The pKa values of N-aryl imidazolinium salts, their higher homologues, and formamidinium salts in dimethyl sulfoxide

2020 ◽  
Vol 18 (10) ◽  
pp. 1910-1917 ◽  
Author(s):  
Nicholas Konstandaras ◽  
Michelle H. Dunn ◽  
Ena T. Luis ◽  
Marcus L. Cole ◽  
Jason B. Harper
Keyword(s):  
Dimethyl Sulfoxide ◽  
Ring Size ◽  
Pka Values ◽  
Imidazolinium Salts

The effects of substitution, ring size and cyclisation on the pKa values of imidazolinium salts, higher homologues and formamidinium salts in DMSO are quantified, considering structural and electronic motifs along with crystallographic analyses.

Acid-Base Equilibria of Substituted Pyridine N-Oxides in N,N-Dimethylformamide and Dimethyl Sulfoxide

1993 ◽  
Vol 46 (2) ◽  
pp. 185 ◽  
Author(s):  
L Chmurzynski ◽  
Z Warnke
Keyword(s):  
Dimethyl Sulfoxide ◽  
Linear Relationship ◽  
Aprotic Solvent ◽  
Heterocyclic Amines ◽  
Aprotic Solvents ◽  
Acid Base ◽  
Acidity Constants ◽  
Pka Values ◽  
Weak Tendency

Acidity constants have been determined potentiometrically for a variety of conjugate acids of substituted pyridine N-oxides in N,N- dimethylformamide ( dmf ) and dimethyl sulfoxide ( dmso ). The pKa values in these solvents varied in the same direction and correlated with the pKa values of these species in water and in the protophobic aprotic solvent acetonitrile. Further, a linear relationship has been established between the pKa values in the two protophilic aprotic solvents under study. The most basic substituted pyridine N-oxides exhibited a weak tendency towards cationic homoconjugation in dmf , whereas in the more basic dmso the homoconjugation equilibrium was not established for any of the heterocyclic N-oxides. The phenomenon of cationic homoconjugation was also not observed with pyridine as a representative of heterocyclic amines, both in dmf and dmso. This finding complies with the results obtained in other polar aprotic solvents.

Targeted and Systematic Approach to the Study of pKa Values of Imidazolium Salts in Dimethyl Sulfoxide

2017 ◽  
Vol 82 (14) ◽  
pp. 7324-7331 ◽  
Author(s):  
Michelle H. Dunn ◽  
Nicholas Konstandaras ◽  
Marcus L. Cole ◽  
Jason B. Harper
Keyword(s):  
Dimethyl Sulfoxide ◽  
Systematic Approach ◽  
Imidazolium Salts ◽  
Pka Values

The SN1CB Mechanism in Non-Aqueous Solution

1988 ◽  
Vol 41 (9) ◽  
pp. 1369 ◽  
Author(s):  
WG Jackson ◽  
RL Angel
Keyword(s):  
Aqueous Solution ◽  
Dimethyl Sulfoxide ◽  
Primary Amines ◽  
Tertiary Amines ◽  
Pka Values ◽  
First Order ◽  
Rate Laws ◽  
General Base ◽  
First Order Kinetics ◽  
Conjugate Base

The reaction between (NH3)5Co-NCMe3+ and dimethyl sulfoxide (Me2SO) to produce (NH3)5Co-OSMe23+ and MeCN in Me2SO solvent is general base-catalysed. The rates and rate laws have been determined for 10 substituted amines. First-order kinetics are observed, and the rates show a dependence which is less than first order on base (B) concentration. These facts are rationalized in terms of a common, reactive conjugate base (NH3)4(NH2)CoNCMe2+, the solvolysis of which occurs at a rate competitive with its rate of reprotonation by BH+. Alternative mechanisms are considered. The measured rates, which span two orders of magnitude, do not correlate with base nucleophilicity, steric features of the amines, nor pKa values as measured for aqueous solution. Primary amines are very effective catalysts; secondary and especially tertiary amines are poorer catalysts. There appears to be no reaction at the bound nitrile function as there is in aqueous solution.

The Effect of Dimethyl Sulfoxide on In Vitro Platelet Function

1976 ◽  
Vol 36 (01) ◽  
pp. 221-229 ◽  
Author(s):  
Charles A. Schiffer ◽  
Caroline L. Whitaker ◽  
Morton Schmukler ◽  
Joseph Aisner ◽  
Steven L. Hilbert
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Dimethyl Sulfoxide ◽  
Platelet Function ◽  
Platelet Volume ◽  
Short Term ◽  
Platelet Factor ◽  
Short Term Exposure ◽  
Structural Abnormalities

SummaryAlthough dimethyl sulfoxide (DMSO) has been used extensively as a cryopreservative for platelets there are few studies dealing with the effect of DMSO on platelet function. Using techniques similar to those employed in platelet cryopreservation platelets were incubated with final concentrations of 2-10% DMSO at 25° C. After exposure to 5 and 10% DMSO platelets remained discoid and electron micrographs revealed no structural abnormalities. There was no significant change in platelet count. In terms of injury to platelet membranes, there was no increased availability of platelet factor-3 or leakage of nucleotides, 5 hydroxytryptamine (5HT) or glycosidases with final DMSO concentrations of 2.5, 5 and 10% DMSO. Thrombin stimulated nucleotide and 5HT release was reduced by 10% DMSO. Impairment of thrombin induced glycosidase release was noted at lower DMSO concentrations and was dose related. Similarly, aggregation to ADP was progressively impaired at DMSO concentrations from 1-5% and was dose related. After the platelets exposed to DMSO were washed, however, aggregation and release returned to control values. Platelet aggregation by epinephrine was also inhibited by DMSO and this could not be corrected by washing the platelets. DMSO-plasma solutions are hypertonic but only minimal increases in platelet volume (at 10% DMSO) could be detected. Shrinkage of platelets was seen with hypertonic solutions of sodium chloride or sucrose suggesting that the rapid transmembrane passage of DMSO prevented significant shifts of water. These studies demonstrate that there are minimal irreversible alterations in in vitro platelet function after short-term exposure to DMSO.

Preservation of Morphological Integrity and Clot Retraction Activity of Human Platelets After Freezing

1964 ◽  
Vol 11 (01) ◽  
pp. 222-229 ◽  
Author(s):  
Isaac Djerassi ◽  
Albert Roy ◽  
Jorge Alvarado ◽  
Keyword(s):  
Dimethyl Sulfoxide ◽  
Liquid Nitrogen ◽  
Human Platelets ◽  
Slow Freezing ◽  
Critical Conditions ◽  
Plasma Medium ◽  
Clot Retraction ◽  
Controlled Freezing ◽  
Direct Immersion

SummaryHuman platelets frozen at −195° C (liquid nitrogen) retain their morphological integrity and ability to promote clot retraction when 5% dimethyl-sulfoxide and 5% dextrose are added to the suspending plasma medium. Slow freezing was more effective than direct immersion in the liquid nitrogen. Although similar results may be achieved with dimethylsulfoxide alone with rigidly controlled freezing rates, the addition of sugars may permit freezing under less critical conditions.Dimethylsulfoxyd und 5% Dextrose dem Plasmamilieu hinzugefügt werden. Das langsame Einfrieren ist effektiver als das direkte Eintauchen in flüssigen Stickstoff. Obschon ähnliche Resultate mit Dimethylsulfoxyd allein unter exakter Kontrolle der Einfrierungsgeschwindig-keit erreicht werden können, erlaubt die Zugabe von Dextrose ein Einfrieren unter weniger kritischen Bedingungen.

Ring size effect in McMurry cyclization of 1,ω-di((azulen-1-yl)-carbonyl) alkanes

2020 ◽  
Vol 65 (1) ◽  
pp. 83-88
Author(s):  
Eugenia Andreea DRAGU ◽  
◽  
Alexandru C. RAZUS ◽  
Keyword(s):  
Size Effect ◽  
Ring Size
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