Strongly basic systems. VIII. The H− function for dimethyl sulfoxide – water – tetramethylammonium hydroxide

1967 ◽  
Vol 45 (9) ◽  
pp. 911-924 ◽  
Author(s):  
Douglas Dolman ◽  
Ross Stewart
Keyword(s):  
Dimethyl Sulfoxide ◽  
Tetramethylammonium Hydroxide ◽  
Strengthening Effect ◽  
Acidity Function ◽  
Substituent Constant ◽  
Substituted Anilines ◽  
Hydroxide Ion ◽  
Substituent Constants ◽  
Hammett Σ Constants ◽  
Increased Activity

An H− acidity function based on the ionization of 24 substituted anilines and diphenylamines has been established in the system dimethyl sulfoxide – water – tetramethylammonium hydroxide. The H− of a 0.011 M solution of tetramethylammonium hydroxide ranges from 12 in water to 26.2 in 99.6 mole % dimethyl sulfoxide – water, an increase in basicity of 14 powers of 10. The increase in basicity is due to the increased activity of the hydroxide ion brought about by the reduction in its solvation in the poor anion-solvating solvent dimethyl sulfoxide, and indicates the extensive solvation enjoyed by the hydroxide ion in water.The pKHA values of the indicator acids vary from 13.9 for 2,4-dinitrodiphenylamine to 25.6 for 3-chloroaniline. From a plot of log KHA versus the Hammett substituent constants (σ) for six monosubstituted diphenylamines, a ρ value of 4.07 is found. Similar results are obtained for the anilines. The acidities of all the substituted diphenylamines do not follow the above-mentioned correlation with the Hammett σ constants; the pKHA values of 4-amino-, 4-methoxy-, 4-methylsulfonyl-, and 4-nitro-diphenylamine are all less than expected from the Hammett σ constants for the substituents in these compounds. The 4-nitro substituent exerts a particularly large acid-strengthening effect on the acidities of aniline and diphenylamine, the decreases in pKHA being approximately 8.4 and 6.8 pK units, respectively. An exalted substituent constant of +1.65 for p-NO2 is needed to account for the acidity of p-nitro-diphenylamine.

STRONGLY BASIC SYSTEMS: III. THE H− FUNCTION FOR VARIOUS SOLVENT SYSTEMS

1964 ◽  
Vol 42 (7) ◽  
pp. 1681-1693 ◽  
Author(s):  
Ross Stewart ◽  
J. P. O'Donnell
Keyword(s):  
Lithium Hydroxide ◽  
Dimethyl Sulphoxide ◽  
Tetramethylammonium Hydroxide ◽  
Acidity Function ◽  
Function Concept ◽  
Substituted Anilines ◽  
Hammett Acidity Function ◽  
Solvent Systems

The Hammett acidity function concept has been used to determine simultaneously the pKa values of 24 substituted anilines and diphenylamines and the H− values of various solvent systems. The following solvent systems were examined (the most basic H− value obtained for each is shown in parentheses): water containing benzyltrimethylammonium hydroxide (16.20); pyridine–water containing tetramethylammonium hydroxide (18.91); sulpholane–water containing tetramethylammonium hydroxide (19.18); dimethyl sulphoxide–water containing tetramethylammonium hydroxide (18.61); water containing lithium hydroxide (14.31).In addition to these results adjustments have been made to previously published scales for hydrazine–water (15.08) and ethylenediamine–water (15.48).

An acidity function in ethanol – sulfuric acid based on the protonation of diphenylamines

1967 ◽  
Vol 45 (9) ◽  
pp. 903-910 ◽  
Author(s):  
Douglas Dolman ◽  
Ross Stewart
Keyword(s):  
Sulfuric Acid ◽  
Nitro Group ◽  
Strong Interaction ◽  
Acidic Solution ◽  
Sulfuric Acid Concentration ◽  
Substituent Effects ◽  
Solvent System ◽  
Acidity Function ◽  
Substituent Constants ◽  
Hammett Σ Constants

A Hammett H0 acidity function based on the protonation of 17 diphenylamines in 20 volume % ethanol – aqueous sulfuric acid has been established. The H0 value for the most acidic solution studied (11.2 M sulfuric acid) is −6.97. This acidity function differs from that based on the protonation of azobenzenes in the same solvent system; the latter diverges to more negative H0 values as the sulfuric acid concentration increases.The [Formula: see text] values for the protonation of the diphenylamines vary from +1.36 for 4-methoxy-diphenylamine to − 6.21 for 4,4′-dinitrodiphenylamine. A plot of [Formula: see text] versus the Hammett σ constants for five monosubstituted diphenylamines yields a ρ value of +3.36. The [Formula: see text] values for 4-methoxy-, 4-methyl-, 4-methylsulfonyl-, and 4-nitro-diphenylamine are all less (more negative) than expected from the Hammett substituent constants. The substituent effects on the basicities of aniline and diphenylamine are the same.The basicities of several nitro-substituted diphenylamines appear to vary regularly, and do not reflect the presence of a strong interaction between the nitro group and sulfuric acid.

The H− acidity function for dimethylformamide–water

1970 ◽  
Vol 48 (21) ◽  
pp. 3354-3357 ◽  
Author(s):  
E. Buncel ◽  
E. A. Symons ◽  
Douglas Dolman ◽  
Ross Stewart
Keyword(s):  
Solvent System ◽  
Tetramethylammonium Hydroxide ◽  
Acidity Function ◽  
Hydroxide Ion ◽  
Indicator Method ◽  
Aqueous Dimethylsulfoxide

The H− acidity function has been determined for N,N-dimethylformamide–water mixtures containing tetramethylammonium hydroxide by the Hammett indicator method. Basicity in the aqueous dimethylformamide system exceeds that in aqueous tetramethylenesulfone but is slightly less than in aqueous dimethylsulfoxide, at equivalent molar compositions of solvent and base. However, the basic aqueous dimethylformamide solvent system is only of limited utility as a result of reaction of hydroxide ion with the dimethylformamide.

CuAAC and RuAAC with Alkyne-functionalised Dihydroazulene Photoswitches and Determination of Hammett σ-Constants for Triazoles

2014 ◽  
Vol 67 (3) ◽  
pp. 531 ◽  
Author(s):  
Henriette Lissau ◽  
Søren Lindbæk Broman ◽  
Martyn Jevric ◽  
Anders Ø. Madsen ◽  
Mogens Brøndsted Nielsen
Keyword(s):  
Molecular Electronics ◽  
Ring Closure ◽  
Reference Systems ◽  
Rigid Structure ◽  
Useful Components ◽  
Substituent Constants ◽  
Hammett Σ Constants

Dihydroazulene (DHA)–vinylheptafulvene (VHF) photoswitches have attracted attention as potentially useful components in molecular electronics. The π-conjugated dihydroazulene system is a rigid structure and can be strategically functionalised to place handles for further elaboration. Here we show that alkyne-functionalised dihydroazulenes can be subjected to copper and ruthenium catalysed azide–alkyne cycloadditions (CuAAC and RuAAC) with tolylazide, furnishing 1,4- and 1,5-disubstituted triazoles. The rates of ring-closure of the corresponding vinylheptafulvenes were compared with those of reference systems, which allowed determination of Hammett substituent constants (meta and para) for N-tolyl-substituted 1,2,3-triazoles.

Effect of para Substitution on Dissociation of N-Phenylbenzenesulfonamides

2004 ◽  
Vol 69 (7) ◽  
pp. 1479-1490 ◽  
Author(s):  
Martin Mansfeld ◽  
Patrik Pařík ◽  
Miroslav Ludwig
Keyword(s):  
Elemental Analysis ◽  
Principal Components ◽  
Latent Variables ◽  
Dissociation Constants ◽  
Additive Model ◽  
Reaction Centre ◽  
Hammett Equation ◽  
Substituted Anilines ◽  
Transmission Effect ◽  
Substituent Constants

The reaction of substituted anilines and benzenesulfonyl chlorides has been used to prepare 49 substituted N-phenylbenzenesulfonamides of general formula 4-X-C6H4SO2NHC6H4-Y-4'. Their purity was checked by elemental analysis. The substituents X and Y include H, CH3, CH3O, Cl, Br, CN, and NO2. The dissociation constants of all compounds were determined by potentiometric titration in methanol, acetonitrile, N,N-dimethylformamide, and pyridine. The obtained dissociation constants, pKHA, were correlated with various sets of substituent constants. It was found that the effects of substituents X and Y on the dissociation are best described by using the Hammett equation with σp constants and the Yukawa-Tsuno equation with σp- and σp constants, respectively. This result confirms the direct conjugation of Y substituent with the reaction centre. The explained variability using the additive model was above 96% in all the solvents used. The data also provided information about the transmission effect of the SO2 group. The average dissociation constants were further processed by the latent variables methods, principal components and conjugated deviations analyses.

THE AMINO PROTON SHIFTS OF SOME SUBSTITUTED ANILINES IN CYCLOHEXANE

1965 ◽  
Vol 43 (10) ◽  
pp. 2668-2677 ◽  
Author(s):  
T. Yonemoto ◽  
W. F. Reynolds ◽  
H. M. Hutton ◽  
T. Schaefer
Keyword(s):  
Negative Deviation ◽  
Hydrogen Bonding Interaction ◽  
Substituted Anilines ◽  
Aqueous Acid ◽  
Low Field ◽  
Low Concentrations ◽  
Bonding Interaction ◽  
Correlation Line ◽  
Hammett Σ Constants ◽  
Infrared Data

The amino proton shifts of 41 ortho, meta, and para substituted anilines at low concentrations in cyclohexane are reported. The shifts for meta and para substituents correlate with Hammett σ constants and it is shown that they are probably proportional to the π-electron density on the nitrogen atom. These shifts also correlate with the pKa values of the corresponding anilinium ions in aqueous acid. The amino proton shifts for the ortho substituents, apart from methyl groups, follow a correlation line which lies about 0.5 p.p.m. to low field from that for the meta and para substituents. This negative deviation is discussed in terms of a weak hydrogen bonding interaction with the ortho substituents and the H—N—H bond angles as derived from infrared data.

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