◽  
H Nmr ◽  
Host Guest Complex ◽  
Proton Resonances

The host–guest interactions between cucurbit[7]uril and a series of novel cationic bis(4,5-dihydro-1H-imidazol-2-yl)arene and 1-(4,5-dihydro-1H-imidazol-2-yl)- and 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)-adamantane guests have been investigated in aqueous solution using UV–vis and NMR spectroscopy, and electrospray mass spectrometry. With the exception of the 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)adamantane (which binds externally to the CB[7]), these guests form very stable inclusion complexes with slow exchange on the 1H NMR timescale. The direction and magnitude of the complexation-induced shifts (CIS) in the proton resonances of the guests are indicative of the residence of the hydrophobic core of the guest within the CB[7] cavity and the charged 4,5-dihydro-1H-imidazol-2-yl units outside the cavity adjacent to the carbonyl-lined portals of the host. The CIS values and the inclusion stability constants have been correlated with the nature of the guest core and with the distance between the charges on the terminal 4,5-dihydro-1H-imidazol-2-yl rings.Key words: cucurbit[7]uril, host–guest complex, dihydroimidazolyl, inclusion stability constants.

Solid-state assembly of carboxylic acid substituted pillar[5]arene and its host–guest complex with tetracaine

CrystEngComm ◽  
2015 ◽  
Vol 17 (4) ◽  
pp. 719-722 ◽  
Author(s):  
Oksana Danylyuk ◽  
Volodymyr Sashuk
Keyword(s):  
Solid State ◽  
Carboxylic Acid ◽  
Inclusion Complexes ◽  
Anesthetic Drug ◽  
Guest Complex ◽  
Host Guest Complex

The first examples of carboxylic acid substituted pillar[5]arene structures in the form of its inclusion complexes with ethanol and the anesthetic drug tetracaine are reported.

Molecular Tweezer and Clip in Aqueous Solution:  Unexpected Self-Assembly, Powerful Host−Guest Complex Formation, Quantum Chemical1H NMR Shift Calculation

2006 ◽  
Vol 128 (14) ◽  
pp. 4831-4841 ◽  
Author(s):  
Frank-Gerrit Klärner ◽  
Björn Kahlert ◽  
Anke Nellesen ◽  
Jan Zienau ◽  
Christian Ochsenfeld ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Self Assembly ◽  
Guest Complex ◽  
Host Guest Complex ◽  
Molecular Tweezer ◽  
Shift Calculation

scholarly journals Host-Guest Complexations of Amine Boranes and Isoelectronic/Isostructural Quaternary Alkylammonium Cations by Cucurbit[7]uril in Aqueous Solution

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Mona A. Gamal-Eldin ◽  
Donal H. Macartney
Keyword(s):  
Aqueous Solution ◽  
Hydrophobic Effect ◽  
Host Molecule ◽  
Guest Complex ◽  
H Nmr ◽  
Hydrophobic Cavity ◽  
Host Guest Complex ◽  
Dipole Interactions ◽  
The Stability ◽  
Amine Boranes

The host-guest complexation of six amine boranes (R3NBH3) by the macrocyclic host molecule cucurbit[7]uril (CB[7]) in aqueous solution has been investigated using 1H and 11B NMR spectroscopy. The limiting complexation-induced 1H and 11B chemical shift changes indicate that the amine boranes are included in the hydrophobic cavity of the host molecule. The host-guest stability constants for neutral  R3NBH3∙CB[7]  complexes (in the range of 105-107M-1) have been determined by 1H NMR competition experiments and are compared with the corresponding values for the isoelectronic/isostructural  R3NCH3∙CB[7] + complexes. Ammonia borane (H3NBH3) does not form a host-guest complex with CB[7]. The trends in the host-guest stability constant with the guest molar volume are examined, and the stability is ascribed to the hydrophobic effect (packing coefficient) and quadrupole-dipole interactions.

Enolization of the benzocyclohexadienone formed during the bromination of 1-naphthol in aqueous solution

1987 ◽  
Vol 65 (8) ◽  
pp. 1714-1718 ◽  
Author(s):  
Oswald S. Tee ◽  
N. Rani Iyengar
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Hydroxide Ion ◽  
A Value ◽  
Ph Range ◽  
Effective Molarity ◽  
Kinetics Of

Benzo-4-bromo-2,5-cyclohexadienone (5) has been observed in the aqueous bromination of 1-naphthol and the kinetics of its enolization to 4-bromo-1-naphthol have been studied in the pH range 0–7. This process is catalyzed by the proton, hydroxide ion, water, buffer acids, and by buffer bases. For catalysis by general bases the Brønsted β = 0.59 whereas catalysis by general acids has a value of α ~ 0. These findings are very similar to those obtained previously for the 4-bromo-2,5-cyclohexadienone 2b, formed during the aqueous bromination of 2,6-dimethylphenol. The mechanistic implications of the results are discussed. The enolization of the related dienone 8, formed from bromine and 1-naphthol-2-carboxylic acid, was also studied. At acidic pHs the dienone 8 is much more reactive than 5, with the 2-COOH behaving as an internal catalyst having an "effective molarity" of about 110 M. The enolization of 8 is also catalyzed by buffer bases.

β-Cyclodextrin Based Nanosponges in Organic Synthesis

2020 ◽  
Vol 23 (21) ◽  
pp. 2366-2377
Author(s):  
Ali R. Kiasat ◽  
Seyyed J. Saghanezhad ◽  
Samaneh Noori
Keyword(s):  
Drug Delivery ◽  
Aqueous Solution ◽  
Organic Synthesis ◽  
Flame Retardants ◽  
3D Structure ◽  
Gas Storage ◽  
Hydrophilic Surface ◽  
Guest Complex ◽  
Smart Fabrics ◽  
Host Guest Complex

The particular β-cyclodextrin 3D structure, with its hydrophilic surface and apolar cavity, has enabled to partially or totally encapsulate hydrophobic molecules of appropriated size and shape in aqueous solution as well as in solid-state through the formation of a reversible host–guest complex. Accordingly, β-cyclodextrin based nanosponges have been prepared and used in previous years for the synthesis of organic compounds. In this review, we are going to mention some of the recent reports on the application of β- cyclodextrin 3D nanosponges in organic synthesis catalysis. Furthermore, it should be mentioned that these compounds have also been utilized for numerous applications including drug delivery, gas storage, rubber manufacture, diagnostics, cosmetics, agriculture, smart fabrics, water purification, and flame retardants.

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