Indicator Studies of Acids and Bases in Benzene.

Mer, Victor K. La; Downes, Harold C.

doi:10.1021/cr60044a004

Cited by 17 publications

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“…The dat a also ar e of inter es t in connection with t he general problem of acid-base equilibri a in media of low dielectric constant. While in cer tain instances such r ea ctions do seem to follow a simple mass law [9] , in other s the behavior is more complicated [10]. In addition to factors such as association of t h e acids and salts, t he formation of complex salts as sugges ted by the presen t studies may introdu ce additional complications, par ticularly in cases wher e cal'bo: xy li c or sulfonic acids are employe d.…”

Section: Conductimetric Titrotionsmentioning

confidence: 99%

Conductimetric titrations of acids and bases in benzene and dioxane

Aa¹

1947

J. RES. NATL. BUR. STAN.

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Acid-base tit rations were made conductimetrically in pure benzene and dioxan e with picric, t ri chloroacetic, and camphorsulfoni c acids, together with primary, secondary, and tertiary amines. Although the conductances of the solutions were extremely low, lower by a'factor of 10-8 or more tllan in water, t h e t itrations gave sharp end points which generally ,;ere accurate to 1 percent or better. The unusual , though similar behavior of all titrations involving trichloroacetic or camphorsulfonic acid, where the conductance of t h e salt was enhanced greatly by the presence of free acid, ,,·as interpreted in term of a reaction between salt and acid leading to the formation o f a complex anion , The occasional variations in conductanc with ti me, in one instance suggesting slow attainment of some secondary ionic equilibrium, and the effect upon the t itrati o n c ur ves of the addition of a small amount o(me thYl a lcohol to the solvent are disc ussed .

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Section: Conductimetric Titrotionsmentioning

confidence: 99%

Conductimetric titrations of acids and bases in benzene and dioxane

Aa¹

1947

J. RES. NATL. BUR. STAN.

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“…Moreover, at the time of the experiments spectrometric equipment enjoyed by present-day chemists was not available. 491,357,573,492,493,355]; conductance and potentiometry were also employed in attempts to derive acidity scales [340]. Reference was made in section 4.5.4b to experiments in which the catalytic effects of a series of carboxylic acids and halophenols, dissolved in chlorobenzene, were related to their aqueous strengths by a simple equation (into which, unaccountably, picric acid did not fit).…”

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confidence: 99%

Acid-base behavior in aprotic organic solvents

Davis¹

1968

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Butyl hydroperoxide and deuteroperoxide. Deuterium isotope effects on hydrogen bonding by Br0nsted acids 40 4.3. Hydrogen-bonded ion pairs 41 4.3.1. Conductance 41 a. Walden's work 42 b. Wynne-Jones' postulate 42 c. Investigations of Kraus, Fuoss, and associates... 43 d. Summary 45 4.3.2. Dielectric constants 46 a. Dielectric polarization of substituted ammonium picrates and halides in benzene 46 b. Dielectric polarization of other acid-base complexes in benzene 47 4.3.3. CoUigative properties 49 a. Cryoscopy 50 Page b. The differential vapor pressure (DVP) method... 51 104 4.5.6. Homoconjugation of other organic and inorganic acids a. Perchloric acid 105 b. Other acids 105 4.5.7. Heteroconjugate anions 105 a. Chemical behavior 105 b. Physical measurements 108 4.6. Concluding discussion of hydrogen bonding 112 4.6.1. Definition of a hydrogen bond. Systems which form hydrogen bonds 112 4.6.2! Some recent concepts of hydrogen bonding 113 5. Acidity and basicity scales in aprotic organic solvents... 114 5.1. Early attempts to determine relative acidities 114 5.2. Log Kbha scales of acidity and basicity 115 5.3. Methods used in determining values of log A^bha 116 5.4. Tables of log ^bha, and AS obtained using aprotic solvents 118 5.4.1. Aromatic and substituted aromatic hydrocarbons 118 a. Benzene 118 b. Anisole and chlorobenzene 126 5.4.3. Carbon tetrachloride 126 5.4.4. Chloroform 128 5.4.5. Miscellaneous aprotic solvents 129 6. Acid-base titrations in completely aprotic solvents 133 6.1. Introduction 133 6.2. Titrations with indicator dyes in completely aprotic solvents 133 6.3. Instrumental procedures for detecting end-points in completely aprotic solvents 133 6.3.1. Conductance titrations 133 iv Contents -Continued Page 6.3.2. Dielectrometric titrations 133 6.3.3. Photometric titrations 134 6.3.4. Thermometric titrations 135 6.3.5. Titrations by the DVP method 135 6.3.6. Cryoscopic titrations 135 6.3.7. Other possible instrumental procedures 135 a. Refractive index 135 b. Density 135 c. Optical rotation 135 6.4. Reference acids and bases for aprotic organic solvents 135 6.4.1. Acids 135 a. Hydrogen chloride 135

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“…Around the same time during 1931 to 1933, La Mer and Downes developed a method for measuring quantitatively the relative strengths of a set of carboxylic acids in the presence of a sufficiently strong base like diethylamine or piperidine in benzene employing Dimethyl Yellow, Bromophenol Blue, Bromocresol Purple, Methyl Red, Propyl Red, and other indicators. The system did not always follow the simple mass law equation, and the anomalous behavior was explained by assuming that either the substrate acid or the indicator acid behaved as a polybasic acid due to association . A few years later, Griffith made use of the method of La Mer and Downes in 1938 to study the equilibrium between a series of carboxylic acids and the base form of 2,6‐dinitrophenol or Bromophenol Blue in the presence of isobutylamine base in chlorobenzene and found their relative strengths in chlorobenzene and in water were closely parallel …”

Section: Early Work (Pre‐1940)mentioning

confidence: 99%

“…The early developments in studies on proton transfer in apolar aprotic solvents since the 1920s Brønsted–Lowry's “proton cult” was reviewed by Hall and by La Mer and Downes in the 1930s. After a gap of nearly four decades, Davis presented a most authoritative review on thermodynamic aspects of proton transfer in these inert solvents in the form of a monograph in 1968 and a book chapter in 1970.…”

Section: Introductionmentioning

confidence: 99%

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Gupta

2016

J of Physical Organic Chem

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Low dielectric constant apolar aprotic solvents, although employed on a limited scale for studying proton transfer reactions as compared with commonly used polar protic or dipolar aprotic ones, offer some particular advantages, namely, specific solute-solvent interactions are virtually eliminated and proton transfer occurs directly in an apolar aprotic solvent. An intriguing feature of these reactions is their general acid-catalyzed/base-catalyzed kinetics with a time scale over microseconds to minutes. In fact, the true or intrinsic relative strengths of acids/bases when measured in such solvents come to the fore much more clearly than those obtained in other classes of solvents. Recently, a review documenting the post-1980 developments relating to proton transfer reactions in apolar aprotic solvents has been published. The present article is a commentary of the pre-1980 developments in this area since the 1920s Brønsted-Lowry's "proton cult" of acid-base theory. dia since 1976 till 2013 when he superannuated as the Dean, Faculty of Science of the University. Currently, he is an Emeritus Professor at Banaras Hindu University, Varanasi. His research interests are origin, non-faradaic chemical effects and applications of contact glow discharge electrolysis, and kinetics and mechanism of proton transfer processes in apolar aprotic media and quantitative structure-reactivity relationships. Further research activities concern transmission modes of anomalous substituent effects on 13 C chemical shifts in aromatic molecules and ferrospinel catalysts.

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Indicator Studies of Acids and Bases in Benzene.

Abstract: In the days before the electrolytic dissociation theory was developed, the term "acid" implied a corrosive substance with a

Cited by 17 publications

References 4 publications

Conductimetric titrations of acids and bases in benzene and dioxane

Conductimetric titrations of acids and bases in benzene and dioxane

Acid-base behavior in aprotic organic solvents

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

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