Flash photolysis of alkali metal anions in tetrahydrofuran and dimethoxyethane

1979 ◽  
Vol 57 (14) ◽  
pp. 1792-1800 ◽  
Author(s):  
W. A. Seddon ◽  
J. W. Fletcher ◽  
F. C. Sopchyshyn ◽  
E. B. Selkirk
Keyword(s):  
Pulse Radiolysis ◽  
Shape Function ◽  
Flash Photolysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Parent Metal ◽  
Initial Formation ◽  
Extinction Coefficients ◽  
Best Fit ◽  
Good Agreement

Flash photolysis of K−, Rb−, and Cs− in tetrahydrofuran (THF) produces the corresponding ion-pairs (K+, es−), (Rb+, es−), and (Cs+, es−), followed by the regeneration of the parent metal anion, M−. In mixed-metal solutions containing Na and M where M is K, Rb, or Cs, photolysis of Na− also forms the (M+, es−) ion-pair and M−, but with the latter then reforming Na− on an extended time scale. Similar results were obtained in dimethoxyethane (DME) at 213 K, but in this case with the initial formation of a loose ion-pair, (M+, es−)loose.Based on a Gaussian–Lorenztian shape function, the 'best-fit' optical bands for the (M+, es−) and M− species were used to simulate the experimental spectra and deduce the corresponding extinction coefficients in both solvents.The overall mechanism is complex but is in good agreement with previous interpretations deduced by pulse radiolysis.

The effect of temperature on the optical spectra and the yields of solvated electrons and ion-pairs in amines

1978 ◽  
Vol 56 (6) ◽  
pp. 839-843 ◽  
Author(s):  
William Arthur Seddon ◽  
John Wallace Fletcher ◽  
Fred Charles Sopchyshyn
Keyword(s):  
Ion Pairs ◽  
Solvent Polarity ◽  
Solute Concentration ◽  
Ion Pair ◽  
Effect Of Temperature ◽  
Gradual Transition ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Extinction Coefficients ◽  
Yield Formula

Optical absorption spectra for the solvated electron, es−, and ion-pairs, (Na+, es−), have been observed in methylamine (MA), ethylamine (EA), and isopropylamine (IPA), at temperatures ranging from 184 to 338 K. Changes in the (Na+, es−) spectra, relative to es−, are consistent with a gradual transition in the ion-pair structure toward a more 'electron-like' entity with decreasing temperature and increasing solvent polarity. Extinction coefficients, εmax(es−) = 3.3 ± 0.2, 3.2 ± 0.5, and 3.2 ± 0.5 × 104 M−1 cm−1 in MA, EA, and IPA respectively. Corresponding values for the ion-pairs, εmax(Na+, es−) = 2.5 ± 0.2, 2.1 ± 0.2, and 1.9 ± 0.2 × 104 M−1 cm−1.In EA and IPA, the yield [Formula: see text] (molecules/100 eV) shows a marked solute concentration dependence. This is consistent with an empirical scavenging model from which the escaped solvated G(es−)esc and spur G(es−)spur electrons are estimated as G(es−)esc = 0.5 and 0.4, G(es−)spur = 1.8 and 1.4, giving G(es−)total = 2.3 and 1.8 in EA and IPA, respectively. In MA, [Formula: see text] = G(es−)esc = 2.25 ± 0.2, independent of solute concentration.

Pulse Radiolysis of Alkali Metal Solutions in Methylamine

1975 ◽  
Vol 53 (23) ◽  
pp. 3571-3579 ◽  
Author(s):  
John Wallace Fletcher ◽  
William Arthur Seddon ◽  
John Joseph Jevcak ◽  
Fred Charles Sopchyshyn
Keyword(s):  
Reaction Mechanism ◽  
Alkali Metal ◽  
Reaction Kinetics ◽  
Pulse Radiolysis ◽  
Ion Pairs ◽  
Solvated Electrons ◽  
Extinction Coefficients ◽  
Ion Species ◽  
Triple Ion ◽  
Metal Anions

Pulse radiolysis studies of solutions of alkali metal methylamides (CH3NHM) in methylamine indicate the formation of solvated electrons, es−, ion-pairs (M+, es−), and alkali metal anions M−. This paper compares the spectra, extinction coefficients, and yields of es−, Li, Na, K, and Cs species, with those observed previously in other solvents. The overall reaction kinetics are complex and, in CH3NHNa/NaI solutions, suggest the formation of a higher aggregate or triple ion species (Na22+, es−). A reaction mechanism, quantitatively consistent with experiment, is presented and discussed in detail for solutions containing Na+.

The dissociation constant for potassium methylamide ion pairs in methylamine

1978 ◽  
Vol 56 (11) ◽  
pp. 1518-1523
Author(s):  
E. Allan Symons ◽  
J. Douglas Bonnett
Keyword(s):  
Dielectric Constant ◽  
Dissociation Constant ◽  
Lower Limit ◽  
Ion Pairs ◽  
Ion Pair ◽  
Solvent Viscosity ◽  
Temperature Range ◽  
Conductance Data ◽  
Heat Of Dissociation ◽  
Good Agreement

The limiting equivalent conductance (Λ0) and ion pair dissociation constant (Kd) have been obtained for potassium methylamide in methylamine from conductance data measured over the temperature range −55 to + 25° C. The value of Kd increases from 6.3 × 10−8 mol L−1 at the highest temperature to 9.4 × 10−7 mol L−1 at the lower limit. The results show good agreement with literature data for potassium amide in ammonia after corrections for differences in solvent viscosity and dielectric constant. The heat of dissociation is −26 kJ mol−1 above −15 °C, but decreases gradually at progressively lower temperatures as a shift occurs from tight to loose ion pair structures.

A Laser Flash Photolysis and Pulse Radiolysis Study of Primary Photochemical Processes of Flumequine¶

2000 ◽  
Vol 72 (4) ◽  
pp. 451 ◽  
Author(s):  
M. Bazin ◽  
F. Bosca ◽  
M. L. Marin ◽  
M. A. Miranda ◽  
L. K. Patterson ◽  
...  
Keyword(s):  
Pulse Radiolysis ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Photochemical Processes

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

scholarly journals Tripodal, Squaramide-Based Ion Pair Receptor for Effective Extraction of Sulfate Salt

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2751
Author(s):  
Damian Jagleniec ◽  
Marcin Wilczek ◽  
Jan Romański
Keyword(s):  
Ion Pairs ◽  
Binding Mode ◽  
Selective Extraction ◽  
Ion Pair ◽  
Hofmeister Series ◽  
Sulfate Salt ◽  
Lower Affinity ◽  
High Affinity ◽  
Binding Domains ◽  
Hydrated Sulfate

Combining three features—the high affinity of squaramides toward anions, cooperation in ion pair binding and preorganization of the binding domains in the tripodal platform—led to the effective receptor 2. The lack of at least one of these key elements in the structures of reference receptors 3 and 4 caused a lower affinity towards ion pairs. Receptor 2 was found to form an intramolecular network in wet chloroform, which changed into inorganic–organic associates after contact with ions and allowed salts to be extracted from an aqueous to an organic phase. The disparity in the binding mode of 2 with sulfates and with other monovalent anions led to the selective extraction of extremely hydrated sulfate anions in the presence of more lipophilic salts, thus overcoming the Hofmeister series.

scholarly journals Potentiometric Surfactant Sensor Based on 1,3-Dihexadecyl-1H-benzo[d]imidazol-3-ium for Anionic Surfactants in Detergents and Household Care Products

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3627
Author(s):  
Nikola Sakač ◽  
Dubravka Madunić-Čačić ◽  
Dean Marković ◽  
Lucija Hok ◽  
Robert Vianello ◽  
...  
Keyword(s):  
Anionic Surfactants ◽  
Negative Impact ◽  
Ion Pair ◽  
Two Phase ◽  
Potentiometric Response ◽  
Titration Curves ◽  
Signal Change ◽  
Nernstian Slope ◽  
Good Agreement

A 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DHBI-TPB) ion-pair implemented in DHBI-TPB surfactant sensor was used for the potentiometric quantification of anionic surfactants in detergents and commercial household care products. The DHBI-TPB ion-pair was characterized by FTIR spectroscopy and computational analysis which revealed a crucial contribution of the C–H∙∙∙π contacts for the optimal complex formation. The DHBI-TPB sensor potentiometric response showed excellent analytical properties and Nernstian slope for SDS (60.1 mV/decade) with LOD 3.2 × 10−7 M; and DBS (58.4 mV/decade) with LOD 6.1 × 10−7 M was obtained. The sensor possesses exceptional resistance to different organic and inorganic interferences in broad pH (2–10) range. DMIC used as a titrant demonstrated superior analytical performances for potentiometric titrations of SDS, compared to other tested cationic surfactants (DMIC > CTAB > CPC > Hyamine 1622). The combination of DHBI-TPB sensor and DMIC was successfully employed to perform titrations of the highly soluble alkane sulfonate homologues. Nonionic surfactants (increased concentration and number of EO groups) had a negative impact on anionic surfactant titration curves and a signal change. The DHBI-TPB sensor was effectively employed for the determination of technical grade anionic surfactants presenting the recoveries from 99.5 to 101.3%. The sensor was applied on twelve powered samples as well as liquid-gel and handwashing home care detergents containing anionic surfactants. The obtained results showed good agreement compared to the outcomes measured by ISE surfactant sensor and a two-phase titration method. The developed DHBI-TPB surfactant sensor could be used for quality control in industry and has great potential in environmental monitoring.

Flash photolysis and pulse radiolysis of the Co(sep)3+-X- (sep = sepulchrate; X = I, Br) systems in aqueous solution

1986 ◽  
Vol 25 (23) ◽  
pp. 4249-4252 ◽  
Author(s):  
Fernando Pina ◽  
Mauro Maestri ◽  
Roberto Ballardini ◽  
Quinto G. Mulazzani ◽  
Mila D'Angelantonio ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Flash Photolysis

Transient carbocations and carbanions generated by laser flash photolysis and pulse radiolysis

1993 ◽  
Vol 93 (1) ◽  
pp. 119-144 ◽  
Author(s):  
P. K. Das
Keyword(s):  
Pulse Radiolysis ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

Ion pair binding by an l-tyrosine-based polymerizable molecular receptor

2015 ◽  
Vol 39 (8) ◽  
pp. 6216-6222 ◽  
Author(s):  
Szymon Zdanowski ◽  
Jan Romański
Keyword(s):  
Ion Pairs ◽  
Functional Polymers ◽  
Ion Pair

A polymerizable molecular receptor able to bind ion pairs and new functional polymers containing the receptor units were synthesized and characterized.

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